Still need help figuring knock...

[Polak420]

Hello I need help figuring out why my knock guage goes off at about 80 % throttle. I run 42psi of fuel pressure at idle with vaccum connected, and my VDO boost guage only reads 13 PSI. All the major mods that I have are in my sig. I run Mobil super+ 93 octane gas. The injectors are 42 1/2 pound.


Thanks for any help,
Polak420

 

[Dan Thompson]

The FP should be set with the vacuum line off.

What gear does the knock occur? Is it during a shift or at the start?

 

[GrndNatnl]

WAY too much fuel pressure (with line connected). Like he said.. set it to 42 psi with the line off.

 

[Polak420]

Thanks I'll try to set the fuel pressure down a bit, but if memory serves me right it still knocked when I had lower pressure in my car, and some tech guy at poston said that I didn't have enough pressure. I notice the guage go up more while shifting than from the start. It happens maybe 2-3 seconds after I floor it.




Once again thanks for hooking me up with info,
Polak420

 

[Dan Thompson]

When you floor it, the boost should go up and for each pound of boost the fuel pressure should go up 1 pound.

My boost on a stock turbo goes up quite fast when I have the gutted cat on.

 

[GrndNatnl]

To make sure your regulator is adjusting fuel pressure correctly, the rule is as follows:

Fuel pressure at any given amount of boost should equal to:

Static (line-off) psi + how many psi boost.


IE: 42 psi static FP, and boost set to 17 psi would mean at max boost, your FP should be ~ 59 to 60 psi. Thats why it pays to have a hood mounted gauge, or have one on a braded line that you can put up to the windshield and watch while tuning.

When I do that though, my gauge is as too much of a friggin angle on the glass to read. It's a PITA.

 

[dyermullet]

Have you ever went to Miami Subs in Highland? Go on a friday or sat night there are a few turbo regals and one TTA. They are friendly people and I am sure they could answer some questions.

Scott

 

[ijames]

Could also be an egr problem, where the chip expects the egr to be working and you have it blocked off, which on some cars can cause knock but when I've seen this it was with no or very little boost. And, some chips just have a problem dealing with part throttle boost. WOT will be okay, and less than 2-5 psi (or so) will be okay, but in the 5-10 psi range or so they knock. I've seen a couple of chips from different vendors that were this way. That's part of why I tell people not to try and run 5-10 psi - either light foot it, less than 2 psi, or go wot.

 

[FreeJack]

I've got the same problem. Around 5 to 10 PSI or at a shift Turbo Link shows me 10 to sometimes 40 degrees of knock. I'll replace the EGR and see what happens.

 

[Polak420]

Hello, sorry it took so long to reply. Don't get much time between schoolwork, job and the bar Anyways, I set the fuel pressure to 42#. There was great improvement. The car will still knock sometimes, but it is much harder for the guage to go off now than before. Mimai Subs in Highland.... never been there not too familer with area. I do go to Purdue Calmuet though so I'm sure it's not too far from there. Do you go to school there too Dyermullet??

Thanks for info,
polak420

P.S. if anyone has anymore ideas to get rid of my knock retard post it

 

[dyermullet]

Well I go to Purdue in Lafayette.



Miami Subs is on 45th. It is a block west of Indianapolis Blvd. There is Christenshin chevy on the corner or 45th and indianapolis. Web ford is also on the other side of indianapolis.

Hope you track down the problem.