I went to New England Dragway yesterday (Saturday) and paid $5 to get 5 runs in. Can't really beat that value. Anyway, the temp was just right (mid 50s) and the track was nice and sticky. Sticky enough that I pulled off 4 2.1x 60' times in a row, on 255/60 Dunlops inflated to 35psi, with an open diff. The sticky track was responsible for me getting my best ET down to 15.704 @ 85.25 mph. I am still having problems on the top end, but they seem only to manifest themselves on the track. On the street where I am flooring it only for a little while (to pass), it seems to wind out like it should...on the track, it was beginning to die at like 58mph - shifts out of 2nd at 64-ish. I did have my fuel pressure guage on, and even did the $0.25 mod between runs. It improved my FP by about 1.5psi, to 14.5 or so. Also, my FP didn't move at all during the runs, meaning my pump is fine. I seem to have spark retard during the runs though, because I was getting between 5 and 15 counts of knock during the runs (data capture). I don't think this is normal...I was running Mobil 89. My exhaust is loud (gutted cat, no muffler), which could be causing false counts. Otherwise, it could be too lean ?

Anyway, thought I'd pass this on...15.7 isn't bad at all, I don't think. If it would have been running like it does on the street, I would have been looking at a 15.6 @ 86...oh well.

So does anybody know what could be causing the knock counts? And should I be getting any at WOT during a drag run?

My runs: http://kmoore.res.wpi.net/My%20Pictu...imeslips_4.htm

 

most likely the mobil 89 is the reason for your knock counts. that is some crappy gas to run under high loads.
also, what mods do you have that you are runnign 14.5 psi of fuel? with heads, intake, and 1.6 rockers i was runnign rich with 15psi, i can't believe that you would need that much pressure unless you have soem serious mods. what was your data capture sayin the milivolts from teh O2 sensor were? that much pressure you are prolly runnign rather rich at WOT.
those are very good times and a good example of what a litle traction can do for ya. keep up the good work.

later
tim

 

Thanks for responding...
My timing is stock (I haven't touched it), so I figured 89 octane is fine for an engine that requires 87.
My mods are pretty much limited to the following:
Gutted cat, no muffler, custom PVC/Caddy TBI intake with K&N cone. The rest of the things I have done didn't pertain to the drivetrain (like suspension). My pressure was 13 psi stock, which is on the high side. Also, keep in mind, I've got 68 lb/hr injectors. My cam is also a bit hotter than the L03 (it's the L98 cam, I think). I was going to try ANOTHER quarter to boost the pressure even higher, just to see which side of the curve I'm sitting on. I'm sure you'll say it won't run any better, but I want to be sure. It's an easy mod, anyway, and it will answer some questions (like if it runs better at WOT - the only problem with this is, I don't have the high-rpm hangup very often on the street, it only seems to come into play on the drag strip).
My data capture showed mostly >900mV during the runs (SLOW-*** capture rate, too). On a couple cells, during a few of the runs, I caught the O2 all the way down in the 600 range once, and again in the 700 range. This SEEMED to occur in the area of the top of 2nd and top of 3rd. I still think it's a timing issue that the gutted cat is mostly causing. I was thinking if I advanced the timing at the distributor 2-4 degrees and did a WOT run on the highway to see counts of knock, if it was not any worse than 0* BTDC, then the counts of knock are false, since if I am truely detonating, it would get worse with more advance, right? I would assume the ESC would keep me from blowing up my engine.

With these excellent launches and the ability to wind all the way out without getting hung up, like I can on the street, I should have pulled 86-87 MPH and that would have been good for a 15.5-15.6. Darn good for an L05 9C1 with stock heads/cam/manifolds/rear.

EDIT: I was able to trigger counts of knock tonight by revving the engine to 2000-3000rpm quickly. The counts didn't seem to trigger until the RPMs were coming down, but that may just be the slow ALDL. Either way, I don't think true detonation can happen at part throttle/no load, so I am even more inclined to blame the gutted cat on causing false counts. What do you think? Doesn't explain the street vs strip thing, but it would help explain some of it, anyway.

 

if you are triggering knocks when the engien is winding down from a quick rev that is fuel pooling.
i wonder about what you captured on track. if the mv's are at 900 that is dead rich, and if your timing is too late you woudl actually see it get richer as the rpms went up. so that soudns a little weird to me.
what do your plugs look like?
differences from street to strip are most likely because teh extended load from runnign all teh way down a track will "clean up" the plugs for ya and give you better combustion if you are a little rich at idle/lower rpm acceleration.
my best guess would be that the car is a little rich at idle but the open exhuast and improved air induction is causing it to get lean at higher rpms. nothing a chip or the Vafpr coudln't take care of.
keep us posted.

later
tim