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Cross Fire Injection. Method of fuel delivery in the L82 motor. The 1984 is the only C4 to use the L82. This is the same engine used in the 1982 C3. ...
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Re: Track results, AFR heads

Subject: Re: Track results, AFR heads
by Josh on 2009/9/6 23:46:24

First post is edited with up to date information. If my math is right, I've added DA numbers here.

Uncorrected, the TFS heads went as fast as 11.9 and 119 MPH, but on different runs on different tracks. The best the TFS heads did, on the same track I was on last night is:

TFS - DA ~2000 feet

1.814 (TFS by .135)
5.176 (TFS by .08)
7.885 @ 89.43 (TFS by .04 / AFR by .84 MPH)
12.115 @ 119.34 (AFR by .003 / TFS by 1.21 MPH)

AFR - DA ~1500 feet

60' - 1.949
330' - 5.256
1/8 - 7.925 @ 90.27
1/4 - 12.112 @ 118.13

You can see that even though I botched the 60' time, the AFR heads are gaining ground on the TFS heads almost all the way down the track, and they did out ET the other heads by a small margin, which is impressive since I was so much slower in the first 60'.

The thing that is troubling me the most is that the the car with the TFS heads on it would pretty routinely pick up 29-30 MPH from the 1/8 to the 1/4. Now, with the AFR heads, last night all it would pick up was 28 MPH, and was as low as 26 on a couple passes. Especially since I was racing in what should have been better air.

I had the same 150 lb. passenger that I had last time. I made one pass without the passenger, but I'm not a consistent enough driver to realize the benefits of losing 150 lbs. in just making a single pass.

Traction isn't an issue. I run 16 inch bias ply ET streets, and they dead hook every time. The thing that kills my short times is the motor bogs down after I launch. I haven't spent as much time in the car as I should, and the finesse of slipping the clutch slightly to effectively launch the car isn't something that I'm gifted at. I am pretty much just dropping the clutch at about 4K, the car lurches forward, bogs, and then I continue the pass. I was getting better at it with the TFS heads (as you can see by the better short times) but it's been awhile since I've been to the strip, so I'm a little rusty. I was also there by myself, no support vehicle, no trailer, nothing... 80 miles from home. If I broke, I was in trouble so that was in the back of my mind every time I staged the car.

I think with some tuning tweaks I can work the bog out of the motor on the launch. The other C4's that I've driven don't have this problem, but they have all been MAF cars as opposed to my speed density. For example, Jonescap has a 96 LT4, 6 speed car. I have made one pass in his car at the strip. On 17 inch nittos, I went 1.76. First time ever in his car. The fastest my car has ever gone, on bias ply slicks, with nitrous, is 1.74. I went nearly as fast as my best ever, with less tire, on my FIRST trip down the track in his car. With some careful tuning of the timing and fuel tables, I think I can get the car to leave better, but I haven't really explored it yet. For testing purposes, it wouldn't be fair to do that now because I didn't do it with the TFS heads. However, now that the testing is over, I will probably pursue it.

Regardless, I am little disappointed with the MPH, but I'm not willing to get too worked up about it until I hit the track again and have a greater sample size from which to draw an opinion.

In the end though, I was hoping for more this track trip.
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