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Old 04-28-2019   #1
XfireZ51
 
Join Date: May 2007
Location: Chicagoland, IL
Posts: 9,708
Default Return of a Tuning Tale. Chasing classic knock

So as some of u know, I ended up discovering a few issues with my motor including oil seepage into cylinders and defective injectors. With the better weather, I have been able to get back out there to now datalog th car w the changes and fixes I did including new FIC injectors, so its back to tuning. However, I am still recording knock altho its not exactly like previous. Before I would seem to get knock almost on a random basis and at a steady cruise
and with little to no change in operating parameters. I now believe that was due to oil seepage causing the detonation. Contributing to that was one particular injector whose aerator had deteriorated and was basically
streaming fuel into the cylinder. That kind of knock seems to have been eliminated.
I have attached some snippets of my logs where the knock continues to occur but inspecting the plugs doesn't show sign of any detonation (I have attached some pics of two plugs, one from each bank). Once I started to log, it was clear that the previous tune had been very rich contributing to why the right bank plugs were black. Oil also contributed to this. I believe what had been occurring is that the left side was signaling LEAN and so it was forcing the right side to make up for it by richening the overall mixture. With the injectors now replaced I could go ahead and re-balance the VE table. I took out quite a bit of fuel. Of course since all other fueling is dependent or based on the VE, I suspect that now the AE needs to be tweaked and that may be the cause of the knock. I can induce knock by simply punching the throttle and I have a couple of examples of that. Also show a screenshot form TPRT w a before and after comparison w current bin v starting point and the amount of fuel removed. In fact, as I look at it, the area I am recording knock appears to be the same region of the VE where the most fuel was removed.
An added piece of information. lLatter C4 Corvettes w ZF6 trans came w dual mass FW due to the square cut of the trans gears and heavy duty nature of the trans, especially Black label ZFs. A popular mod is to replace w a SM Fidanza. At idle the trans rattles depending on state of tune.
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Last edited by XfireZ51; 03-08-2024 at 03:05 PM.
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