Turbo too small?

[Searcher]

I've been working on a friends Limited the last week or so and finally got it to run pretty good, SOTP. No track visit yet, perhaps in a couple weeks.

Anyway, I noticed with the Direct Scan that at the top of Third, just about where the 1/4 mile line is, it'll get a couple degrees knock retard. And if I run it out the back door, as it were, the retard will go nuts up to 15-16 degrees. The the car will do 23psi, the wideband says 11.3-4, T-pro says MAT's are peaking about 130, the chip is set for 19/16.5 degrees and alchohol injection is in use. The turbo is not known for sure, but is a TA type. The intercooler is a stretched stock mount.

I was curious about the high speed knock retard, since I haven't seen that before, and wondered if anyone here had any info they'd share. Thanks

 

[Ormand]

If it's getting 23 pounds of boost, and it's knocking, it's not the TURBO that's too small. It's too much advance, too little fuel, (or too much- may be "rich knock") spark plugs too hot, or other cause of detonation. And double digit knock is not good for the engine.

 

[Marc87GN]

I've been working on a friends Limited the last week or so and finally got it to run pretty good, SOTP. No track visit yet, perhaps in a couple weeks.

Anyway, I noticed with the Direct Scan that at the top of Third, just about where the 1/4 mile line is, it'll get a couple degrees knock retard. And if I run it out the back door, as it were, the retard will go nuts up to 15-16 degrees. The the car will do 23psi, the wideband says 11.3-4, T-pro says MAT's are peaking about 130, the chip is set for 19/16.5 degrees and alchohol injection is in use. The turbo is not known for sure, but is a TA type. The intercooler is a stretched stock mount.

I was curious about the high speed knock retard, since I haven't seen that before, and wondered if anyone here had any info they'd share. Thanks

Are you 100% sure it is actual knock because with those KR numbers it should be quite audible? With those A:F numbers, low timing and alky, I can't see any reason that you should be getting any knock at all unless it's false knock. Do you know if the chip is commanding the T/C lock at that point even though it still shouldn't knock?

That just seems odd because with a similar chip with low timing, I can get away with 20-21 psi with no knock on straight 93 so, with Alky, 23 psi would be easy. Maybe check engine temp readings, downpipe for markings from hitting the frame & T/C lockup, if in fact, it does lockup around that point. Just some thoughts I had. Keep us posted.

 

[Searcher]

Well, the reason I asked it that way is that I'm working with another TR, this one a GN, that is about identical with the exception of an an older TE-63 and a Great Eastern front mount. The GN will make the entire pass, plus more, cleanly and with about an extra 10mph on the trap spreed (11.80's@116). We haven't put the wideband on the GN yet, but a dyno's in-the-tailpipe WB looked good IIRC (it's been a few months).

So I was thinking that the Limited has a heat build-up issue since it looks like it'll do 99.9 percent of the pass without a problem. I was wondering if anyone had some insight into whether it was from too high MAT's, or if perhaps there was too much exhaust pressure resulting increased cylinder heat from exhaust contamination of the intake charge.

As it turns out, the question is academic anyway as I found out this morning that the owner is buying a larger turbo because he wants the better top end pull like that GN has. Oh well, it just means I get to have more fun-time tuning on a Buick.

 

[Searcher]

Are you 100% sure it is actual knock because with those KR numbers it should be quite audible? With those A:F numbers, low timing and alky, I can't see any reason that you should be getting any knock at all unless it's false knock. Do you know if the chip is commanding the T/C lock at that point even though it still shouldn't knock?

That just seems odd because with a similar chip with low timing, I can get away with 20-21 psi with no knock on straight 93 so, with Alky, 23 psi would be easy. Maybe check engine temp readings, downpipe for markings from hitting the frame & T/C lockup, if in fact, it does lockup around that point. Just some thoughts I had. Keep us posted.

Now that you mention it I didn't hear anything, but it was up over 100mph so maybe wind noise could've drowned it out.

According to the DS the engine temps max about 173. I'd post a file but it's on this ancient 486 laptop (with Windows 3.1 ferchrissake) that I don't even think has an floppy drive, and we sure don't have an external LOL! Then agoin how'd we put DS on it. Hmmm I'll have to look this evening after people start getting home.

As for lockup, no it's not commanded. For some reason the ECM doesn't recognize AC request so we can't set that parameter. Something else on the list to do...