Hey all, I will be posting pics and making MY thread about being a new corvette owner in the next week when the car arrives, but I have a question! 2008 ls3 manual, totally stock, what RPM is best to shift at for all out acceleration? I am telling myself that someone here will tell me that redline RPM does not always make the most power nor the best place to shift, but when you rev higher your shift into the next gear will start at a higher RPM due to shifting from the higher previous RPM. someone please straighten this out for me, any advice helps thanks!!!!

 

For best 1/4 mile performance stock I was shifting at 6500 rpm and now with a cam i shift around 6900-7000 rpm

 

6500 rpm.

You are correct that at 6500 you are making less than peak HP, but the goal is to maximize average HP so shifting at redline is the way to go.

 

has anyone ever tried this at the track to see the time and mph difference is starting at 6000 to 6500 in 100 rpm increments?

 

I've done it in an auto and seen that it works. I don't think I'm consistent enough to do it in a manual.

 

setting the shift points with a tuner?

 

yes. doing a run, noting the time & mph and then changing the shift points with the software and take another pass.

 

Anybody try shifting at max torque rpm before you start loosing torque? In my last dyno tune my curve shows that to be about a thousand rpm before redline and before peak HP. It seems like one would get best times by driving as close to max torque as possible.

 

The theory is that it's not so much about shifting at max HP but rather to have your shift extension fall back down to where your peak torque occurs.

I've applied this to my car (as well as several others) and it seems to work very well because when I'm getting a car dialed in, the overall ET is really just one part of the equation. I'll actually break a timeslip into 5 different intervals and measure each one to see where I'm showing improvement (or possibly going in the wrong direction) based on each shift rather than the entire timeslip.

With an automatic it's definitely easier because if the transmission behaves itself and shifts where it's supposed to (which mine now does THANKFULLY) you just adjust your shift points accordingly and you're all set. With a manual transmission however it can be greatly affected by driver skill because someone who doesn't shift as quickly could potentially have the RPMs drop too low and right out of peak torque.

To give you an example using real numbers, my car shifts right around 7200RPM and falls back to 5600 which is toward the top end of my very flat torque curve (which ranges from 5050RPM up to 5900RPM). If my car were a manual transmission I would look to replicate that in order to run my best possible time.

I wasn't sure how much the RPM drops on each shift for a stick car so I took a look at one of Joe G's scans (hopefully he won't mind) and he typically loses about 1700-1800RPM after each shift. Therefore, if he was driving my car and it had a stick his target shift would be at 7300-7400RPM to have it drop down to the 5600 that seems to work very well with my engine. For a different driver who might shift much more quickly (say, losing only 1400RPM after each shift) his target RPM would be slightly lower at only 7000RPM.

Sorry for the longwinded explanation but I happen to be extremely bored at work today and thought this'd be a good way to kill a few minutes, ESPECIALLY SINCE I'VE BEEN RAINED OUT TWICE NOW AT THE DRAGSTRIP AND IT LOOKS LIKE THE NEXT TWO SCHEDULED RACES WILL BE TOO!!!.

Oh I'm sorry, was that out loud???

 

Good explanation and sound thinking. Thanks for your thoughts.

 

I knew this would spark some good Q & A thanks

 

I don't think that's the theory for an M6. You have a high stall torque converter and are likely getting some additional torque multiplication from it upon the upshift. Switching back to the stock torque converter might get a different result. Likewise, switching to a 4200 stall might result in a different optimal shift point for your motor.

The relative location of Peak HP and Peak TQ are pretty highly correlated on LSX motors, so I'm not sure our data is good enough to answer the debate.

The interesting example is the Z06 which holds its HP well beyond peak HP. TQ is dropping significantly as it runs up to redline due to the fact HP is slightly dropping and rpms are increasing. I believe Ranger has stated that the best performance is achieved from running that car right up to its redline. I have not cranked the numbers, but there is a pretty good chance that shows that maximizing average HP is better than maximizing average TQ.

 

reviving this thread.....

08 z-51, MN6 bone stock.

Does anyone know when running the 1/4 mile if shifting at 6500-6600 rpm (redline) will net the best/fastest time assuming all other conditions stay the same?

 

ttt

 

Yes it will.

 

Here's some good info on this topic.

http://forums.corvetteforum.com/c6-t...eleration.html

 

Your always helpful, thanks Joe G.