Just wondering if anyone has tried to find the max power per gear via a dyno and setup a shift light and set that particular rpm for that gear via the shift light for racing??


I know it may be extreme for most. But I was just wondering if anyone has done something similar. I see a lot of higher power dynos with big dips before redline which in reality would make the car slower while racing by holding it to redline as suppose to shifting at the top of the power band.

So lets say you raised your rev limiter and its now 8k but peak power is 7100rpm in a certain gear which matches the next gear power band. So instead of shifting at 8000rpm u obviously shift 7100.


Below is an example of a modded 996tt. Stock Rev limiter.

The difference between shifting at 6000rpm and 6750rpm is nearly ~100wtq and ~70whp.


Just something I have been pondering. Seems there are some guys that can drive and some that aren't as good, guys running 9's per say which is somewhat rare on this platform. The guy from USP I believe (chris green) who runs nines and I see people consistently saying "he can drive." But also knowing the best shift/power points would be most important?? Any thoughts?

 

To be precise , you have the dyno sheet now ,,now you need to find the gear ratio's in your trans>> Then there is a formula to figure out the RPM drop, gear recovery, between each shift from the gear ratios..
A general rule of thumb is its always better to shift above peak HP by 10% higher RPM or past when HP starts to drop off...
That is because an engine accelerates faster as it climbs and past peak power,so when you shift you want to be in that upper zone..If the RPMs drop lower it will take more time to accelerate to the higher HP curve..
A few months ago I got into a more detail post on another thread about this..
The only exception usually is the 1st to 2nd shift because you need the TQ to get off the line,,thats if you can use it all with the cars setup of traction and chassis, some short shift to use second more so then first because the launch may be to violent with a lot of HP or a wide gaer ratio spread between 1 and 2,,,Like we have..
That's why most factory redlines are always above the peak HP rating..

 

The above dyno is not mine. I see what ur saying. I guess dynoing each gear would make it more precise as suppose to utilizing ratios. I was just saying around that range but yes shift 15% into the next power band so that shift and rev drop still keeps you in the power range.

Just seeing if guys have done it and if it makes a big difference.

 

With all the bike dynoing I did on my dyno,,
It is not that important to do each gear,,you can , because if you get a good pull it will still be pretty close to the rest as far as seeing the power drop off level and that's all you are concerned about..

 

Its a great question. I hear about guys raising the rev limiters without actual data and wonder the same thing.

 

Its good to have a higher rev limit especially for the 1 to2 shift because its a wide spread between those gears as compared to the rest, the biggest RPM drop, so the higher up in RPMS you shift from 1st it will land higher in the HP power range area when it goes into 2nd..Thats the only shift I go to 7400 with..

 

Here's a little chart I worked up for a stock 911TT.


As you can see, buy the blue areas, you would shift when your making more torque (to the rear wheels) in the next gear than staying in the current gear, or when you hit redline.


Basically shift at redline in 1st through 3rd and then shift at 6,000 for 4th and 5th.

 

Here's one I worked up for my GT610 with a 7,000rpm rev limit.


On this chart I use wheel hp/tq number versus engine hp/tq on the other graph.


Later, Steve

 

Added Rep points to you buddy!!! Nice going.

 

Keep in mind you are going for a big build with 3076 turbos, correct?

Your peak horsepower will be at redline or near it for every gear, because those turbos are large enough to need all the air our 3.6 engines can provide.

Even if you raise the rev limiter, I bet those turbos are still in their efficiency range at 7k to even 8k rpm.

It only makes sense to short shift if you are running out of turbo in the upper rpm range... and you won't be.

 

Thanks!!! Makes sense.

 

You Really need to know the gear ratios and then you can figure out the RPM drop between each gear with the formula( which I have in my tech books if needed), so you will know when to shift to keep the RPMs from dropping down to low,,thus not taking more time to get into the upper HP curve,, Then you apply it to your dyno sheet curve..
That is the best and only way to plot a gear shift point for maximum acceleration...Its proven ,,, try shifting your car a peak thru the gears and then go about 10% or more above and I will bet you will have faster times..
The only one gear shift that might not apply is the 1 to 2 shift because of the limitations of traction and HP relationship,,,The TQ range is important off the line..
How many of you have ever seen a redline at or below peak HP on a race vehicle,,I don't think to often...
Just sharing my info and experience here...

 

The heads and cams effect the shape of our power curve as well as the size of our turbos.


Even with my small GT28/64 turbos, I need all 7,000rpm in every gear.


Later

 

Here is USP doing 9.4 @ 153, says its the new record for a 996, video was just posted on my youtube channel.

You can see at 20 seconds and on where he is shifting (in car camera), he is shifting earlier for 1st and 2nd and shift later in 3rd gear and just holds out 4th for the quarter, pretty interesting to see!!! Funny how this just posted today too!

 

It appears to me that he is shifting at the same RPM in every gear.


Later, Steve