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Hi, hoping to get some suggestions on what to try here.
Got significant knock at last track day, never had it previously.
Running an evo 9 engine in an evo 6 with a boomslang adapter connecting evo 9 ecu to evo 6 loom. (plus additional wiring loom run to run mivec etc).
On e85 with basic mods:
exhaust, CAI, standard turbo, FIC ansu 1050 injectors, COP kit, walbro 460 with hardwire triggered to come on with Hobbs switch as per MrFred.
Started on Lap 1 and was present mostly at around 5500 - 6000 at WOT in 4th gear down straights (the track is mostly fourth gear) but also present in 3rd and 4th. Also showed up at 50% throttle in 3rd a couple of times.
Unfortunately i didn't log knock voltage before i pulled the pin on the day.
Water temps started at 160F and went to 170F.
Oil temps started at 125F and went to 165F.
Also logged fuel pressure and it matched boost + base very well.
AFR's, timing and boost look ok?
I logged it the night before (2 x 3rd gear pulls) and no knock.
It has since been run up on the dyno with det cans - no audible knock and only 1-2 counts on logs.
Things I have tried:
checked spark plugs - no sign of detonation, looked good, all very similar in color.
checked continuity of knock sensor signal and earth - all good.
checked torque on knock sensor - to spec.
checked ethanol content in fuel - 85% confirmed.
checked underbody for anything touching or rattling - all good.
The only changes I made between last track day (no knock) and this one was:
cold air intake feed to airbox - i thought this may have been causing it so i removed the feed to the box at the track....but it still knocked.
racefab sump - i have noticed my catchcan at the pcv had some oil in it after the track day. (ran oil level at high mark from habit but have heard with the big sumps need to run at a lower level or this will happen).
Raised shifter cage.
Was considering replacing the 2 year old knock sensor ?
Any help or advice greatly appreciated.
Your timing is too high even for Ethanol. These engines do not need alot of timing.
You want something closer to this ramp from 1-3 on the hit, 5-7 at 5500 and then make your way up to 12-14 by 8000.
If you can get on a dyno you can see exactly what that additional degree of timing will get you. If the gains aren't substantial then the timing comes back out.
Timing is going to have a big effect on how the engine lives. I'd also recommend having it professionally tuned.
If it has a small plug gap/strong ignition having an AFR around 11.3-11.5 is a good target to shoot for IMO. The afr is just an average of 4 cylinders and the added fuel will help keep it cooler on the roadcourse/street. The added fuel is a safety margin if the ignition is correct. I typically like to have something richer then leaner if the power is the same.
FWIW, I ran my stock engine on the dyno at 11.2 and 11.8 on 80% ethanol and the power was the same. Now, on my built engine being closer to 11.8 does make more power but thats with compression/camshafts and headwork.
Alot of people shoot for 12.0-12.2 and thats fine for short runs or excellent fuel, but thats not always the case.
I agree that the richer side of ethanol needs a strong ignition or a tighter gap since its going to be harder to ignite.
I've been a big fan of your work.
For discussion purposes what AFR would you try and target for these cars on the roadcourse. 11.5-12.0 is pretty close. Sadly without fuel correction the stock ecu is only going to get so good thru out the day. If only the X Ecu was a bolt on with the new flex fuel patch and afr correction. Easier then a standalone and most could make their way thru it.
Thanks for the replies. Is 11.5 ok to aim for? It gets real hot here and often track at 95F.
For timing take 2 degrees out all the way?
Also, it has standard evo 9 iridium plugs (standard gap) with a sparktech cop kit.
Would you suggest a colder plug and/or less gap?
Thanks again
The most common fault when tuning E85 is too much timing.
If you've got a combination of E85, stock rods and too much timing, the common result is bent rods.
Once one of your rods have bent just a bit, it'll still run but the bottom of the piston hits the counterweight and it knocks............phantom knock. But maybe only at full noise/ full RPM
A compression test is easy to do.
I'm not saying that's the cause.
But the knock makes the ECU pull the timing but the knock doesn't decrease as a result.
Last edited by RightSaid fred; Apr 24, 2017 at 08:26 PM.
Thanks for the comments. Knock sensor was replaced with a new one and we took out a fair bit of timing and the result was the same....at the track.
I did a straight line third gear pull the day before track day there is no knock logged. When it was run up on the dyno there was no knock logged nor was there anything heard with the det cans.
Plugs looked good (no sign of det) and comp tested at 145 across all 4.
Sump is off and bottom end looks good. No movement of rods up/down or forward/backward.
Oil sample is getting tested and filter getting cut open next week.
If oil sample tests ok i'm going to put a stock sump back on and test again.
The extended trapdoor sump makes a lot of rattling noise with exaggerated vibration even when full of oil and I'm still getting oil in the pcv catchcan (didn't collect any prior to the new sump going on).
Wondering if this is the cause? Logs of oil pressure show its not losing pressure around right handers but this knocking seems to have something to do with going around corners at the track.
Any thoughts appreciated.
"but this knocking seems to have something to do with going around corners at the track."
I had a similar issue , I don't do circuit . The place where I tune has a couple of fast right handers and left handers, car puts out 5-6 counts of knock.
Check for loose/broken gear mount , loose bolts near transfer case and guatry.
Apr 14, 2017, 07:00 PM
