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I finally did a datalog on my 92 Vette and she has lots of KR. I have been chasing an issue where she has a turbo like boost above 3500 RPM, but is completely stock. Except for exhaust and bosch III injectors. When I datalogged she had spark advance around 24 right at idle. When I accelerated, not even getting on her, she immediately showed 4-5 KR and then jumped to 8 and then to 14. I have the stock exhaust manifolds, but a freeflow flowmaster exhaust system on her.
Should she have so much initial timing? 24 at idle seems excessive. Is this pointing to a cheap opti? When I recently did the timing chain I had the opti off and it did not look like a quality unit.
From: Liliha Bakery stuffing my face with coco puffs!
24 does seem a little excessive but if that's what GM intended it to be, than it should run as advertised without issue. With that said, were all the issues at first delivery or after items i.e. bosch III injectors were changed??? I'm wondering if the replacement injectors are delivering the exact precise amount of fuel. I understand that the ECM can compensate for fuel trims but let's just say your BLMs are all in the 135-140 range does this 5-10% lack of fuel compensated by the ECM carry over into AE TPS AE MAP which is akin to an accelerator pump/pump shot on a carb. When installing bigger injectors (more fuel), I've reduced those parameters by proportionate gain and with a bigger throttle body (more air), increased based on prop gain. Too many what we don't know and what I'm saying is returning everything back to what GM intended it to be, it should run like top. If you think it's a fuel delivery issue, I wonder what happens (KR) if you repeat the datalog with the vacuum line of the fpr disconnected??? If the KR diminishes, maybe time to crank the fuel pressure up??? Care to post up your datalog??? Idk what bcc you're running but attached is the spark map from an '92 LT1 auto...
I tried posting my data log, but it's not a supposed file. I'll try screen shots. My car did this issue with the stock injectors. Plus these Bosch IIIs are the same flow rate as stock. I also see a couple of errors in the file. It says error in closed loop and has errors for the injectors. I am going to do more research into the data logging and make sure I don't have any mechanical issues before tuning it.
It will not go into Closed Loop if your O2 Sensor(s) are faulty /failed. You can post you Datalog file just add an extra ".txt" to the end of the filename
From: Liliha Bakery stuffing my face with coco puffs!
Idk what the cause for the errors are. Are you not getting a CEL for the code 43? Upon purchase my 90 C4 had a code 43 which is the knock sensor circuitry. It would pull a preset amount timing as long as that fault was set. Had some crossed wires near the starter but possibly could be caused by wrong KS or I've heard damaged from over tightening. Tune doesn't look bad. BLMs do go rich in the low MAP range and upon decel. Before and after code 43...
Last edited by stew86MCSS396; Jul 22, 2022 at 04:50 AM.
Thank you for the input. I haven't had any codes come up. This issue has been persistent since I got the car. I will look at the KS wiring closer though.
I don't know if this car had been tuned by the PO or any history on it. The guy I bought it from inherited it from his Uncle. He said it was his uncle's baby, until the last few years when his health declined. The guy I bought her from ran an off road shop. I am already disappointed in the quality of work done as he used some grey chaulky sealer when he did the gaskets. He did the WP and opti and the opti looks like the cheapest one he could find. I'm just getting into this tuning so I am trying to figure out what is what. I got lots of research and reading to do. I appreciate all the help and tips.
I didn't want to comment too much as Idk which KS the '92 LT1s use 3.9K or 100K. Granted it's an older L98, my screenshots show a whopping 20* retard at higher kPa. This has me questioning if the LT1 pulls less with a code 43 or if in fact you are getting real knock???
I really don't think this is real knock. The pulls were no where near full throttle. Most of them were light throttle turning the car around and driving up my street and then out to the main street. I'll do those tests on my KS and see where I'm at. Thank you for the link.
1992 Data logging results
