Detuning a car to make P/W ratio
Discussion
Hi guys, our championship has just announced they're changing the rules for the coming season by switching from minimum weight and maximum engine size to power to weight.
They're setting the power to weight at 6.2kg per bhp and the car has to be weighed without driver and with whatever fuel is left over at the end of a race (typically 10 laps).
For me this presents a big problem as I spent last year chasing the limits of the regs only to be told I've got to now lose 36bhp OR add 190kg to my car (it absolutely sucks but if I want to race it is what it is).
Obviously I'd like to balance the car then go about cutting power which realistically mean cutting about 28bhp from the cars power (it makes about 195bhp now at the wheels).
I don't know anything about ecu tuning but I'm going to have to learn by the look of it. I have a completely customisable ecu as it is. Is there a way to cut that kind of power from the car safely without cocking up the engine?
They're setting the power to weight at 6.2kg per bhp and the car has to be weighed without driver and with whatever fuel is left over at the end of a race (typically 10 laps).
For me this presents a big problem as I spent last year chasing the limits of the regs only to be told I've got to now lose 36bhp OR add 190kg to my car (it absolutely sucks but if I want to race it is what it is).
Obviously I'd like to balance the car then go about cutting power which realistically mean cutting about 28bhp from the cars power (it makes about 195bhp now at the wheels).
I don't know anything about ecu tuning but I'm going to have to learn by the look of it. I have a completely customisable ecu as it is. Is there a way to cut that kind of power from the car safely without cocking up the engine?
VYT said:
can you just lower the rev limit?
I can but because of vtec the power curve has a huge step in it meaning id go from no power to the limit of permitted power in a short amount of time. Ideally I'd like vtec to come in earlier and to do something at the top end to flatten out the power curve keeping me at or near the limit.
Surely you should be looking to get the engine retuned for max torque by cam timing changes etc.
Remember the old saying power sells engines but it's torque that wins races.....
Adding weight just slows acceleration, braking etc. Another old saying from a guy that built up a certain race car and road car company was that we add in lightness.... His cars won a good few races, world F1 championships, indy 500 etc etc ;-)
Remember the old saying power sells engines but it's torque that wins races.....
Adding weight just slows acceleration, braking etc. Another old saying from a guy that built up a certain race car and road car company was that we add in lightness.... His cars won a good few races, world F1 championships, indy 500 etc etc ;-)
Don't add weight. A tyre does not have a linear coefficient of friction. The more you load it vertically the lower the lateral coefficient of friction will be. That's why an antiroll bar reduces grip at that end of the car. So if you add weight you'll have less grip and just more inertia to change direction of which will slow the response of the suspension.
Having spent yesterday chasing the people setting the rules I have pleaded with them to review the new rules, which they seem to be doing.
I honestly believe they didn't look at the situation and the implications, hence the reason they've said they will look at the situation.
As things are the draft rules that were issued have been revised so that the weight used to calculate the Power to Weight shall be the Driver, any remaining fuel load at the end of a race and the car itself...previously they expected the weight to be taken as the car only.
They seem to have also been under the impression that out of a requested (by the other drivers) power to weight ratio of 6.0kg per bhp to 6.2kg per bhp the 6.2 would have been the faster of the 2 options so I've corrected them and they seem to have listened as the chief technical advisor has said he will revise the draft rules to 6.0 but cant promise that anyone above him won't revert it back to 6.2 again.
IF they go ahead with the 6.0 I think scrubbing 11 bhp wont be an issue...fingers crossed and thankyou for the advise. I shall update everyone what course of action I took in case it proves to be useful to someone else later.
I honestly believe they didn't look at the situation and the implications, hence the reason they've said they will look at the situation.
As things are the draft rules that were issued have been revised so that the weight used to calculate the Power to Weight shall be the Driver, any remaining fuel load at the end of a race and the car itself...previously they expected the weight to be taken as the car only.
They seem to have also been under the impression that out of a requested (by the other drivers) power to weight ratio of 6.0kg per bhp to 6.2kg per bhp the 6.2 would have been the faster of the 2 options so I've corrected them and they seem to have listened as the chief technical advisor has said he will revise the draft rules to 6.0 but cant promise that anyone above him won't revert it back to 6.2 again.
IF they go ahead with the 6.0 I think scrubbing 11 bhp wont be an issue...fingers crossed and thankyou for the advise. I shall update everyone what course of action I took in case it proves to be useful to someone else later.
I mapped grahams car ^^ and had to trim a bit of advance out at peak power to just get the power to weight limit.
You're in a good position in that you can just trim the bit of the power curve where you are over the limit, and leave the rest as it is.
For best effect you need to have fly by wire throttle, that way you can do it by reducing throttle angle in the affected area, and reintroduce it when the power starts to drop of again.
Using the ignition advance method is ok if you only have to lose a few hp, but nearly 30hp is a lot, you don't want your exhaust temps rocketting down revitt straight for example ..
A fixed restrictor achieves a similar same thing, but you can't modulate the restriction like you can with a fly by wire throttle. By controlling the restriction electronically you can put the car absolutely on the hp limit over as wide a rev range as possible
You're in a good position in that you can just trim the bit of the power curve where you are over the limit, and leave the rest as it is.
For best effect you need to have fly by wire throttle, that way you can do it by reducing throttle angle in the affected area, and reintroduce it when the power starts to drop of again.
Using the ignition advance method is ok if you only have to lose a few hp, but nearly 30hp is a lot, you don't want your exhaust temps rocketting down revitt straight for example ..
A fixed restrictor achieves a similar same thing, but you can't modulate the restriction like you can with a fly by wire throttle. By controlling the restriction electronically you can put the car absolutely on the hp limit over as wide a rev range as possible
spitfire4v8 said:
I mapped grahams car ^^ and had to trim a bit of advance out at peak power to just get the power to weight limit.
You're in a good position in that you can just trim the bit of the power curve where you are over the limit, and leave the rest as it is.
For best effect you need to have fly by wire throttle, that way you can do it by reducing throttle angle in the affected area, and reintroduce it when the power starts to drop of again.
Using the ignition advance method is ok if you only have to lose a few hp, but nearly 30hp is a lot, you don't want your exhaust temps rocketting down revitt straight for example ..
A fixed restrictor achieves a similar same thing, but you can't modulate the restriction like you can with a fly by wire throttle. By controlling the restriction electronically you can put the car absolutely on the hp limit over as wide a rev range as possible
Thats a result I'd say - 190kg is a shed load of weight to add!You're in a good position in that you can just trim the bit of the power curve where you are over the limit, and leave the rest as it is.
For best effect you need to have fly by wire throttle, that way you can do it by reducing throttle angle in the affected area, and reintroduce it when the power starts to drop of again.
Using the ignition advance method is ok if you only have to lose a few hp, but nearly 30hp is a lot, you don't want your exhaust temps rocketting down revitt straight for example ..
A fixed restrictor achieves a similar same thing, but you can't modulate the restriction like you can with a fly by wire throttle. By controlling the restriction electronically you can put the car absolutely on the hp limit over as wide a rev range as possible
itdontgo said:
Don't add weight. A tyre does not have a linear coefficient of friction. The more you load it vertically the lower the lateral coefficient of friction will be. That's why an antiroll bar reduces grip at that end of the car. So if you add weight you'll have less grip and just more inertia to change direction of which will slow the response of the suspension.
On the other hand, more power will get you more straight line speed on the tracks with decent straights...If you were really clever you could tweek your power and weight to get you the best advantage for each track
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