Strange tuning question for you guys.......................

[LuvmyC5]

I'm having an A&A Vortech SQ blower kit installed now and I spoke to the tuner and he said that the car is going fat at 3400 rpm with 18° of timing, but when it runs with 16°'s it's much better. It's going from commanded 12:1 to 11.3:1 in this range. He said that he'll probably leave it at 16°'s and just command the AFR to 12.1:1 to make up for the lost 2°. At 3400 rpm/18°, he said that he was getting 2° kr, which I thought was weird because wouldn't getting more gas stop knock? He was still getting slight knock at 16° though. How can changing the timing effect the AFR? It's got me stumped! Any help would be Greatly Appreciated!

[tblu92]

Now you have me confused--!!! but I think you said that he changed it from the 12.1 to 11.3 at 3400rpm's-- so he is going richer hoping to get rid of the 2* knock retard--which makes sense--richer fueling would get rid of some small knock--but more or less timing shouldn't change the AFR---exacty opposite more or less AFR would allow more programmed timing or not allow more programmed timing--either you mis-understod him or you wrote it down wrong--but I can't really figure out what you are trying to say--unless what i suggested is correct----

[LuvmyC5]

Originally Posted by tblu92

Now you have me confused--!!! but I think you said that he changed it from the 12.1 to 11.3 at 3400rpm's-- so he is going richer hoping to get rid of the 2* knock retard--which makes sense--richer fueling would get rid of some small knock--but more or less timing shouldn't change the AFR---exacty opposite more or less AFR would allow more programmed timing or not allow more programmed timing--either you mis-understod him or you wrote it down wrong--but I can't really figure out what you are trying to say--unless what i suggested is correct----

Thanks for the reply!

The only thing that he changed was timing. He put 2° in it and then the AFR changed by itself. The commanded AFR was 12:1, and fattened to 11.3:1. and still got knock. I can't figure it out because changing timing should have no effect on Commanded AFR.

Please tell me if this explanation made more sense.

[tblu92]

Ok i think I understand what you mean----The data you are missing is the ACTUAL AFR---the commanded really dosen' mean anything--what hapens is after all the mods--unless the VE table is corrected the commanded does not match the actual anymore---On my C5 cammed vette I have to command a 12.15 in order to achieve a WOT AFR of 12.8---There is really no drawback to that however as long as you know you are not getting what you ask for---the only way to make sure what you are ending uo with is to loog the AFR's with a wideband 02 sensor---that is the tell all final word on what the ACTUAL AFR really is.....
PS: to correct the VE table is a time consming affair and takes hours of street driving with the MAF disconnected logging and pasting PT fuel trims up to 4000 rpm's in every cell---then after you have the PT coreected you have to do the same with the WOT wide band AFR's and correct it there with either the IFR table or the MAF tabl
The only other thing that might be happening is that your computer is going in the "cat overtemp protection " mode intermitently and what that does is richen up the AFR for a while to cool the cat off and that AFR is in he 11's--look at that table to see if it is exactly 11.3--if it is then that's whats happeninig--have him disable it and it won't happen again----

[LuvmyC5]

Thanks for the reply!

I still have cats on the car and want to ask the tuner if he turned COT off. Another thing is to check OLFA to see what it's set at. If either of these are off, then WOT fueling would be off. I'll just have to wait and see.

I don't have the tune in front of me (he was suppose to send it to me Friday but didn't, so I've got nothing to look at. Which doesn't matter because I couldn't read it anyway bwecause I've got EfiLive and he uses HP Tuners).

[tblu92]

what is OLFA ?? not a term I'm familiar with

[CorvetteTechInc]

Originally Posted by tblu92

what is OLFA ?? not a term I'm familiar with

Open Loop Fuel/Air.