Loss of traction in 3rd gear with tune?

[E30 Racer]

For those of you with FBO and Stage 2 tunes, do you lose traction during hard straight-line acceleration in 3rd gear (i.e., due to wheelspin)? Please respond only if you have direct 1M experience, as 135/335 models don't have an LSD and the tires are narrower.

[octainejunkee]

i used too.
Get your geometry set up to run less camber and more toe in at the rear, then fit 295,30,19 michelin pss rubber on the rears and you wont be able to spin up in second let alone third..

cheers jamie

[SpencerMH]

I'm running 295/30/19 and definitely can't spin them in third unless it's wet out and I have plenty of power, not fbo, but running e85 all the time, bigger tires are great on this car. Now if you don't have mdm selected you can get the traction control to kick in, in third, but mdm fixes that.

On stock sizing and in mdm, I could get wheel spin in 4th.

[Kgolf31]

Originally Posted by E30 Racer

For those of you with FBO and Stage 2 tunes, do you lose traction during hard straight-line acceleration in 3rd gear (i.e., due to wheelspin)? Please respond only if you have direct 1M experience, as 135/335 models don't have an LSD and the tires are narrower.

Garrick, what tires are you running in the rear?

Could it be a combination of colder tires (not up to temp), not enough toe, or simply just too much boost?

[E30 Racer]

Originally Posted by SpencerMH

I'm running 295/30/19 and definitely can't spin them in third unless it's wet out and I have plenty of power, not fbo, but running e85 all the time, bigger tires are great on this car. Now if you don't have mdm selected you can get the traction control to kick in, in third, but mdm fixes that.

On stock sizing and in mdm, I could get wheel spin in 4th.

Wheelspin in 4th? Hard to believe you'd see that on dry roads (with traction/stability control fully disabled)? What power/torque are you seeing, and what intercooler are you using?

[E30 Racer]

Originally Posted by Kgolf31

...what tires are you running in the rear?

Could it be a combination of colder tires (not up to temp), not enough toe, or simply just too much boost?

I'm still on stock-sized PS2s as the car only has 25xx miles on it. I don't see traction loss in 3rd personally, even with the cold Ohio temperatures we're experiencing. That's what surprises me...I was expecting it to be an issue.

[SpencerMH]

Yes I know but on track it was a issue for the 3-4 shift, it had to be babied, and if in gear coasting through a brake zone, when I return to the gas it again needed serious modulation. I am on stock intercooler, downpipes and axle back. I run a jb4 g5 though with e85 daily and on track I fill up with race gas, on the maps that take advantage of the octane I'm certainly at FBO power levels, I would guess higher but haven't been to a Dyno with the 1m. I highly recommend a piggyback and e85 for dd, it's awesome, smooth, high advance, high boost power. I have tried to avoid fmic and dp's specifically to try to save some sort of warranty, but I may forsake that idea soon.

[Pete_vB]

You should stick 3rd, I'd only be surprised you didn't.

The stock 1M is borderline on traction in 1st: with PS2s it won't stick, but with PSS and good pavement it sometimes will. In a straight line in 2nd you'll sometimes break traction in the dry on bad pavement, but it's rare. Wet, bad pavement or a hard shift in 2nd can be an issue.

In order to break traction in the same way in other gears the car needs to have the same amount of thrust to the wheels. A stock 1M in 1st has about 3500 lbs of thrust, in 2nd about 2200 lbs of thrust, 3rd 1500 lbs.

Three ways to increase thrust at the wheels: increase engine torque, reduce the effective gear ratio (smaller tires, shorter gears), reduce losses (friction, rotating inertia). Leaving the losses and gear ratio constant, you'd need to increase engine torque ~50% to have 3rd gear break loose like 2nd does stock, or increase torque by ~130% to have 3rd break loose like 1st. That would be ~800 ft lbs of torque at the wheels.

[Kgolf31]

Originally Posted by E30 Racer

I'm still on stock-sized PS2s as the car only has 25xx miles on it. I don't see traction loss in 3rd personally, even with the cold Ohio temperatures we're experiencing. That's what surprises me...I was expecting it to be an issue.

Whoops, didn't read OP correctly.

Can't wait to see the 1M, you should bring it out for AutoX once for giggles.



I'm surprised you don't lose traction. When I drove the 1M in NC it was hard to keep power down in 2nd with out spinning.

[E30 Racer]

Originally Posted by Pete_vB

You should stick 3rd, I'd only be surprised you didn't.

The stock 1M is borderline on traction in 1st: with PS2s it won't stick, but with PSS and good pavement it sometimes will. In a straight line in 2nd you'll sometimes break traction in the dry on bad pavement, but it's rare. Wet, bad pavement or a hard shift in 2nd can be an issue.

In order to break traction in the same way in other gears the car needs to have the same amount of thrust to the wheels. A stock 1M in 1st has about 3500 lbs of thrust, in 2nd about 2200 lbs of thrust, 3rd 1500 lbs.

Three ways to increase thrust at the wheels: increase engine torque, reduce the effective gear ratio (smaller tires, shorter gears), reduce losses (friction, rotating inertia). Leaving the losses and gear ratio constant, you'd need to increase engine torque ~50% to have 3rd gear break loose like 2nd does stock, or increase torque by ~130% to have 3rd break loose like 1st. That would be ~800 ft lbs of torque at the wheels.

Have you personally driven a 1M with a tune? With elevated boost and stock sized PS2s, second gear traction is a problem at WOT. With 500ft-lbs at the crank, I would expect 3rd gear traction to be limited as well.

[tracer bullet]

Originally Posted by E30 Racer

...tires are narrower.

Keep in mind that all things being equal (car weight, tire psi, sidewall strength, etc), a wider tire does not put more rubber on the road, it only changes the shape of the contact patch. To put more rubber down you need to lower the tire pressure (or increase the weight placed on it). Those 2 things would increase your grip, as would have course getting a "stickier" brand / model of tire or warming them up ahead of time.

(Obviously that's a super simplistic version of it all, just saying not to think that something like say a 20% wider tire automatically means 20% more rubber on the road and 20% more grip)

I expect you already know this, mostly just trying to suggest considering a psi change or pre-warming up of what you have, if you haven't tried it already.

[Kgolf31]

Originally Posted by tracer bullet

Keep in mind that all things being equal (car weight, tire psi, sidewall strength, etc), a wider tire does not put more rubber on the road, it only changes the shape of the contact patch. To put more rubber down you need to lower the tire pressure (or increase the weight placed on it). Those 2 things would increase your grip, as would have course getting a "stickier" brand / model of tire or warming them up ahead of time.

(Obviously that's a super simplistic version of it all, just saying not to think that something like say a 20% wider tire automatically means 20% more rubber on the road and 20% more grip)

I expect you already know this, mostly just trying to suggest considering a psi change or pre-warming up of what you have, if you haven't tried it already.

He drives an E30 in DSP for SCCA Solo, and is good doing it. He knows a little bit about tire pressure

[tracer bullet]

Originally Posted by Kgolf31

He drives an E30 in DSP for SCCA Solo, and is good doing it. He knows a little bit about tire pressure

Cool

[Pete_vB]

Originally Posted by E30 Racer

Have you personally driven a 1M with a tune? With elevated boost and stock sized PS2s, second gear traction is a problem at WOT. With 500ft-lbs at the crank, I would expect 3rd gear traction to be limited as well.

Nope. But I'm used to significantly more powerful/ traction challenged cars. I've driven and done the math with lots of cars, from supercharged vipers to my 911s to various competition cars. It's straightforward, and I can point you to some racing simulators that you can use to double check or calculate it for yourself if you're interested. The rules are the same if you're talking a 1M or Hennessy's 267 mph texas mile GT.

A gear simply divides torque, that's its function. 500 ft lbs at the crank is only ~25% up from real world stock, the 3rd gear ratio is 1.542, 2nd is 2.315. Even just 2nd to 3rd you're losing more torque from the gear reduction than you're gaining from the extra boost, simple as that.

[1'M Blue]

Stage 3 Evolve here ... 3rd gear WOT lights up !

[Pete_vB]

Originally Posted by 1'M Blue

Stage 3 Evolve here ... 3rd gear WOT lights up !

Under what conditions and with what tires, exactly?

[1'M Blue]

Originally Posted by Pete_vB

Under what conditions and with what tires, exactly?

Normal road conditions and stock michellins .

[Pete_vB]

So I'd suggest that if on a good road in warm temperatures you can roll in and light up the stock michelins there is something wrong. Most likely the PS2s are heat cycled out.

On a stock car I can light up 265 R-S3s in 3rd when it's cold, but I'd say that's got everything to do with the tires and nothing to do with the car.

[bdaddylo]

Originally Posted by Pete_vB

So I'd suggest that if on a good road in warm temperatures you can roll in and light up the stock michelins there is something wrong. Most likely the PS2s are heat cycled out.

... or rear alignment issues.

[Alexim]

I'm running yoko ad08 295/30/19 now and when going wot on 3rd, i get the dtc light.. but if it's off, then I don't really feel any loss of traction anynome... with stocks, it was a nightmare!!

[1'M Blue]

Originally Posted by Pete_vB

So I'd suggest that if on a good road in warm temperatures you can roll in and light up the stock michelins there is something wrong. Most likely the PS2s are heat cycled out.

On a stock car I can light up 265 R-S3s in 3rd when it's cold, but I'd say that's got everything to do with the tires and nothing to do with the car.

Pete thanks for your input. But Im not really getting what you are saying ..

I mentioned that I have a powertfull tune (Stage 3 evolve) and my rear tires and stability lights as well flash even at about 3rd gear on a wide open throttle.. Umm Is there a problem with that that I am not seeing ?

[Pete_vB]

Originally Posted by 1'M Blue

Pete thanks for your input. But Im not really getting what you are saying ..

I mentioned that I have a powertfull tune (Stage 3 evolve) and my rear tires and stability lights as well flash even at about 3rd gear on a wide open throttle.. Umm Is there a problem with that that I am not seeing ?

Most would consider having more traction a good thing. If it's just the stability light flashing, however, you may not have an issue. Depending on the tire, car and pavement, peak traction is reached at ~8% slip (and as much as 20%, but that's not with good tires on a good road). Traction control kicks in well before then, so the TC lighting doesn't mean you've exceeded traction.

Assuming you think traction is a good thing (not everyone does) decent tires in good conditions will easily let you hold traction in 3rd gear.

A little more about friction and tire slip under acceleration for those interested:
http://www.motortrend.com/features/p...ction_control/