changing gears at torque peak?
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 1,036
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From: Dubai - UAE
changing gears at torque peak?
I read an article once that it is best to change to the next gear at a speed which the rpm of the next gear will coincide with the engine's maximum torque.. they say this will provide the maximum accelaration for the car through its gears
Elaborating:
Suppose maximum torque rpm is 3,500;
I am on second gear and want to change to 3rd;
Therefore i should change to 3rd gear at a speed that will be coinciding with 3,500rpm-3rd gear..
Any comments? <img src="graemlins/yltype.gif" border="0" alt="[typing]" />
wael
996 99 c2
Elaborating:
Suppose maximum torque rpm is 3,500;
I am on second gear and want to change to 3rd;
Therefore i should change to 3rd gear at a speed that will be coinciding with 3,500rpm-3rd gear..
Any comments? <img src="graemlins/yltype.gif" border="0" alt="[typing]" />
wael
996 99 c2
4th Gear
Joined: Oct 2002
Posts: 4
Likes: 0
From: New York, NY
Nah, depends on the torque curve. For max acceleration in a given gear, you want the maximum area under the torque curve I.E. in theory you could have a good flat torque curve from 3000-4000...say 200 lb-ft...and it peaks at 4500 around 215 lb ft, then drops rapidly after 4500 -- in that situation you would accelerate faster by starting your next gear in a much lower rpm than your peak of 4500 because power would drop rapidly after that (not usually the case in porsches...but just an illustration) 
Brad
Brad
Thread Starter
Burning Brakes
Joined: Oct 2002
Posts: 1,036
Likes: 0
From: Dubai - UAE
Well that means that in theory still, changing gears at redline can prove to be wrong, right?! <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" />
Wael <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />
Wael <img src="graemlins/jumper.gif" border="0" alt="[jumper]" />
4th Gear
Joined: Oct 2002
Posts: 4
Likes: 0
From: New York, NY
Most definitely. Shifting at redline is many times not a good idea for max acceleration. A chipped audi S4 is a great example, the stock turbos are small so when you up the boost they choke out significantly before redline, but during the mid range you get a huge boost in the torque curve, so it's best to keep your revs in that range (shift about 500 rpm shy of redline). Most 911's breathe very well and don't choke out on the top end, so redlining a 911 could very well be the best method for rapid acceleration.
There are a few exceptions to this rule - for example if you're in that S4 (or whatever) and you're on a track, autoX, or dragstrip, sometimes you go faster if you hold it in gear past your 'optimal' shift point. Shifting takes time and coordination.
Brad
There are a few exceptions to this rule - for example if you're in that S4 (or whatever) and you're on a track, autoX, or dragstrip, sometimes you go faster if you hold it in gear past your 'optimal' shift point. Shifting takes time and coordination.
Brad
