Silvia Club of NSW

Just wondering when is the best time to shift gears. I find that once i hit about 6500revs the car doesnt seem to gain any more power. Is it worth pushing it all the way to 7500 or what? This might seem like a really stupid question, just wondering what you guys think??

What revs you change at depends on your cars setup changing at 6500 would be harsh for every day driving but it sounds like your after the performance gear change so take into effect what revs the engine is at when you shift into the next gear and how far off coming on to boost you are and hoe long it takes to come on boost compared to shifting at 7500 and also how long it takes to get from 6500 to 7500

for example when you change at 6500 the revs go down to 2000 and boost comes on at 3000 and it takes 15 seconds to get on boost so total time is 15 seconds + gear change compared to shifting at 7500 it takes 5 seconds to get from 6500 to 7500 and when you change gears the revs drop to 2700 and it takes 5 second to get on boost so the total time is 5 seconds for revs+ gear change +5 seconds to get on boost so the total time is 10 seconds + gear change
so in this example it would be better to change at 7500 being 10 seconds compared to shiftting at 6500 being 15 seconds

this is only made up revs, times and boost point so you will have to work out your own times, revs and boost point and find out what is the quickest getting on boost if you get on boost straight away on both 6500 would be better

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There is a very fine line between "hobby" and "mental illness."

i barely know anything about gear ratios, so i could be wrong,
i think its best to redline when racing, gear ratios are set up to pull the car at certain speeds, for example if 1st gear goes to 65kmh, then 2nd gear will pull best once the car has reached 65kmh(or more putting the clutch into the equation)

so changing at lesser revs will mean your going into the next gear at a lower speed, therefore it will be too much load, its like changing gears at 3000rpm then trying to hammer it throughout the next gear.

the only time i think it could be to the advantage is if your car is modded so much that the gear ratios should be changed, but then again it depends on the length of the race, if the race is short the gears should be small anyway, if youve ever played gran tourismo and messed around with the gear ratios on the car perfomance tests youd know what im talking about.

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is that clutch or brake i smell?

Or in your case, daily driving?

j/k

Tripper - WTF??
That totaly confused me, would not have a clue what you were trying to say.
All I now it takes me car about 1 sec to come on boost and in 1st gear about 1/2 a second to get from 6000 to 7500. Once on boost, quick shifts and a BOV mean she never gets off boost.
15sec to get on boost???? so what quarter mile times are you expecting 2 min??

And to answer your Q phill, with a standard revlimit and ECU there is not much piont going much beyond 6200, well in my car that is, but I would presume that would be fairly close in other sils. Even on a Dyno you will see your torque and power tapper off beyond this point.

Agreed MYS15T. The wear of your engine is directly related to rpm so why push the motor past its power making revs? All you will do is flog the guts off it without going quicker.

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S13 Silvia Tuning - The Definitive SR20 Modifying Site

Thanks for the advice guys. I'm still a bit confused by what tripper was trying to say. I thought it would be best to shift as soon as the car stopped gaining power rather than pushing to redline.

Trippers numbers were just big to make it easy to see what he is saying other wise there would be half seconds and stuff in there. I think he is just saying you dont want to go below the boost rev line when changing to reduce lag etc etc etc
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SMOKE KILLS

yep your right saintpoida just wanted to point the less time off boost if any the better. the times where large for that reason

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There is a very fine line between "hobby" and "mental illness."

yeh but if u rev higher in say 1st, you'll be at a higher rpm in 2nd when you change, and thus closer to your optimum power band. once you get past 6k rpm or whatever, youre not really making power but your not losing it much either. the best way to test is to get to the track and experiment a bit i suppose

it rreally all depends on when ur ride produces its peak power in the rev range,

luckily for most nissans, its @ 6400rpm, and redline about 7/7500

not much point goin past this, as like most ppl say, the power drops off. it drops off quite rapidly for me, and it would place more strain on the mechanicals then nessary (spelling).

only time to full rev all the way to the limited for increased speed is on GT3

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You know who we be, N.A love for the S one three
S R twenty DE yo, will f**k on vtec like i f**k them hoes

If you really wanted to work it out properly the best way is to get a dyno run which goes all the way out to redline and source you gear ratios. Multiply your torque (not power) by the gear ratio and where the result is largest thats the gear you should be in. What you'l find is that in lower gears (as in 1st, 2nd, not lower gear ratio) you'll be holding the gear closer to redline, in higher gears because there is less difference between ratios you'll be changing a bit earlier.

If you want to change your torque curve characteristics (ie, have more torque up top) you'll need new cams as these are the big limiting factor. If you go for a mild street cam (say 256 in 264 ex) from a company which has done some decent testing and research (HKS, Jun, Tomei etc) you will generally find you won't lose anything down low but will gain quite a bit up top. I strongly recommend new cams, they transform the motor.

Cams are expensive though

Also a good method is to plot the actual Gs te wholw way through eac gear. Either steal one of those floating balls from a Pajero or just set up a hanging weight that sways backwards during acceleration. Graph the Gs vs rpm of all the gears and where the lines overlap is the optimum shift points.

an article on Autospeed does this in a way that is really easy to understand (not like me)

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S13 Silvia Tuning - The Definitive SR20 Modifying Site

Just dont make the weight to heavy so when you gun it it swings and hits you in the head knocking you out, or worse swings back into the windscreen and smashing it