Rich knock...?? Help with Tuning (Please)

[GSXlaunch]

I did some searching but didnt find any particulars. My main mods are as follows: SCM61, 75lb/hr (780cc) injectors, rewired wal 255, GM MAft (blow thru) and v. 2.01 translator, FP2 cams, front mount, Ported EVO Exhaust manny and 2.5" exhaust -no cats and pretty much all the supporting mods. I am using a simple logger to tune. The cams were just installed last Sunday and last night I went logged some wot runs on pump gas. First off, the car pulls very hard with the boost set at 16-17 with spikes to about 18.5 psi (much harder than my EVO3 did at 23psi using C16) I still think I am running too rich and was hoping someone could chime in and support me on this or inform me otherwise if possible. I did notice some knock on the first wot run thru 3rd and part of 4th that reached about 16 counts. The run right after...very little at 3-6 counts. My thinking is rich knock. The car smells pig rich...I actually got a headache from it I think. I also noticed the engine backfires quite a bit at the first sign of letting of the throttle after getting on it pretty good. Anyhow, my SAFC (old 5-knob style) are as follows:

RPM Setting
800 -14%
2400 -10%
4000 -10%
5600 -10%
7200 -10%

My translator settings are set to 450cc with the idle knob set to (1) and everything else 0'd out.

EGT's accelerte normally to about 860-880c. Injector duty cycle at 18psi is 93%. IMO, these shouldnt reach 90% til at least 25psi??

It feels like its on the edge of hesitating at the top of 2nd but not sure if that is the computer kicking in the rev limiter as I was shifting by power drop off (if you will). According to my logger, 2nd gear shifts were right at 7400rpm. I've got a Magnus Intake manny sitting in my garage that will be installed this weekend. I probly forgot something but does anyone have any thoughts and or suggestions? Before the cam install, I had 0 knock up to about 22psi...these cams must move a lot more air then the stockers.

 

[sbiggi]

Your only at -10% with 750cc injectors? Did I miss something in your mod list?

I didnt see anything about a chip/dsmlink.

If thats the case.... and your translator is set for 450's, then you should be at -50% or more on the afc (although it only goes -50%).

If its setup the way you said it is.... you must be dumping a shit load of fuel in.

-Seth

 

[GSXlaunch]

Yup..I forgot to mention that...no chip/dsmlink. My afc only goes to -30%. I tried setting the maft for 750's but the car would not even run it was so lean. My a/f ga wouldnt even register a signal. I want to lean it out but since my logger is so irratic I need something else to judge it by...I am thinking of leaning it out 4% accross the board and go from there. I'll just keep an eye on the knock...and forget about the trims. Actually, I wont do anything else until I get the magnus intake installed. That might lean things a little on its own.

 

[guitarXgeek]

You've got all of those mods in the car and no wideband o2? Seriously though, that will tell you exactly what's going on instead of taking an educated guess that you're too rich/lean.

On a side note, what's up with the timeslip in your vehicle profile? 8.2@86 in the 1/8th and 13.8@76 in the 1/4?

 

[sbiggi]

Yup..I forgot to mention that...no chip/dsmlink. My afc only goes to -30%. I tried setting the maft for 750's but the car would not even run it was so lean. My a/f ga wouldnt even register a signal. I want to lean it out but since my logger is so irratic I need something else to judge it by...I am thinking of leaning it out 4% accross the board and go from there. I'll just keep an eye on the knock...and forget about the trims. Actually, I wont do anything else until I get the magnus intake installed. That might lean things a little on its own.

Yeah thats because your injectors are way to big to controll with a piggyback.
Try setting the maft back to like 650's and then crank the idle knob up.

If your injectors are indeed 750's, then your dumping in lots of fuel. Its going to idle lean when you set it for 750s because of the deadtime on the injectors, but turning the idle knob up should get it to idle correctly.

Full Throttle Tech Tuning Guide

-Seth

 

[GSXlaunch]

You've got all of those mods in the car and no wideband o2? Seriously though, that will tell you exactly what's going on instead of taking an educated guess that you're too rich/lean.

On a side note, what's up with the timeslip in your vehicle profile? 8.2@86 in the 1/8th and 13.8@76 in the 1/4?

I want and need a wideband...just dont have the funds now. It might a month or two before I get it. So for now, I am trying to get it in the ball park with the silly little logger. It should be enough to get into the 12's. Once I do that, I'll get better equipment and go for 11's.

As for the 1/4 mile time...That was with my EVOIII set up. I had to let off right at or just after the 1/8 marker. I was shifting too fast and missed 4th...twice in a row.
Both runs were almost identicle...both were 1.8 60ft and 8.2 in the 1/8. At least my driving is consistent.

 

[GSXlaunch]

Yeah thats because your injectors are way to big to controll with a piggyback.
Try setting the maft back to like 650's and then crank the idle knob up.

If your injectors are indeed 750's, then your dumping in lots of fuel. Its going to idle lean when you set it for 750s because of the deadtime on the injectors, but turning the idle knob up should get it to idle correctly.

Full Throttle Tech Tuning Guide

-Seth

Thanks...that is some good information. Once the Magnus is installed I will set to 550, then 650 if needed. I didnt mention but I already had the translator idle knob set to "1" which I beleive is 5% richer . If these injectors truly are 75lb/hr (they have "75H" stamped on them) and if I did the math right then thse are closer to 788cc injectors. I never even thought about "dead time". This is why my logger is so irratic! I like this idea and I think it is going to work. I had asked this question on full throttle a long time ago and never got a response. Thanks again. I will let you know how it turns out.