aggie_corvette

I plan on running N2O (100shot wet) but before I do I borrowed my friends EFI Live to check out my engine. I was surprised to see so much knock retard. I did a 3rd gear pull (mn6) from 2k to 6k on the freeway. Starting at 4300 rpm I started getting knock. Imagine straight lines connecting these points.

Rpm 4312—6088
Adv 19.5 29.0
Knock 4.75 1.67
Maf 7976 8773
Maf 152 200
Map 98.0 98.0
Ltft b1 17.2
Ltft b2 15.6
Iat 80*F

Car currently has NGK tr6, gapped to 0.036, K&N dual intake, and a catback. The car has NEVER been tuned but with these basic mods pulled 329 hp at 5900 and 339 ft/lbs at 4500, AFR on WB02 is unknown.

To me this seems like allot of knock retard and allot of timing, especially if I plan to run nitrous. I don’t have tuning software yet… maybe I should….

What do you guys think?

TIA
Will

Another_User

False knock or bad gas. It's hard to tell. It happens sometimes. Tuning software is excellent, especially if it has built-in logging...hmmm....I bet I know which one you should get, LOL! My wife is probably getting upset with how much time I spend in front of fuel trim histograms and VE tables. For the hours it has kept me preoccupied it has been worth it.

nbmls1ta

Another thing is your ltrims are very positive. That means that your car is adding that many "points" of fuel to correct for a lean condition. I had a lot of knock also and once I tuned my ltrims to ~0 or slightly negative the knock disappeared. Just a thought but I would definetely try to get your trims down before you spray that may solve your knock problem. This is just a thought and it could just as easily be a bad batch of gas or false knock.
Hope this helps.
Matt

Another_User

Yeah, that is a good point. There is a lot of compensating going on in your trims. Probably too much. Is your MAF descreened?

jimmyblue

iTrader: (11)

That MAF reading is very low for 6000RPM. I
see >10000Hz on mine at 6000RPM. I would
suspect either fouling (gooey K&N) or filing
(porting) at the root of it all.

aggie_corvette

Well the car is a '99, so i believe the maf is supposed to have a screen, but mine doesn't (bought it used). I do know that it is not ported.
the filter was recently cleaned but the oil might have fouled the maf?? how do i clean that?

great advice so far.

deezel

You can clean the MAF wires with brake cleaner or alcohol. Be careful not to damage the wires or resistors.

Another_User

Yeah, rubbing alcohol works great. Use a Q-tip and gently brush it against the resistor. Don't rub, or press down at all. One of the little resistors is probably going to be black. I have noticed that one always turns black, but it will clean up.