I am scratching my head about this and I want your help.

A 2005 Evo with a TBE (high flow cat), a drop-in filter and cams is knocking no matter what was tried it is knocking. The car runs of 91 pisstane.

The AFR is very tame. It starts @ 10.83 @ peak boost and falls to 10.64 by redline/cutoff. The AFR does not rise to or above 11. The AFR was measured at the downpipe with my Innovate unit.

The timing is set to:

3000---4
3500---4
4000---4
4500---4
5000---5
5500---7
6000---7
6500---10
7000---13
7500---15

The boost is set to 21 psi with an MBC. The only tables that have been changed in the Rom are the high octane/ignition maps. Nothing else is touched AFAIK.

The knock seems to start around 5700 rpm and there are about 8-9 counts, but I am working from memory since I do not have any logs except my AFR log. I could not log from the ECU since that was taken with Evoscan and these logs are not mine.

I know that this is real knock since when 100 octane is used all the knock goes away.

What would make this Evo so knock prone? What else should I look for? I am fresh out of ideas and looking for some input.

 

Naji, I run a little less timing than that for Shell 91 out here. I've attached a 3rd gear pull and my timing map. Car is completely stock, just the boost solenoid restrictor pill removed.

 

I have the same problem with my car it knocks from 6k up to redline. My AFR is about 10.8-10.6. I am wondering if the cams might be the cause. I have heard that a few cars are experiencing knock with cams installed. I dont have access to 100 octane unless I want to buy 5 gals for $50 so I am gonna retard timing and see what it does. Good luck with figuring it out.

 

Did you get knock before the mods? Maybe it has nothing to do with the tune and your knock sensors are picking up hits from your downpipe or exhaust banging against the car.

 

I am adding alky kit hopefully next weekend to cure my knock problems.

 

This is not phantom knock because when 100 octane gas is used the knock goes away. Just for safe measure, we also checked the dp/exhause and nothing was banging.

 

I think your on the right track with the low timing you are running. I hope you do not mind if I try your timing map on this Evo. I am not a big fan of advanced timing anyway.

 

did you run it that rich with the 100 octane?

if nothing else has worked, I think I would be desperate enough to try leaning the mix, I mean it isn't helping you any... being so rich.

do you get the same 5700 knock when you start your pull at a higher rpm? say 4500 rpm.

 

Here is the log of the 100 octane. This log was made after the 1st attempt that the tuner made to tune the car. In this log the AFR was on the lean side of things for 91 octane. I do not have logs after the second attempt since the logs belong to the tuner.

I will get the car logged though, probably next weekend. The car is not mine, but it is intriguing me and I want to try and solve this problem.

 

Here is the current AFR that the car is running. There is no rpm since I did not have access to the ECU port.

 

pull your plugs, take a real bright flashlight, and get a look at the piston tops. They should be uniform in color with no "wet" spots.

I was able to find a bad injector this way, props go to andrew @ dyno4mance for telling me to do this....

I was having similar problems, turned out to be a bad injector in my case, three piston tops were sooty black, once just had the slightest hint of brown color to it, this was the bad injector cylinder and was running way lean.

 

I am going to pull my plugs right now and check my car too. Thanks for the info.

 

Naji, thank you for posting this dilema of ours.
guys, thanks a lot for the info. me and naji are already running out of options. i'll check the cylinders tonight if it's the injectors. throw in any ideas and we will give it a shot.
has anybody experienced a bad knock sensor on evo8?

 

havent heard of any issues with knock sensors. Just out of curiousity what are youre plugs gapped at? I had issues before and my plugs were gapped too big

 

I don't think it would be injectors or plugs since 100oct. seems to cure it. Not 100% sure though.

Not sure if this makes sense but. I ran my 8 with 7* at 5500@11.2 afr's 93oct. 21psi. and it pulls timing down to 4-5*.
Now I run 11*@ 11.5afr's 93oct. and no knock detected. With no change in mods.

So I was wondering if being a little on the rich side would also cause it to knock?
Or maybe your H/F cat is clogged causing egt's to rise.