928 RS4 Project... needs 378hp
03-10-2010, 03:19 PM
#16
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I have this can of worms sitting on my desk so I thought I’d open it…
My target power to weight ratio for the 928 RS4 Track Project is: (0.14).
For the sake of discussion lets ignore torque and focus on peak Hp.
Ideas? Comments? Support? Hating? What am I missing or over looking? Let me hear it…
My target power to weight ratio for the 928 RS4 Track Project is: (0.14).
For the sake of discussion lets ignore torque and focus on peak Hp.
Ideas? Comments? Support? Hating? What am I missing or over looking? Let me hear it…
Peak HP shoud be the least of your concern even for the sake of discussion. You should in fact give the torque numbers and curve the most critical analysis you can depending on how you will use the car.
The car does not always run at peak RPM, and the peak will be just that, peak. Whereas if you have a lower peak number, but higher average, or specifically, higher torque curve with more area under the curve, this similarly weighted vehicle will accelarate faster than the vehicle with the higher HP peak.... (Most road race tracks have turns, and this is where the TQ will count unless you are in a gear at the peak all the time, in which case, you will be rebuilding motors quite often..)
The other thing you did not mention, is budget.. It is easy to get 400HP from a 928 motor.. The question is always how much do you have to spend on it...?
IIRC, You mention DE type events and possibly street use... The cheapest way may be to put on a properly sized supercharger as a bolt on...... Then again it may not if you count ancilliaries that you will need to keep the SC'd car on the track over the long haul...
Another option could be an ITB kit with better cams and pistons for a track car running aftermarket ECU......
My guess is you will be at 2800Lb wet and need 400 HP at the crank to get your 7:1 ratio... However, again, I would look at the TQ values over the range, as that is what really counts.....
Just my $0.02, hope it helps...
03-10-2010, 03:57 PM
#18
Race Director
are you sure its CRANK HP...since most race groups require dyno sheets which of course are WHEEL HP.... 2500lbs race 928 will be VERY difficult...since the lightest around is 2600lbs nearly empty without driver (Mark Andersons)....a typical race weight is 2700'bs for a 5 speed S4....less for a 16V....for example the old Holbert racer was about 2760lbs....the Lemons racer (auto) is a tick under 2800 nearly empty...and Scotts 82 5.0L 16V is right at 2700lbs....
If the power-weight also requires driver....you need to adjust your HP higher....since your racing weight probably will be in the 2900-3000 range...and remember they weigh the car AFTER the race...
378 crank HP is VERY doable any 32V engine..since thats only 320whp, or boosted 16V......properly built 5.0L have achieved 387whp already...& the "newest" one should beat that!!
It all comes down to budget.....but here is my advice...speaking as someone who bought an all out racer in the "Widow" (in avatar) with a 302whp in 2850lbs......as my 1st race car (don't know if you have raced before).....START SMALL.....for your 1st racer less is more.....I learned more as a driver driving spec miatas while the widow was blown up then I ever did driving the Widow....now I race the Lemons racer at 195whp in 2800lbs and LOVE IT...with tiny 225 tires too....its just TOO much fun out there....and the running costs are far less too
When you are new to racing-track driving...ALWAYS spend you $$$ on seat time + instruction...don't fall into the trap of spending big $$$$ to make a FAST car....you need to build up to the hotrod car to be able to handle it properly......
the best advice I ever got was "you want to be fast, learn to be fast in a slow car 1st"......
Okay stepping off soapbox
If the power-weight also requires driver....you need to adjust your HP higher....since your racing weight probably will be in the 2900-3000 range...and remember they weigh the car AFTER the race...
378 crank HP is VERY doable any 32V engine..since thats only 320whp, or boosted 16V......properly built 5.0L have achieved 387whp already...& the "newest" one should beat that!!
It all comes down to budget.....but here is my advice...speaking as someone who bought an all out racer in the "Widow" (in avatar) with a 302whp in 2850lbs......as my 1st race car (don't know if you have raced before).....START SMALL.....for your 1st racer less is more.....I learned more as a driver driving spec miatas while the widow was blown up then I ever did driving the Widow....now I race the Lemons racer at 195whp in 2800lbs and LOVE IT...with tiny 225 tires too....its just TOO much fun out there....and the running costs are far less too
When you are new to racing-track driving...ALWAYS spend you $$$ on seat time + instruction...don't fall into the trap of spending big $$$$ to make a FAST car....you need to build up to the hotrod car to be able to handle it properly......
the best advice I ever got was "you want to be fast, learn to be fast in a slow car 1st"......
Okay stepping off soapbox
03-10-2010, 06:03 PM
#19
Nordschleife Master
Of course, it might be more fun being able to show the GT3 drivers a stock-looking engine..
For stock-looking, S3 cams, headers, X-pipe and a sharktune should put you at your target on an S4 engine. All fairly easy bolt-on so if you destroy rod bearings and total the block, you can move them to another S4 block.
03-10-2010, 07:15 PM
#20
Nordschleife Master
Brian,
You are EXACTLY right! My racer (Anderson's old car) with auto trans, modified cage (swing open side impact bars), handcontrols and dual vacuum assisted power brake M/C's and 1/4 tank of gas is 2670#. I don't even want to know how LITTLE HP I am making out of my poor old Euro S engine! I can tell you it is not enough!
As for racing and number Brian, PCA does not require a dyno sheet. They look at what the engine is. V8, H6, whatever, then they look at displacement and then boosted or not, 1 cam or 2 cam, etc. They have estimated a best power for that engine type and then weigh the car on site and then place you in the proper p/w class...
If they had done that a few years ago (the last time I club raced my car) I would have fared better and worse...I would have ended up in a class I was competitive with (sort of) and probably would have finished well down the order...that is the worse part, the better part is that they didn't do that and there were only TWO cars in my class so I got 2nd! LOL!
You are EXACTLY right! My racer (Anderson's old car) with auto trans, modified cage (swing open side impact bars), handcontrols and dual vacuum assisted power brake M/C's and 1/4 tank of gas is 2670#. I don't even want to know how LITTLE HP I am making out of my poor old Euro S engine! I can tell you it is not enough!
As for racing and number Brian, PCA does not require a dyno sheet. They look at what the engine is. V8, H6, whatever, then they look at displacement and then boosted or not, 1 cam or 2 cam, etc. They have estimated a best power for that engine type and then weigh the car on site and then place you in the proper p/w class...
If they had done that a few years ago (the last time I club raced my car) I would have fared better and worse...I would have ended up in a class I was competitive with (sort of) and probably would have finished well down the order...that is the worse part, the better part is that they didn't do that and there were only TWO cars in my class so I got 2nd! LOL!
03-10-2010, 09:13 PM
#21
Been selling Twinkies on Ebay,
have some extra cash right now.
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have some extra cash right now.
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03-10-2010, 09:21 PM
#22
Nordschleife Master
You have NO IDEA how painful it was to watch EVER SINGLE car in the fast group accelerate away from me when the green flag would fly! Ugh! I could usually catch the last two in the first corner and pass them, but the next lap they had the ENTIRE straight to get away from me...so depressing!
03-10-2010, 09:54 PM
#23
Race Director
You have NO IDEA how painful it was to watch EVER SINGLE car in the fast group accelerate away from me when the green flag would fly! Ugh! I could usually catch the last two in the first corner and pass them, but the next lap they had the ENTIRE straight to get away from me...so depressing!
Which is why you HAVE TO race in lemons!!!!!!!!!!!!!!!!!! There literally isn't a car out there we can't pass!!!
The fasters ones take a bit of planning, but only a little......I really enjoy knowing that I can at least pace every single car out there.....for example one of the fastest cars out there is our teammate in the V8olvo (ford 302 in 84 volvo sedan 5 speed, LSD, 2900lbs, 225whp 268 torque)..so it has an edge on us with the LSD, 5 speed and power....but I watched it following Anderson at the slowest corner on the track.....guess what.....the 928 PULLED IT.....it did not start to catch it until the end of the little straight!!!! 
& that was with their BEST driver.....the same driver who was 2.5 seconds faster in the 928 than the V8olvo Sure he got around on the next lap....... but they were driving a much harder pace than we were!There was a team using handcontrols at Infineon.....I never got a chance to checkout their setup....but it was clear the teams are welcomed!!!
03-10-2010, 09:59 PM
#24
Nordschleife Master
The guys that have a lot (have not built a house yet) across the street and a hanger over in the hanger section do the LeMons race with an old Audi! They LOVE IT! They have raced it like 3 or 4 times. Crazy stuff! I think my race car looks FAR to good and cost FAR to much money to be let in to Lemons! 
03-10-2010, 10:02 PM
#25
Race Director
The guys that have a lot (have not built a house yet) across the street and a hanger over in the hanger section do the LeMons race with an old Audi! They LOVE IT! They have raced it like 3 or 4 times. Crazy stuff! I think my race car looks FAR to good and cost FAR to much money to be let in to Lemons!
You would have to find an appropriately crappy 928 like I did.....all of yours are far too nice.....were talking pick n pull type 928's....something really ugly with a salvage title and body damage
03-10-2010, 10:52 PM
#26
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More good feedback. For the record, this is my DE and autox car... so there are no class rules I'm forced to work within. Also, you guys are absolutely right about seat time being more important than mods. I've been going to the track for about 10 years now and autox'n for about the same... 99% of cars exceed their driver's ability. Taking even a stock 928 to it's limit is beyond mosts ability. However, I'm trying to avoid doing this twice so I'm trying to get the engine right the first time around... if such a thing is possible.
03-10-2010, 10:54 PM
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Iccy,
Peak HP shoud be the least of your concern even for the sake of discussion. You should in fact give the torque numbers and curve the most critical analysis you can depending on how you will use the car.
The car does not always run at peak RPM, and the peak will be just that, peak. Whereas if you have a lower peak number, but higher average, or specifically, higher torque curve with more area under the curve, this similarly weighted vehicle will accelarate faster than the vehicle with the higher HP peak.... (Most road race tracks have turns, and this is where the TQ will count unless you are in a gear at the peak all the time, in which case, you will be rebuilding motors quite often..)
The other thing you did not mention, is budget.. It is easy to get 400HP from a 928 motor.. The question is always how much do you have to spend on it...?
IIRC, You mention DE type events and possibly street use... The cheapest way may be to put on a properly sized supercharger as a bolt on...... Then again it may not if you count ancilliaries that you will need to keep the SC'd car on the track over the long haul...
Another option could be an ITB kit with better cams and pistons for a track car running aftermarket ECU......
My guess is you will be at 2800Lb wet and need 400 HP at the crank to get your 7:1 ratio... However, again, I would look at the TQ values over the range, as that is what really counts.....
Just my $0.02, hope it helps...
Peak HP shoud be the least of your concern even for the sake of discussion. You should in fact give the torque numbers and curve the most critical analysis you can depending on how you will use the car.
The car does not always run at peak RPM, and the peak will be just that, peak. Whereas if you have a lower peak number, but higher average, or specifically, higher torque curve with more area under the curve, this similarly weighted vehicle will accelarate faster than the vehicle with the higher HP peak.... (Most road race tracks have turns, and this is where the TQ will count unless you are in a gear at the peak all the time, in which case, you will be rebuilding motors quite often..)
The other thing you did not mention, is budget.. It is easy to get 400HP from a 928 motor.. The question is always how much do you have to spend on it...?
IIRC, You mention DE type events and possibly street use... The cheapest way may be to put on a properly sized supercharger as a bolt on...... Then again it may not if you count ancilliaries that you will need to keep the SC'd car on the track over the long haul...
Another option could be an ITB kit with better cams and pistons for a track car running aftermarket ECU......
My guess is you will be at 2800Lb wet and need 400 HP at the crank to get your 7:1 ratio... However, again, I would look at the TQ values over the range, as that is what really counts.....
Just my $0.02, hope it helps...
03-10-2010, 10:56 PM
#28
Nordschleife Master
Sounds like you have done a lot of track work then already! EXCELLENT! That is the best thing and you are absolutely right. Most 928 owners can't and won't ever get close to the limits of their car w/o accidentally exceeding them!
You are going to have a BLAST with this car and when you get in the top DE classes you are normally driving with friends that you have known for years and it is damn near racing for all practical purposes. So many of the guys I have raced with run together in the red or white groups and they race each other every lap! Fun stuff!
You are going to have a BLAST with this car and when you get in the top DE classes you are normally driving with friends that you have known for years and it is damn near racing for all practical purposes. So many of the guys I have raced with run together in the red or white groups and they race each other every lap!
Fun stuff!
03-10-2010, 11:44 PM
#29
Race Director
More good feedback. For the record, this is my DE and autox car... so there are no class rules I'm forced to work within. Also, you guys are absolutely right about seat time being more important than mods. I've been going to the track for about 10 years now and autox'n for about the same... 99% of cars exceed their driver's ability. Taking even a stock 928 to it's limit is beyond mosts ability. However, I'm trying to avoid doing this twice so I'm trying to get the engine right the first time around... if such a thing is possible.
Okay so you have been around the racing block so to speak!!! Thats a VERY good thing
Typically when racecars are built...they are built for a specific class in a specific series.....but 928's are an odd fit in most conventional race series....despite how FUN they are on track!! Mark Anderson builds his cars for the POC, Kibort for the SCCA and I built lemons for lemons!!!
03-11-2010, 07:34 AM
#30
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Throwing in my thoughts on your question:
1. For the money, do a stock engine rebuild with some extra head work for better flow, drilled crank for the 2/6 oiling problem, oil pan and oil scraper mods to help with track oiling issues and install an accusump system. It's not fun building up a racer and having the engine go boom on you.
2. Install a super charger system that has a proven track survivability history.
3. Install headers, Y pipe and a light single exhaust system, 3.5" or 4" will be perfect. Before anyone flames me look into the capability of flow through such a system. Anything below 500 HP this system will be fine.
4. Use the Shark Tuner and a dyno to tune that engine and super charger properly. Money and time well spent or else you will most probably suffer engine damage. At least not run the engine at it's optimum.
5. Don't go too crazy with suspension mods or brake mods. The 928 can do very well with most of it's suspension and brake system, especially the S4 brakes, left alone but with a few tweaks. Better brake pad compounds, sway bars front and rear, known springs and shocks. You can dump a lot of money here with little gained over tweaked stock systems. Just because you can adjust shocks two or three ways doesn't mean you will do so correctly.
A word about horse power, it's nice but torque is a great commodity on the track and what will shoot you ahead out of a corner over a higher horsepower car with less torque. BTDT.
Have fun,
1. For the money, do a stock engine rebuild with some extra head work for better flow, drilled crank for the 2/6 oiling problem, oil pan and oil scraper mods to help with track oiling issues and install an accusump system. It's not fun building up a racer and having the engine go boom on you.
2. Install a super charger system that has a proven track survivability history.
3. Install headers, Y pipe and a light single exhaust system, 3.5" or 4" will be perfect. Before anyone flames me look into the capability of flow through such a system. Anything below 500 HP this system will be fine.
4. Use the Shark Tuner and a dyno to tune that engine and super charger properly. Money and time well spent or else you will most probably suffer engine damage. At least not run the engine at it's optimum.
5. Don't go too crazy with suspension mods or brake mods. The 928 can do very well with most of it's suspension and brake system, especially the S4 brakes, left alone but with a few tweaks. Better brake pad compounds, sway bars front and rear, known springs and shocks. You can dump a lot of money here with little gained over tweaked stock systems. Just because you can adjust shocks two or three ways doesn't mean you will do so correctly.
A word about horse power, it's nice but torque is a great commodity on the track and what will shoot you ahead out of a corner over a higher horsepower car with less torque. BTDT.
Have fun,