[ma71supraturbo]

I have some questions about shifting.

1. When you downshift. I notice that if you want to downshift and the next gear would take you into high rpm, it is extremely difficult to put the trans into that lower gear. I have heard about rev-matching to keep the car from getting squirley at the limit, but would revving the engine allow the gear to engage more easily? And on the note should you close the throttle before shoving it into gear, or does it matter if the engine is under load as long as RPM is right?

Your synchros are probably worn. I recomend double-clutching to prolong your transmission's usable life. Say you're in 5th at 2000rpm and want to downshift into 4th at whatever rpm that is for the same speed (say 3000).

step 1. Push in clutch, move the lever to neutral, and release clutch

step 2. Rev to appropriate rpm for the next gear (~3000 rpm in this case), and push in the clutch, moving the shift lever to 4th

step 3. maintain 3000rpm while letting out the clutch.

 

[ma71supraturbo]

Ive read that shifting 200rpm past your pk hp is the optimal shifting point, not redline. Motors start to run out of steam. As far as redline downshift dbl clutch, Ive never had to do that just a quick stab at the gas pedal down shift and shes smoothed out and "synced up".

Take a look at your dyno graphs. Figure out about how long you'll be in each gear, and then find the optimum rpm range that gives you the most power. You certainly will be shifting above peak hp -- how much higher will depend on your hp curve


But it is even more complicated that that -- you make more power at the ground in lower gears (thats why people who dyno in 3rd make more power than those who dyno in 4th). So you generally will rev higher in lower gears than you will in the higher gears. And the rpm range in the 1st 3 gears is greater than in 4th and 5th.

Additionally, sometimes you won't upshift even if the next gear would offer more power. If you're close to the finish in the 1/4, its probably faster to wind out the gear you're in instead of wasting time shifting. Or if you are on a straightaway approaching a curve -- its probably faster to bump the rev limiter once or twice instead of upshifting only to downshift before the corner...

 

[ma71supraturbo]

Double clutching is a leftover from pre syncro days and is really a waist of time with modern cars.

It is not a waste of time if you drive a car with weak synchros (like the original poster). My mr2 will not downshift nicely into 1st, 2nd, or 3rd without double-clutching. Most people would just rebuild it, but I have no problems double-clutching. And frankly I find it quite enjoyable

 

[ma71supraturbo]

Re: THANK YOU EVERYONE

yes you want to hold the throttle open enough to maintain whatever rpm you expect to see in the next gear. If you are upshifting you may want to leave the throttle closed while the engine slows down