Those of you who are familiar with my web site will understand the subject. I was in the process of swapping my dual-cat y-pipe for a pair of Dynomax bullet dumps (essentially home-made header mufflers) in preparation for a trip to the dyno. When I propped the y-pipe against the wall, I heard some stuff fall to the floor. Turned out to be bits of piston ring that didn't make it through the cat. Poop!

I think it broke because I forgot to change my "minimum advance" table from 28* to 24* when I changed the advance vs rpm table. 28* plus 15 psi plus 91 octane = detonation = boom.

 

Thank you for the heads up. I know what I would do with a brain if I had one.

 

for all its worth, your site's has been a great help! God knows what you have planned

 

The highest value in my stock min advance table is 23 degrees at 5600rpm. Why would this table ever be increased?

 

I undoubtedly did it myself years ago when I was trying to get the logged timing to match what I put in the advance vs rpm table. Then I forgot about it. It didn't bite me till I put in the ys-trim. It's a safe bet that I'll go through every table shown in LT1-Edit and Tunercat before I go WOT again. Live 'n' learn.

 

LJ, did you ever find out the source of the mysterious added timing?

I'm getting 2-3* added in at WOT. Can't seem to find it in the tables anywhere (like most people).

Oh, and sorry about your car. I'm sure it'll be running again soon. God-speed!

 

Yeah, Jody Shapiro, who has been "reading" the code and building on the disassembly work of others, found where the timing is added in. This is what he sent me:
0deg when 0 <= RPM <= 1517
1deg when 1517 < RPM <= 3034
2deg when 3034 < RPM <= 4551
3deg when 4551 < RPM <= 6068
4deg when 6068 < RPM <= 7585

 

LJ So what you are saying that at 15# with 91 octane you would normally have 24 degrees at WOT?

Can I ask what type of IAT temps you have?

Sorry to hear about Boom 9. I have read your site many times.

I'm trying to dial in an appropriate WOT timing for mine. I have a 15# pulley - although I see 13#'s and the IAT start at about 90 degrees and increases to about 110 at WOT. I use 94 octane though You got a guess what timing should be safe right now? (CR 8.9:1)

I have it at 26 and it APPEARS not to detonate although I have a stumble and loss of power abouve 5000 I'm pretty sure it is ignition. Trying to get an idea if 26 sounds OK.

Shaun

 

I just dug through my laptop looking for the log from my 5/30/03 visit to the strip, but it has disappeared. I found one 4.3 second WOT freeway blast (50 to 98!) during which IAT went from 34 to 54*C. The blast also started with 10* KR, but it tapered off to 0.1* by the time I lifted.

26* with 94 octane and 15 psi sounds reasonable to me, but I sure wouldn't push it any higher. I never heard any detonation. In fact, I didn't realize the engine was wounded till I poured out the ring bits. It sounded healthy and pulled hard.

 

I read about the latest fiasco on the blown list and bit my tongue, but it's killing me.. LOL

Is this another rebuild that could have been avoided by switching to an aftermarket ECM??

you were "gigged", you "gigged" back, now it's your turn.

best of luck getting that beast back together.. I'm still fighting some wicked igniton problems/failures..