knock/fuel trims/MAFT

[DSMcamaro]

mods are listed in my profile, I'm using a MAFT for tuning and MMCD for logging. I also currently have a exhaust cut out on my car for some free flowing exhaust, which also causes me to creep from 15 psi to about 19. which is fine with me for at the track. So my high fuel trim is really lean at about 132, my mid and low are decent around 100 and 110. My current setting are as follows.

base= 450 cc
low= 35%
mid= 25%
high= -20%

So I figure making the high trim richer should help. Nope! I try bringing the high around -10 to 0 and the car will cut out.
With the settings the way they are the car will pull decent, but I get anywhere from 17-20 counts of knock through-out the pull with the timing at about 15 degrees. Now when I go to track I will use race gas, which should help, but I'm wondering if I NEED bigger injectors? Should try changing my base injector size? right now its set for the stock 450's, which I have. Any ideas?

fyi: its also about 73 degrees outside today.

 

[talontd92tsi]

What is your logger showing for duty cycles on your 450's?

 

[DSMcamaro]

just tested it quick with the exhaust cut out cover back on (so only boosting 15psi) and the injp maxed out at about 22 ms.

 

[Talonguy5]

From the mods listed in your profile, you don't have any way of lowering/removing fuel cut.

Running a stock ECU, with stock injectors, and raised boost is a recipe for fuel cut.

Find some way to get rid of the fuel cut, or, get bigger injectors and lower the airflow signal enough with the MAFT to stop it from happening.

 

[DSMcamaro]

So when its about 10 degrees warmer with the same settings I get no knock. Makes sense right? thinner air requires less fuel. So I've basically came to the conclusions that I NEED bigger injectors. Would it make sense that the injectors are cutting out when I tell them to add more fuel(through the translator) than they can deliver? Thats about all I can come up with.

 

[Talonguy5]

It's not that you're necessarily asking the injectors to deliver more fuel than they can. (You MAY be, but that's not what is giving you the fuel cut). It's that when you richen it up using the translator, you are adding more "airflow signal". When you add more airflow signal, you run into the airflow limit put in place by Mitsubishi. (2.03grams/rev) When you hit that aiflow limit, the ECU shuts off the injectors. (Fuel cut).

 

[donmagicjuan]

As Talonguy5 alluded to just there, there is a correlation between IDC and the onset of fuel cut, but the relationship is not causal (although it typically happens somewhere around 100% IDC). With this in mind, you can see how eliminating fuel cut will not necessarily fix your problem, as you've now only made your injectors more susceptible to self-destruction. Based on the evidence in your posts, I would say bigger injectors are the way to go, and at the very least a good idea. Just to be sure of course, I'd run a quick boost leak test (if you haven't yet) to narrow it down.