I have this topic on the TPI forum, but thought I'd mention it over here also.
I swaped my TBI for TPI on my '94 Silverado, and left the stock heads/cam, every vendor I talked to said that was fine. Now I get massive amounts of detonation upon any kind a accelleration, more on lighter accelleration it seems, and any where from 6-10 degrees at highway cruising speed not even accellerating.
Things I've tried to resolve it:
Timing, adjusted from 12 BTDC to 4 ATDC, not much affect.
Fuel pressure adj from 44# line off to 55# line off, it likes 50# best, knocked worse at the others.
Colder plugs, had R45TS, tried R43TS, no change there.
Filled tank with 101 race gas, helped a little, reduced knock by about 3-4 degrees.
Didn't have EGR, hooked one up to vacuum hose but not thru ECM, and it functions fine but is open all the time, but should help knock either way, but it doesn't help either.
Checked for vacuum leaks, in fact, capped all lines on TB and plenum accept fp and PVC, still knocks.
Disconnected knock sensor, and I can hear the ping then, so its definitely not false knock.
Tried different thermostats, 160, 180, 195, seems to do best with the 180, but really not much change.
Changed the entire ECM, no change.
Tried several different chips, even the stock cal chip from GM tables, no change.
This is a TPI setup from a 92 IROC.
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There may have been more things I tried but can't remember, this has been an ongoing 2-3 month project.
Any more ideas are greatly appreciated


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Rob
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[This message has been edited by 2QUIK6 (edited January 21, 2001).]

 

Well, When you mean Detonation, Im going to hope You mena ping.

If this is the case, Ping is Premature detonation ( ha ) Wich can Be casued By To Much Compression, To much advance ( the obvious one ) Or one you may not have considerd, Excessive carbon deposits in the combustion Chamber.
How Many Miles are on the engine ?

I would Consider this, however, To be Unlikely.

Im going to Guess To Much Ignition advance.

Im not entirely familiary with the TPI setup, But Im sure Someone Will Chime In with the proper procedure to Make Sure your Advance is where it should be.

To Much will cause crazy ping!



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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver

Livin' the Stereotype

 

Yea, it could still be that, but I've tried several different programs/chips, even the stock one that came with the TPI on the 92 IROC. Carbon deposits, well the motor was flushed with top end cleaner.
Oh yea, clogged cat, nope, I dropped the exhaust, still pinged, forgot that one.
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Compression, thats a good question?? I did a compression test, and got 170-180psi cranking compression on each cylinder. One shop thinks that is way too HIGH, says it should be around 125?? Others say its nothing to be concerned about unless its over 200? Not sure on that one.
If its any help, my O2 readings are usually around .800 - .950 mv.

 

I've seen your other posts and I am reading everything you have done. With an EGR, you can run higher advance than without. That is one of the things they do for you. But @ WOT, they don't function.

Currently, if your EGR is not hooked up to the ecm, then it isn't really functioning. You would need a little less advance then. But given the changes you have made (including a large retarding of the ignition), you should have at least overcome the knock detection at part throttle.

I am now leaning (no pun intended) to a possible vacuum leak. Also, a possible injector inbalance where one or more injectors may be running lean. I really feel that you have a lean condition occurring. And it has to be something that your fuel pressure isn't overcoming (ie. eprom).

 

Someones text above made me think of something. Have you actually verified you are getting timing advance? Its easy to check with an adjustable timing light. Might be that something went amiss in the swap and the timing is messed up.

 

Well, I can see the timing is being advanced as I rev the motor while in park. I was wondering the same thing if a shop had a treadmill or dyno, then someone could verify its being advanced correctly while under the hood and running at 70mph.
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Injector inbalance, ..when FIS had it, they said they flow tested the injectors, and also, wouldn't the plugs indicate something amiss, but they all 8 looked identicle, dry and brownish red in color. I was hoping to find a white one, but didn't.
Vacuum leak..well, last night a capped off all the vacuum lines on the TB and plenum, except for the PVC and brake, and there was no change. Now I guess there could be one on the manifold where it meets the heads? But on a vac test, it pulls 18 inches of vac? That sound normal?
As I said in my other post, I'm really starting to lean towrds the programming/timing tables in the chip, having a programmer take a look at it next week.

 

What knock sensor are you using? Have you tried a new one?

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