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Optimum shift point

mickr32gtr

By mickr32gtr,
in Engines & Forced Induction

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mickr32gtr

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Probably a stupid question. Ive got an r32 GTR and plan to take it down the 1/4 mile soon. To get the best time and assuming all other things being equal, should i be shifting at the point of max torque (4400 rpm) or max power (8000 rpm)? Got a PFC and AVCR installed and A/F ratios perfect through the entire rev range.

Cheers

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Guest two.06l

Guest two.06l

Posted
Posted
Probably a stupid question. Ive got an r32 GTR and plan to take it down the 1/4 mile soon. To get the best time and assuming all other things being equal, should i be shifting at the point of max torque (4400 rpm) or max power (8000 rpm)? Got a PFC and AVCR installed and A/F ratios perfect through the entire rev range.  

Cheers

Hi Mick32gtr

Advice from drag racing guru's (croydons) and our experience has shown that changing at the point where torque starts to drop away, high in the rev range is the optimum time. Can you look at your dyno print out and see where the torque starts to drop away?

mickr32gtr Explorer

mickr32gtr

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Stacey

looking at the dyno chart, the horizontal is speed. The left vertical is kw and the right vertical axis is in "N". If u read the chart the top curve "power", it climbs from 50kw at 80kph to 160kw at 130kph, the gets a little less steeper but keeps climbing to a peak of 208awkw at 180 kph. I have no idea what rpm this was and i think the readings were taken in 4th gear which would make it about 4500 - 5000 rpm from experience (ive had it at 211 kph at 6500 rpm before). If the std r32 gtr has peak torque at 4400 rpm mine (with the PFC) has peak torque about 5500 then. Does that sound right to you?

blk180 Veteran

blk180

Posted
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I would think there is Two things to think about when changings as is already said around when torque drops off and you would aslo want to keep the car on boost the hole time ie; changing at 5500rpm would drop your car off boost in the next gear and u would lose some time while it spoles again.

my 2c

WazR32GTSt Grand Master

WazR32GTSt

Posted
Posted
why not just go out there and find out what works for yourself. Its not like you're going to do one pass and call it a day.

too true. best way to learn is from exerience.

we can sit here all day speculating, but at the end of the day if you take the car to the strip and do a change @ 4400rpm and the car drops off boost, then i guarantee you will never do it again.

try different shift points in different gears and you will learn alot.

my 2c... :)

oh, and when you find a good shift point combo, post it up for others in future with the same question

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