Super lean.

[WOTDSM]

90 GSX... Hacked MAS (removed lower honeycomb, silencer and screw backed out), 3 in. exhaust, 2g throttle body elbow and mbc set at 15 lbs. I get crazy knock (10-45 counts) between 3-5k and my o2 sensor voltage is between .80-.89 from 3-7k and my fuel trims are 109, 118.7, 118.7% (low, mid, high) and the o2 trim is between 118-160%. Clearly I need SAFC and a 190 lph and some 550's because I am maxing out the stock injectors.

My question is, should I be tuning for an AFR of .9ish and no knock or try for 100% fuel trims?

 

[SBR Joe]

The proper way is to get a wideband o2 and the fuel upgrades. You cant really go off the fuel trims because with the fuel mods the ECU doesnt know wtf is going on so theyre not very effective as a reference. You can tune for just knock with the afc and it will get it pretty close, but the proper and much more effecient and effective way is to pick yourself up a WB and tune for like 11.2 ish to be safe.


Joe
SBR

 

[WOTDSM]

Thanks for the tips Joe.

Is there a certain point where the ECU "recognizes" phantom knock? I know at about 7-14 counts it will retard timing... For instance, after 10 counts will it not retard timing? Clearly I am having some phantom knock issues and I'm not sure if dumping a bunch of fuel in would correct it...

 

[GVR4592]

You cant really go off the fuel trims because with the fuel mods the ECU doesnt know wtf is going on so theyre not very effective as a reference.

Explain to us how the ecu determines the fuel trims and why it's not accurate with the fuel mods he has?

 

[GVR4592]

Thanks for the tips Joe.

Is there a certain point where the ECU "recognizes" phantom knock? I know at about 7-14 counts it will retard timing... For instance, after 10 counts will it not retard timing? Clearly I am having some phantom knock issues and I'm not sure if dumping a bunch of fuel in would correct it...

The ecu can't determine the difference between phantom knock and real knock. The ecu will retard timing at 1 count of knock and will continue doing so up to 43 counts of knock. Dumping in fuel won't affect phantom knock.

At what rpm is the phantom knock occuring?

 

[Turbo Talon DL]

I had a similar problem when I was using my 1g hacked MAS. Anything less than WOT the car would just run like butt, stumbling, studdering, and crappy idle. You can either install an AFC, richen up your AF ratio until your O2 sensor cycles back and forth like it should, or put on an unhacked 1g MAS. You're drawing in too much unmetered air for the ECu to compensate.

 

[T9S1i]

First off, i would turn down the boost, no point in running 15psi if you are knocking and have no means of fixing it. Second get a logger and some means of fuel tuning, along with fuel mods.

Good luck and happy boostin.


FWIW, when i re-built my motor, i could only get away with 10psi on a small 16g and 450cc injectors, my IDC's were in the 90's. Fixed that with some 660's and my aFPR and a couple changes with DSMLink.