supercharger philosophy
04-05-2004, 06:56 PM
#61
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Let's get one thing clear on this subject, there are two remaining Callaway twin turbo 928s done 20+ years ago that have done just fine. That is 20 years guys! Show me another boosted 928 even made in the early 80s (there were a few..even in the 70s) The ones that had issues were not intercooled. Do we know the maintenance on these cars? Do we know if they ran 86 octane fuel? Nobody really knows, but I can tell you two intercooled twin turbo 928s have remained after 20 years.
How long have these CS kits been around, 3 or 4 years tops? Chris at Delta P has some interesting viewpoints. Personally I think his fuel management methods are superior to a rising rate regulator that pushes the injectors past their design pressures. He is also talking air to air charge cooling, which I also believe to be superior technology for a street car. Drag racing, the air to water wins, no arguement, but I don't drive with ice in my car, do you?
If you guys think for a minute that designing a CS setup for a 928 involves more than 1/2 the engineering as for the turbo setup, well that is just crazy. It is a true bolt on, yes, but it is not hard to do. The turbo setup takes far more engineering.
People hear "supercharger", then tell you there is lag with the turbo and point to the CS as superior. Talk about the worst of both worlds with the CS, you get the parasitic draw like the positive displacement blower, then have to wait till 2/3 to 3/3 redline to get appriciable boost. I call that "infinite lag". Anybody who uses the arguement of less lag when comparing to a centrifugal supercharger to a turbo simply does not know what they are talking about. Positive displacement you have a leg to stand on, but don't talk about lag when comparing a CS to a turbo because the CS has the ultimate lag.
I suggest those of you who talk about this stuff blowing up and think you can do better, to prove it. You guys all talk a lot, but what are you doing to make products or develop anything for the 928? So some Callaway cars blew up, so what? How many Porsche factory cars blew up for various reasons? There is always more to the story and I find nothing magical about any of these CS kits that makes them superior to other options that have been done over the last 20+ years.
BC, I squeezed 440 crank HP out of a little 4.5 liter with stock heads and cams. Does that impress you? You can talk all you want about dyno HP numbers and the like, what it all boils down to is useable power with drivebility to the road. The turbo is the far better in the real world, thus the reson Porsche uses it. The CS is perfectly suited to posting very high peak HP numbers on a dynojet, but I keep telling you guys this is not the entire picture.
How long have these CS kits been around, 3 or 4 years tops? Chris at Delta P has some interesting viewpoints. Personally I think his fuel management methods are superior to a rising rate regulator that pushes the injectors past their design pressures. He is also talking air to air charge cooling, which I also believe to be superior technology for a street car. Drag racing, the air to water wins, no arguement, but I don't drive with ice in my car, do you?
If you guys think for a minute that designing a CS setup for a 928 involves more than 1/2 the engineering as for the turbo setup, well that is just crazy. It is a true bolt on, yes, but it is not hard to do. The turbo setup takes far more engineering.
People hear "supercharger", then tell you there is lag with the turbo and point to the CS as superior. Talk about the worst of both worlds with the CS, you get the parasitic draw like the positive displacement blower, then have to wait till 2/3 to 3/3 redline to get appriciable boost. I call that "infinite lag". Anybody who uses the arguement of less lag when comparing to a centrifugal supercharger to a turbo simply does not know what they are talking about. Positive displacement you have a leg to stand on, but don't talk about lag when comparing a CS to a turbo because the CS has the ultimate lag.
I suggest those of you who talk about this stuff blowing up and think you can do better, to prove it. You guys all talk a lot, but what are you doing to make products or develop anything for the 928? So some Callaway cars blew up, so what? How many Porsche factory cars blew up for various reasons? There is always more to the story and I find nothing magical about any of these CS kits that makes them superior to other options that have been done over the last 20+ years.
BC, I squeezed 440 crank HP out of a little 4.5 liter with stock heads and cams. Does that impress you? You can talk all you want about dyno HP numbers and the like, what it all boils down to is useable power with drivebility to the road. The turbo is the far better in the real world, thus the reson Porsche uses it. The CS is perfectly suited to posting very high peak HP numbers on a dynojet, but I keep telling you guys this is not the entire picture.
04-05-2004, 08:05 PM
#62
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I think *all* of it is cool.
DeltaP, your work, Murph, Andy, Devek, etc...
It's all good.
It's great that you are happy with the results on your car.
I guess I am just saying that it is one thing to compare one person's car to another person's,
and something else to compare overall benefits of a "program" of boosting the 928.
You have dyno numbers for a turbo 4.5 liter.
So as soon as someone has dyno charts fron a CS 4.5 liter, we can compare.
Or perhaps numbers from a stroked 4.5 liter. Without all the other NA mods.
Or a positve displacement twin screw on a 4.5 liter car...
But if you want to debate the overall quality, or durability, or success of a program
of boosting horsepower for the 928, then you really do have to look at the pricing,
ease of use, testimonials, instructions, etc... So when it comes to kits, pricing,
dyno numbers, etc, the supercharger guys have a definate advantage.
But right now, we are comparing apples to oranges.
DeltaP, your work, Murph, Andy, Devek, etc...
It's all good.
It's great that you are happy with the results on your car.
I guess I am just saying that it is one thing to compare one person's car to another person's,
and something else to compare overall benefits of a "program" of boosting the 928.
You have dyno numbers for a turbo 4.5 liter.
So as soon as someone has dyno charts fron a CS 4.5 liter, we can compare.
Or perhaps numbers from a stroked 4.5 liter. Without all the other NA mods.
Or a positve displacement twin screw on a 4.5 liter car...
But if you want to debate the overall quality, or durability, or success of a program
of boosting horsepower for the 928, then you really do have to look at the pricing,
ease of use, testimonials, instructions, etc... So when it comes to kits, pricing,
dyno numbers, etc, the supercharger guys have a definate advantage.
But right now, we are comparing apples to oranges.
04-05-2004, 11:29 PM
#63
Originally posted by John..
He is also talking air to air charge cooling, which I also believe to be superior technology for a street car. Drag racing, the air to water wins, no arguement, but I don't drive with ice in my car, do you?
People hear "supercharger", then tell you there is lag with the turbo and point to the CS as superior. Talk about the worst of both worlds with the CS, you get the parasitic draw like the positive displacement blower, then have to wait till 2/3 to 3/3 redline to get appriciable boost. I call that "infinite lag". Anybody who uses the arguement of less lag when comparing to a centrifugal supercharger to a turbo simply does not know what they are talking about. Positive displacement you have a leg to stand on, but don't talk about lag when comparing a CS to a turbo because the CS has the ultimate lag.
I suggest those of you who talk about this stuff blowing up and think you can do better, to prove it.
He is also talking air to air charge cooling, which I also believe to be superior technology for a street car. Drag racing, the air to water wins, no arguement, but I don't drive with ice in my car, do you?
People hear "supercharger", then tell you there is lag with the turbo and point to the CS as superior. Talk about the worst of both worlds with the CS, you get the parasitic draw like the positive displacement blower, then have to wait till 2/3 to 3/3 redline to get appriciable boost. I call that "infinite lag". Anybody who uses the arguement of less lag when comparing to a centrifugal supercharger to a turbo simply does not know what they are talking about. Positive displacement you have a leg to stand on, but don't talk about lag when comparing a CS to a turbo because the CS has the ultimate lag.
I suggest those of you who talk about this stuff blowing up and think you can do better, to prove it.
No John John. YOU prove it. 3/3? Appreciable boost? BS.
We don't pull stumps with our cars, so there is no reason for "full boost" at 2500 rpm. Once past 4k in first under full accelleration, the shifts return the rpm to around 4-4.5k. Uh huh. So what is boost at 2500 going to do? And as I recall, when you properly size turbos for 2500, they will run out of steam at what, 5k? Yeah, thats usefull with a 6800 or so rev limit.
04-05-2004, 11:42 PM
#64
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I'll be at Wichita the weekend after July 4th, Solid 86.5 with the Autorotor. Not a racer, but will be a definite snake bitter. All commers bring your best and let's see what works.
04-05-2004, 11:51 PM
#65
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It's fine to debate techniques, but hard to do without dyno numbers on comparable engines. I want to see each boost method on a stock s2, and a stock s4, at 8 pounds of boost on each, and see the dyno numbers, to compare the curves. Hopefully at the same venue, on the same machine. I think we will see something like that in the next year or so... Otherwise it is just chest beating...
(Queue chest beating monkey gif...)
(Queue chest beating monkey gif...)
04-06-2004, 01:18 AM
#66
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Originally posted by John..
...with the CS, you get the parasitic draw like the positive displacement blower, then have to wait till 2/3 to 3/3 redline to get appriciable boost... ...You can talk all you want about dyno HP numbers and the like, what it all boils down to is useable power with drivebility to the road. The turbo is the far better in the real world, thus the reson Porsche uses it. The CS is perfectly suited to posting very high peak HP numbers on a dynojet, but I keep telling you guys this is not the entire picture.
...with the CS, you get the parasitic draw like the positive displacement blower, then have to wait till 2/3 to 3/3 redline to get appriciable boost... ...You can talk all you want about dyno HP numbers and the like, what it all boils down to is useable power with drivebility to the road. The turbo is the far better in the real world, thus the reson Porsche uses it. The CS is perfectly suited to posting very high peak HP numbers on a dynojet, but I keep telling you guys this is not the entire picture.
I don’t agree with several of your standpoints:
1) "parasitic draw" - At cruise / on light throttle, the CS is not compressing air, thus not using significant HP. When in boost, the CS is only using a fraction of the HP which it is producing; there is NEVER a sense of anything reducing the engine's power at any throttle position or rpm. Compared to before I added the CS, there is now more power at all throttle positions and at all rpm's from just off idle to redline. Why do you continue to approach this issue as though a turbocharger does not also require a certain amount of HP (in the form of exhaust backpressure, which demonstrably affects engine output)?
2) "appriciable boost" – The pressure in the intake manifold does not correlate to engine output torque when comparing CS and turbo, but is rather a function of factors such as blower design, engine breathing and backpressure. To discuss how much pressure is developed at a certain rpm range is academic but pointless as a comparison between CS and turbo torque curves.
3) "drivebility" and “useable power” - According to the posted power curves, the CS has a flatter power curve than turbo. Obviously, a flatter torque curve integrates more useable power. It is also this flatter curve that enhances the drivability of a car. Nonlinear power production is not welcome behavior from a powerful engine. Needing to modulate the throttle suddenly to avoid wheelspin or oversteer is not only bothersome, but potentially hazardous. The flatter the torque curve, the easier it is to control the car and the safer and more relaxing it is to drive hard. Why do you continue to ignore the dyno data and refute the testimonies supporting CS suitability in the 928?
Yes, this topic of CS vs. turbo is not exactly an apples-to-apples comparison, but the data we have is all we have to go on for now. Given enough development, either technology can produce excellent drivability... but as a community, we are most interested in what is available *now*. Can you say that your next project will have a flatter torque curve?
04-06-2004, 10:23 AM
#67
Three Wheelin'
Originally posted by John..
People hear "supercharger", then tell you there is lag with the turbo and point to the CS as superior.
People hear "supercharger", then tell you there is lag with the turbo and point to the CS as superior.
It's obvious that you've never even rode in one, but here you are making all your typical 'ranting of a madman's' claims, as usual. If you would read any magazine articles, or the Corky Bell book you claim that you have which evidently just collects dust somewhere, they ALL say the same thing with respect to lag. Why is it that only you claim otherwise? All evidence points to that once again, you have no idea what you're talking about.
Talk about the worst of both worlds with the CS, you get the parasitic draw like the positive displacement blower, then have to wait till 2/3 to 3/3 redline to get appriciable boost. I call that "infinite lag". Anybody who uses the arguement of less lag when comparing to a centrifugal supercharger to a turbo simply does not know what they are talking about. Positive displacement you have a leg to stand on, but don't talk about lag when comparing a CS to a turbo because the CS has the ultimate lag.
See above post. And go look at ANY 928 dyno chart instead of running your 'admittedly big mouth', which unfortunately is clueless most the time.
By the way, your term 'infinite lag' is what one experiences while waiting 2 seconds for the turbos to spool up after flooring it. By that time, the other guy is long gone and snickering at the docile Porsche.
There is a listing somewhere of a 944 putting out 480 rwhp (..somewhere around there, it was outrageous), and his listed 0-60 time is listed exactly as below:
0-60: 5.5 seconds (TURBO LAG!)
480 rwhp and that kind of 0-60 time is nothing short of spectacularly disappointing. The interesting thing about it all was that the guy was up-front about it, and did not attempt to make excuses for it by claiming a centrifugal supercharger may have been within a 5 mile radius of him at the time.
That Porschhhh951 guy who was hanging out here for awhile complained about turbo lag, and I think he mentioned it took him 2-3 seconds to spool up.
My Dad's '86 951 takes about 2 seconds to spool up. By the way, those are really nice cars despite the lag.
So why is it that it's only you who says that turbo lag is not an issue? And now your latest attempts to say that centrifugals experience lag make you look even goofier than before (..if it were even remotely possible).
Which by the way, according to some of your more inspired rantings in the past, it's obvious again you've never raced anyone in your life since your account of a hypothetical race would never occur as stated, at least with a competent driver that is.
If it's a rolling start out on a highway, both cars will 'stage' first which means both cars are in the proper gear for whatever the current speed is, which means at the start of the race, both cars should be spinning at least 4000 RPM. Three honks of the horn later it's on and it's a shift at 6400-6500 RPM where the RPM drops down to 4400-4500 RPM and it's all the way to 6500 RPM again.
So as Brendan has already advised you, what good is it having 'extra' power down low since after my shift at 6500 RPM the RPM drops only to 4500 RPM? What good is an extra 'X' amount of horsepower/torque at 2500 RPM going to do for me now since I'm shifting at 2000 RPM above that? That is called 'RPM Race Range', 4500-6500 RPM, which according to your posts, you know nothing about as evidenced by your 'racing' scenarios.
Now I'll grant you that if one is into towing large things behind their 928 like bulldozers and cranes, or are just flat-out lazy driving around lugging their engines in 5th gear and 30 MPH, then go ahead and beef up power at 2500 RPM so that it runs out of breath at 4500 RPM. 4000 RPM and above is where racing takes place.
BC, I squeezed 440 crank HP out of a little 4.5 liter with stock heads and cams. Does that impress you?
You can talk all you want about dyno HP numbers and the like, what it all boils down to is useable power with drivebility to the road. The turbo is the far better in the real world, thus the reson Porsche uses it. The CS is perfectly suited to posting very high peak HP numbers on a dynojet, but I keep telling you guys this is not the entire picture.
I'll concede that you must have the 'picture' nailed to your living room wall with respect to towing large objects though. Even so, according to the dyno charts, the centrifugal is right in that mix too.
04-06-2004, 01:15 PM
#68
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FWIW. I have had both kinds of applications, turbo charged and CS/C cars. In fact I have one of each today. The A6 Bi-turbo has a noticeable lag......my Murph 928Supershark does not. If the CS/C is parasitic, it is not noticeable to me. Both are great cars........However, the Audi will be long gone and Gretch will still be in her place in my garage.......
I don't want turbo power except in small engines.......and I vote with my money. Evangelizing is irrelevant to me.
I don't want turbo power except in small engines.......and I vote with my money. Evangelizing is irrelevant to me.
04-06-2004, 02:21 PM
#69
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Originally posted by Gretch
I don't want turbo power except in small engines.......and I vote with my money. Evangelizing is irrelevant to me.
I don't want turbo power except in small engines.......and I vote with my money. Evangelizing is irrelevant to me.
04-06-2004, 03:09 PM
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the nissian 300zx has twin turbos that seem to be instantanious - I've ridden and driven my uncle's a few times...at a mere $3k each, the ball bearing units rev quickly - I think 1 is tuned for low rpm, the other is for higher rpm...used a turbo on my airplane for years - big lag, and shock cooling was always a concern, but at 10k MSL w/constant power settings it was fine....lots of diesels use them too...IMHO, turbos are fine if engineered properly for the application...
same w/superchargers...any FI system has to deal w/heat, detonation, cost, performance, and reliabilty issues - it's a complex balancing act with mutually exclusive endpoints at any extreme(power vs cost/reliability, etc), dependent on application and user constraints(marketing stuff)....
for my shark and I, a blower was just easier, since several "kits" are now available in a range of prices and capabilities(nice to have choices!)...if a turbo "kit" was around that delivered the same HP/$$, etc then it would just be a coin toss...
philosophy? at $2.65/gallon for premium - there is no free power...and in SOCAL, there is no free parking either...
same w/superchargers...any FI system has to deal w/heat, detonation, cost, performance, and reliabilty issues - it's a complex balancing act with mutually exclusive endpoints at any extreme(power vs cost/reliability, etc), dependent on application and user constraints(marketing stuff)....
for my shark and I, a blower was just easier, since several "kits" are now available in a range of prices and capabilities(nice to have choices!)...if a turbo "kit" was around that delivered the same HP/$$, etc then it would just be a coin toss...
philosophy? at $2.65/gallon for premium - there is no free power...and in SOCAL, there is no free parking either...
04-06-2004, 10:04 PM
#74
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shell or mobil, acton, ca...in van nuys.... union 76 has unleaded 100 octane at a pump (closer to $3.00/gal)....good to know in case I screw up the compression or boost calcs... probably wouldn't be so bad if I actually got some in the car instead of on the ground & self...now that's a philosophy to preach!!
oh yeah - sorry...CFM? aren't those the shoes hotties sometimes wear?
oh yeah - sorry...CFM? aren't those the shoes hotties sometimes wear?
