injector going static problem

[NC87GN]

Burned a chip for 50's to break in a new motor. The first 100 miles were very easy and did not use DS. Have 200+ miles and decided to hook up DS and dial it in a bit. Got around 7 degrees of knock at 18# of boost but have some fine tuning to do. However I looked at my injector duty cycle and it was 130%!!!. My base fuel pressure is 40-41# and 02's look good 780-800mV. In scope mode the curves are crossing which is not good. How do I prevent the injectors from going to 130%? I have the ability to do chips but I'm fairly new to 50's. I know I'm not overrunning the injectors as my combo is a 62, stock heads with valve job, 50's, 2800-3000 stall and stock bottom end. My inj. constant is 45 which is my first problem but I just found that out. TIA..

M. Banas
87GN

 

[bruce]

It's not easy to do correctly.
First, I'm going to assume you mean your injector constant is set at 45.

Given that, you need to set it to 50, and then recal the MAF tables to where your BLs are about 128.

Then you can set you PE AFR vs temp commanded AFRs to rough estimates of what you want.

At this stage having a WB is handy so you can compare Commnaded AFRs to actual AFRs.

Then you want to use the PE vs RPM corrections to get the commanded and indicated AFRs to line up.

Getting 50s to make good HP, at a 90% DC, takes adding Water from what I've seen.

The one 50 chip I helped with, took adding fuel in the MAP tables, to get the 128s. Which running the 45 IC would do, but doing things that way messes up using the PE AFRs, since the numbers can go out of range.

Go slow, take lots of plug readings, and complete notes.
As you get into running into the mid-90% DC is when you can have troubles, as you go from your 130 to 90.

The big advantage of using big injectors is that you can start a lil lean, and go up. Just running a 70%DC with a 72 is about as much fuel as you have now. So then you could slowly add more fuel watch the boost, and then see how the performance is. And you never get into the range of the injector being erratic.

 

[NC87GN]

I changed IC to 50 set the boost to 16-17# and BLM @ idle are now 150. Went into PE vs RPM and raised fuel @ 800 rpm to 15% richer. BLM are near 134 . Also went from 20* to 18* @ 255 to eliminate some knock I'm concerned about. I still have some more tunin but its getting there.. TANX Bruce!

M. Banas
87GN

 

[BoostKillsStres]

NC87
PE RPM is just that, fuel added or removed only when in PE. The change you made will have no effect and usually you can't even get the car to go into PE until your in the high 2000 RPM range. Make sure you don't have any vacuum leaks with the BLM's trying to go that high and remember you need a good 5-15 min drive cycle through all rpm's for the BLM's to learn stable values. Any BLM value +/- 10 from 128 is good in my book.

 

[NC87GN]

You are right Mark.. Did not even think about PE. I'm going to go through and check the car for leaks.. I thought I heard a cross-over pipe leak but I was trying to pay attention to everything else. Tanx..

M. Banas
87GN