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still get a little "spark knock" no matter how far I retard dizzy


big-phil

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OK my stats are below, would it be my N47 head not flowing as good as the P90 would???

If I retard the dizzy I still get some knock, or tap, then If I retard it to the the point where it does not run as well I still get a little knock. The knock is at full throttle on the highway 4th and 5th gear, and I start to hear it at about 5000 rpm. Of coarse once it starts I get out of it kwick!

 

1st 2nd 3rd all can go to about 6000rpm and I never hear, the car is not all that loud so its not that I can't hear it, it just doesn't happen unless on the highway, could it be wanting more fuel?????????

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10 psi is about the upper limit of non-intercooler stock L28ET, with stock injectors running on pump gas.

 

For your setup, 10 psi might be to much, due to the higher static CR, and possibly the N47 head design.

 

You also might be leaning out due to dirty injectors or a failing fuel pump.

 

Try 7-8 psi and see what happens.

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Further to previous comments about dirty fuel pumps. Buy some redline fuel system cleaner and run that through it. As a cheap'n'nasty fix it might help clear out the injectors if they are dirty.

 

You really should do it properly with programmable computer and intercooling.

 

Oh and I'd bet money that if you can hear it at 5000 that its there all the time just softer and less.

 

Dave

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Guest bastaad525

I dynoed 6 runs on a mostly stock setup, 10 psi of boost with no I/C, bone stock EFI, and yeah right about 5000 rpm it went pretty lean, leaner than 13:1 air/fuel, and steadily leaned out towards redline. Stock compression, running 91 octane, I never heard any ping on that setup, and there was no sign of it on the dyno (usually shows up as an erratic power line). But knowing how lean it was, and how hot the T3 runs at 10psi with no I/C, and given the higher compression of your setup I'd say it's not a surprise you're getting some knock. Turn the boost down til you can get some more fuel and an I/C :-D

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Guest bastaad525

also, which distributor are you using? '81 style with the seperately mounted CAS? or '82-83 with internal CAS?

 

The reason I ask is I found that on my setup with the '81 CAS (mounted to the front of the engine) I could only adjust the timing about 6 degrees TOTAL, from about 17* BTDC to about 23*. So not much adjustment there for the full range... so I was wondering just how far you retarded the timing while still getting ping.

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