Who's faster than us?

[Suprgnat]

Originally Posted by iminhell1

Yes really.

It's due to the HP curve. Peak numbers are really meaningless in the real world. It's teh rate of change that matters when it comes to acceleration.

No clue what is done to this car but the numbers look about correct for this discussion,




If you pay attention to the slope of the HP you'll see it starts to flatten out after about 4,500 RPM. That translates to accelerating slower after that point.
If you go out to 6,500 the power is dropping significantly. Shifting here will give you a 13 second car. Great for sandbagging on Subi's,


Do a bunch of acceleration datalogs. Compare times to shift RPM.

The two lines crossing at ~5250 RPM is no coincidence. With all that torque behind it, that's where I'd shift-ish.

[iminhell1]

Originally Posted by Suprgnat

The two lines crossing at ~5250 RPM is no coincidence. With all that torque behind it, that's where I'd shift-ish.

That's just math, HP = (TQ x RPM) / 5252

[Suprgnat]

Originally Posted by iminhell1

That's just math, HP = (TQ x RPM) / 5252

Exactly (math's cool), but on the higher HP maps, they're all dropping off by ~5600-5700 RPM. No point in going there when a shift drops you into the meat of your torque.

[chris_flies]

N52's going all the way to the happy place, baby! 6600rpm and then it's shiftin' time, because NA

[asiflicious]

Originally Posted by chris_flies

N52's going all the way to the happy place, baby! 6600rpm and then it's shiftin' time, because NA

I was wondering when you'd chime in with your NA supremacist propaganda

[chris_flies]

Originally Posted by asiflicious

I was wondering when you'd chime in with your NA supremacist propaganda

What can I say? It's my thing!

EDIT: And I never mean to be a douche about it, it just can come across like that to some people, unfortunately...

[asiflicious]

Originally Posted by asiflicious

Going to Mexico tonight to meet up with an STi, Evo, and maybe a pure stage 2 turbo N55 135i. I'll come back with the results

Well looks like the nice weather is gone. Now it's raining again normally I wouldn't care too much but my rear tires are completely bald and idk if going 100+ on Mexican highways is a good idea lol

[chris_flies]

Originally Posted by asiflicious

Well looks like the nice weather is gone. Now it's raining again normally I wouldn't care too much but my rear tires are completely bald and idk if going 100+ on Mexican highways is a good idea lol

Darn those tropical conditions

[Fender13Bender]

Raced my buddies stock C5 Z06 from about 60 to 120 ish. 2012 N55 135i here.

I have catless downpipe, intercooler, MHD stage 2+ 93 octane tune.

We were dead even until I went into the upper rpm range. His car pulls hard up top and mine falls flat. He had about a fender on me.

E30 tune I should be able to beat him.

[k3vin0615]

RS7 and TT Rs will spank you guys like unruly children

[duder13]

Originally Posted by Suprgnat

Exactly (math's cool), but on the higher HP maps, they're all dropping off by ~5600-5700 RPM. No point in going there when a shift drops you into the meat of your torque.

It's more complicated than that, because you have to take the next gear's ratio into account. There's a calculator than you can dig up online that allows you to enter torque and gear ratios to give you the optimum shift points.

edit: here it is http://glennmessersmith.com/shiftpt.html

[asiflicious]

Originally Posted by k3vin0615

RS7 and TT Rs will spank you guys like unruly children

They'd have no problem with any F30 either

[k3vin0615]

Originally Posted by asiflicious

They'd have no problem with any F30 either

absolutely.

[Suprgnat]

Originally Posted by duder13

It's more complicated than that, because you have to take the next gear's ratio into account. There's a calculator than you can dig up online that allows you to enter torque and gear ratios to give you the optimum shift points.

edit: here it is http://glennmessersmith.com/shiftpt.html

I am familiar with the calculators (made my own, actually) and am familiar with both 135i and 128i gear ratios.

[BimmerAg]

Originally Posted by duder13

It's more complicated than that, because you have to take the next gear's ratio into account. There's a calculator than you can dig up online that allows you to enter torque and gear ratios to give you the optimum shift points.

edit: here it is http://glennmessersmith.com/shiftpt.html

Yep, precisely. It's called tractive force, and it's basically a calculation of the force applied through the tires to the road. F=m*a, or we can rearrange to find that acceleration=Force/mass. From this, we can see that to maximize acceleration we want to maximize the force applied to the road. Using the torque curve and gear ratios, we can find the tractive force vs speed in each gear. The optimum shift point is where the lines intersect, and the force from the higher gear is higher than the force from the lower gear.

[iminhell1]

Originally Posted by k3vin0615

RS7 and TT Rs will spank you guys like unruly children

No. They won't.
And they weren't too happy about it either. LOL

Got me a Hellcat Charger not too long ago too. Was close and I really have to be on my shift game.

[Suprgnat]

Originally Posted by BimmerAg

Yep, precisely. It's called tractive force, and it's basically a calculation of the force applied through the tires to the road. F=m*a, or we can rearrange to find that acceleration=Force/mass. From this, we can see that to maximize acceleration we want to maximize the force applied to the road. Using the torque curve and gear ratios, we can find the tractive force vs speed in each gear. The optimum shift point is where the lines intersect, and the force from the higher gear is higher than the force from the lower gear.

Ran the numbers when I got home from work. I'm truly shocked . The torque curve on map 7 looked far more precipitous after ~4600 RPM than is reality. I should have actually done the math (or used one of my own calculators, doh!).

[iminhell1]

It's interesting. Using the dyno data I posted and that calc with the auto gearing, it says optimal shift should be around 6,000 RPM.
But I can tell you I won't shift that high. In all my drag passes last year shifting before that was where I was fastest. And it was 100% repeatable. Pretty much for every (about) 250 rpm over my (about) 5,200 goal I'd loose 0.10 sec on my ET.

[Suprgnat]

Originally Posted by iminhell1

It's interesting. Using the dyno data I posted and that calc with the auto gearing, it says optimal shift should be around 6,000 RPM.
But I can tell you I won't shift that high. In all my drag passes last year shifting before that was where I was fastest. And it was 100% repeatable. Pretty much for every (about) 250 rpm over my (about) 5,200 goal I'd loose 0.10 sec on my ET.

Perhaps it's a traction issue. Too much torque for your tires? Time for some Hoosier DOT drag radials?

[k3vin0615]

Originally Posted by iminhell1

No. They won't.
And they weren't too happy about it either. LOL

Got me a Hellcat Charger not too long ago too. Was close and I really have to be on my shift game.

I bet you also walk teslas P100d.

Iwant2beleaf.jpg

[chris_flies]

Originally Posted by k3vin0615

I bet you also walk teslas P100d.

Iwant2beleaf.jpg

Past 155, of course!

That is, if his car is delimited...

[iminhell1]

Originally Posted by k3vin0615

I bet you also walk teslas P100d.

Iwant2beleaf.jpg

No I don't. I hate racing those things.
A full weight on Ludicrous tune, consistent 7.0x in the 1/8th @ 102'ish MPH. Best I have managed was 7.4x and 99MPH.
A lightweight one, was doing 6.7x's.

I'd like to get out of the hole that fast. Just don't know that the trans will agree with it.