Optimal Gear Transition

[marcinw]

Hey Guys,

Yet another new MPS owner picked up the 2010 GenII MPS just over a week ago and can't get enough.

I have a general question in regards to getting the best performance out of the car (on the track etc).

I've noticed the car is a little lazy around 1st and 2nd gear, i'm guessing this is due to the boost being electronically limited at these gears?

At what RPM should the optimal gear changes occur

i.e

1st - 2nd
2nd - 3rd
3rd - 4th
?

Or to put it another way, what is the best combo in your opinion to approach the claimed 0-100km/h time of 6.1 seconds.

Thanks

Marcin

[SarcasticOne]

not sure about the new model MPS's....
if it's a stocker, you probably want to change gears around 5750-6000 rpm
if you get it tuned, they can raise the rev limit so that you hit 100 in 2nd

[bd581]

peak power is around 5,500rpm. Power drops off rapidly after that, so not much point revving further than that.

[Caffeine Fiend]

peak power is around 5,500rpm. Power drops off rapidly after that, so not much point revving further than that.

Yeap, I don't take mine past 5500.

On a stock car that's when the throttle plate starts closing and the wastegate starts opening


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[luke 3mps]

gen 2's dont get the drop like the gen 1. id say 6000rpm after looking at the tunehouse dyno day we had. if u changed at 5500 u will still drop into the meat of the next gear

[Doug_MPS6]

Look at the torque curve for your mod settings. There's one on the back of the brochure your car came with. It's pretty flat over 5,000-5500. Not much point in pushing much past that, as all you are doing is generating noise, attracting attention and more significantly, running higher piston speeds than required, the prime cause of engine wear. Select a shift point so the next gear lands you squarely at the bottom of the steepest part of the torque curve, and where the turbo is spooling nicely, so you have maximum pull for the longest time before the next shift is required. I almost never see 5,000 on mine as the bottom end is so strong.

[bd581]

The ONLY benifit of changing at redline or higher than 5500-6000rpm would be if your going for a fast 0-100km/h time as you will eliminate the time taken to change gear.
This was proven on Aussie Top Gear by Shane Jacobson (Kenny) who couldn't get anywhere near the 0-100 times claimed for the Corvette ZR1.
After he decided to not change from 2nd-3rd he came much closer to the claimed times.
But that all depends on he car an its ratios.

But i wouldn't recomend doing that. And it will have little benifit in circuit racing. Keep the revs in the engines maqimum torque band.

[rogwick]

Agree with the above comments but just to add, the BNR stage III turbo pulls hard right up to 6,000RPM.

[Doug_MPS6]

ROG, Hi, exackle! That's why I noted "Look at the torque curve for your mod settings". In your example with the bigger turbo, blowing more air in means your engine won't run out of breath as early as, say, a stock setup. Simply improving breathing, such as with DP and TIP will do the same thing to a degree. Once you get much beyond this, plus bigger turbo and/or raised ECU boost psi settings and more open exhaust, then one would start to look at different cam profiles to get more air in. Has anyone explored different cam profiles for these cars and the question of how such consideration interacts with the variable valve timing?

As an added note, I reckon if you are going to start routinely running at higher rpm, then you need to consider a good blue-printing and dynamic balancing job. As a generalization, with most of the sorts of engines we are playing with, under 5,000 rpm is safe enough but start running them out way past 6,000 on a regular basis, it'd be nice to know they weren't going to fly apart due to balance issues. If I keep my car long enough for it to require any kind of rebuild, I'll consider a full balance and upgraded internals, fuel pump and clutch, bigger turbo, improved exhaust and tweaked cam profiles then, but not much sense in pulling it down now while it's going so well. Hard enough to stay legal as it is!

[luke 3mps]

garrett 3071/76 will pull u to 7-8 rpm