Top Speed Per Gear, Is This Right?

[SargeRX8]

Hey all,

Well this has been baffling me a little and I don't know if its normal or not.

Anyway, Ive got a relatively stock R33(exhaust, fmic, 10psi, ecu). Ive noticed that first gear up to about 4500 - 5400 is best. Anything above 5400 rpm does not seem to do anything. Is this right. I hit about 59 - 61km in first gear by 5300rpm then the rest til red line is just noise with no speed gain, torque or power. Is this right? I never noticed this with my old R33 as by the time I got to 4000 id hit 7krpm in no time and be out of the gear. I find its best just to get out of the gear at about 5krpm.

This is the data I got about gear ratios and speeds per gear.

RPM 1st Gear 2nd Gear 3rd Gear 4th Gear 5th Gear 6th Gear 500357912-100059131823-1500814202635-20001118273547-25001423344458-30001627405370-35001932476182-40002236547093-450025416179105-500027456788116-550030507496128-6000335581105140-6500355987114151-7000386494123163-75004168101131175-80004473108140186-85004677114149198-90004982121158210-95005286128166221-100005491134175233-

My tyres are 245/45/R17. According this this chart I should hit the speed I recall by redline.

My next question is raising the rev limiter. Is this as simple as using my PFC hand controller and raising the limit to say 7500? Would this give allow me to hit the above speed of 65km/h?

[89CAL]

ummmm..... If your car is reving more and not gaining any speed what does that tell you?

Make sure your clutch isnt slipping

If your engine is still increasing speed then your gearbox should be increasing speed.... Raising the rev limiter is not going to fix this. Think about it.....

[PM-R33]

As Callan has said. If you are increasing RPM but not increasing speed you are getting clutch slip.

[SargeRX8]

Yeah the only thing I could think about is clutch slipping but I can't smell it. The car is going on dyno soon so til then no more planting it. What else could it be?

[89CAL]

unless its an auto.... nothing really........

depending on the clutch you might not smell it

I never smelt my exedy Cushion button on the way out and it was fairly wrecked when i pulled it out

[SargeRX8]

Could it be that in the top end of the gear say from 5400rpm to 6500rpm the speed gain is very small?

Ive smelt my clutch before and believe me this isn't one of those stink free clutch. Its also a relatively fresh clutch.

[PM-R33]

You have to think about how a car works. Hopefully with this explanation you can understand:

PHIL'S RPM EXPLANATION

Say an engine spins at 1000rpm. This means the flywheel is spinning at 1000rpm. This is the RPM that you are seeing on your tacho.

Now say you are in 4th gear with a gear ratio of 1:1. This means that the driveshaft coming out of the gearbox is spinning at 1000rpm.

Say your final drive ratio in your diff is 4:1. This means that the wheels are turning at 250rpm.

So as you can see, if you simply increase the engine rpm to 2000rpm and keep everything the same, the wheels would now be spinning at 500rpm.

Increase the engine rpm to 4000rpm and now the wheels are spinning at 1000rpm.

See how there is a constant relationship? It doesn't matter how much power the car has, the speed always remains at a constant relationship since it is simply being multiplied by gearing. The thing that power alters is how quickly - acceleration - it gets to the higher RPM.

So if a 100HP car does 100km/h at 3000rpm and 130 km/h at 4000rpm. That same car with a power increase to 400HP will still do 100km/h at 3000rpm and 130 km/h at 4000rpm.

This is a very rough and basic explanation but it is ment to show you the relationship of engine RPM and wheel RPM. It is a fixed relationship that always has to stay the same.

So to answer your question, no. The end of a gear from 5400rpm to 6500rpm will still be giving the same constant linear increase in speed.

[Adriano]

Phil, nice write up, but you need to go back to school, the diff ratio reduces the axle speed.

[PM-R33]

Shit! lol that's what happens when I type quicker than I think

Fixed haha.

[89CAL]

lol i was gonna say that, but I wasnt 100% sure (confused myself thinking haha)

But yes input on the left output on the right

[Branelly]

Woah, how are you hitting 59-61 kph at 5300rpm and im only able to hit 50 kph by 7000rmp?

Didnt think series 1 and 2 were that different lol.

[Dani Boi]

Woah, how are you hitting 59-61 kph at 5300rpm and im only able to hit 50 kph by 7000rmp?

Didnt think series 1 and 2 were that different lol.

I've got a series 2 and can only do about 50-55kph at 7k rpm as well?

Edited March 6, 2011 by Dani Boi

[SimonR32]

the active diff in a series 2 may be a different ratio?

[SargeRX8]

I really don't know. Coming up the road earlier today, I was just sitting there watching my KM sit at about 58 and the revs increase.

I already understand the concept of how things work in relation to speed of engine to the wheels vs power is how quickly you get through the gear.

Ill take it out for a quick boot and check what shits what. Ill do it safely though, rather that watch the cluster Ill just use my hand controller to record the max data logged by the end of the gear, the clear it then try it to 6krpm, then clear it, 5krpm. ill get an indication of where this shits at.

[89CAL]

Use the graph on the hand controller to see if the speed peaks then holds while the revs increase. Log speed and rpm and then click next twice and it should get you to the graph

This is if you have a power fc. That's what I was guessing

[PM-R33]

the active diff in a series 2 may be a different ratio?

Nah all the GTST's have 4.11's in the rear.

[89CAL]

I guess it could be a speed sensor fault but I think they usually work or don't. There's no real middle ground.

[PM-R33]

Yeah exactly.

[Birds]

Could also be a lagging tacho, i.e. you're hitting 7000 when it says 5000...

Ordinarily I would say slipping clutch, but I have experienced similar issues with mine. My tacho goes friggen wired between 3000 and 4500...just shoots up almost instantly, but outside of that range it works perfectly fine.

If you can actually hear/feel your engine increasing speed though, then the speedo drive / dash is buggered. Car will feel like you've hit a brick wall in terms of power after a certain RPM.

[89CAL]

Thats tru to.. But I guess he should be able to hear the limiter if its actually reving alot higher then it is. Hard to say

Maybe try a new tacho, and if you have a power fc, graph speed vs rpm on there (as I described above) and see if you can see the revs continue to rise when the speed has flattened