Crowbar187

I'm trying to eliminate high RPM knocks and I've noticed my BLM at 160 and INT at 140 under hard acceleration. I recently installed headers, high flow runners and an afpr which I have set to 50 psi. BLM is just about a perfect 128 throughout every other driving range. I find it hard to believe that I'm moving so much more air that the otherwise stock fuel system can't keep up. I've had the car over 10 years and never did the fuel pump so I'm kind of suspicious that whatever piece of crap pump is in there can't keep up with the new demand. I'm wondering if there's any way to prove this or if someone else has come across this. I searched the forums and everyone else seems to have the opposite problem (160 @ idle, 128 @ in higher rpms). I'm also wondering if this is something that can be compensated through tuning which I've been thinking about doing but haven't gotten into yet. Thanks.

Edit. Brand new fuel filter

ULTM8Z

If the pump is bad, the fuel pressure will drop significantly during high demand situations.

Crowbar187

Good point. Looks like I'm taping my gauge to the windshield. Maybe power braking will do it.

ULTM8Z

Power braking is unlikely to replicate it. You need to see what the pressure is during the high demand condition...

Crowbar187

So I took it for a ride and had my buddy watch the gauge. He said it stayed between 40-45 when I was getting on it. I'd rather it hit 50 but maybe that's unrealistic to assume it would. Sitting idle it definitely goes to 50 with vacuum off and 42 with vacuum on. I decided to disconnect the battery and reset the tables. After a 20 minute ride it now stays in the 150s under heavy load. If it stays within adaptable range I guess I'm happy enough. Would still rather it didn't spike at all. Might have gotten a little better because it only knocked 16 times in 20 minutes and I was beating the hell out of it. Again, I'd rather it didn't knock/retard at all but that might not be realistic.

ULTM8Z

What is the engine combo you're running?

Crowbar187

Damn near stock 87 305/auto with a bunch of bolt ons.

ULTM8Z

So sounds like your pump is ok.

Question- why did you set the pressure to 50 psi? That's 10 over stock.

How are you reading data? With tuner pro? If so, maybe post a log file showing when the issue pops up...

Crowbar187

Pressure used to be 45. I only wanted to jack it up a few psi but the adjuster bolt is hitting the under side of my intake. I'd read of people running it at 50 so I figured I was ok there until I feel like pulling it apart again and modifying the bolt. I read it with my modis.