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GTR shift points???

7heavn
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7heavn Experienced

7heavn

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My GTR's power band drops off at about 7600rpms and at the drag I usually swap gears at about that . After doing abit of reading some guys are holding on to 8000-8500 with std internals and a similiar setup I don't see how this benifits anything, opinions please ???? :).

I have been having alitte bit of trouble with trap speed and it seems alot of guys on here with less power are doing better trap speed's then me maybe I'm not holding onto the gears for long enough??.

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Sydneykid Grand Master

Sydneykid

Posted
Posted
My GTR's power band drops off at about 7600rpms and at the drag I usually swap gears at about that . After doing abit of reading some guys are holding on to 8000-8500 with std internals and a similiar setup I don't see how this benifits anything, opinions please ???? :(.  

I have been having alitte bit of trouble with trap speed and it seems alot of guys on here with less power are doing better trap speed's then me maybe I'm not holding onto the gears for long enough??.

Gear change point depends on the average power over the range used, not the max at one rpm point. On the upchange from first to second the engine drops 3,000 rpm. Say your engine looses 15 kw from 7,600 rpm to 8,200 rpm, and it looses 25 rwkw from 5,200 rpm to 4,600 rpm, Then you have higher average power changing at 8,200 rpm.

Your dyno graph tells you where you should be changing gears.:)

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Mik Experienced

Mik

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hey Mik yeh looking to run a decent 11 then call it a day (atleast as fast as your dad's old 33)  got alittle bit more power now and will be cheating abit with tyres and some weight reduction .  

Thanks for the input sydneykid usefull information as always .

:P

I'm keen to go back again soon too. But I'm going to run on street tyres with full weight, spare tyre and 3/4 tank of fuel...hehe

Will be nice to have a run when the temperature is less than 29 degrees though.

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wrxhoon Grand Master

wrxhoon

Posted
Posted
My GTR's power band drops off at about 7600rpms and at the drag I usually swap gears at about that . After doing abit of reading some guys are holding on to 8000-8500 with std internals and a similiar setup I don't see how this benifits anything, opinions please ???? :P.  

I have been having alitte bit of trouble with trap speed and it seems alot of guys on here with less power are doing better trap speed's then me maybe I'm not holding onto the gears for long enough??.

You will find that changing at higher rpm will get you a better e.t. and mph .

With the turbos you have i would change very close to the cut -out .

400-500 rpm will make a lot of difference .

I will be taking the 34 back as soon as its ready and tuned ...

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JCMarshall_Law Proficient

JCMarshall_Law

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I have just the thing for you, take a look at this thread and the program in it. If you input the correct data it can accuratly tell you the most efficient shift points for your particular car (dyno chart).

http://www.skylinesaustralia.com/forums/sh...how+to+estimate

It estimates a whole lot of other performance parameters as well.

It is a really good program and I think you will find it usefull.

It already has data for one of my mates 32 GTR's and the programs are very close to reality.

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JCMarshall_Law Proficient

JCMarshall_Law

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Something else to think about

Shift points to give you the max terminal speed for the 1/4 mile. These points are essentially where the torque curves cross each other on the Traction chart. Note these points are not always exactly right as the wind slows the vehicle during gear shift making the best shift point estimation more difficult.

However, to achieve the best ET you generally need to change gears a little later. This is because shifting later means you are going faster for the during of the shift time. This means more distance will be covered. The optimum shift point is when the advantage of shifting later if offset by the loss of being too far past where the torque curves cross. These points are easily found by trial and error. Start with the best shift points for terminal speed and increase the shift rpm from there. For most engines the best ET will be achieved by revving to redline.

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