How Many High Rpm Launches Will A Gtr Box Take

[tricstar]

one of my favourites

shit tyres, a bit to much wheel spin.

[N1GTR]

Here's a good one, have to sit through the talking etc but some of the launches are just awesome to watch and listen to

[tricstar]

Here's a good one, have to sit through the talking etc but some of the launches are just awesome to watch and listen to

wish could speak japanese, wow one of those GTR's really laid some rubber , 0-300km in 16 seconds I'd love to try that ( the 0-300, not that I think I'd do it in 16 seconds )

[N1GTR]

On that topic, seen this? http://www.skylinesaustralia.com/forums/topic/362234-temora-1000m-sprint/page__view__findpost__p__5780684

[linkems]

I'm into the hundreds of launches in my race car.

the most important thing is not to shock it by dropping the clutch cold.

just before launching put the handbrake on and let the clutch out a little to put the drivetrain under load. when the light goes out, drop the handbrake, drop the clutch, floor the throttle and watch it go.

I can see how this is loading the drivetrain, the hand brake is stopping car from moving forward while the clutch is slightly slipping, so on complete engagement of clutch and release of hand brake there is reduced shock on the complete drivetrain.

yeah anywhere between 6500--limiter, the handbrake is just to load up the drivetrain before you launch.. on the line put on handbrake in 1st gear, let clutch out a little so it pushes against the handbrake, then clutch back in, handbrake off, don't let car roll back and drivetrain is loaded..right foot down and step off clutch..hang on..

I can't see how this is much different to leaving the car stationary and dropping the clutch.

Can someone confirm which is the proper method of loading up the drivetrain?

Edited May 12, 2011 by linkems

[R31Nismoid]

The bigger/laggier the turbo setup the more RPM you will need.

-9s @ 6000-6500rpm

Since going to -5s... 7000rpm+ or nothing happens as boost is noticeably lazier to build.

[N1GTR]

Thats a good point actually, i can fry them up from 6000rpm easy enough but Pauls GTR needs 7800rpm or it bogs down

[Deano 1]

meh.....limiter dumps FTW

[R31Nismoid]

Thats a good point actually, i can fry them up from 6000rpm easy enough but Pauls GTR needs 7800rpm or it bogs down

Yeah, you saw how my wee turbos worked nicely on a launch. Didn't need much RPM at all even though it was a 2.6 still.

Now - I've really gotta dial up some RPM, and as a result its harder to get right as sometimes it hooks up, sometimes it just spins

[N1GTR]

Just thought, Paul has an OSGiken gearbox, that first ratio isnt helping him off the line

[R31Nismoid]

Yeah not helping him at all.

[tricstar]

I can see how this is loading the drivetrain, the hand brake is stopping car from moving forward while the clutch is slightly slipping, so on complete engagement of clutch and release of hand brake there is reduced shock on the complete drivetrain.

I can't see how this is much different to leaving the car stationary and dropping the clutch.

Can someone confirm which is the proper method of loading up the drivetrain?

well my understanding was once you've been through that process all or most of the slack has been taken up, cogs meshed, diffs slack taken up etc, provided the car doesn't roll and you don't take it out of gear, then the drive train is loaded, ie most of the slack taken up.. this the process that was explained to me, correct me if I'm wrong, I can't see the difference between the two discriptions, I seriously doubt Duncan is sitting on the line with the handbrake on slipping the clutch holding 6000rpm+

[tricstar]

Just thought, Paul has an OSGiken gearbox, that first ratio isnt helping him off the line

I'm in the same boat, OS box, TO4Z, big cams, 2.8L, 7000rpm+ bump or bog down, where as with previous GTR I owned standard with high-flows, launch @6000rpm and just hock up.. I don't think the long first of the OS help to get off the line?

And yeah I saw that 0-1000 run, Still considering it and I'm in Perth, what are the thoughts, with standard ratios, OS box and around 800hp ( at the engine ) is 300km/h achievable ??

[Duncan]

hmmm multiquote does not work in ie9 or google chrome. lucky i have firefox too.

Is that based on feel or can you just guess the range base on the graph?

nope...that might be a starting point but surface and tyres and temp of tyres and surface make a big difference. I don't know any science...I just try different revs and see what I get.

Importantly...the perfect launch has a little wheelspin for 1-2 sec then hooks up. too much wheelspin feels fun but is not as fast. bogging down is worst and wastes the 4wd advantage.

I can see how this is loading the drivetrain, the hand brake is stopping car from moving forward while the clutch is slightly slipping, so on complete engagement of clutch and release of hand brake there is reduced shock on the complete drivetrain. I can't see how this is much different to leaving the car stationary and dropping the clutch.Can someone confirm which is the proper method of loading up the drivetrain?

I shared my secret tip its been working for years with very quick launches and no breakages.

...I seriously doubt Duncan is sitting on the line with the handbrake on slipping the clutch holding 6000rpm+

Just to clarify, that is exactly what I am doing. Yes it can and will burn the clutch with too much clutch out or too long. You will feel it pull forward on the handbrake a little but the car not moving...that is the correct feel.

With race starts, red light goes on for 3-5sec. So I hold the revs at the right number, handbrake on. When the red light comes on, I let the clutch out until I feel it start to bite (car moves load onto handbrake). So the car will spend 1-3 seconds on the clutch and handbrake at 6000ish. Nasty. But very effective.

eg...last race start. 8th to 2nd in 2 corners against commonwhores, wrxs, emos.

With hillclimbs, drags etc (anything where the timer starts when you move), the method is much simpler because you decide how long you are on the handbrake. Keep it to .5 sec you will be fine every time.

[N1GTR]

I'm in the same boat, OS box, TO4Z, big cams, 2.8L, 7000rpm+ bump or bog down, where as with previous GTR I owned standard with high-flows, launch @6000rpm and just hock up.. I don't think the long first of the OS help to get off the line?

And yeah I saw that 0-1000 run, Still considering it and I'm in Perth, what are the thoughts, with standard ratios, OS box and around 800hp ( at the engine ) is 300km/h achievable ??

Yeah the first gear ratio isnt your friend. I kept launching Pauls one time and time again at a motokhana and it bogged down everytime. I was baffled! Couldnt believe that each time i tried, i increased rpm and it kept bogging down. Final launch of the day just gave it 8000rpm and we were off, no dramas!

I wish I knew what speeds we can get to over 1000m, Ive done some searching but cant find any hard evidence. Does your box have the stock 5th? What power at the wheels? There's only one way to find out for sure There's a bucketload of air to move out of the way above 200kmh so I dont think anyone can accurately predict top speeds

[Nee-san]

hmmm multiquote does not work in ie9 or google chrome. lucky i have firefox too.

nope...that might be a starting point but surface and tyres and temp of tyres and surface make a big difference. I don't know any science...I just try different revs and see what I get.

Importantly...the perfect launch has a little wheelspin for 1-2 sec then hooks up. too much wheelspin feels fun but is not as fast. bogging down is worst and wastes the 4wd advantage.

I shared my secret tip its been working for years with very quick launches and no breakages.

Just to clarify, that is exactly what I am doing. Yes it can and will burn the clutch with too much clutch out or too long. You will feel it pull forward on the handbrake a little but the car not moving...that is the correct feel.

With race starts, red light goes on for 3-5sec. So I hold the revs at the right number, handbrake on. When the red light comes on, I let the clutch out until I feel it start to bite (car moves load onto handbrake). So the car will spend 1-3 seconds on the clutch and handbrake at 6000ish. Nasty. But very effective.

eg...last race start. 8th to 2nd in 2 corners against commonwhores, wrxs, emos.

With hillclimbs, drags etc (anything where the timer starts when you move), the method is much simpler because you decide how long you are on the handbrake. Keep it to .5 sec you will be fine every time.

When the grand prix teams were really looking into driver aids like TC and LC they found (especially Renault) that a minimum of wheelspin ( a few % front to back in terms of wheel speed) was really beneficial for launching from standing starts ( just look at the early to mid 2000 Renault starts to get an idea, took off like an electric car set !)

For some reason the GT-R's seem to launch way harder then other awd's its probably the way ATTESSA works with the rearward weight transfer.

[Duncan]

yeah I don't understand why the gtr launches harder than other 4wds...but it sure does it has happened over and over in the last 5 years for me

[tricstar]

hmmm multiquote does not work in ie9 or google chrome. lucky i have firefox too.

nope...that might be a starting point but surface and tyres and temp of tyres and surface make a big difference. I don't know any science...I just try different revs and see what I get.

Importantly...the perfect launch has a little wheelspin for 1-2 sec then hooks up. too much wheelspin feels fun but is not as fast. bogging down is worst and wastes the 4wd advantage.

I shared my secret tip its been working for years with very quick launches and no breakages.

Just to clarify, that is exactly what I am doing. Yes it can and will burn the clutch with too much clutch out or too long. You will feel it pull forward on the handbrake a little but the car not moving...that is the correct feel.

With race starts, red light goes on for 3-5sec. So I hold the revs at the right number, handbrake on. When the red light comes on, I let the clutch out until I feel it start to bite (car moves load onto handbrake). So the car will spend 1-3 seconds on the clutch and handbrake at 6000ish. Nasty. But very effective.

eg...last race start. 8th to 2nd in 2 corners against commonwhores, wrxs, emos.

With hillclimbs, drags etc (anything where the timer starts when you move), the method is much simpler because you decide how long you are on the handbrake. Keep it to .5 sec you will be fine every time.

ok I'll stand corrected, will give that technique a try this weekend now I have a clutch I can trust, have welded a couple of clutches trying something similar in the past..

[Duncan]

ok I'll stand corrected, will give that technique a try this weekend now I have a clutch I can trust, have welded a couple of clutches trying something similar in the past..

lol I have too

but it works when you get it right

[tricstar]

Yeah the first gear ratio isnt your friend. I kept launching Pauls one time and time again at a motokhana and it bogged down everytime. I was baffled! Couldnt believe that each time i tried, i increased rpm and it kept bogging down. Final launch of the day just gave it 8000rpm and we were off, no dramas!

I wish I knew what speeds we can get to over 1000m, Ive done some searching but cant find any hard evidence. Does your box have the stock 5th? What power at the wheels? There's only one way to find out for sure There's a bucketload of air to move out of the way above 200kmh so I dont think anyone can accurately predict top speeds

yeah there is only one way to find out, thats why it would be a grate event to go to..

the box has OS-giken 1-5 so I don't think it's much different to stock, 710awhp hub ( so around 650hp roller ? ) had a mates data box in the car one event recorded 0-100 in 3.4 seconds... gears are 1st = 85km/h, 2nd = 140, 3rd = 185, 4th = ?, 5th = ??, all at 8500rpm it'd have to be close.. hope I get to find out !! if I do, I'll let you know.