just got done bolting in a MAD front ypipe and DRs and then went down to the street races at my local track. my previous best was a 13.44 at 102.51 with a 1.94 60ft on street tires. i tried to do a burnout when i lined up, but the DRs were hooking a little to well and i couldnt really spin, it just sorta hopped a few times. so i staged and brought the revs up to 1300 and full throttle launched on the last yellow. i took off with zero wheel spin and finished waaaay behind a Ttype (who ran a 11.5!). when i got my slip, the offical kicked me out for being under 14.0 without a helmet. they had never kicked me out for this before, so i figured i must have gone way fast. boy was i wrong! 13.53 at 102.11 with a 1.94 60ft! ok, something doesnt add up here. i just replaced the front ypipe with one that eliminated the precats and was a little wider for better flow, and with the same 60ft as my previous best run i went slower! this doesnt make sense! the only thing i can think of is that i was having probems with the ypipe install and was geting a little exhaust leak by the manifolds. i believe the "ticking" noise coming from the exhaust manifolds was registering as knock and retarding my timing. i cant really think of anything else. the only other thing i changed was going from a dirty K&N to a clean paper filter.

i hooked up a Matco OTC 4000 scan tool to the Vette this afternoon and went out for a test drive. i read two different "modes" in the data stream : knock retard, and timing advance. the figures for these modes in differet rpm ranges are as follows :

idle
KR = 0
TA = 18-21*

1800 rpm cruise
KR = 0-4*
TA = 44-46*

WOT
KR = 18-24*
TA = 31*

i always thought total advance under WOT should be 36*... if so mine is off by 5* or so. any suggestions?

i'm guessing your talking about the vette. what do you have done and what were you expecting it to go........if all you have is a y-pipe and dr's on a stock driveline and suspension then it doesn't sound far off at all.

they weren't and aren't that fast stock.

It's hard to compare two runs on two different days. The weather could've been different, more/less weight in the car. Too many things change from run to run.
That does look like alot of knock retard though. I havn't checked mine in while but it was like 8-10* at WOT.

I usually run about 40-42d of timing at cruise, maybe 28-32d at WOT. We need to know some specs on your car to help you out more.

alright, here are my specs. its a 350 tpi motor mated to a 700R4 trans. gears are 3.07s. i always run base timing (6*), and i have my fuel pressure set to 48psi with the vac hose disconnected. with that said, here are my mods :

previous best time 13.44 at 102.51 with 1.94 60f
MODS = cut air lid with K&N filter, removed MAF screens, relocated MAT sensor to air inlet boot, airfoil, ported plenum, holley AFPR, removed water pump "frisbee", upgraded ESC module, 160* stat, flowmaster force 2 catback exhaust

Fridays run 13.53 at 102.11 with a 1.94 60ft
MODS = same as above + 1) i put the MAT back into the stock location because the hole in my inlet boot was giving a false air reading causing a rough idle 2) i removed the K&N filter cause it was dirty and didnt have the cleaning kit, so i put in a new paper filter 3) MAD precat eliminating front ypipe 4) BFGoodrich DRs

im confused because i should have seen a gain in mph with the better flowing front ypipe, especially since the 60fts were the same on both runs. instead i saw a decrease in power

When I am at the track and remove my air filters I constantly see about .08-.1 off my e/t in my camaro. Try running with no filters, and K&Ns supposedly flow better than paper filters even when dirty.

Well, for one reason or another you are logging some decent knock counts at WOT which is definately going to take away from your performance. It is hard to say if that exhaust leak stuff is to blame for the Knock counts, but the leak could possibly be causing errors in the O2 readings as well and should be repaired ASAP.... What kind of PROM is in this thing?

as far as i know its the stock PROM. ive had the car for 4 years now, and ive never changed it

If your were getting a 1.94 60 ft time with streets and you went to DRs and got the same 60 ft then it could easily be the rolling resistance of the sticky DRs contributing to your lower ET could it not?

I think you need to get a few more Runs in To get an accurate comparison.

Less than a tenth Change in ET is totally reasonable to expect between any two Given Runs.

that's what makes bracket racing Fun