Ultimate hp test 100-300kph
11-11-2006, 01:33 PM
#61
Instructor
Join Date: Jun 2005
Location: london, uk
Posts: 196
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Jean
Leon
I will just comment and correct you on the point that is of interest to me, far from, I said he said...
If you jump ahead in the beginning and gain 5mph from the initial few feet, it will take the other car a while to get the distance back, and to do so, he would have to be more powerful. However, he can be carrying more speed than you even being still behind you... Your assumption is incorrect, you wouldn't be so far ahead, if any, not necessarily at least..
It is obvious from the video that you were ahead of him buy a couple of cars throughout the run until you had to slow down. You guys were accelerating at the exact same pace, until end 5th gear where you started pulling thanks to better aerodynamics.
Your car is a true VmAx animal, no doubt about it, but there is more than power to it.
Best
I will just comment and correct you on the point that is of interest to me, far from, I said he said...
If you jump ahead in the beginning and gain 5mph from the initial few feet, it will take the other car a while to get the distance back, and to do so, he would have to be more powerful. However, he can be carrying more speed than you even being still behind you... Your assumption is incorrect, you wouldn't be so far ahead, if any, not necessarily at least..
It is obvious from the video that you were ahead of him buy a couple of cars throughout the run until you had to slow down. You guys were accelerating at the exact same pace, until end 5th gear where you started pulling thanks to better aerodynamics.
Your car is a true VmAx animal, no doubt about it, but there is more than power to it.
Best
11-11-2006, 02:16 PM
#62
Instructor
Join Date: Jun 2005
Location: london, uk
Posts: 196
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Jean
Leon,
Just one question, are you sure you can beat Toby's car in a similar run to 190mph for instance (no gearing issues) or any other acceleration run again, and are you willing to put your money where your mouth is?
Cheers
Just one question, are you sure you can beat Toby's car in a similar run to 190mph for instance (no gearing issues) or any other acceleration run again, and are you willing to put your money where your mouth is?
Cheers
11-11-2006, 03:24 PM
#64
Instructor
Join Date: Jun 2005
Location: london, uk
Posts: 196
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Stummel
the RT12 should do the trick...
You should bring both to the V-Max next year 8-)
You should bring both to the V-Max next year 8-)
i want to run them against eachother aswell 
11-13-2006, 06:39 AM
#65
Intermediate
Join Date: Apr 2006
Location: Cambridge, UK
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Jean asked me about my "credentials". I do not own a Porsche that can be used on the road. I do have a Porsche race car and I am a professional mechanical engineer and a member of the Institute of Mechanical Engineers in London. My real experience comes from racing the car in the UK and Europe. I have built many engines and tested many different configurations with results ranging from total failure to reasonable success! The most important thing I have learnt over the years is that power is not the most important factor in a circuit car. It is the complete package including engine, handling, roadholding, brakes and aero. I am lucky enough to have won over 100 races in the past 14 years (or so!!) and in most cases I have not had the most powerful car. I have had, though, the best package!!
Back to the thread. It is torque at the wheels that accelerates the car. Nothing more, nothing less. As far as the torque curve is concerned Jean is correct in saying the further you can keep the torque going (in revs terms) the more power you make. Power is simply the rate of doing work and in our terms this means that the power is directly proportional to the engine speed and the torque. (You have to be careful with the units but the relationship is simple). The area under the torque curve is also very important as this is a measure of the "energy" produced by the engine or again in our terms it is the "feel" of the engine in any particular gear. Think of the difference between a diesal and a petrol engine. The diesal will produce massive torque at low revs (I know the new ones are much more similar to petrol but for this illustration think of an older style engine!) and thus will feel really quick initially but the ultimate power will be limited due to the way in which the torque drops quickly with revs. A petrol car may produce a similar ultimate torque reading but this will inevitably be at much higher revs. Thus it will feel sluggish initially but the "power" will keep on coming. Turbo engines designed for the road tend to have high torque values and flat torque cuves; ie the best of both worlds. There has been an assertion that due to the torque produced by the turbo a faster accelareation time will be achieved by using a higher gear. I hope I have managed to explain that theoretically this is wrong. However, it does depend on the speed of your gearchange. My assertion is that for the best 100 -300 kph run you would make two gearchanges. I assume the other school of thought is that you make just one. In my previous reply I stated that with a dog box my average gearchange time was 0.15 seconds. I have checked this and this is a little misleading! The 1st to 2nd and 3rd to 4th changes are 0.15 but the changes requiring a change of gate take 0.3 seconds. (I have a conventonal H pattern 5 speed box). However, with my car I am substantially quicker using all the gears to accelerate than allowing the engine to pull third gear from relatively low revs. (data at Croft, a fabulous circuit in the North of England, shows over 1 second advantage from 110kph to 215 kph. I can see that other car/engine configurations would make this difference smaller but remebering the flat torque curve produced by a turbo and the torque multiplying effect of the gear ratio I would be very suprised if it tipped the balance!
I did some project work many, many years ago regarding aerodynamic drag. I seem to recall (my notes are long gone!) that the aero drag is the largest single factor in car drag once the velocity is above 100 kph. There are loads of assumptions in that statement but if there is an aerodynamicist out there I would love to know if my memory is correct.
Is anyone willing to share real power figures and real engine development work on this forum? I would love to as I have nothing to hide and I am probably the only person in the world to have run the "screw in liners" and special heads! It would be interesting to see but of course the big German tuning companies could not as they have too many commercial secrets! However, believe me, it is not rocket science!
Richard.
Back to the thread. It is torque at the wheels that accelerates the car. Nothing more, nothing less. As far as the torque curve is concerned Jean is correct in saying the further you can keep the torque going (in revs terms) the more power you make. Power is simply the rate of doing work and in our terms this means that the power is directly proportional to the engine speed and the torque. (You have to be careful with the units but the relationship is simple). The area under the torque curve is also very important as this is a measure of the "energy" produced by the engine or again in our terms it is the "feel" of the engine in any particular gear. Think of the difference between a diesal and a petrol engine. The diesal will produce massive torque at low revs (I know the new ones are much more similar to petrol but for this illustration think of an older style engine!) and thus will feel really quick initially but the ultimate power will be limited due to the way in which the torque drops quickly with revs. A petrol car may produce a similar ultimate torque reading but this will inevitably be at much higher revs. Thus it will feel sluggish initially but the "power" will keep on coming. Turbo engines designed for the road tend to have high torque values and flat torque cuves; ie the best of both worlds. There has been an assertion that due to the torque produced by the turbo a faster accelareation time will be achieved by using a higher gear. I hope I have managed to explain that theoretically this is wrong. However, it does depend on the speed of your gearchange. My assertion is that for the best 100 -300 kph run you would make two gearchanges. I assume the other school of thought is that you make just one. In my previous reply I stated that with a dog box my average gearchange time was 0.15 seconds. I have checked this and this is a little misleading! The 1st to 2nd and 3rd to 4th changes are 0.15 but the changes requiring a change of gate take 0.3 seconds. (I have a conventonal H pattern 5 speed box). However, with my car I am substantially quicker using all the gears to accelerate than allowing the engine to pull third gear from relatively low revs. (data at Croft, a fabulous circuit in the North of England, shows over 1 second advantage from 110kph to 215 kph. I can see that other car/engine configurations would make this difference smaller but remebering the flat torque curve produced by a turbo and the torque multiplying effect of the gear ratio I would be very suprised if it tipped the balance!
I did some project work many, many years ago regarding aerodynamic drag. I seem to recall (my notes are long gone!) that the aero drag is the largest single factor in car drag once the velocity is above 100 kph. There are loads of assumptions in that statement but if there is an aerodynamicist out there I would love to know if my memory is correct.
Is anyone willing to share real power figures and real engine development work on this forum? I would love to as I have nothing to hide and I am probably the only person in the world to have run the "screw in liners" and special heads! It would be interesting to see but of course the big German tuning companies could not as they have too many commercial secrets! However, believe me, it is not rocket science!
Richard.
11-13-2006, 06:52 AM
#66
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Richard, is that all?
With 100 wins, wouldn't be Chamberlain I presume?
My gearshifts with the sequential gearbox take me 0.25 seconds on average but I have not been able to fit the cutoff switch yet, so I need to lift somewhat between shifts. I don't have the H pattern, with an H pattern, it would certainly be more time. 0.15 seconds is blinding fast with an H pattern box.
The other thing is that what matters is to carry the positive long Gs while shifting, which is the main advantage, with the sequential , I don't see negative Gs at all.
You explained it much better than me. Torque at high RPMs is (known as) Horsepower, which is why I am saying HP is what matters, meaning torque at high RPMs... Take for instance an F1 car, it has HP, not torque to go fast.
I fully agree with you concering the drag issue which is why I brought it up earlier, in this specific thread, the better aerodynamics of the RUF could have represented more than 20HP difference easily at top speed. It will even have an impact a 60-130mph run for sure.
not sure what you mean by real power figures, this is what we are all about here Richard, chassis dyno sceptics, any specific questions please ask.
Thanks.
P.S. you can post some pictures of your race car, it would not hurt!
With 100 wins, wouldn't be Chamberlain I presume?
My gearshifts with the sequential gearbox take me 0.25 seconds on average but I have not been able to fit the cutoff switch yet, so I need to lift somewhat between shifts. I don't have the H pattern, with an H pattern, it would certainly be more time. 0.15 seconds is blinding fast with an H pattern box.
The other thing is that what matters is to carry the positive long Gs while shifting, which is the main advantage, with the sequential , I don't see negative Gs at all.
Originally Posted by 935racer
Back to the thread. It is torque at the wheels that accelerates the car. Nothing more, nothing less. As far as the torque curve is concerned Jean is correct in saying the further you can keep the torque going (in revs terms) the more power you make..
I fully agree with you concering the drag issue which is why I brought it up earlier, in this specific thread, the better aerodynamics of the RUF could have represented more than 20HP difference easily at top speed. It will even have an impact a 60-130mph run for sure.
not sure what you mean by real power figures, this is what we are all about here Richard, chassis dyno sceptics, any specific questions please ask.
Thanks.
P.S. you can post some pictures of your race car, it would not hurt!
11-13-2006, 07:10 AM
#67
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Originally Posted by 935racer
. I seem to recall (my notes are long gone!) that the aero drag is the largest single factor in car drag once the velocity is above 100 kph. There are loads of assumptions in that statement but if there is an aerodynamicist out there I would love to know if my memory is correct..
For a GT2 flared 993TT body like TB993TTs, the drag at 193mph is almost equivalent to about 365HP (negative), while for a TT like Leon's, it would be equivalent to 335HP approximately, based on a CD of 0.33. That's about 30HP in fact.
So drag represents an impact of more than 50% of total power at 193mph.
11-13-2006, 08:35 AM
#68
Intermediate
Join Date: Apr 2006
Location: Cambridge, UK
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Jean, I have been found out! Yes, my surname is Chamberlain and I do have the orange Porsche. It's a fabulous car but it really is like a woman - it takes all my time and money to look after it!!!!
Torque and gear ratios are a fantastic subject! The world rally cars use a step up box to double the gearbox input shaft speed. This allows them to use much smaller gears in the box and still increase reliability (whilst speeding shift times due to the lower inertia). It seems they dont loose too much through the extra drag. I would love to be involved in that for a few months!
I see negative G on a gearchange - surely no matter how fast the change the car will start to slow down as the gears are in "neutral" - it is just that the faster you change the shorter the negative G interval? You need to sort out your ignition cut as flat shifts must be something else! I built a motorbike engined kit car for a friend and we fitted a flat shift change. It really was fabulous! I would like a sequential in my car but its expensive. This year we have been struggling to keep the gearbox alive so all the "goody budget" was spent on spares! I now use a semi dry sump arrangement, two pumps and four coolers and can keep the gearbox temperatures to around 100 centigrade in a 25 ambient. I'm pretty pleased with that!
Thank you for the drag approximation. I can easily believe it. An interesting point to mull over, whilst sitting on your own(!!!) may be that whilst the frontal area of the car has a linear relationship with drag the bases of the coefficient of friction is much more complicated. Fliud, air in this case, will accelerate without too much loss ( half a velocity head(?)) but it hates slowing down. If we want to make some big inroads into aero efficiency prehaps we should look at the back of the car, not the front. This is not really my field but I am an interested amateur. Certainly, I have done a fair bit to clean up the wake from the car but frankly I have not seen any difference in performance! It just feels better in my head!!!
I dont want to start a huge debate again but I am not interested in absolute engine power numbers. I need to know when I have made an improvemet (or indeed gone backwards). The only way to do this is on an engine dyno. Here, the conditions can be controlled and repeatability can be achieved. However, its still very difficult with a turbo as there is just SO much heat. Vmax runs and acceleration runs are fine but you cannot use them to compare the engine in car A to that in car B. However, they are an absolute test of the performance of car A to car B so it really depends on what you are trying to achieve.
I dont know how to post pictures so if someone can help I will have a go. My son says I am too old for the computer age!!
Richard.
Torque and gear ratios are a fantastic subject! The world rally cars use a step up box to double the gearbox input shaft speed. This allows them to use much smaller gears in the box and still increase reliability (whilst speeding shift times due to the lower inertia). It seems they dont loose too much through the extra drag. I would love to be involved in that for a few months!
I see negative G on a gearchange - surely no matter how fast the change the car will start to slow down as the gears are in "neutral" - it is just that the faster you change the shorter the negative G interval? You need to sort out your ignition cut as flat shifts must be something else! I built a motorbike engined kit car for a friend and we fitted a flat shift change. It really was fabulous! I would like a sequential in my car but its expensive. This year we have been struggling to keep the gearbox alive so all the "goody budget" was spent on spares! I now use a semi dry sump arrangement, two pumps and four coolers and can keep the gearbox temperatures to around 100 centigrade in a 25 ambient. I'm pretty pleased with that!
Thank you for the drag approximation. I can easily believe it. An interesting point to mull over, whilst sitting on your own(!!!) may be that whilst the frontal area of the car has a linear relationship with drag the bases of the coefficient of friction is much more complicated. Fliud, air in this case, will accelerate without too much loss ( half a velocity head(?)) but it hates slowing down. If we want to make some big inroads into aero efficiency prehaps we should look at the back of the car, not the front. This is not really my field but I am an interested amateur. Certainly, I have done a fair bit to clean up the wake from the car but frankly I have not seen any difference in performance! It just feels better in my head!!!
I dont want to start a huge debate again but I am not interested in absolute engine power numbers. I need to know when I have made an improvemet (or indeed gone backwards). The only way to do this is on an engine dyno. Here, the conditions can be controlled and repeatability can be achieved. However, its still very difficult with a turbo as there is just SO much heat. Vmax runs and acceleration runs are fine but you cannot use them to compare the engine in car A to that in car B. However, they are an absolute test of the performance of car A to car B so it really depends on what you are trying to achieve.
I dont know how to post pictures so if someone can help I will have a go. My son says I am too old for the computer age!!
Richard.
11-13-2006, 12:39 PM
#70
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Pleasure to have you here Richard, you are certainly one of the (if not THE) most awarded turbo Porsche racer ever, certainly in the UK at least, Your car is an inspiration. I will gladly post your pictures, I will send you an email with my email address
Re. aerodynamics, I am far from being an engineer, so you are getting a little too technical for me I do know that you have been helped by one of the best in the industry to streamline your aero, drag and downforce and they must have done something right!
The downside with the engine dyno is that everytime you want to do a change it takes immense effort to put it back on the dyno and testagain as you know, however I agree with you, it is the only way to have accurate (and a wealth of) information.
An easier way to see what works, as long as you are tracking all the engine vital info, is through the performance loggers such as the ones we use. Very easy to snap on and it works perfectly. Some reknown tuners are starting to use them as a calibration tool!
As far as gear changes and Gs, I see a drop in Long Gs when I shift of course, however it remains in positive territoty, meaning the car is still accelerating. I will post a chart that shows my gear changes vs. TB993TT, I am the black line, which remains positive in Gs.
Concerning the cutoff switch, it is not too bad as is, I just have to lift very very briefly, but it still needs to be fixed. Some simple work has to be done I just don't have the qualified people here to do it. It is something that needs to be done for sure. The box will not stay on the car so I am not sure I want to open the enigne for it.
As far as your liners and heads, I believe you were using the Perfect Bore stuff? It seems like it has worked quite well with your engine. I know you had some issues, but nothing major I believe. Were you running Secan intercooler?
Looking forward to see more of your contributions. Thanks for coming here.
Re. aerodynamics, I am far from being an engineer, so you are getting a little too technical for me
I do know that you have been helped by one of the best in the industry to streamline your aero, drag and downforce and they must have done something right!The downside with the engine dyno is that everytime you want to do a change it takes immense effort to put it back on the dyno and testagain as you know, however I agree with you, it is the only way to have accurate (and a wealth of) information.
An easier way to see what works, as long as you are tracking all the engine vital info, is through the performance loggers such as the ones we use. Very easy to snap on and it works perfectly. Some reknown tuners are starting to use them as a calibration tool!
As far as gear changes and Gs, I see a drop in Long Gs when I shift of course, however it remains in positive territoty, meaning the car is still accelerating. I will post a chart that shows my gear changes vs. TB993TT, I am the black line, which remains positive in Gs.
Concerning the cutoff switch, it is not too bad as is, I just have to lift very very briefly, but it still needs to be fixed. Some simple work has to be done I just don't have the qualified people here to do it. It is something that needs to be done for sure. The box will not stay on the car so I am not sure I want to open the enigne for it.
As far as your liners and heads, I believe you were using the Perfect Bore stuff? It seems like it has worked quite well with your engine. I know you had some issues, but nothing major I believe. Were you running Secan intercooler?
Looking forward to see more of your contributions. Thanks for coming here.
11-13-2006, 01:11 PM
#71
Intermediate
Join Date: Apr 2006
Location: Cambridge, UK
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
Jean thanks for your kind words. A racer is only as good as the last result and this year has been poor! We have been fastest every time out but poor reliability has kept me from the winners table! Its all trivial stuff that has let us down but everything has to work to win a race. Hopefully, normal service will be resumed next year!
I certainly agree about the hassle involved with an engine dyno. Its no secret that I use one of the cells at Engine Developments (Judd) and I have been really pleased with the results. However, it takes the best part of a day to set up and half a day to strip down and that does not include taking it out of the car!
With regard to the screw in liners - yes they were from Perfect Bore. The development has now been sold to an American company so PB have no further interest in them! I have not raced them as there are some serious issues with them. I still believe they can help in terms of reliability and I am still working on them. In fact, it seems as though I am doing all the development work for the new owners but that is another issue! Both my engines that I race are conventional in having "standard" barrels and heads (the heads are the PB ones (now American) and are made from excellent material) and resonably standard other components. The weakest link on the engine is the barell to head interface (no suprise there!) which is why I am hopeful of an improvement with the screw in liners.
I am interested in your comment about acceleration during a gearshift! I am going to ask a simple question that I believe I know the answer to but that at least 50% of engineers disagree with me!!!! How can you car continue to accelerate when you are in neutral? As you are not putting any energy into the system surely it must slow down. I have asked engineers about rev limiters. Once the engine has hit the hard cut rev limiter surely it cannot gain anymore revs and must slow down. I am really interestedin your or anyone elses answers as I find it confusing. I believe I am right but there are many more intelligent people than me who say I am wrong! Think of a tennis ball. When the raquet is in contact with the ball it is accelerating as energy is being put intothe system and as soon as the ball leaves the raquet face it is slowing down. Don't worry, I am trying to convince myself as I am writing this! As I say, please someone put me out of my misery!!
Cheers,
Richard.
I certainly agree about the hassle involved with an engine dyno. Its no secret that I use one of the cells at Engine Developments (Judd) and I have been really pleased with the results. However, it takes the best part of a day to set up and half a day to strip down and that does not include taking it out of the car!
With regard to the screw in liners - yes they were from Perfect Bore. The development has now been sold to an American company so PB have no further interest in them! I have not raced them as there are some serious issues with them. I still believe they can help in terms of reliability and I am still working on them. In fact, it seems as though I am doing all the development work for the new owners but that is another issue! Both my engines that I race are conventional in having "standard" barrels and heads (the heads are the PB ones (now American) and are made from excellent material) and resonably standard other components. The weakest link on the engine is the barell to head interface (no suprise there!) which is why I am hopeful of an improvement with the screw in liners.
I am interested in your comment about acceleration during a gearshift! I am going to ask a simple question that I believe I know the answer to but that at least 50% of engineers disagree with me!!!! How can you car continue to accelerate when you are in neutral? As you are not putting any energy into the system surely it must slow down. I have asked engineers about rev limiters. Once the engine has hit the hard cut rev limiter surely it cannot gain anymore revs and must slow down. I am really interestedin your or anyone elses answers as I find it confusing. I believe I am right but there are many more intelligent people than me who say I am wrong! Think of a tennis ball. When the raquet is in contact with the ball it is accelerating as energy is being put intothe system and as soon as the ball leaves the raquet face it is slowing down. Don't worry, I am trying to convince myself as I am writing this! As I say, please someone put me out of my misery!!
Cheers,
Richard.
11-13-2006, 01:15 PM
#72
Addict
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Richard I have what you need re. the rev limiter info, I have tested it before and will post the findings as far as long Gs are concerned. Will do so later on as my device's battery is dying.
11-13-2006, 02:27 PM
#73
Rennlist Member
935 racer, I think I know why things can continue to accerate after force has been stopped/car is in 'neutral' as you say (others please correct me if I'm wrong). I haven't thought about stuff like this for many years but, here it goes... There is a difference between constant acceleration and non-constant acceleration. Constant acceleration refers to an object which is accelerating at constant velocity change over time, were as non-constant acceleration refers to velocity that changes differently over a specific time interval. So, say at one second intervals, in constant acceleration, you may be increasing by say 2meters/second each at each one second interval so that after 3 seconds you are going 6meters/second. In non-constant acceleration you may be increasing your velocity by 2meters/second the first second then 3meters/second the second second and 4 m/s the third second. I think Jean's car is experiencing non-constant acceleration. If you stop your force/go into neutral - if you are experiencing constant acceleration, you velocity will start to slow/remain constant after the third second and no longer accelerate (as in your descriptions) where as with non-constant acceleration, your acceleration will change and be no longer accelerating at the rate you were, but will be continuing to accelerate for a short period in reducing/non-constant acceleration prior to having negative accelertion/slowing down. Something to do with kinetic energy/impulse/momentum ......
11-13-2006, 05:58 PM
#75
Boost Junkie
Lifetime Rennlist
Member
Lifetime Rennlist
Member
Join Date: Jan 2004
Location: Plymouth MN and Scottsdale AZ
Posts: 2,534
Received 42 Likes
on
34 Posts
there will be a bit of stored energy in the drive train that may continue to help acceleration during shifting. Think about wrinkle wall drag slicks "unwinding". The halfshafts may do a bit of this as well.
