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How Many High Rpm Launches Will A Gtr Box Take

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R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Probably closer to 600 - but ye it'll come down to gearing, aero and power and it's a funny combination of the 3 when you think about it.

Pretty sure the O/S 5th is pretty much the same as stock in terms of ratio. Its the 1st thats a lot different.

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tricstar Mentor

tricstar

Posted
Posted

Probably closer to 600 - but ye it'll come down to gearing, aero and power and it's a funny combination of the 3 when you think about it.

Pretty sure the O/S 5th is pretty much the same as stock in terms of ratio. Its the 1st thats a lot different.

yeah I'm not worried about the figure, it feels fast enough.. but 15% less is probably a bit much. I know all dynos read different but that is almost no loss from engine to hubs ?

I've got to get it on a roller once and for all.. before the last tune it was 550rwhp on a roller then a week later 525awhp on the hub, so definately noticable when I picked it up at 710awhp hubs

anyway thats all a bit offf topic

zebra Grand Master

zebra

Posted
Posted

High speed aero is a funny thing.

Most cars will do the old ton (160km/h) even our 55kw cordia would do 160 pretty easily, but to get to 180 would need around double the power.

There is a way of roughly working out how much power you need to get to a certain speed, but its late and CBF finding the formula.

But as an example, I know of a 450rwkw BA XR6 turbo that over a 3km run hit 306km/h.

Big car yes, but it gives you an idea, in fact the Drag co-efficant would be faily similar to the r32, which is like a block of flats.

Anyway kinda off topic lol

N1GTR Grand Master

N1GTR

Posted
Posted

That's why personally I'm going for a time rather than a speed.

Where did the ford find 3km of straight flat road?

Also I think it's great to be able to wind out gears, regardless of what speed they get to, in a legal and safe environment. Try it on a freeway and if you're caught that's it, life over. So the way I figure it, doing this thing is a no brainer and between runs watching the other 100 or so cars launching will be damn good aswel :D

iplen Mentor

iplen

Posted
Posted

I wend to WSID running shitty Nexens and stock apart from boost, ran 1.6 60 ft all night by staging, loading it up, then sitting just off the take up on the clutch, on the limiter when ready I would slip the clutch really quick, no bangs or shudders just takeoff!!

linkems Collaborator

linkems

Posted
Posted

I wend to WSID running shitty Nexens and stock apart from boost, ran 1.6 60 ft all night by staging, loading it up, then sitting just off the take up on the clutch, on the limiter when ready I would slip the clutch really quick, no bangs or shudders just takeoff!!

limiter bashing probably isn't the best idea for a stock motor with stock oil pump, probably best to keep the engine below 7000rpm as well :O

  • 2 weeks later...
HOT_R33 Proficient

HOT_R33

Posted
Posted

OS Giken ratios: 2.695, 1.703, 1.236, 1.000, 0.826

Standard ratios: 3.214, 1.925, 1.302, 1.000, 0.752

Should be able to work it out based on this alone.

I don't see why 1st should be bogging down in the OS sets. It appears to be a lower ratio.....or am I working it out the wrong way?

Piggaz Grand Master

Piggaz

Posted
Posted

OS Giken ratios: 2.695, 1.703, 1.236, 1.000, 0.826

Standard ratios: 3.214, 1.925, 1.302, 1.000, 0.752

Should be able to work it out based on this alone.

I don't see why 1st should be bogging down in the OS sets. It appears to be a lower ratio.....or am I working it out the wrong way?

All at 8000 RPM

OS 1st = 87 Km/h

2nd = 138 Km/h

3rd = 190 Km/h

4th = stock - 235 km/h

5th = 290 IIRC (Although I have the stock gear in my box)

Stock off the top of my head

1st = 75 Km/h

2nd = 120 Km/h

3rd = 180 km/h

4th = 235 Km/h

5th = 310 Km/h

After stripping every tooth off my 3rd gear I put in the OS set. On the street it can be a pain in the arse. 2nd gear slowish corners (say 60km/h) you dont have that nice shove in the back like you did before ... due to not as much RPM. It might not look like much of a difference but it can either work for you or against you, depending on the situation.

  • 1 month later...
Brandon Veteran

Brandon

Posted
Posted

So I've had the car back and done a few hundred ks of running in of the rebuilt gearbox and new Nismo Coppermix Twin. Now I find I cant dump the clutch and launch the car like I used to with the stock clutch.

I tried dumping twice, 5k and 7k and both drop to 2k as soon as I lift my foot off the clutch pedal and it doesnt have the shooting off feeling as the stock one. My question is, is launching a twin plate the same as the stock?

My mechanic told me to load up the drivetrain by slightly letting off the clutch pedal before dumping. I will try that but it still puzzled me why its not working by simply dumping. I do not have a lot of experience launching the GTR or any car for that matter. Including the 2 with the new clutch, I only did a total of 5 times so pardon me if I sound noob.

I hope there's nothing wrong with the clutch or the gearbox. Everything feels normal and I'm not getting anything out of the ordinary.

Strik3r Experienced

Strik3r

Posted
Posted

I'd say your doing it wrong :P

Only way you are dropping from ~7k to 2k is if your foot isn't on the loud pedal when you drop the clutch. If you bring it up to 7k and then sit their part throttling and then drop the clutch, then yes, it will bog down because as soon as load is applied to the engine, its bogging down because you're only 1/4 throttle. Try holding the rev's at ~4k, then when you're ready to launch, plant your right foot, wait 1 second then dump the clutch. That should get you going.

At the drag strip, i've found that holding it at about 3.5-4 while staging, then as soon as the first light on the xmas tree appears, plant right foot, by the time the xmas tree hits green, you're JUST touching the limiter. If you don't want to bang the limiter, then wait an extra half second before you plant the right foot.

In your car (which is more responsive than mine), as long as you're right foot is planted when you want to launch, anything over ~6k rpm is going to get you going

Brandon Veteran

Brandon

Posted
Posted

I'd say your doing it wrong :P

Only way you are dropping from ~7k to 2k is if your foot isn't on the loud pedal when you drop the clutch. If you bring it up to 7k and then sit their part throttling and then drop the clutch, then yes, it will bog down because as soon as load is applied to the engine, its bogging down because you're only 1/4 throttle. Try holding the rev's at ~4k, then when you're ready to launch, plant your right foot, wait 1 second then dump the clutch. That should get you going.

At the drag strip, i've found that holding it at about 3.5-4 while staging, then as soon as the first light on the xmas tree appears, plant right foot, by the time the xmas tree hits green, you're JUST touching the limiter. If you don't want to bang the limiter, then wait an extra half second before you plant the right foot.

In your car (which is more responsive than mine), as long as you're right foot is planted when you want to launch, anything over ~6k rpm is going to get you going

Thanks Gervase. I can sort of understand that explaination. I am guessing I was able to not bog because of the delay in full drivetrain/clutch engagement due to the ridabilty and slipping of the stock clutch. Since the new twin bites better, I'm probably missing the spot/timing of engagement.

I will get some pointers from you next week if you're at the drag.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

I'd say your doing it wrong :P

Only way you are dropping from ~7k to 2k is if your foot isn't on the loud pedal when you drop the clutch. If you bring it up to 7k and then sit their part throttling and then drop the clutch, then yes, it will bog down because as soon as load is applied to the engine, its bogging down because you're only 1/4 throttle. Try holding the rev's at ~4k, then when you're ready to launch, plant your right foot, wait 1 second then dump the clutch. That should get you going.

+1

If i dial up 4500 and jump off the clutch at a 100% throttle press, it's smoking all 4 wheels no problems.

Rears start turning and then the fronts kick in and it's a smokeshow!

Month or so ago @ MotiveDVD Drag Battle i had Hoosier Drag Radials on - combined with PowerFC Pro.

Set the limiter to 7300 - foot to the floor and let the clutch go and hang on. Happy in pants launches for 2 days. I expected to break a gearbox for sure... must have done at least 30 launches like that... but no... the gearbox held fine

Eventually destroyed the front diff (which is much worse), so i'd not reccommend such action if you don't like breaking stuff hehe.

Nismo diff on the way, and then i'll be out there doing it again :pirate:

Brandon Veteran

Brandon

Posted
Posted

+1

If i dial up 4500 and jump off the clutch at a 100% throttle press, it's smoking all 4 wheels no problems.

Rears start turning and then the fronts kick in and it's a smokeshow!

Month or so ago @ MotiveDVD Drag Battle i had Hoosier Drag Radials on - combined with PowerFC Pro.

Set the limiter to 7300 - foot to the floor and let the clutch go and hang on. Happy in pants launches for 2 days. I expected to break a gearbox for sure... must have done at least 30 launches like that... but no... the gearbox held fine

Eventually destroyed the front diff (which is much worse), so i'd not reccommend such action if you don't like breaking stuff hehe.

Nismo diff on the way, and then i'll be out there doing it again :pirate:

Looks like loading up the drivetrain is the better option? I'll probably have to try and trial what rpm to rev to while loading before flooring the accelerator.

R31Nismoid Grand Master

R31Nismoid

Posted
Posted

Perhaps although i doubt it would have saved the diff, huge RPM launches on sticky rubber - something was gonna give.

Mind you that diff must have seen at least triple figure launches in its life. So it's done good service for a stocker

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