OK, I finally got my 2.3L build complete and for the life of me, I can't launch at the track to save my life. Today I hit a bad 12.4@115 (last week hit a 12.2@116), both runs in the 2.0* 60 ' range. I've tried launching at 34 psi tire pressure, dropped it down to 25 psi, and lastly 20 psi. 25 and above-wheel hop. At 20 psi, lost traction and basically spun through 1st. Unfortunately I was getting 4th gear lockout on my other runs (front motor mount will be put on in the morning as well as adjusting clutch pedal). Last week, I did hit a 1.7 60 foot at 25 psi, but wheel hopped so backed off a bit..and 4th locked out. Anyone running NON-DR tires have any suggestions on the best way to launch? Usually I hit 2 step (5500 rpms), slip clutch and roll. I have a BBK full ported and want to hit 11's on 93 octane only, street tires, full weight. basically a daily driver that runs 11's like i run on the street. On the street when I launch, it launches like a roller coaster ride, but at the track...no go. Should I drop the pressure below 20 psi? Any suggestion appreciated, next Sunday is last test and tune day of the year and want to hit this before I slap on either a BBK-B BB or FP Black BB next season.

 

On a street tire I would never go below 25 psi. Actually I usually run them at the OEM specs or close to that. Maybe 32 psi front and 29 psi rear. I'd rather have the harder tire to MPH better.

What clutch do you have? depending on the clutch it is a balance of 2 step rpm and clutch slip. The more you do it the better you get at it. 1.7's on any street tires should be pretty easy with a AWD car.

I would suggest coming off the 2 step at a higher rpm with a decent amount of slip. Once the car is moving forward let it eat.

Hope this helps.

 

Thanks, i appreciate it. from the info I'm gathering, maybe I'm slipping the clutch too early causing wheel hop. Using exedy Twin HD. next week I may try the 32/29 combo and slip the clutch a little slower. My clutch has not had the "burnt" smell yet, so maybe that's it. Thanks again, hopefully next time I'll get my 11's

 

Gonna try to keep this brief. Stock Bottom end+58 trim turbo kit (30R) 29psi best time on 1/8 7.3 @95.3mph HKS twin disk clutch. 2 step is @ 6500rpm. Best 60ft is 1.641. My tire pressure is 15psi up front and 12psi in the Rear. I am on 225/45 17 Toyo R1R's.

 

OK, now I'm confused Anyone else have any suggestions? I'm torn of stock psi or dropping it below 25 psi. Unfortunately the track runs in sessions during test and tune and only get two runs in before I run out of time.
On another note, I installed my front motor mount and adjusted my clutch pedal one full turn and wow, that made a HUGE difference. Granted my teeth were chattering at 7K rpms, but 4th gear dropped right in place every time.

 

Why are you confused? I am telling you what I run in my car. My post isn't hypothetical it is my experience. 15psi up front and 13psi in the rear. I won't go lower than that. My advice is to turn it down until you feel like its working for you. There is no cheat sheet to tire pressure really. Just adjust as u go because track conditions+your set up might be totally different than the other guys.

 

All-season 18s. Lowered mine 20f and 18r and cut a 1.64 on stock turbo/block full weight ssl. I started off with 25f and 23r and cut a 1.8. next run lowered it and cut the 1.64.

 

Drop the tire pressure and raise your two step rpm.

The lower tire pressure allows for more flexing and gripping of the tire. A higher tire pressure yields better gas mileage due to less friction.

 

As you are probably aware 1/10th off the 60' time is usually good for at least 2/10ths off the ET, all other things remaining equal. So on your 12.2ET/2.0 60' pass a 1.7 60' should be good for an ET of 11.6 or better.

Getting your best 60' time depends on many variable's including your HP/TQ level, suspension, tires, clutch, track prep, etc. There is no 1 right answer.

What works for us on cheap all season radials is 25-26 psi front & rear, 6200 RPM 2-step, slip the clutch until you start to roll (load the drive train) then quickly let it out all the way. Slip the clutch too fast and you bog...too slow and you burn the clutch, find the sweet spot.

Results:
Best 60' = 1.59 with consistent 60' times of 1.6XX

Our 60' time would probably be a bit better with slightly lower tire pressures, but to help save the drive train I like to have all 4 tires spin/squeal just a bit off the line.

Dan (drb)

 

I have Michelin ps2 tires and set them to 18psi for my best 60ft. On the stock clutch I was cutting 1.5 60fts. On my exedy SD twin I was cutting 1.6 60fts. Now I have an exedy HD but no track times yet. Do not drive them on the street at this psi though.

 

Sweet, thanks all. I was confused since one person said run oem, others mentioned below 20 psi. I'll try my first run at 20 psi and maybe lower it second go around. Thanks for the ballpark figure. I didn't want to spend my only two runs deciding between stock and 15 psi I went ahead and ordered but side mounts, hopefully they should be here by Friday to slap them on.

 

I've managed several 1.6 60 foots on cheap all seasons. I normally run between 15-20psi in the tires. Let the clutch soak up the load and it should help with wheel hop. I didn't see but what is your 2 step set at rpm wise? How much boost

 

I'll give that a shot next week then. My 2 step is set at 5500 rpms, and as for boost I'm peaking 27 psi, but running speed density with a launch map and haven't logged a launch yet.

 

What's your boost when you're at 5500rpms in 2 step?

 

First off, don't let everyone mess with your head about tire pressure. If you do that you're going to be changing it too much and worrying about the wrong thing.

The problem right now IS your driving and no amount if tire pressure changes will help you. With your tires at the pressure they are for the street you should be easily hitting 1.7's with good driving. Like in science, change variable at a time, your driving in this case.

Also, you're better off between 5850-6200 launch rpm