Lowering HP-torque for class racing!!!! ???
12-23-2010, 08:24 PM
#16
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Ballast the car to make weight put it as far rear as possible a bit to the right side. Your car would handle best with about 60% of the weight on the rear allows for better acceleration. 50/50 is not ideal just much better than 60% front 40 % rear of many "muscle cars" .
12-23-2010, 09:08 PM
#18
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Adding weight penalizes you on braking and handling. Choose your method of restricting airflow. Plugged air filter is too big a variable, compared with a throttle restriction. Add a real restrictor or just block the throttle from going full open.
12-23-2010, 09:52 PM
#20
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great ideas all around
I would love to get 18x10's with big tires all around.....but my budget is NOWHERE near that....so I am stuck with 16x8's all around with tiny 245/45-16 for a while..... I am sure the car will handle better with more rubber....but its not like it handles bad now...even with tiny tires and no power....
I will schedule a dyno day on the MCE dyno towards the end of Jan....probably the Friday before Art of Racing weekend.... I will pull timing 1st...back to the stock setting.....If I can get 195whp-230torque that would be great.....I'll be happy with anything under 3100lbs.....
Of course the NASA norcal GTS director also happens to be the GTS2 champion.....such is my luck...however I have been talking to him and he is a great guy....he went LIGHT-LIGHT-LIGHT in his Mercedes 190-16..since his racing weight is under 2500lbs!!! His lap times are faster than mine...so I will have to step up my driving to get there.....
It should make for some great battles between the heavier-more powerful car vs the lighter-more nimble racer.... I might have to call in the BIG GUNS to give him a run.....MK-Anderson...you listening?
I would love to get 18x10's with big tires all around.....but my budget is NOWHERE near that....so I am stuck with 16x8's all around with tiny 245/45-16 for a while..... I am sure the car will handle better with more rubber....but its not like it handles bad now...even with tiny tires and no power....
I will schedule a dyno day on the MCE dyno towards the end of Jan....probably the Friday before Art of Racing weekend.... I will pull timing 1st...back to the stock setting.....If I can get 195whp-230torque that would be great.....I'll be happy with anything under 3100lbs.....
Of course the NASA norcal GTS director also happens to be the GTS2 champion.....such is my luck...however I have been talking to him and he is a great guy....he went LIGHT-LIGHT-LIGHT in his Mercedes 190-16..since his racing weight is under 2500lbs!!! His lap times are faster than mine...so I will have to step up my driving to get there.....
It should make for some great battles between the heavier-more powerful car vs the lighter-more nimble racer.... I might have to call in the BIG GUNS to give him a run.....MK-Anderson...you listening?
12-23-2010, 10:04 PM
#21
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Im listening! 
So is MA too, I'm sure!!
Ill bring my rims up and you can run on 275s and 305s
Pull that fender out! you can put some big spacers up front and get more cornering grip . I forget the calculation, but every 1" you widen the car, its like lowering it 1" or dropping 50llbs as far as G loading capability. (something like that) even with the 245s up front, you widen the car up front and rear and you will help the handling.
are you using a KN filter or paper? if KN, use paper, do a dyno run and then wrap it in a tee shirt. that should provide about 10hp loss I would guess. or, you can do a throttle position stop, but that is tough to do too. there is not much HP difference between full throttle and a little before full throttle, but it would be interesting to check.
mk
So is MA too, I'm sure!!Ill bring my rims up and you can run on 275s and 305s
Pull that fender out! you can put some big spacers up front and get more cornering grip . I forget the calculation, but every 1" you widen the car, its like lowering it 1" or dropping 50llbs as far as G loading capability. (something like that) even with the 245s up front, you widen the car up front and rear and you will help the handling.
are you using a KN filter or paper? if KN, use paper, do a dyno run and then wrap it in a tee shirt. that should provide about 10hp loss I would guess. or, you can do a throttle position stop, but that is tough to do too. there is not much HP difference between full throttle and a little before full throttle, but it would be interesting to check.
mk
12-24-2010, 12:18 AM
#24
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Brian
I will be bringing a set of 16" R6's ,Plus two sets , 295's front and 305's rear. One set of wets and the BFG slicks and a fender roller! Lots of combinations to try it will be interesting to see if you can get enough heat in the big fat meats to make them work.
I will be bringing a set of 16" R6's ,Plus two sets , 295's front and 305's rear. One set of wets and the BFG slicks and a fender roller! Lots of combinations to try it will be interesting to see if you can get enough heat in the big fat meats to make them work.
12-24-2010, 02:11 PM
#25
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ill have my set, (on the car, and maybe a couple rears) and the Louieville slugger! we will get you guys ALL set up before Im done!
12-25-2010, 12:32 PM
#26
Nordschleife Master
Some internet engineering below:
First you need to figure out the power curve shape that maximizes the [x,1.5x] average hp over different x rpm subject to the constraint that (max hp + max torque)/2 = c and 1.5x <= the physical rev limit of the engine. It's all a fools errand before you do that.
The class rules really reward high revving engines. My guess is that the high mid-range torque is really hurting you. If my guess is right, the logical solution is to put in a much bigger cam for starters. Then adjust the timing in a way that it kills the mid-range torque peak if it shows up below x rpm. Anything that hurts the top end breathing is likely to be counterproductive.
Whether you should lower c or increase weight depends mainly on tires. I don't know what the real tradeoff there is, but I think it's a lower c for twisty tracks and higher c for fast tracks.
It still makes sense to lighten the car as much as you can. The best thing to do is to make the weight by bolting a lead plate under the car. One wants to minimize the polar moment of inertia while keeping the mass center as close to the middle of the car as possible.
First you need to figure out the power curve shape that maximizes the [x,1.5x] average hp over different x rpm subject to the constraint that (max hp + max torque)/2 = c and 1.5x <= the physical rev limit of the engine. It's all a fools errand before you do that.
The class rules really reward high revving engines. My guess is that the high mid-range torque is really hurting you. If my guess is right, the logical solution is to put in a much bigger cam for starters. Then adjust the timing in a way that it kills the mid-range torque peak if it shows up below x rpm. Anything that hurts the top end breathing is likely to be counterproductive.
Whether you should lower c or increase weight depends mainly on tires. I don't know what the real tradeoff there is, but I think it's a lower c for twisty tracks and higher c for fast tracks.
It still makes sense to lighten the car as much as you can. The best thing to do is to make the weight by bolting a lead plate under the car. One wants to minimize the polar moment of inertia while keeping the mass center as close to the middle of the car as possible.
Last edited by ptuomov; 12-25-2010 at 05:52 PM.
12-25-2010, 07:19 PM
#27
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dont expect too much with tuning. the long stroke and big V8 of the 928 will give it some big torque, and thats just a product of things you wont be able to change. (unless you want to tune it to 8000rpm. )
I mean , com'mon, if you get the torque down to 200,your power will probably be near 150, which will kill the car.
Just restrict it a bit to drop the hp. dont worry too much about 200lbs of balast. it will take down the lap time by about 1 second. but, you can make up for it with bigger tires. (or stickier tires).
wident the foot print as much as you can. buy some 1" bolt on spacers from the GTS for the rear, or at least GT spacers.
Lets make you fenders look like mine, front and rear. 76" rear width, 73" front width.
)I mean , com'mon, if you get the torque down to 200,your power will probably be near 150, which will kill the car.
Just restrict it a bit to drop the hp. dont worry too much about 200lbs of balast. it will take down the lap time by about 1 second. but, you can make up for it with bigger tires. (or stickier tires).
wident the foot print as much as you can. buy some 1" bolt on spacers from the GTS for the rear, or at least GT spacers.
Lets make you fenders look like mine, front and rear. 76" rear width, 73" front width.
Some internet engineering below:
First you need to figure out the power curve shape that maximizes the [x,1.5x] average hp over different x rpm subject to the constraint that (max hp + max torque)/2 = c and 1.5x <= the physical rev limit of the engine. It's all a fools errand before you do that.
The class rules really reward high revving engines. My guess is that the high mid-range torque is really hurting you. If my guess is right, the logical solution is to put in a much bigger cam for starters. Then adjust the timing in a way that it kills the mid-range torque peak if it shows up below x rpm. Anything that hurts the top end breathing is likely to be counterproductive.
Whether you should lower c or increase weight depends mainly on tires. I don't know what the real tradeoff there is, but I think it's a lower c for twisty tracks and higher c for fast tracks.
It still makes sense to lighten the car as much as you can. The best thing to do is to make the weight by bolting a lead plate under the car. One wants to minimize the polar moment of inertia while keeping the mass center as close to the middle of the car as possible.
First you need to figure out the power curve shape that maximizes the [x,1.5x] average hp over different x rpm subject to the constraint that (max hp + max torque)/2 = c and 1.5x <= the physical rev limit of the engine. It's all a fools errand before you do that.
The class rules really reward high revving engines. My guess is that the high mid-range torque is really hurting you. If my guess is right, the logical solution is to put in a much bigger cam for starters. Then adjust the timing in a way that it kills the mid-range torque peak if it shows up below x rpm. Anything that hurts the top end breathing is likely to be counterproductive.
Whether you should lower c or increase weight depends mainly on tires. I don't know what the real tradeoff there is, but I think it's a lower c for twisty tracks and higher c for fast tracks.
It still makes sense to lighten the car as much as you can. The best thing to do is to make the weight by bolting a lead plate under the car. One wants to minimize the polar moment of inertia while keeping the mass center as close to the middle of the car as possible.
12-25-2010, 09:22 PM
#28
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What ? .... " the long stroke and big V8 of the 928 will give it some big torque,...." Few would consider a 4.7 liter to be a BIG V-8 ! and tuning can and does make a big difference...you should try it sometime
12-25-2010, 10:16 PM
#29
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I meant big, as in displacement compared to the normal race engines out there that are in the 2.0 to 3.6 liter range.
Tuning, how come anderson hasnt done any. oh yeah, he has enough hp now without it.
I would "try it" if anderson would send me a salvage tuning cable with connector so I can splice it in and use a shark tuner to see what I got. sure, i think there is more power there. but back on topic, its pretty tough to take out25% of your torque and not degrade HP at the top end, where it is used.
sure, not impossible, but tough. better to lose the 20hp up top, keep the torque (HPdown at post shift ) and call it a day. he wont know what he has until he gets on a dyno and does some testing, but pulling the timing way out might lose 10hp, 10ftlbs of torque and that might do it. my guess he will end up at 230t and 190 rwhp. add the weight and start racing. then, spend time saving up for some kind of rim package that gives you 10 to 11" rims.
Tuning, how come anderson hasnt done any. oh yeah, he has enough hp now without it.
I would "try it" if anderson would send me a salvage tuning cable with connector so I can splice it in and use a shark tuner to see what I got. sure, i think there is more power there. but back on topic, its pretty tough to take out25% of your torque and not degrade HP at the top end, where it is used.
sure, not impossible, but tough. better to lose the 20hp up top, keep the torque (HPdown at post shift ) and call it a day. he wont know what he has until he gets on a dyno and does some testing, but pulling the timing way out might lose 10hp, 10ftlbs of torque and that might do it. my guess he will end up at 230t and 190 rwhp. add the weight and start racing. then, spend time saving up for some kind of rim package that gives you 10 to 11" rims.
12-26-2010, 01:48 AM
#30
Nordschleife Master
Either it's me or the rest of the world on crack. Don't recall smoking.
(hp + torque)/2 constrained when torque > hp means that at minimum you have to bring the torque down to the max hp level.
Hello?
You need to kill the excessive torque in the mid range no matter what. You can't restrict the total air flow, you have to restrict the air flow per cycle. Short big intake runners, oversized headers, big cam, etc.
(hp + torque)/2 constrained when torque > hp means that at minimum you have to bring the torque down to the max hp level.
Hello?
You need to kill the excessive torque in the mid range no matter what. You can't restrict the total air flow, you have to restrict the air flow per cycle. Short big intake runners, oversized headers, big cam, etc.