Subject: Re: Track results, AFR heads by anesthes on 2009/9/7 1:55:31
Quote:
Josh wrote: 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)
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.
The ET is more of a representation of the driver + traction. MPH should be pretty consistent no matter what, and really shows how much power the car is making.
In regards to launching a manual, it takes time to learn. For the purpose of this test, I'd probably WOT and slip the clutch out of the gates to keep out of bog.
As of right now, if I knew nothing about the combos, just looking at the time slips I'd say the TFS combo made more power based on the MPH at the end of the track. Obviously the tune is botched for both combos, so it makes it kinda hard to evaluate.
Although, with all of that said, I believe the AFR's were cheaper out of the box than having the TFS heads modified, so since performance is about on par with a bad tune we can say the AFR is the better value.
