ok, this got me thinking, forgive me first of all, if someone already asked this question on this section or any other section. here's my info to back my question up; i have an auto 99z(2.4L) it is said to have 150hp at 5600 rpms and 155tq at 4400rpms(using my car as an example). now i know the whp is quite lower because it looese power goin from engine to the wheels, but i dont think that concerns to what im getting at. ppl say that either manual or auto, shifting at 6200-6500rpms is the necessary rpm to shift for acceleration. but from basic understanding, if the engine is only producing the max hp of 150 at 5600rpms, and any higher is pointless cause hp is decreasing, why rev up to or over 6000rpms? thanks in advance

You rev over the peak horsepower mark in order to stay in your powerband. If you shift at peak power, it will take longer to get back up there than if you had gone over to redline.




2000 2200 Cavalier: 9/14/2000--10/23/2006
2007 G85 SS S/C: 10/23/2006--Present
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because of gear ratios. if you try shifting at peak torque the next gear would reduce engine speed too low and you would be out of your power band. same with peak hp. except you would be closer to your power band. if you shift at 6200-6500 then the gear ratio would put you at around 4000-4500 rpm and then you are in the meat of the power band.

to summarize: when you shift you want the rpm's to fall no less than the peak torque. then ride the hp to the next shift.

ah ic the logic behind this now, but isnt over-revving past the peak hp the same as if u shift at the peak of the power? because since u're not making anymore higher power u're loosing the power after wards?





*Devil Z*

but the gear ratios put you farther into the power band once you shift from 6500rpm. even though you are technically loosing power you spend less time trying to accelerate.

hmm ic now, thx guys





*Devil Z*

that sounds all good and what not but in my 2000 2200 5 spd my rev limiter kicks in like right at 6000rpm, if not a lil sooner

fst_99Z24 wrote:ah ic the logic behind this now, but isnt over-revving past the peak hp the same as if u shift at the peak of the power? because since u're not making anymore higher power u're loosing the power after wards?

Why would you want to shift right when you're making the most power?

It's not as if the power is all gone at 5650 rpm. It's a curve, so even though power is starting to drop off, there's still more power there than where you'll end up if you shift.

i was under the impression that since the power peaks at about 5600, shifting or letting the auto shift a bit after the 5600-ie5650 would give the best power and the rpm would go back down to a preset rpm for the next gear. now originally i posted that i wasn't sure if over revving close to 6000-6200 would be the same as from starting at a lower rpm-loosing power, but after what jpo96sungt
and Pyros777
about over revving past the peak hp then shifting and the band would now be at a higher rpm for the next shift seems logical now for me. i thought the rpm was preset for each gear after shifting one ihhger up the next. what a newb i sounded like





*Devil Z*