Tiptronic, Loss of Torque/HP vs. Manual?
09-22-2005, 08:59 PM
#16
"Race prepped A/T?? Give me a break. Let's not confuse a Porsche Tiptronic with the typical sequential manual gearboxes that are found in many race cars and some Ferrari's, BMW's etc. The tiptronic is really a standard A/T that Porsche "taught" to hold gears and shift on command."
You obviously don't even know what i'm talking about.(no disrespect intended)
I'm talking about a conventional A/T with shaved clutch plates, extra clutch packs, and a reworked manual/automatic valve body. Not a paddle shifter.
"I have driven multiple "Tips""
All of which were stock i'd bet.
"and there is no way you can tell me that I can't shift my manual in less time than it takes you to push the thumb button on the steering wheel"
In a properly prepared A/T you don't have to push any buttons at all. The trans does all the work. There is NO WAY anyone on alive can shift as fast as the A/T in my 928S(just as an example), the shift is virtually instantaneous(up or down). The lever is never moved from D with a WOT kickdown override installed(like mine has).
"The shift the Tip makes is reasonably fast, but the "lag" prior to the shift ruins that quick shift. "
Which is the entire point behind reworking the valve body. A reworked valve body has NO delay at all. The shift is instantaneous.
"Add an extra 100 or so pounts for the Tip (and a power robbing torque converter) and you can see why the term "race prepped" is a little funny."
You've never been to a drag strip, have you?
"Now.......a true sequential manual......that can shift faster than any human ever born!"
They shift no faster than a conventional A/T with a race prepped valve body. That is a fact.
When you 'race prep' an A/T you are reworking the shift 'logic' of the valve body. This will allow automatic WOT redline shifts in all gears(with the lever in D), tremendously fast/hard shifts, and you're installing more clutch disks(by shaving the individual clutch plates) to increase friction grip, heat dissipation, and to drastically reduce clutch engagement slip.
Coupled with a high stall converter, the A/T will not engage until a pre-selected RPM(ie the heart of your powerband), ensuring that you're always making close to peak HP at all times, and very high RPM launches are enabled.
Even more important is consistency. An A/T car is far more consistent than a manual. Every launch and every shift will be the same at a given rpm every single time.
You obviously don't even know what i'm talking about.(no disrespect intended)
I'm talking about a conventional A/T with shaved clutch plates, extra clutch packs, and a reworked manual/automatic valve body. Not a paddle shifter.
"I have driven multiple "Tips""
All of which were stock i'd bet.
"and there is no way you can tell me that I can't shift my manual in less time than it takes you to push the thumb button on the steering wheel"
In a properly prepared A/T you don't have to push any buttons at all. The trans does all the work. There is NO WAY anyone on alive can shift as fast as the A/T in my 928S(just as an example), the shift is virtually instantaneous(up or down). The lever is never moved from D with a WOT kickdown override installed(like mine has).
"The shift the Tip makes is reasonably fast, but the "lag" prior to the shift ruins that quick shift. "
Which is the entire point behind reworking the valve body. A reworked valve body has NO delay at all. The shift is instantaneous.
"Add an extra 100 or so pounts for the Tip (and a power robbing torque converter) and you can see why the term "race prepped" is a little funny."
You've never been to a drag strip, have you?
"Now.......a true sequential manual......that can shift faster than any human ever born!"
They shift no faster than a conventional A/T with a race prepped valve body. That is a fact.
When you 'race prep' an A/T you are reworking the shift 'logic' of the valve body. This will allow automatic WOT redline shifts in all gears(with the lever in D), tremendously fast/hard shifts, and you're installing more clutch disks(by shaving the individual clutch plates) to increase friction grip, heat dissipation, and to drastically reduce clutch engagement slip.
Coupled with a high stall converter, the A/T will not engage until a pre-selected RPM(ie the heart of your powerband), ensuring that you're always making close to peak HP at all times, and very high RPM launches are enabled.
Even more important is consistency. An A/T car is far more consistent than a manual. Every launch and every shift will be the same at a given rpm every single time.
Last edited by m21sniper; 09-22-2005 at 11:28 PM.
09-23-2005, 05:08 PM
#17
Ironman 140.6
Rennlist Member
Rennlist Member
Originally Posted by m21sniper
You obviously don't even know what i'm talking about.(no disrespect intended)
Originally Posted by m21sniper
I'm talking about a conventional A/T with shaved clutch plates, extra clutch packs, and a reworked manual/automatic valve body. Not a paddle shifter.
In a properly prepared A/T you don't have to push any buttons at all. The trans does all the work. There is NO WAY anyone on alive can shift as fast as the A/T in my 928S(just as an example), the shift is virtually instantaneous(up or down). The lever is never moved from D with a WOT kickdown override installed(like mine has).
In a properly prepared A/T you don't have to push any buttons at all. The trans does all the work. There is NO WAY anyone on alive can shift as fast as the A/T in my 928S(just as an example), the shift is virtually instantaneous(up or down). The lever is never moved from D with a WOT kickdown override installed(like mine has).
However, they don't need to shift as quickly to beat you. The extra weight on your transmission and the power loss from your torque converter will slow you down enough so that a good driver with a manual will still win (both cars with stock power). You're set-up with a moddified A/T might work ok on a drag strip but it would be horrible for a race track (far worse than a standard tiptronic). Your car will upshift braking into every corner and then be in the wrong gear for corner exit where it will downshift and upset your balance (at least a tiptronic will work right in this respect). The A/T you describe will want to upshift in steady state corners (again leaving you in the wrong gear for exit). Finally, if you try to shift it manually it won't rev match downshifts (and it will shift very hard on upshifts) upsetting the balance of the car.
You've never been to a drag strip, have you?
Are you going to tell me that and extra 100 lbs. and the parasitic loss from a torque converter don't matter to a drag-racer? Why do you think Porsche's acceleration and top speed stats are always lower for their A/T cars. You can rework the valve body to get a quicker shift, however I would argue you still aren't going to make up the difference (just close the gap) (stock power levels for both cars obviously)
It may not matter to the guy running with a 600-1,200 hp monster motor (certainly not what is being discussed in this thread btw), but I'm sure it matters quite a bit to the average joe who is driving (not trailering) to the track in his street car. (based on the signature picture your 928 is not quite developed to that level. It is going to take more than nitrous to put you in a league where 100lbs and torque converter losses don't matter)
Originally Posted by m21sniper
They (sequential manuals) shift no faster than a conventional A/T with a race prepped valve body. That is a fact.
While I am sure that "automatics" will continue to play a staring role in the worlds minivans and suv's for the forseeable future (and you are probably correct that they may make sense for a the drag racer with such a monster motor that traction (not weight and parasidic power loss) is the limiting factor) I believe in the future real sports cars will continue to use manual transmissions and increasingly sequential manuals or DSG type transmissions. They are simply better for traversing a twisty road or driving on a road course.
IMHO of course
09-23-2005, 06:22 PM
#19
What new car? What fuel issue?
I think ya got me confused with another poster bro. The last car i bought was my 928S about three years ago.
I am contemplating picking up a nice 86 MB 300E off a buddy, but i havn't pulled the trigger yet.
"Re-read the topic of this thread, the original poster is clearly discussing tiptronic transmissions. You are altering the topic."
The Tip is an A/T, and it has a valve body. Everything i've said applies to the tip just as it applies to the M/B unit in a 928, or a GM TH400, or whatever.
"However, they don't need to shift as quickly to beat you. The extra weight on your transmission and the power loss from your torque converter will slow you down enough so that a good driver with a manual will still win (both cars with stock power)."
Go to a dragstrip and you will see that's just not the case unless the manual driver is VERY good.
"You're set-up with a moddified A/T might work ok on a drag strip but it would be horrible for a race track (far worse than a standard tiptronic). Your car will upshift braking into every corner and then be in the wrong gear for corner exit where it will downshift and upset your balance (at least a tiptronic will work right in this respect) ."
That would be INCORRECT.
My 928S with the parallell kick down switch installed ALWAYS behaves as if it's at WOT, automatically downshifting to the lowest possible gear regardless of gear lever position or throttle setting.
If i'm in it full on at 150mph, and nail the brakes as i approach a curve, the trans will AUTOMATICALLY shift down sequentially(and instantaneously) through the gears as soon as it can do so while remaining at 5k rpm or less.
Ask some guys on the 928 board about this mod, it is very common, and utterly transforms the performance of the M/B A/Ts.
"The A/T you describe will want to upshift in steady state corners (again leaving you in the wrong gear for exit)."
Wrong. With the paralell kickdown switch engaged- REGARDLESS of throttle position, the car will hold every gear until redline, from 1st, all the way to 4th. If at any time my Rs drop down to a point where a downshift can occur and the downshift will not exceed 5000rpm, the trans will again AUTOMATICALLY perform that downshift, and hold THAT gear until redline, or until speed drops enough for it to AUTOMATICALLY downshift again.
"Finally, if you try to shift it manually it won't rev match downshifts (and it will shift very hard on upshifts) upsetting the balance of the car."
Wrong again. With my converter when i let off the throttle the engine freewheels in lowgear until RPMs hit about 2400rpm, at which time the converter re-engages and reapplies power to the trans.
"And, you've never had your 928 on a race track, have you?? I have been talking about a track not a strip, but I'll indulge you."
Not in the 928(been to the drag strip in it several times though), but i've turned some laps at Pocono superspeedway in my Buick T-Type turbo(a much, much faster car than either a 928S or a Boxster S btw). That was an auto too.
"Are you going to tell me that and extra 100 lbs. and the parasitic loss from a torque converter don't matter to a drag-racer?"
I'm going to tell you if the trans is properly prepared the advantadges outweigh the disadvantadges, and the A/T car will be faster.
"Why do you think Porsche's acceleration and top speed stats are always lower for their A/T cars."
Because they're stock trannies calibrated for comfort, mileage, and emmisions.
"You can rework the valve body to get a quicker shift, however I would argue you still aren't going to make up the difference (just close the gap) (stock power levels for both cars obviously)"
A single trip to the drag strip will destory that illusion forever. It's very hard to find a car running in the 11s with a manual(there are of course a few, mostly brand new LS-7 Z06s). Why? Because as power levels increase autos are just better and better vs manuals for straightline acceleration.
"It may not matter to the guy running with a 600-1,200 hp monster motor (certainly not what is being discussed in this thread btw), but I'm sure it matters quite a bit to the average joe who is driving (not trailering) to the track in his street car."
You must consider that 'average joe' is not going to be anywhere near as consistent on launch or shift-to-shift vs a strip-prepped A/T. He may have a slight advantadge if he perfectly nails every shift and the launch, but the consistentcy of the A/T is going to win the day against all but the very best manual drivers. You also have to consider that a car with a 2800rpm stall converter(mine is in about that range) can stage at up to 2800rpm on the line, pre-loading the tires so that the instantaneous shock load is much lower when the light turns green. That = FAR better launch traction.
"(based on the signature picture your 928 is not quite developed to that level. It is going to take more than nitrous to put you in a league where 100lbs and torque converter losses don't matter)"
My 928S already has run a best time of 13.67@103.1 mph, and that was about 150lbs of weight savings ago. A 100hp nitrous wetshot is on the docket though.
The 83 US i ran(mine is also an 83), i beat by 12 car lengths 0-100.
"A sequential manual on a street Ferrari can shift in as little as 150 milliseconds. Their racing transmissions shift even faster than that. Audi's new DSG transmission preselects the next gear so that it is engaged prior to the shift. Are you certain on your "facts"?, because I have never heard of and conventional automatic (even a modified one) that will shift that fast."
If there is a difference it will be in the ms range you quote. I figure my race prepped TH350 in my Buick T-type turbo shifted in about 1/100th of a second(which is about par for a well setup TH350 like mine was).
" I believe in the future real sports cars will continue to use manual transmissions and increasingly sequential manuals or DSG type transmissions. They are simply better for traversing a twisty road or driving on a road course."
Actually, the advantadge manuals hold on road courses is HEAT buildup. A/Ts just can't handle the high heat for an extended period of time, and grenade.
"IMHO of course"
We're all entitled to one bro.
I think ya got me confused with another poster bro. The last car i bought was my 928S about three years ago.
I am contemplating picking up a nice 86 MB 300E off a buddy, but i havn't pulled the trigger yet.
"Re-read the topic of this thread, the original poster is clearly discussing tiptronic transmissions. You are altering the topic."
The Tip is an A/T, and it has a valve body. Everything i've said applies to the tip just as it applies to the M/B unit in a 928, or a GM TH400, or whatever.
"However, they don't need to shift as quickly to beat you. The extra weight on your transmission and the power loss from your torque converter will slow you down enough so that a good driver with a manual will still win (both cars with stock power)."
Go to a dragstrip and you will see that's just not the case unless the manual driver is VERY good.
"You're set-up with a moddified A/T might work ok on a drag strip but it would be horrible for a race track (far worse than a standard tiptronic). Your car will upshift braking into every corner and then be in the wrong gear for corner exit where it will downshift and upset your balance (at least a tiptronic will work right in this respect) ."
That would be INCORRECT.
My 928S with the parallell kick down switch installed ALWAYS behaves as if it's at WOT, automatically downshifting to the lowest possible gear regardless of gear lever position or throttle setting.
If i'm in it full on at 150mph, and nail the brakes as i approach a curve, the trans will AUTOMATICALLY shift down sequentially(and instantaneously) through the gears as soon as it can do so while remaining at 5k rpm or less.
Ask some guys on the 928 board about this mod, it is very common, and utterly transforms the performance of the M/B A/Ts.
"The A/T you describe will want to upshift in steady state corners (again leaving you in the wrong gear for exit)."
Wrong. With the paralell kickdown switch engaged- REGARDLESS of throttle position, the car will hold every gear until redline, from 1st, all the way to 4th. If at any time my Rs drop down to a point where a downshift can occur and the downshift will not exceed 5000rpm, the trans will again AUTOMATICALLY perform that downshift, and hold THAT gear until redline, or until speed drops enough for it to AUTOMATICALLY downshift again.
"Finally, if you try to shift it manually it won't rev match downshifts (and it will shift very hard on upshifts) upsetting the balance of the car."
Wrong again. With my converter when i let off the throttle the engine freewheels in lowgear until RPMs hit about 2400rpm, at which time the converter re-engages and reapplies power to the trans.
"And, you've never had your 928 on a race track, have you?? I have been talking about a track not a strip, but I'll indulge you."
Not in the 928(been to the drag strip in it several times though), but i've turned some laps at Pocono superspeedway in my Buick T-Type turbo(a much, much faster car than either a 928S or a Boxster S btw). That was an auto too.
"Are you going to tell me that and extra 100 lbs. and the parasitic loss from a torque converter don't matter to a drag-racer?"
I'm going to tell you if the trans is properly prepared the advantadges outweigh the disadvantadges, and the A/T car will be faster.
"Why do you think Porsche's acceleration and top speed stats are always lower for their A/T cars."
Because they're stock trannies calibrated for comfort, mileage, and emmisions.
"You can rework the valve body to get a quicker shift, however I would argue you still aren't going to make up the difference (just close the gap) (stock power levels for both cars obviously)"
A single trip to the drag strip will destory that illusion forever. It's very hard to find a car running in the 11s with a manual(there are of course a few, mostly brand new LS-7 Z06s). Why? Because as power levels increase autos are just better and better vs manuals for straightline acceleration.
"It may not matter to the guy running with a 600-1,200 hp monster motor (certainly not what is being discussed in this thread btw), but I'm sure it matters quite a bit to the average joe who is driving (not trailering) to the track in his street car."
You must consider that 'average joe' is not going to be anywhere near as consistent on launch or shift-to-shift vs a strip-prepped A/T. He may have a slight advantadge if he perfectly nails every shift and the launch, but the consistentcy of the A/T is going to win the day against all but the very best manual drivers. You also have to consider that a car with a 2800rpm stall converter(mine is in about that range) can stage at up to 2800rpm on the line, pre-loading the tires so that the instantaneous shock load is much lower when the light turns green. That = FAR better launch traction.
"(based on the signature picture your 928 is not quite developed to that level. It is going to take more than nitrous to put you in a league where 100lbs and torque converter losses don't matter)"
My 928S already has run a best time of 13.67@103.1 mph, and that was about 150lbs of weight savings ago. A 100hp nitrous wetshot is on the docket though.
The 83 US i ran(mine is also an 83), i beat by 12 car lengths 0-100.
"A sequential manual on a street Ferrari can shift in as little as 150 milliseconds. Their racing transmissions shift even faster than that. Audi's new DSG transmission preselects the next gear so that it is engaged prior to the shift. Are you certain on your "facts"?, because I have never heard of and conventional automatic (even a modified one) that will shift that fast."
If there is a difference it will be in the ms range you quote. I figure my race prepped TH350 in my Buick T-type turbo shifted in about 1/100th of a second(which is about par for a well setup TH350 like mine was).
" I believe in the future real sports cars will continue to use manual transmissions and increasingly sequential manuals or DSG type transmissions. They are simply better for traversing a twisty road or driving on a road course."
Actually, the advantadge manuals hold on road courses is HEAT buildup. A/Ts just can't handle the high heat for an extended period of time, and grenade.
"IMHO of course"
We're all entitled to one bro.
09-23-2005, 10:15 PM
#20
Three Wheelin'
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I am no match for either of your guys knowledge about transmissions, but I have timed myself for years on the same stretch of road with a lot of different cars. Almost all had three pedals. One was a near 400HP 911 in an SC package, and my times in most every section in my stock 00 996 Tip are faster, the more >100 degree turns in a section the greater difference in the time. The reason, as I see it, is that I can shift the tip with either the brake or accelerator and I can control how many downshifts with throttle blips on hard braking and never take my hands off the wheel. I didn't figure this out myself. there was an interview with a Porsche factory driver in an article several months ago that explained how to drive the tiptronic. It took some practice, and I'm not great, but better than ever before. I've been driving Porsches since the 70s. All this and the road has become so crowded that now I have to make that trip in the dark to really cut loose without risking taking out a crotch rocket, and my reflexes, eyes, etc aren't what they once were either. However, I haven't taken a 6 speed 996 across that mountain, but there is no contest with the Boxster I had or my wife's 968 6 speed. Perhaps that says I'm not a very good driver with a manual transmission, but I don't think so.
09-24-2005, 12:09 PM
#21
What sort of kickdown switch does the boxster have?
In the 928 there is a momentary switch under the throttle pedal, and at WOT(wide open throttle) the switch is closed, and the car acts as one would expect an A/T to perform when floored.
What the paralell kickdown switch does is close the kickdown circuit at all times(once engaged), 'tricking' the A/T into thinking it's alway at WOT. This provides automatic up/downshifts as speed/RPM dictates as if you had it fully floored, even though you may actually be fully off the gas and under hard braking for a curve.
It's a very, very effective and inexpensive modification on 928s with the M/B trans, and it is possible that a tiptronic would respond in a similar fashion with the installation of a paralell kickdown switch(i really don't know because as i said i'm not real familiar with the tiptronic).
At any rate, it's something i'd definitely look into if i had a tiptronic equipped P-car. Just for the record this is not the same as 'race prepping' an A/T, but it does make the trans behave in a very performance oriented fashion.
Here's a pic of the paralell switch as installed in my 928S. It's the protected red military/nitrous style toggle switch pictured below.(you can see it just peeking out from behind the steering wheel on the D/S of the center console):
In the 928 there is a momentary switch under the throttle pedal, and at WOT(wide open throttle) the switch is closed, and the car acts as one would expect an A/T to perform when floored.
What the paralell kickdown switch does is close the kickdown circuit at all times(once engaged), 'tricking' the A/T into thinking it's alway at WOT. This provides automatic up/downshifts as speed/RPM dictates as if you had it fully floored, even though you may actually be fully off the gas and under hard braking for a curve.
It's a very, very effective and inexpensive modification on 928s with the M/B trans, and it is possible that a tiptronic would respond in a similar fashion with the installation of a paralell kickdown switch(i really don't know because as i said i'm not real familiar with the tiptronic).
At any rate, it's something i'd definitely look into if i had a tiptronic equipped P-car. Just for the record this is not the same as 'race prepping' an A/T, but it does make the trans behave in a very performance oriented fashion.
Here's a pic of the paralell switch as installed in my 928S. It's the protected red military/nitrous style toggle switch pictured below.(you can see it just peeking out from behind the steering wheel on the D/S of the center console):
09-24-2005, 07:18 PM
#22
Ironman 140.6
Rennlist Member
Rennlist Member
Originally Posted by m21sniper
Go to a dragstrip and you will see that's just not the case unless the manual driver is VERY good.
- Automatics weigh signifiantly more than manuals
- Automatics have a significant driveline loss disadvantages over manuals
You continue to try to cloud the issue by bringing driver skill and full on drag cars into the discussion. Let me state again again that a A/T might be a fine choice for running a drag car that can make a 12 second pass (or lower). In that case the car is producing so much power (and trapping so fast) that some extra weight and parasidic losses are not going to be the limiting problem (traction is the big problem and to a lesser degree aerodynamic drag at the end of the run).
This thread is about street Porsche's (Boxsters specifically). They are a mid 13 second (the S) to mid 14 second cars.........period (again without major mods). For these cars the A/T weight and torque converter losses are Very Significant. You can modify the stock transmission to shift faster and it still will not eliminate those disadvantages. (BTW, You assertion about driver skill can cut both ways as a poor driver in an automatic is not going to know how to brake torque the car to get a good launch.)
On a road course there is absolutely no argument. With an experienced driver the manual is flat out faster (why do you think Porsche doesn't offer the GT2, GT3, or Carrera GT with an A/T????). I will concede that a tip will probably be faster with a poor driver as it will allow that individual more opportunity to concentrate on line and braking points.
As far as the future is concerned it is clear that Sequential Manuals are the technology to beat. They flat out shift faster (despite your ealier assertion to the contrary) and offer more driver control than an "automatic" will ever provide. Not only are these transmissions vastly superior on a road course, they will most likely prove to be superior in a drag race. BMW's and Ferrari's in Europe are already available with "launch control" systems that allow the transmission, wheel sensors, and the ecu to work in concert to manage traction, power, and shifts.
Again....none of this is on topic with the thread!! I will list the original post below for reference...
Originally Posted by perfectlap
I read an article in Excellence "Best Convertibles" where the magazine asked many contributors to rank their favourite Porsche convertibles. One contributor
ranked the Carrera GT and BoxsterS at the top. He cited the BoxsterS in a manual gearbox because according to him the tiptronic transmission shaves power in between shifts resulting in a loss of torque when its needed (in between gears).
Another forum member says that the contributor was wrong or biased (or both) and that the tipS produces more torque than the manual transmission because the increased Torque from the torque converter.
any thoughts on who is right?
ranked the Carrera GT and BoxsterS at the top. He cited the BoxsterS in a manual gearbox because according to him the tiptronic transmission shaves power in between shifts resulting in a loss of torque when its needed (in between gears).
Another forum member says that the contributor was wrong or biased (or both) and that the tipS produces more torque than the manual transmission because the increased Torque from the torque converter.
any thoughts on who is right?
09-24-2005, 07:55 PM
#23
"Here are the facts that cannot be disputed."
Well let's see...
"- Automatics weigh signifiantly more than manuals"
Depends on the automatic, and depends on the manual. Many of the best manuals have steel trans bodies with a separate aluminum bellhousing. Almost all A/Ts post powerglide are aluminum.
A TH350 for instance is much lighter than a Borg Warner T-10.
Also, for those that go to the drag strip, a manual has to have a scat shield installed once you're under a certain ET(i think it's a 12.99 or less, but i'm not sure), whereas an auto does not.
In the case of the boxster(or the 928) AT/Manual trans, you are correct.
The extra 75lbs on a boxster A/T will equate to a .075 slower ET(or 0-60 time), all other things being equal.
"- Automatics have a significant driveline loss disadvantages over manuals"
Depends on the automatic and the manual. "Straight cut" gear manuals(which are much stronger and therefore used in most professional racing circuits) have a lot more driveline loss than typical street manuals do.
Some automatics are very efficient(the new 7 speed MB unit being a good example). Look at the TH-350 vs the TH-400. A TH-400 takes almost 40hp more than a TH-350 to spin.
The converter actually also has a lot to do with efficiency. A high stall hi performance torque converter is much more efficient than an OEM converter is(and also a lot smaller in diameter which of course means it's a lot lighter).
"You continue to try to cloud the issue by bringing driver skill and full on drag cars into the discussion."
Driver skill is ENTIRELY relevant. It is driver skill/consistency (or the lack thereof), that gives a properly prepared A/T a competitive edge, and so popular among performance enthusiasts. Just look at the continuing proliferation of the aforementioned F1 style sequential A/Ts in top end supercars as further proof of manufacturers trying to make up for lack of driver skill.
Drag racing is very popular in the US, even among porschephiles(though certainly to a lesser degree). And if you live in a big city in the US, drag racing performance is very relevant to 'real world' street performance. In the US 98% of your time is spent at 70mph or less, and when you punch it, it will be to get out of a light first to get over into your turning lane, or punching it from a relatively low speed to merge on a highway off an onramp, etc, etc.
" Let me state again again that a A/T might be a fine choice for running a drag car that can make a 12 second pass (or lower). In that case the car is producing so much power (and trapping so fast) that some extra weight and parasidic losses are not going to be the limiting problem (traction is the big problem and to a lesser degree aerodynamic drag at the end of the run)."
I agree with the spirit of your comments above.
"This thread is about street Porsche's (Boxsters specifically). They are a mid 13 second (the S) to mid 14 second cars.........period (again without major mods)."
Agreed.
"For these cars the A/T weight and torque converter losses are Very Significant."
In stock form i'll agree with that too.
"You can modify the stock transmission to shift faster and it still will not eliminate those disadvantages."
Well if you note the fellow a few posts above used his 911 Tip as an example of his A/T being faster in the real world than his stick.
"(BTW, You assertion about driver skill can cut both ways as a poor driver in an automatic is not going to know how to brake torque the car to get a good launch.)"
That is also true, but it is a much easier skill to master(as i'm sure you'll agree), and once mastered is far more consistent(as i'm sure you'll also agree).
"On a road course there is absolutely no argument. With an experienced driver the manual is flat out faster (why do you think Porsche doesn't offer the GT2, GT3, or Carrera GT with an A/T????)."
I agree with that too. Though a properly race prepped A/T will close the gap quite a bit, effectively making the weight difference the one major disadvantadge of the A/T.
Also, A/Ts have a problem with heat buildup in long endurance races, which is really the #1 reason that all professional racing circuits use manuals or manual-automatics.
"I will concede that a tip will probably be faster with a poor driver as it will allow that individual more opportunity to concentrate on line and braking points."
I agree.
"As far as the future is concerned it is clear that Sequential Manuals are the technology to beat. "
Agreed again...this is easy.
"They flat out shift faster (despite your ealier assertion to the contrary) and offer more driver control than an "automatic" will ever provide."
I'll concede the first point(though the difference is very small), but i will not concede the second point. Neither of us knows what the future holds, so neither of us can definitively say for sure if A/Ts will ever be as good for professional circuit racing as manual-automatics. Further, i don't think you fully appreciate just how effective a paralell kickdown switch is at improving A/T performance drivability.
But really the sequentials are hybrids, part manual, part automatic.(the best of both worlds?)
"Not only are these transmissions vastly superior on a road course, they will most likely prove to be superior in a drag race."
I actually agree with them being better for drag racing IF the thumb button is replaced with fully automatic shift control.
"BMW's and Ferrari's in Europe are already available with "launch control" systems that allow the transmission, wheel sensors, and the ecu to work in concert to manage traction, power, and shifts."
Yeah, we can actually retrofit our older P-cars with those features to if we use top end aftermarket engine control systems. I actually hate traction control and electronic drivers aids though.(but that's another story, lol).
"The manual will produce more horsepower and torque at the wheels. Care to disagree? Change topic again?"
Depends on the manual and the A/T in question.
I would put the new MB 7 speed A/T up against an M-33 Muncie for power losses and would not be at all surprised if the MB unit was more efficient.
The reason i 'went off topic' is because i simply do not agree that a properly prepared(ie race prepped) A/T will lose time between shifts, and in fact i know that the opposite is true...which is why i mentioned it to begin with.
And while we may have gone 'off topic', we also had a very interesting and informative debate....and that's always a good thing.
How was it relevant to the poster that started this thread? It tells him that if he's willing to spend the money to have his trans worked that he will have be competitive with manuals in REAL WORLD driving, and that in some instances he will actually have the advantadge.
Regardless, i enjoyed/am enjoying the discussion, and i hope you did/are too.
If you're ever in the Philly area shoot me a PM and i'll give ya a ride in my 928S A/T so you can experience just how well a properly set up A/T can perform. It's a real eye opener.
Well let's see...
"- Automatics weigh signifiantly more than manuals"
Depends on the automatic, and depends on the manual. Many of the best manuals have steel trans bodies with a separate aluminum bellhousing. Almost all A/Ts post powerglide are aluminum.
A TH350 for instance is much lighter than a Borg Warner T-10.
Also, for those that go to the drag strip, a manual has to have a scat shield installed once you're under a certain ET(i think it's a 12.99 or less, but i'm not sure), whereas an auto does not.
In the case of the boxster(or the 928) AT/Manual trans, you are correct.
The extra 75lbs on a boxster A/T will equate to a .075 slower ET(or 0-60 time), all other things being equal.
"- Automatics have a significant driveline loss disadvantages over manuals"
Depends on the automatic and the manual. "Straight cut" gear manuals(which are much stronger and therefore used in most professional racing circuits) have a lot more driveline loss than typical street manuals do.
Some automatics are very efficient(the new 7 speed MB unit being a good example). Look at the TH-350 vs the TH-400. A TH-400 takes almost 40hp more than a TH-350 to spin.
The converter actually also has a lot to do with efficiency. A high stall hi performance torque converter is much more efficient than an OEM converter is(and also a lot smaller in diameter which of course means it's a lot lighter).
"You continue to try to cloud the issue by bringing driver skill and full on drag cars into the discussion."
Driver skill is ENTIRELY relevant. It is driver skill/consistency (or the lack thereof), that gives a properly prepared A/T a competitive edge, and so popular among performance enthusiasts. Just look at the continuing proliferation of the aforementioned F1 style sequential A/Ts in top end supercars as further proof of manufacturers trying to make up for lack of driver skill.
Drag racing is very popular in the US, even among porschephiles(though certainly to a lesser degree). And if you live in a big city in the US, drag racing performance is very relevant to 'real world' street performance. In the US 98% of your time is spent at 70mph or less, and when you punch it, it will be to get out of a light first to get over into your turning lane, or punching it from a relatively low speed to merge on a highway off an onramp, etc, etc.
" Let me state again again that a A/T might be a fine choice for running a drag car that can make a 12 second pass (or lower). In that case the car is producing so much power (and trapping so fast) that some extra weight and parasidic losses are not going to be the limiting problem (traction is the big problem and to a lesser degree aerodynamic drag at the end of the run)."
I agree with the spirit of your comments above.
"This thread is about street Porsche's (Boxsters specifically). They are a mid 13 second (the S) to mid 14 second cars.........period (again without major mods)."
Agreed.
"For these cars the A/T weight and torque converter losses are Very Significant."
In stock form i'll agree with that too.
"You can modify the stock transmission to shift faster and it still will not eliminate those disadvantages."
Well if you note the fellow a few posts above used his 911 Tip as an example of his A/T being faster in the real world than his stick.
"(BTW, You assertion about driver skill can cut both ways as a poor driver in an automatic is not going to know how to brake torque the car to get a good launch.)"
That is also true, but it is a much easier skill to master(as i'm sure you'll agree), and once mastered is far more consistent(as i'm sure you'll also agree).
"On a road course there is absolutely no argument. With an experienced driver the manual is flat out faster (why do you think Porsche doesn't offer the GT2, GT3, or Carrera GT with an A/T????)."
I agree with that too. Though a properly race prepped A/T will close the gap quite a bit, effectively making the weight difference the one major disadvantadge of the A/T.
Also, A/Ts have a problem with heat buildup in long endurance races, which is really the #1 reason that all professional racing circuits use manuals or manual-automatics.
"I will concede that a tip will probably be faster with a poor driver as it will allow that individual more opportunity to concentrate on line and braking points."
I agree.
"As far as the future is concerned it is clear that Sequential Manuals are the technology to beat. "
Agreed again...this is easy.
"They flat out shift faster (despite your ealier assertion to the contrary) and offer more driver control than an "automatic" will ever provide."
I'll concede the first point(though the difference is very small), but i will not concede the second point. Neither of us knows what the future holds, so neither of us can definitively say for sure if A/Ts will ever be as good for professional circuit racing as manual-automatics. Further, i don't think you fully appreciate just how effective a paralell kickdown switch is at improving A/T performance drivability.
But really the sequentials are hybrids, part manual, part automatic.(the best of both worlds?)
"Not only are these transmissions vastly superior on a road course, they will most likely prove to be superior in a drag race."
I actually agree with them being better for drag racing IF the thumb button is replaced with fully automatic shift control.
"BMW's and Ferrari's in Europe are already available with "launch control" systems that allow the transmission, wheel sensors, and the ecu to work in concert to manage traction, power, and shifts."
Yeah, we can actually retrofit our older P-cars with those features to if we use top end aftermarket engine control systems. I actually hate traction control and electronic drivers aids though.(but that's another story, lol).
"The manual will produce more horsepower and torque at the wheels. Care to disagree? Change topic again?"
Depends on the manual and the A/T in question.
I would put the new MB 7 speed A/T up against an M-33 Muncie for power losses and would not be at all surprised if the MB unit was more efficient.
The reason i 'went off topic' is because i simply do not agree that a properly prepared(ie race prepped) A/T will lose time between shifts, and in fact i know that the opposite is true...which is why i mentioned it to begin with.
And while we may have gone 'off topic', we also had a very interesting and informative debate....and that's always a good thing.
How was it relevant to the poster that started this thread? It tells him that if he's willing to spend the money to have his trans worked that he will have be competitive with manuals in REAL WORLD driving, and that in some instances he will actually have the advantadge.
Regardless, i enjoyed/am enjoying the discussion, and i hope you did/are too.
If you're ever in the Philly area shoot me a PM and i'll give ya a ride in my 928S A/T so you can experience just how well a properly set up A/T can perform. It's a real eye opener.
Last edited by m21sniper; 09-25-2005 at 01:15 AM.
09-25-2005, 10:14 AM
#24
You need to enter gearing into this thread.
What is not being considered here is gearing, and it is paramount when applying torque to the wheel. I don’t think the tip is all that slow with shift speed when compared with other ATs. However, the disparity in 0-60 acceleration of the Boxster is wide in comparison to other ATs.
I am no expert on this but my intuition and driving impressions of the Boxster tip (986 anyway) tells me the gearing of the tip driveline—transmission, final drive—is not optimal. If peak engine torque is applied to less-than-optimal gear ratios, you will not be able to get the maximum possible torque at the wheel.
If you compare the Porsche tip drivelines to other cars such as BMWs, I’d bet you find better gearing in the bimmer ATs. And it is no wonder since ATs are their bread and butter. I’m really speculating here but you have to wonder why the Porsche corp of engineers which is considered top-shelf can’t get more out of the AT.
I think is has to do with the Porsche agenda. 9 out of 10 Porsches sold have manuals. That says something about the car and the clients, and I’d bet they want to keep it that way. Of course this will have to change with automatic clutches such as DSG and SMG. I submit Ferrari and its 9 out of 10 cars sold with auto clutch, soon to be 10 out of 10 by default. However Ferrari is purely a race car where Porsche needs to double as road and track rat. Will be interesting to see how many DSGs Porsche sells.
By the way… Ray, if you consider the title of this thread and not the first post, m21sniper is on topic. The net concern here with the tip is loss of acceleration, so all factors have to weigh in, even if they are tangent. I think this thread is too interesting to lose it.
(PS – Want to really see how horrible gearing really neuters engine torque? Drive a WRX with AT back to back with the manual. If it got any worse with its AT, the engine would just stall off the line and never be able to move. I don’t know if they improved it with the new one, but the previous version was the absolute pits.)
I am no expert on this but my intuition and driving impressions of the Boxster tip (986 anyway) tells me the gearing of the tip driveline—transmission, final drive—is not optimal. If peak engine torque is applied to less-than-optimal gear ratios, you will not be able to get the maximum possible torque at the wheel.
If you compare the Porsche tip drivelines to other cars such as BMWs, I’d bet you find better gearing in the bimmer ATs. And it is no wonder since ATs are their bread and butter. I’m really speculating here but you have to wonder why the Porsche corp of engineers which is considered top-shelf can’t get more out of the AT.
I think is has to do with the Porsche agenda. 9 out of 10 Porsches sold have manuals. That says something about the car and the clients, and I’d bet they want to keep it that way. Of course this will have to change with automatic clutches such as DSG and SMG. I submit Ferrari and its 9 out of 10 cars sold with auto clutch, soon to be 10 out of 10 by default. However Ferrari is purely a race car where Porsche needs to double as road and track rat. Will be interesting to see how many DSGs Porsche sells.
By the way… Ray, if you consider the title of this thread and not the first post, m21sniper is on topic. The net concern here with the tip is loss of acceleration, so all factors have to weigh in, even if they are tangent. I think this thread is too interesting to lose it.
(PS – Want to really see how horrible gearing really neuters engine torque? Drive a WRX with AT back to back with the manual. If it got any worse with its AT, the engine would just stall off the line and never be able to move. I don’t know if they improved it with the new one, but the previous version was the absolute pits.)
09-25-2005, 10:47 AM
#25
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Designman,
You are incorrect about your statement on the number of Porsches sold. Porsche sells more tiptronics than manual transmissions, and the car they sold the most in 2003 was the C4S tiptronic. Nearly 65% of the Boxster S's sold in either 2003 or 2004 (can't remember which) were tiptronic.
The reason the tip is slower in the Boxster than in some other vehicles is because the torque is rather low. The difference is far less noticeable and in fact could be equal in a car such as the 996 TT, where the torque more than makes up for the loss in the torque converter.
You are incorrect about your statement on the number of Porsches sold. Porsche sells more tiptronics than manual transmissions, and the car they sold the most in 2003 was the C4S tiptronic. Nearly 65% of the Boxster S's sold in either 2003 or 2004 (can't remember which) were tiptronic.
The reason the tip is slower in the Boxster than in some other vehicles is because the torque is rather low. The difference is far less noticeable and in fact could be equal in a car such as the 996 TT, where the torque more than makes up for the loss in the torque converter.
09-25-2005, 01:26 PM
#26
Good points by both the last two posters.
Gearing is very important(not so much in overall ratio, but rather in spacing), and obviously a six speed will have closer spacing than a 4 speed A/T. Of course more closely spaced gears means more shifting. So while it helps a lot on circuit driving, it may actually be a hindrance in straight line acceleration...depending on the A/T vs Manual in question. I really don't know enough about the boxster trannys to comment beyond that though.
WRT torque i agree again. A lack of torque converter stall speed in a car that makes it's power higher in the RPM range(such as the boxster) will make the car perform and feel like a dog. The example used by the one poster of the WRX is a perfect example. Add 1000rpm of stall speed to the WRX A/T, and it would feel like a totally different animal...and perform like one too.
In a V-8 powered 928 there is a LOT of power low in the RPM range, so they're hurt a lot less than the smaller motors are by being mated up with a compromise OEM stall converter(which has to consider mileage, noise, long term durability, and emmissions- not just performance). Even bone stock the Manual 928s are only .2-.3sec faster than the A/Ts, and that gap is entirely erased once the Mercedes benz A/T is modified with a higher stall speed and paralell kickdown switch with the modulator adjusted for extremely firm shifts. Adjusting the modulator is a feature provided on the stock unit, and a paralell kickdown switch installed costs all of $25 bucks. By going the rest of the way and getting the valve body reworked for optimal performance up/downshifts IMO the A/T 928 is actually a significantly faster car in the real world than the manuals are.
Gearing is very important(not so much in overall ratio, but rather in spacing), and obviously a six speed will have closer spacing than a 4 speed A/T. Of course more closely spaced gears means more shifting. So while it helps a lot on circuit driving, it may actually be a hindrance in straight line acceleration...depending on the A/T vs Manual in question. I really don't know enough about the boxster trannys to comment beyond that though.
WRT torque i agree again. A lack of torque converter stall speed in a car that makes it's power higher in the RPM range(such as the boxster) will make the car perform and feel like a dog. The example used by the one poster of the WRX is a perfect example. Add 1000rpm of stall speed to the WRX A/T, and it would feel like a totally different animal...and perform like one too.
In a V-8 powered 928 there is a LOT of power low in the RPM range, so they're hurt a lot less than the smaller motors are by being mated up with a compromise OEM stall converter(which has to consider mileage, noise, long term durability, and emmissions- not just performance). Even bone stock the Manual 928s are only .2-.3sec faster than the A/Ts, and that gap is entirely erased once the Mercedes benz A/T is modified with a higher stall speed and paralell kickdown switch with the modulator adjusted for extremely firm shifts. Adjusting the modulator is a feature provided on the stock unit, and a paralell kickdown switch installed costs all of $25 bucks. By going the rest of the way and getting the valve body reworked for optimal performance up/downshifts IMO the A/T 928 is actually a significantly faster car in the real world than the manuals are.
09-25-2005, 01:28 PM
#27
Originally Posted by schvetkaaks
Designman,
You are incorrect about your statement on the number of Porsches sold. Porsche sells more tiptronics than manual transmissions, and the car they sold the most in 2003 was the C4S tiptronic. Nearly 65% of the Boxster S's sold in either 2003 or 2004 (can't remember which) were tiptronic.
The reason the tip is slower in the Boxster than in some other vehicles is because the torque is rather low. The difference is far less noticeable and in fact could be equal in a car such as the 996 TT, where the torque more than makes up for the loss in the torque converter.
You are incorrect about your statement on the number of Porsches sold. Porsche sells more tiptronics than manual transmissions, and the car they sold the most in 2003 was the C4S tiptronic. Nearly 65% of the Boxster S's sold in either 2003 or 2004 (can't remember which) were tiptronic.
The reason the tip is slower in the Boxster than in some other vehicles is because the torque is rather low. The difference is far less noticeable and in fact could be equal in a car such as the 996 TT, where the torque more than makes up for the loss in the torque converter.
As far as low absolute torque, I will disagree with you there also. Check other cars with even lower torque, and you will find there is less disparity between their ATs and manuals. If any given car uses the same engine, the auto transmission should lose acceleration only due to shift speed and torque converter, not gearing. And it should not be by much, or not at the level that it is lost with the Boxster, and as I pointed out with the WRX.
Low engine torque is often cited as the reason the tip languishes but it is oversimplified and perhaps spurious. It’s more than that. Torque doesn’t go from the engine straight to the wheel. It is compromised by a number of factors—transmission gearing, differential, tire grip and slip, clutch pressure and slip, hydraulic pressure in the torque converter, friction, weight and weight distribution, shift timing and rev capability which is a component of horsepower... etcetera. This is where engineering comes into play. I can’t say the following unequivocally, but I believe the Porsche tip is not engineered as well as it could be and, as I mentioned above, I believe this COULD be by design... in other words, sandbagging.
09-25-2005, 01:52 PM
#28
I would expect that the vast majority of 911s are manuals, and though i can't be sure, i'd suspect a slim majority of Boxsters are too.
But then there's the Cayenne, and i bet almost all of those are autos. Including a big, 6000lb Mall Terrain Vehicle in the P-car lineup therefore skews the auto/manual sales ratios.
I do know that in the 928s the A/T is much, much more common, and i suspect the opposite is probably true for 944s.
I have no hard figures for any of those observations though, i'm just basing it on my experience with other p-car enthusiasts and the types of people that are buying the various models.
But then there's the Cayenne, and i bet almost all of those are autos. Including a big, 6000lb Mall Terrain Vehicle in the P-car lineup therefore skews the auto/manual sales ratios.
I do know that in the 928s the A/T is much, much more common, and i suspect the opposite is probably true for 944s.
I have no hard figures for any of those observations though, i'm just basing it on my experience with other p-car enthusiasts and the types of people that are buying the various models.
09-25-2005, 02:04 PM
#29
Yep, I'm just considering non-Cayennes and post 986s/996s. I would imagine tip in the upcoming Panamera will be out of the question as it will probably get DSG and manual. I HOPE manual.
09-26-2005, 11:18 AM
#30
Ironman 140.6
Rennlist Member
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Originally Posted by m21sniper
Regardless, i enjoyed/am enjoying the discussion, and i hope you did/are too.
If you're ever in the Philly area shoot me a PM and i'll give ya a ride in my 928S A/T so you can experience just how well a properly set up A/T can perform. It's a real eye opener.
