85 K5 Blazer with TBI retrofit

[rokcrawlin85]

Does anything stand out as odd? I noticed when playing it back that the BLM's rise to add fuel initially then drop down to lean it out. Is it normal for the BLM's to cycle this way at times?

[rokcrawlin85]

Hey guys, I'm back after a long long long break. Finally got an itch to get back on my rig. Hoping to ask a few questions and pick your brains for tuning my motor. Spent the better part of today running back and forth from burning to driving. Long story short, I've run out of injector duty cycle. It falls flat on it's face and can't pump enough fuel after climbing above 2000 RPM and about 3/4 throttle. I was getting very excited tuning today. Things were actually going quite well. Actually seeing improvements with every tune I tried. Then I've come to the sad conclusion, I'm out of injector.

Here's what I've done so far,

Upped the fuel pressure from 15 to 18 PSI. Lowered the entire fuel table by .85 to compensate for the added fuel then started tuning again. I took a screen shot so you can look at and notice the massive demand for fuel on the table. I can't give it enough to make it happy.

I guess I'm in need of knowing if I'm going to have to upgrade to larger injectors to satisfy this motor, or are there some numbers/parameters I can change in the tables to make it pump more? I know I've left out a lot of info I'm sure you'll want. Please please just ask and I'll post it up. Would really like to know what my next step is going to have to be. Thank you much for any help.

ECM-1228747
If you can read it, all that info should be across the header on the screenshot.

Attachment 10361

[rokcrawlin85]

Just was looking around in the bin, does 98 for a BPW sound correct? As far as I'm aware, I'm just using the stock 350 TBI injectors, so 55#? If my searching is correct that most bins with 55# injectors run a BPW of 138? By changing this number in the bin, what effect does it have on the injectors? Smaller the BPW=? Larger the BPW=?

[dave w]

I use the Base Pulse Width (BPW) Calculator for figuring out injector flow rates vs. BPW, see attached .zip for the MS Excel spreadsheet.

dave w

[rokcrawlin85]

Thanks Dave. I plugged in my numbers and it spits out 150 for me. So I guess I'll plug that into the bin and see what change it makes for fuel demand.