running poorly, no clue why

[tstkl]

ok so last april 5th I went to the drag strip and my car was feeling pretty good. Highest trap was 97.98 mph (yea, low....) but heres how that run went. First run of my life, I stage, and before I even realize it, the lights are going and my car's still idling, so I slam on the gas at the first yellow light and drop the clutch by the second. The log shows I got up to 2500ish rpms and bogged to 1300 and went from there. Missed third three times on that run, and trapped 97.98 mph.....

now yesterday I went again, didn't change anything except the sparkplugs because now for some reason it was missfiring and getting more knock than before. I slapped in 15 dollars worth of 100 octane to add to my probably 7-9 gallons that were in the tank. (well thats if the tank is in fact 16gallons, I always get an empty reading at like 11 gallons.) and don't change anything else. That run with a pretty bad launch I get 94 mph and I didn't even miss 3rd. Next run I add 5% because my wideband was reading ~12.8 afr throughout the run. I had the wideband in april, but the power supply was hooked up incorrectly, so I don't know what afr I was running that day. Next run I get an ok lauch and don't miss third and with an afr of ~12.1 I trapped 95mph.

the third run I added another 5% (this is global, I haven't learned to use the rpm mode of the maft yet.) so Im sitting at ~11.8 afr. This time I launch it about as well as Im capable of, and pick up one more mph and end at 96.36. Nice to know that with a 1.933 60' time (give me a break, I've only gone to the track twice now, and I spun my tires on that launch) compaired to the 2.1 60' I got on the 97.98 mph run in april, I still go slower even though I didn't even miss third.

why did I lose so much power? nothing changed really, what could it be? I could feel the loss of power even before I had the trap times to conferm it. It struggles in the top end on the freeway (above legal speed limit quite a bit, don't give me a lecture on speeding, I know its illegal, I know this site doesn't promote it in any way, and Im not suggesting it to someone, this is purely information I feel will help someone diagnose my problem) It feels as though the top speed of the car has dropped drastically. The only thing I have control of tuning is the gm maf signal with the maft. Im thinking it might be the knock I was getting taking its toll on the engine, but Im hopping its just like a boost leak or something, but that doesn't explain the missfires.

one thing on the missfires: at 12.8:1 as I was going down the track, it missed a lot, with brand new plugs that were gapped and installed that day at 1:30. At 12.2:1 I got like 1-3 misses going down the track. At 11.7:1 I got like 25-30 backfires going down the track. Apparently 11.7 afr is too rich.... I dunno.

 

[GVR4592]

What plugs are you using what is the gap? Do you have any datalogs of the runs?

 

[tstkl]

I was using ngk bpr6es's and when I took them out they were white from being too hot and brown from being too rich, I switched to bpr7es's with a .28 gap and it ran a tad bit better but not much. The 6's were undergaped for some reason,... I don't know why but Paul said most likely in my case it was not a mechanical thing that caused them to be undergapped. Paul is my mechanic and the person who installed the 6's last year and the 7's on wednesday. I think its either a boost leak or bad compression. My best guess is bad compression because it was running lean, not rich.

 

[danyz250f]

Do a leak test, I have had the same kind of problems. Your maft is in a blow through if I remember right so I hear that makes tuning alot harder. Mine is in a blow through and it was hard to tune. My sputter problems were do to being to lean, and I only new this because I checked my plugs. Also I had problems with boost leaks and plug wires. hope this helps.

 

[tstkl]

found it




blew the j pipe gasket again



damnit...

 

[danyz250f]

I hate that gasket it always seems to leak. My friend has a 95 gst with a 14b and we had a hard time getting that not to leak with the aftermarket j pipe so we found if you use mr. gasket gasket maker and rtv on both sides of the gasket it will hold.

 

[tstkl]

well my car has a vicegrip on my licp, so thats why mine's blowing, but thanks. I just have to prevent my engine from moving or let my licp move more. Im thinking poly motor mounts with a flex section on the licp and all will be good. Hmm, #### it, Ill buy some poly's right now...