1/4 Mile Help!!!

[vipernet55]

Ok, I'm seriously contemplating entering the Ultimate Scottish Street Car Competition at Crail a week today in my rev2 Tubby. Now, I've almost perfected my launch and I've managed to get a couple of sub 5 second 0-60 times using my g-meter. However my 1/4 mile times arenn't great and I seem to be struggling as to when to change from 3rd to 4th. I've done a few 13.7 runs @104mph using the g-meter (private road at 2am ) but I need a 13.6 to qualify.

Can anyone give me some advice such as the best rpm to change at? will I be quicker if I remove the t-bar? any crash diet tips etc etc...... I'm hoping that I should be able to get a 13.6 just from the fact that the Crail surface will be better than the crappy road I was using to get my times!

[jonno]

Drop the pressure in your rear tyres, try something like 18-20psi.

[Daveb]

A fast time seems to be all about getting a good fast launch and 60ft time. Gone as soon as light hits green.

Changing gear - best to listen to what the engine is telling you and what it feels like.

[Mark Edwards]

As Neil says, drop the pressures. Do a burnout before your run to get some heat in the tyres and change gear as quick as you can (my problem, as i can do it quicker than the gearbox ). I pretty much always change gear when the tacho reads 7k but it really depends on where in the rev range your maximum power is.

[mr2mk1chick]

I'm not really a whizz with engine stuff, but leaving that aside - have you shed some weight??
not your waist size, but lost the spare tyre, passenger seat etc. may help a little....

[nisnos]

same boat as you mark with the box
its easily killing a half second off my times along side the clutch slip.

i launch at 6k after a burn out but it depends on your own setup.

try it from 5k then 5.5k then6k etc to see which gives you the best hookup.

Xxxx said to me " if it feels like the fromt is lifting off then its right"

best to date 12.8 at 106.9
60ft time 1.8sec

keep on the practice.

are york on sunday?

[2barGee]

Drop the pressure in your rear tyres, try something like 18-20psi.

I heard when i was at santa pod not 2 drop the pressure in your tyres as that when you blow the gearbox/drive train? Or can the 2 take the power? Draggin this sunday i dont want it 2break!!!!

[Mark Edwards]

Drop the pressure in your rear tyres, try something like 18-20psi.

I heard when i was at santa pod not 2 drop the pressure in your tyres as that when you blow the gearbox/drive train? Or can the 2 take the power? Draggin this sunday i dont want it 2break!!!!

It's all about traction and how you use the clutch to launch. The lower pressures will give you better traction off the line and the only way that will break the box is if you somehow get too much traction and just side step the clutch pedal. I've launched VERY hard plenty of times and have never broken the box on launching, only on gear changes.

[2barGee]

[It's all about traction and how you use the clutch to launch. The lower pressures will give you better traction off the line and the only way that will break the box is if you somehow get too much traction and just side step the clutch pedal. I've launched VERY hard plenty of times and have never broken the box on launching, only on gear changes.[/quote]

Any tips you can give me 4 a good launch?? Also what would be best 18s or standard rims? Traction would be better with the 18s????

[Mark Edwards]

You really need tyres with some sidewall flex so the stock ones would be better in that respect, but the width of the 18's would also help. Idealy you want small diameter but wide wheels with wide tyres.

The way i launch is to find the right rpm (takes a few goes to work it out) and then just side step the clutch as you put your foot down. From there just be as quick and clean as you can with the changes.

[ENSMR2]

Go on a dyno, see where the power starts to drop off and change gear then?

Makes sense to me.

[Mark Edwards]

Go on a dyno, see where the power starts to drop off and change gear then?

Makes sense to me.

That is the best way yes, 6950 for mine.

[Matty_GTS]

Mark - what you mean side step the clutch?

[vipernet55]

Mark - what you mean side step the clutch?

With the clutch fully depressed instead of coming up normally, simply taking your foot off the clutch pedal sideways so that it springs up sharply.

[JekylandHyde]

If you are practicing launching on the street and then try to run on a prepared track you are going to be in for a rude awakening. A well set up track is going to be significantly stickier than a regular road surface and where you had your "perfect launch" you are now going to bog.

Tip 1:You may need as much as 500-1000 rpms more at the track.

Warning:If you are using a regular street tire doing a burnout is a very bad idea. You will actually make the tire slipperier and you will will struggle for traction. On a regular street tire just do a dry hop ... one dump of the clutch to spin debris off of the tire. If the track puts down water for burnouts, drive aroud it.

Tip 2:Keep your front tires at max pressure and drop the rears.
A typical street tire should perform well around 19-24 psi.

Suggestion:Formula for shift points:
Lower gear ratio / higher gear ratio X RPM at peak Torque = Shift RPM
Using the same formula for a stock CT26 MR2, I get shift points:
1st --> 2nd = 6595 rpms
2nd --> 3rd = 5643 rpms
3rd --> 4th = 5595 rpms
4th --> 5th = 4915 rpms

Tip 3: Move your seat one click more forward than you are used to. You will clutch better this way as you are being thrown back into the seat on a hard run. This will really help the accuracy of the 1->2 shift.

Tip 4: Keep your tank empty. 2-3 gallons of fuel is plenty.

Tip 5: Fold your mirrors in.

Tip 6: Make sure your ignition components are fresh (new Toyota cap/rotor/wires and some good copper plugs).
MR2s have been documented to be down as much as 30 rwhp because of worn ignition components. I replace mine once per year.

Tip 7: Unplug the sensor on the engine lid. That will allow your intercooler fan to run constantly

Weight savings: http://www.jekylhyderacing.com/weight.htm

Advanced technique: If you can stay at full (or at least partial) throttle while shifting you will gain time and keep the turbo spooled up.

Good luck and have fun!


440 RWHP/365 RWTQ @ 22 psi · 11.44@120 mph
Thank you 2005 Hyde Sponsors! ATS Racing, World Motorsports, KBOX,
Chico Race Works, Wolfkatz, PA Auto Racing, LuckyCasino7, Spaz Chicken,
NoShoes, Spiral Moons, Fisher's Metal Finishing, MRControls, TWOSRUS,
TURBOHOSES, Heidi Nolen, Peter Doane, Jeff Herstine, Ardell & Robert Simon

[Quigonjay]

Warning:If you are using a regular street tire doing a burnout is a very bad idea. You will actually make the tire slipperier and you will will struggle for traction. On a regular street tire just do a dry hop ... one dump of the clutch to spin debris off of the tire. If the track puts down water for burnouts, drive aroud it.

quite a statement there jeff
peeps on here have always recommended doing a burnout
is there any evidence to backup the statement about making your tyres slippier? (i think thats how you spell it )
surprised to see you didnt mention drag radials as well? or is there not much point using them with not much more than stock power?

Jay

[JekylandHyde]

quite a statement there jeff
peeps on here have always recommended doing a burnout
is there any evidence to backup the statement about making your tyres slippier? (i think thats how you spell it )
surprised to see you didnt mention drag radials as well? or is there not much point using them with not much more than stock power?

Jay

Drag radials are a great idea if you have enough power that it is hard to launch without spinning the tires or you want to be able to launch harder than you currently are. Drag radials DO need to be bunrout to hook up, but not abig one. They also need a lot less tire pressure.

http://www.carcraft.com/techarticles/80058/

The biggest crowd pleaser in drag racing may also be the least necessary. Unless your car really needs a big burnout, in most cases you can spare your tires the wear and tear. With BFGoodrich’s drag radials, for example, an excessive burnout can produce small rubber balls that react like greasy ball bearings and can cause poor 60-foot times from the loss of traction.

That's a drag radial ... this situation is muc worse for a street tire.

p.s. My dictionary says slipperier.


440 RWHP/365 RWTQ @ 22 psi · 11.44@120 mph
Thank you 2005 Hyde Sponsors! ATS Racing, World Motorsports, KBOX,
Chico Race Works, Wolfkatz, PA Auto Racing, LuckyCasino7, Spaz Chicken,
NoShoes, Spiral Moons, Fisher's Metal Finishing, MRControls, TWOSRUS,
TURBOHOSES, Heidi Nolen, Peter Doane, Jeff Herstine, Ardell & Robert Simon

[JekylandHyde]

http://www.kennedysdynotune.com/Track%2 ... 20Tips.htm

Street tired cars should not do a big smoky burnout. The rubber in street tires is designed to operate best at typical ambient temperatures. The tires get slipperier, not stickier, when they get too hot.

Want any more references?

[Quigonjay]

p.s. My dictionary says slipperier.

i never was that good at spelling

[JekylandHyde]

I'm not good at spelling either ... I looked it up beofre I posted

Here's Hyde's complete track history:
http://www.jekylhyderacing.com/slips.htm

If you look at 10/3: Englishtown from last year you will see a run I did not street tires. I had a flat in my drag radial after the previous run so I borroed another MR2's street tires.

I DID do a burnout knowing that it would make the tire worse off.
Why did I do the burnout? Because it was a national event, I had no chance of winning so I thought I would do a crowd pleaser.

2.1 in the 60' slipping the whole way. *sigh*