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how to get your gtst to launch!!!!!!!!

meggala

By meggala,
in Engines & Forced Induction

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meggala Grand Master

meggala

Posted
Posted

Ok I thought I would start this cause quite a few of us have issues with the launch at the drags especially.

what can you do and whats a low cost way of getting a good take off.

we are only discussing using street tyre's in this thread.

my thought.

I think pinapples will help set up the geometry for traction.

after market hard shocks don't help so a set of stock rear shockers might be the go.

the other issue is tyre profile and pressure.

I'm thinking 20 psi with a 50 or 45 series on a 16 " rim might be the way to go.

which tyres hook up well I'm looking for clues.

lets keep this low budget type stuff and see how we can go .

getting a rear wheel alignment might help.

has any one here got a 60' time below 2 seconds with a gtst on street tyres?

meggala

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51jay Mentor

51jay

Posted
Posted

20psi is still a bit high you can go to about 14-15 I run at 16psi

rears only of course. my 60fts are between 2.25 and 2,6 usually about 2.4 using either Falkons 255 40 17 or Pirelli P Zero 245 40 17

whatsisname Grand Master

whatsisname

Posted
Posted

My best 60ft so far is 2.153

Run on - 255/40/17 Falken's

3k launch (just a nice easy launch)

38psi in the rears

Stock rear suspension

215.5rwkw

Weight - 1540kg

13.1 @ 109.5mph

When I had 150rwkw I managed a 2.186 60ft on my 2nd ever attempt @ the 1/4, that was running on Falken Ziex too!

IMHO I really don't see that dropping the rear pressures on a 17-18" low profile is going to make a huge difference anyway? After all there's stuff all sidewall to play with, + "most" low profile tyres aren't designed to hook-up on the drag strip.

The 2 "main" areas to work on for a quick street tyre drag time are suspension & tyre quality (in terms of grip).

Low (in most case excessively) extremely hard Japanese rear suspension is the about the worst combo for quick 60's / ET's (I'm sure we all already knew this). Add to this a set of average quality rear tyres (poor grip) & it's going to take 20-30-50rwkw more than is needed to crack into the 12's, not that there's anything wrong with this, hell I'll probably use power rather than grip to do it :D A drag launch needs maximum rear weight transfer, hard rear suspension does an excellent job of preventing this.

I watched a J spec S15 with 200rwkw run a 1.9 60ft (12.8 @ 110mph) It was on 17" low profile Yokohama Advan street tyres (good quality rubber) & stock suspension.

One last quick one, get a decent alignment done to check your rear camber is not excessive! A Skyline/300ZX/S13-14-15 will really suffer from excessive rear camber in straight line!!! Even a 1" drop in rear ride height is enough to cause problems.

Guest INASNT

Guest INASNT

Posted
Posted

in a recent Zoom magazine artice there was sum launch control device when u dial in the rpm u want the car to leave the line at and for how long and no matter how hard u r on the throttle it will told that rpm for that time so u get a clean launch each time!

BOOSTMEISTER Mentor

BOOSTMEISTER

Posted
Posted

I can now comment on this after dropping around half a second off my 60 ft times.

First Example

2.4 60ft

HARD suspension

Worn clutch

Worn tyres

3000rpm

Second example

1.9 (1.994 but still under 2sec :D )

Soft suspension

New heavy duty clutch

New soft compound tyres

5500 rpm

My theory:

This is what I believe is the requirement for a good launch.

First you need tyres that will grip, my 40 series 18" grip really well after a burnout so I am happy to use them if you are running higher profile then deflating them to around 15psi is the way to go, at the end of the day go for the widest tyres you can use just make sure they are grippy.

Second, you need the suspension to be setup right. No rear negative camber and soft front and rear springs/shocks the reason you need soft in the rear AND front is that for the rear to drop and transfer weight to the drive wheels the front must be able to lift. most hard suspension has the wrong bound/rebound for drags. The ideal setup would be front shock/setup with high rebound and no/low bound so that it lifts but doesn't drop to easilly and rear shocks/springs with the opposite to allow it to drop but not raise easilly.

Thirdly your clutch needs to be able to handle a good riding from high RPM if it can't you will loose out when you hit second, you have to ride the clutch a bit on the launch or you will just wheel spin. Unless you have heaps of power don't touch a twin plate, we have found it hard to launch without spin with decent rpm.

Clint32 Mentor

Clint32

Posted
Posted

Get some offset bushes for the rear upper control arms. You can then fun neutral camber on the back, or even slight positive so when the weight transfers you will have full tyre contact.

I am going to get some super sticky brigestone tyres (still road legal) and mount them to 16'' rims with 225's and a low pressure they should give decent grip.

b2barker Enthusiast

b2barker

Posted
Posted
Originally posted by INASNT

in a recent Zoom magazine artice there was sum launch control device when u dial in the rpm u want the car to leave the line at and for how long and no matter how hard u r on the throttle it will told that rpm for that time so u get a clean launch each time!

Was it

T-Sport's Launch Control and Flat shift. I am getting one of them ASAP.

Cubes Grand Master

Cubes

Posted
Posted

I run Simex 225 50' 16's.

The Simex tyres made an unbelievable difference to grip..

Pressure is at 40psi and i now find it very hard to light up the rears. I may get a slight squeel but thats about it.

Before I ran Goodyear F1's 225 50's, Barums and Donuts.

Goodyear's were pretty good, Donuts where about the same and the Barums were crap.

For example with approx half throttle with all of the above tyres except for the Simex it would simply spin really easy when coming on to boost with the clutch already out.

Slapped the Simex's on and no wheel spin. The only way I get a little bit of wheel spin is to slip the clutch at 4200-4500rpm, it chirps a little then pop the clutch and before I know i'm hitting second gear.

Simex's funny thing is are the cheapest tyres i've ran which only cost $139 each.

Also I now cannot pull out of a corner and hit boost in second gear and go sideways :)

Try the Simex's Meggala if you are after a good long wearing tyre, that is quiet.

The only problem with them is they don't grip that well in the wet.

2rismo Grand Master

2rismo

Posted
Posted

I did a 2.6 then a 2.4 on Wednesday night at the creek.

Bareing in mind that these were my 1st runs ever :)

I think I could get it down a lot lower with a more aggressive launch and more faith in that lovely stuff called VHT!!!

Cheers

Cubes Grand Master

Cubes

Posted
Posted

So has any one got any ideas what sort of 60ft time's I'd be doing as I have stock suspension pretty soft shockers with lots of grip and not much wheel spin only at the start of the launch to get the initial jump?

You think i'd be around the 2 mark or maybe under?

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