emptnest

I ran my first PDX - HPDE yesterday with my 1993 stock LT1 C4 Vette. Great event at Summit Point WV, organized by Washington DC SCCA.

The day began rainy, and wet track conditions kept speeds low. Dry afternoon conditions allowed greater speeds, leading to this question.

I accelerated for the full length of the straights, and at the end of the main straight, approaching the braking zone for turn 1, RPMs would max the tach at 6000. In hindsight, I probably should have shifted from 4 to 5, but being literally only 50 yards or less from the braking zone, I stayed in 4th. A couple of times in that condition, I noted a momentary loss of power (almost like a miss), and simultaneously hit the brakes and backed off the throttle. As I shifted to 3rd, hit the apex and added throttle, all was well.

Does the C4 have a rev limiter? Might that explain the momentary power loss? Or was something else going on? She ran perfectly afterward each time. My instructor was a Porsche guy, and couldn't explain it.

Diagnosis please.....

ErnieN85

yes it has a revlimiter, most likely what you experienced
I'm not sure what it is set to though

Bill Dearborn

I think the LT1 is set at 6K. The L98s were set at 5600 but the HP curve peaked at 4300 rpm and fell off a cliff after 4500 rpm which made it feel like you stopped moving.

Bill

emptnest

Thanks guys. I studied the track via Youtube, and used one particular video from a C5 or C6 ZR1. That driver stayed exclusively in 3rd and 4th, so I tried to do the same. It worked pretty well, except now I realize he has more RPMs available to work with.

I will watch my tach closer, and adjust accordingly.

Its a great pastime, that I greatly look forward to; especially with the great support of CF and my new friends at the track.

emptnest

So, I obviously need to shift into 5th in the final portion of the straight. So do I just give up some 4th gear range in order to save some track distance for 5th? Otherwise, I will be shifting down out of 5th as soon as I shift up into it. Either of these options will likely cost me some speed, but so be it. I can't take the car beyond its limits, so I have to improve my own.

Of course, the best solution will be to improve my exit from turn 10, and to enter the straight at higher speed so that I get some decent time to run in 5th. Any other suggestions will be appreciated.

ErnieN85

that is the easiest way until you have mastered it, then the next step is to change rear gears either lower if you can stomach burning more gas as a daily driver ( provided first isn't too low) or change higher so fourth lasts longer (higher speed)

jaa1992

OK, the car has torque out the ying yang.
Shift to 5 before start finish and floor it until you get to the braking zone.

emptnest

More use of 5th it shall be.

So, at the risk of further hijacking my own thread, what about the downshift from 5 to 3?

I know that topic has been kicked around thoroughly. I found this long (and sometimes hilarious) thread: https://www.corvetteforum.com/forums...-question.html

Anyone care to weigh in on 5-4-3 vs direct 5-3 (skipping 4th)?

mgarfias

You don't have a sequential. Choose the right gear for your situation.

jaa1992

As long as you rev match 5 - 3 is ok.
Other wise:
90%of braking done - shift to 4
brake the rest - shift to 3

So until you get it down - lots and lots and lots and lots of practice
Give yourself lots of room.

I have to do a 4 - 2 shift going from turn 6 to turn 7 at Road Atl.
I still don't have it perfect after hundreds of laps

93Rubie

The tachs on LT1 cars are notoriously inaccurate. It gives you a general idea. I shift from the sound anymore.

jbondfl

Take most of your advice from folks that run at Sumitt regularly.
That being said,,,,,, at sebring I have that option regularly on the back stretch. My solution is to hold throttle for a few seconds and not shift, then tell myself, "next time, get 16 right and you won't need to worry about it!"

If you find you aren't improving as fast as you'd like (like many of us) you could simply try a different size tire on the back. That would effectively change your RPM And best of all it is a temporary change, unlike changing the differential.
(Just a thought)