I am tuning a C7 and we are getting tons of kr up to 11. Car was getting 1-2 before we put E85 in it and now it's really knocking. It starts in right after wot as low as 2400rpm and it doesn't let up much through 4k. I've added fuel and nothing, taken out more timing and nothing. Car is only commanding like 15-16 degrees but its still knocking and ends up making like 5-7 degrees during the pull. What are you guys going for this? Seems like the LT1 motors are a real pain to tune.
Using a WB?
My wideband doesn't have a lambda feature so I didn't connect it for this. The car was dialed in fine on 93 and no matter how much fuel I throw at it we still get knock.
I turned down the knock sensors a bit and it seemed to do the trick.
What are the new Knock Sensor Level multiplier values?
I have all 8 cylinders set to 6.5 for the complete range.
They were waaay lower then that. I think I bumped them up to 5 and no more knock.
Did you rule out real knock? I thought I had false knock on my 18 ZL1, but I pulled a ton of timing by simply copying over the low octane table, and it was gone. I have my sensors desensitized by about 10 percent, but did not want to go any further.
So my question is this: Is this considered a safe practice? For those experienced with these engines, what is a reasonable amount to desensitize the knock sensors?
Thanks
Whenever I got a tune from Weapon-X they made all my settings 10 across all the cylinders. I thought that was way to high but they assured me if there is real knock then it would still show with a setting of 10. Since, I have lowered it to 6.5.Originally Posted by BMWMD82
Yes, we did rule out real knock. The engine made no audible knock and we were seeing 10 degrees of kr. I would think you could hear that. We also pulled out tons of timing and added fuel and still pulled 10kr. It seems like a bunch of guys run their sensors in that 5-7 range with knock still coming up when it is warranted.
DI cars will also show knock from being too rich or having injection timing wrong, keep in mind. Also, this is a torque based controller and it can also pull timing at will if you don't have it set up right and sometimes it shows up as Knock retard.
Put some race gas in it and if you find knock retard then it's not real, IMO. If it goes away completely then you know it's real.
We had E85 in it. Car was still knocking. We did have some initial torque issues causing the throttle not to fully open but that was an easy fix.
Get some to retune your car ASAP. Before u damage it
Tune cost couple hundred. Motor cost couple thousand
That is good info. Maybe I?ll bump mine to 5 or 6 and see how it looks.
I am by no means an expert, but I do not think you will necessarily hear KR. The fact that it started acting up when you switched fuels without a wideband reading would make me a little nervous.
What are your thoughts on KR? Are you okay with seeing some in the logs? When I was learning on the gen 4 stuff some years back, Dave Steck told me he ignores anything less than 2 degrees KR.
Right now I am seeing up to 4 degrees above 5000 rpm or so. No throttle closure issues or anything. The car is a 18 ZL1 with headers and an intake. I recently added a 2.30 upper pulley, but had been chasing the KR before that. I am targeting .80 lambda right now.
I have removed as much as 4-5 degrees from the stock high octane table in the affected area, but I am not sure if this is normal or not. We just have 91 octane, so I add half a bottle of torco per tank to get it up to 93 ish.
I need to do some more experimenting, but any tips would be appreciated.
i don't really have a set amount of ignorable knock but you will run into knock before MBT on pump gas so on my cars I like to run on the cusp of retard. 2 degrees, I would pull some lead out. if it does it one pull but not on another I consider it an anomaly and leave it alone.
the issue with these cars is simply removing spark over and over again may not be the correct solution depending on what is causing it. overadvanced lead? cylinder pressure from early injection timing? torque management? etc.
That makes sense. Thankfully, my combo is very close to stock. Injection timing and cam are stock. I log torque management spark, and it does not seem to be that.
Last night I made a few pulls. The first one had zero KR. The next I saw about 2.8. It is typically on only one or two cylinders at a time. Looking at the log, it had a peak of about 4.5 degrees on cylinder 1. Then 5 degrees on cylinder 7. Nothing notable on any other cylinders. It is not consistent, though. On another log, I picked up 4.8 degrees, but it all was on cylinder 2.
Does that sound like false knock?
seems like real knock
Is it common to only get KR on one or two cylinders on a pull?
i think it would be uncommon to get knock in all cylinders all the time, unless the tune was horrible....
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