Hey man, whats up? I wanted to ask your opinion on something.
I just installed a 15lb pulley on my truck and tried to tune it. I did have a 12lb on it. It had a 8lb pulley on when you rode in it.
Now, since I have to tune it in open loop and started to run higher boost I have run into a problem. When first getting into it, my wideband shows 10.3 and as the boost comes up to 13lbs I am at 11.9. It is very sluggish at first and then takes of like a rocket at 11.2ish. I have to tune it that rich so when the boost comes up it won't run lean.
Now, my buddy and I have a idea. I will reinstall my FMU and tune it at 11.2 at low boost and have the FMU add fuel as the boost comes up. Reaching 11.7ish at full boost. What do you think? Will the FMU support that much boost?
After I get it tuned I will install a 50 shot. I will see what a stock bottom end will hold. My other motor is almost done.

 

FMU's do their job well, you just have to make sure that you get the right step up. If your FMU is adjustable then you will be able to adjust for this.
Try not to run over 80 lbs of fuel pressure.


The one thing to remember with FMU's is that they aren't consistant. Usually within +/- .5 a/f point.


You may also want to take a look at your MAF frequency. If the freqency is flatlining at a fixed value (say 12000 hz) then you are maxing out your MAF. This will cause the a/f to take off at the end of every run.
You can bandaid this problem (to a point) by increasing your MAF fail frequency and adjusting your MAF table up to its max (512 g/sec)

Additionally, you can make adjustments to your Main VE table in the upper RPM at 105 MAP to bring the a/f back down. (nice for GM to put this in here for us. Atmospheric pressure is 103 MAP, so the 105 MAP is mostly applicable only for boost conditions). You have a supercharger, so boost is going to be constant for what RPM you are running. Try to locate the RPM that the a/f starts heading north and adjust that RPM value on the main VE table. Try multiplying in 10% steps (up increases fueling). It takes a generous change on the VE table to see a difference. Make sure your fuel system is up to this task before you end up with a goofed up tune.

Good Luck


That thing must be a monster now. When I was in it, it almost seemed wrong for a truck to go that fast.

 

Well I am going to reinstall the 12lb pulley. My 15lb is slipping to much, I haven't seen even 13lbs. I also installed a bigger intercooler so it should make more power regardless. However, this will be easier to make the proper a/f ratio though the entire powerband. I also figure the juice will make up for the loss of 2lbs of boost.
There is something very cool about a truck traveling at that speed. You can look down on people while you are passing them.
I again want to thank you for all your help. I never once seemed cocky or acted like a *******. You are the man.