LVDell

So, if you are looking at the following 3 charts published by PAG for our cars (MkII 6GT3) how do you interpret the optimal shift point. I can't imagine banging up to redline for every gear is the optimal for maintaining max torque.

Would like to be able to shift at more appropriate spots on the curve to maximize the power of the motor.

Of course, this is for track use.

TIA!

KOAN

7000 rpm looks pretty good to me. When you shift in most gears, you fall to about 5000 rpm or above, and stay in a pretty high torque band. I'm glad you raised this question. Since the GT3 is new to me, I was wondering where to shift, and have not gotten around to figuring it out. I'll not get a chance to drive for at least 6-7 weeks.

LVDell

Not sure if there is a mathematical formula that can be employed here but just "eyeball" statistics tell me that between 6500 and 7000 rpm would keep you in the proper range as anything above 7000rpm drops off sharply on the torque curve.

JMeager

The basic idea is that you change at the highest power point that provides you the best torque when it falls back to the next gear. (ie so you are in the meat of the turque curve). Using the above power curve you want to ensure you stay from 5000rpm and above, 7000rpm in most gears will do this...

Using the graphs,
First, 7500 will drop to 4300 in second. It could be argues to rev this slightly longer than 7500rpm
Second revving from 4300 - 7200 ish. Change around 7200rpm which drops you into third at a touch over 5000rpm.
Third, 5000 - 7000rpm, drops you to 5500 in 4th
Fourth 5500 - 7000rpm, drops to 5750 in 5th
Fifth - 5750 - 7ish..... from here....just go.......

db_gt3

Depends on what lays ahead of you at any given point. Your eyes are the fastest thing on the track. It's all about visualization. Most guys who are really fast are doing a lot of short shifting; no need to abuse the drive train.

multi21

I agree with Meager and db on both accounts. The power on this car is from 5k-7k. I go above 7k if it's not worth shifting again before a corner, but anything lower than 4k and the engine tends to bog down a little.

The auditory and feel of the engine tell me where it's at in the rev range without looking at the tach. The symphony starts at 6k. As it approaches 8k, the sound tends to be a more whiny and the feel of the engine doesn't seem to be as tight. This last one is somewhat hard to explain, but I can feel the difference in the pedal and of course, the butt o meter.

LVDell

Pete, I totally understand what you are getting at. I shift at ALL places on the traack based on auditory feel as well as visual markers knowing where I need to be. The one place I actually do look at the tach is the LOOOOOOOOOOONG back stretch. The reason I posed this question is that I am going to hook up the RPM sensor to my traqmate and I want to see if where I think I am shifting is where I actually should be shifting.

Great input from all! Thanks everybody

KOAN

I really like the traqmate data. It has surprised me on some tracks, and has helped me dial in my visceral input to correspond what is actually happening. I was sure, for instance ,that I was full throttle on the last turn before the front straight at Road Atlanta....NOT! It is great to see whether shifting or not shifting for a short stretch is time worthy, like 9-11 at Mid Ohio. The seg. analysis over laps performed both ways is very useful.

jesc996tt

drop in RPMs while shifting will depend also how fast shift/clutch release happens and also type of clutch/flywheel ( lighter c/f = faster/greater drop in RPMs)
the graphs apply to stock oem clutch/fwl.
my understanding from PDE/racers shift close/or at redline.

Paul 996

wow really? must of missed that one somewhere.. You sure a different clutch and flywheel are going to change the cars gearing? Might want to re-think that one. The lighter flywheel does let the rpms drop faster as you say "before" the next gear is engaged but once the gear is engaged the rpms are "exactly" where they would always have been related to your speed... that is all.

Paul 996

Hey Dell,

from the chart it looks like the GT3 has one heck of torque spike from 4750 to 5250.. If I was coming out of a corner that is where I would want to land and def avoid landing right in the torque valley from 5250 to 6500... but that seems like a lot of "thinking"

For upchanges the chart shows one hell of a sweet spot for HP from 7500 shift landing right back at 550 0 in most gears.

Guess the traqmate was "made" for this type of thing huh.

jesc996tt

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wow really? must of missed that one somewhere.. You sure a different clutch and flywheel are going to change the cars gearing? Might want to re-think that one. The lighter flywheel does let the rpms drop faster as you say "before" the next gear is engaged but once the gear is engaged the rpms are "exactly" where they would always have been related to your speed... that is all.

it has nothing to do with gearing!
have you driven a gt3 with a light f/c?or in any other car for that matter?
when you downshift, you rev match and find at ideal rpms, but upshifting the SMALL WEIGHT AND INERTIA of lwt fwl will quickly bring rpms down ( the same way that will speed up rpm gain when accelerating) so your shifting will need to quicker. yes, at the time of full engagement the rpms will be at where they always be.
and ,yes i have had more than one track car with a lwfw( including two with tilton racing lwfw).
so, most often than not , we would bring rpms close to redline for upshifting ( with variation , such as upshifting at lower rpms before( fast) corners that may reach redline before exiting...

JMeager

I think you think you know what you're saying but don't. The graphs you talk about that are with the stock flywheel wouldn't make a difference what flywheel was in the car. The graph shows revs to speed. That is only variant on the gearbox, not the flywheel. The fact you have a light flywheel and will suffer a quicker drop in revs doesn't change the fact that when you re-engage the clutch the same revs will be on the tacho whether or not you have a light flywheel.....the fact you have to engage faster so the revs don't fall to low doesn't change the gearbox speed.

The point is, rev drop has nothing to do with this discussion at all. Quit simply at the ground speed you decide to change gears, the gearbox ratios will command a particular engine speed for the next gear which is irrelevant of the clutch or flywheel you choose to use.

MM-Racing

Has any boody this diagram with 4:0 final drive?

NJ-GT

redline in every gear with the exception of 4th to 5th where there is no need to run up to 8,200 rpm. 4th and 5th are so close that shifting at 8,000 rpm still gets you on the power band at 6,600 rpm. 5th is limited to 8,000 rpm and the car does not reach readline in 6th gear.

You want to have the biggest area under the horsepower curve at any gear, torque has no business on ideal shift points.

This car has more torque from 4,000 rpm to 6,000 rpm than from 6,200 rpm to 8,200 rpm (redline). If the torque was the answer, I could stay between 4,000 and 6,000 rpm and accelerate faster than another driver running between 6,200 rpm and 8,200 rpm, but this is not truth.

You want to maximize acceleration at any speed on racing conditions.

The 997 GT3 Cup is properly geared for the power characteristics of this engine. Every upshift after 2nd gear (done at the 8,000 red line) lands on next gear at 6,650-6850 rpm.

Lots of explanations to this on Racing groups. Also plenty of videos on the web with Pro drivers shifting gears on these cars where they should.

MM-Racing,

I use this internet calculator. Much better than a graph, because the graph does not consider rear tire diameter differences across multiple brands.

http://www.f-body.org/gears/