Help Me Analyze Time Slips

Well guys, I went to the track last Sunday...lets just say I was very dissappointed. I'll post my times and then I'll explain if you care to read on, but I would appreciate any insight as to why my car ran like this:

(all these times are in order through the day)

14.747 @ 93.1 mph 2.275 60' .163 r/t
15.531 @92.10 mph 2.595 60' .113 r/t
15.005 @93.26mph 2.271 60' .075 r/t
14.975 @ 93.73mph 2.590 60' .133r/t
15.232 @ 92.89mph 2.67 60' .149 r/t
15.475 @ 91.68mph 2.758 60' .055 r/t

This was racing into a sick 10-15mph headwind too

Car:
1990 IROCZ
350 w/ headerback exhaust
Accel Coil/Wires
8* advanced timing
BFG 255/60 in rear
300lbs less than previous owners

Mods done at track:
12* advanced after 2nd run
Belt that bypassed PS, AC, Alternator (Battery read a solid 12v entire time)
20psi in rear tires
40psi in fronts
Weight reduction

NOW, the previous owner ran it bone stock on stock tires and ran a 14.6 with a 2.2 60' time and trapped at 95mph.



MY EXPLANATION:
My first run was pretty smooth, did a nice little burnout and hooked up nicely at the launch..as I was going down the track I felt good and after I saw the slip, I thought "this is going to be a good day".

I thought the second run was a fluke, however I got zero traction off the line and I tried to launch exactly the same, preloading the same as well (est. 2500rpm, tach is broken)

After the third run, I found out some nice information: my friend in his turbo beetle behind me informed me that ONLY ONE of my tires was spinning on the burnout before the staging...I was roasting only the DRIVERS SIDE TIRE. This, would mean that I lost the posi aspect of the posi rear...
I realized a few weeks ago that I had a bad axle seal because I was getting oil stains on the inside of my drivers side wheel...denoting that I was losing gear oil...but I didn't think it was that bad, since on the street, I was getting nice traction with both tires. Would a loss of gear oil make my rear operate like an open diff? Which was essentially what happened at the track, after run one, I was all over the place off the line...could it be the burnouts that just killed my rear? I really tried to baby it off the line after the 2nd and 3rd runs to keep from slipping, because I realized what was happening, but that just didn't help much.

But still even with that information...how is run #3 so far off from the previous owners?

Most of your problems are traction related and 2 of those are your own fault.
When running street radials you need to run near normal air pressure. When you air them down they cup up off of the track in the center loosing traction.
Secondly street tires do NOT need a burn out. All a burn out does is heat them to a point where they're slipperier than normal.
You have enough torque with the TPI to need drag radials for the track. They would help a lot.
As for the posi. The track is often the straw that broke the camels back. Many posi units that are marginal will work decent on the street and fail in the burnout box. I see this a LOT.
Freshen the posi and put a sticky tire on it and you would be astonished at what it'll run on a 1.9 60 foot.

Thanks for the tip with the airing down of the tires. I was told by alot of people that this was the right thing to do. I'll remember that for next time.

The easiest way to examine a run is to break it down into sections. Take each run figure out how long it took to go through each section.

ie:
60' = 2.200
60' - 330 = 4.000
330' - 660' = 3.000
660' - 1000' = 4.000
1000' - 1320' = 2.000

Add all the times up to get an ET of 15.2

Now when you do that with every run, you can see at what point on the track the car is speeding up or slowing down.

On your third run you have a good 60' time but the car is slow. On the fourth run you have a poor 60' but a good ET and MPH. Chances are the head wind killed off a bunch of HP preventing better ET and MPH on all the runs.

20 psi in street tires is a no no. Radial tires have stiff sidewalls and won't roll over like a slick. As mentionad above, the center of the tire will lift off the pavement and give less traction. With a typical tire pressure of 32 psi, radial tires normally like 30-35 psi. I'd never drop a radial pressure below 28 and don't be afraid to go higher looking for better 60' times.

While I agree with the concept of radial tires and more psi/stock psi through personal experience I found the opposite to be true as have many others in our group back in the day running on radials. Personally on my 245/60-15 hard as rocks low buck radials I found the only way to get consistant traction ws to drop tires to 18psi and do one heck of a smokey to net consistant low 1.9? 60's. BUT I've also raced other car models on stock radials and found a few liked "closer" to stock psi and short burnouts or just simply driving around water box and a quick burp to clean the surface area of the tire.

This will be one area that is car specific since too many variable come into play to say one size fits all. Kinda like telling sombody their "carb is too big" LOL!! On track numbers tell the tale on black and white, so it's just a matter of finding what this exact combo wants to work correctly.

Running a stick really adds to the mix since it's cruitial to find a staging rpm and right amount of clutch slippage to make launch teetor on the raged edge of maximum traction and not bogging down or excessive clutch slippage. Not to mention where he is staging will also effect the numbers as well, we all know varying staging depth even an inch will change numbers so driver needs to concentrate on making sure he stages in the exact same spot EVERY time to make any numbers solid enough to gain information. This is why you see soo many experienced racers juuuust bumping into the beams enough to baaaarely light the staging bulb. If you just drive into the beams and turn on the stage light, lord only knows where the heck your at since the deeper you go in the slower your ET's will be.

This is why you see soo many experienced racers juuuust bumping into the beams enough to baaaarely light the staging bulb. If you just drive into the beams and turn on the stage light, lord only knows where the heck your at since the deeper you go in the slower your ET's will be.

Yeah, I kept a consistant deep stage every time. Lol, my second time up, I guess the tower didn't like the fact that I took so long to stage because as soon as the bulbs lit up, the tree started, and I had zero time to preload.