furiousd

Hey guys,
I'm still new to owning an evo but learning a lot real quick with this troubled car. I'm having trouble with knock (I know I know, same old problem different car).

History: Bought the car used, EVO VIII MR, the boost gauge was broken so I installed a new one. Car holds good vacuum (18-20in Hg) but it was only boosting to 12psi (waste-gate pressure), but still pulled smooth. Got a bad tank of gas around the same time and car started hesitating at WOT on highway, feels the same as when timing is pulled. After a couple of tanks, same thing. Pulled the plugs and replaced them and started to pull smooth (still only 12psi). I took it to a Tuner and he installed a 3port boost control solenoid and put it on the dyno. The car boosts to 23psi easy. Here is where it gets weird. Some pulls were good some had 30 counts of knock sum. Phantom knock problem??? Tuner said he can't help me with it. Doesn't know what the problem could be. He said he has only seen 3 evos with the same problem.
I got home and checked under the car, and the heat shield around the downpipe looks a little bent around the cross bar area. Don't know if that could be causing "knock".
Then I took the intake off and took pics of the compressor blades, there was some damage. See pic. Can vibration due to a not balanced compressor wheel cause this "knock"????
I attempted a 3rd gear pull and succeeded the first time, very smooth, lots of power. Second attempt was not so good 29 counts of knock. See pics.
Also my ignition and fuel maps are bellow.
ANY HELP WOULD BE APPRECIATED

MR Turco

iTrader: (16)

No. But you might want to check for shaft play.

What are your mods?

Your timing jumps around a lot during spool which could be initiating something. That is a LOT of knock and you have a pretty conservative timing table. Have you check for loose components in the engine bay? Boost leak test?

SpoolinUp

iTrader: (57)

I'd take a second look at your exhaust (especially where you noticed it may be contacting the cross bar) and under the car. Rattles could be picked up by the knock sensor if it's at just the right frequency as Turco was eluding to.

Also, check to see if your intake manifold bracket is all bolted up and not smacking against the block or head.

furiousd

Thanks for the quick replies.
This morning I tried to floored it when the car was not fully warmed up (I know, not the best thing) but it pulled very well, no hesitation.
This leads me to believe that as the exhaust heats up and vibrates a bit more there could be more play in the downpipe (time for new hangers?). So I’m leaning towards the downpipe rubbing on the cross-bar. I will pull it off today and try to log.
The manifold bracket is tight, I checked it last night. And no loose parts in engine bay that I can see/feel.
Turbo shaft has absolutely no radial/axial play. It spins very freely by hand. The reason I was asking if it could be the blades was because it does look like the “knock” starts at around the same time as spool up. Now, 30 counts is ridiculous and leads me to believe that this is not REAL knock.
One more thing, the injectors are ticking very loud. I’m not sure if this is normal on EVOs but I can post a video later one today. I put a long screwdriver on the injectors and the other end to my ear and you can definitely tell it’s coming from injectors.

Mods:
Tanabe medallion catback
That’s it!
I wanted to keep the car stock for a while.

furiousd

I pulled off the cross bars and tried to log but I'm still getting knock. I'm tempted to put in 100octane to determine once and for all if it is real knock.
What should be the next step? boost leak test?

scheides

iTrader: (10)

Boost leak test and higher octane to see if it goes away. That is not really what I'd call compressor damage. I've seen bent and chipped fins, they will still make power...as long as its not rubbing around the outside its alright. Here's a pic of a 20G I put on my 1G DSM back in 2004:



Still made like 280whp on pump gas, stock cams. I would look elsewhere for your problems!


28 counts of knock is HUGE and if its intermitent, that is tough to diagnose. Perhaps you have a noisy TOB or maybe somethings broken? After you do the boost leak test, do compression and leakdown tests (research how to do a leakdown properly, in a quiet environment) and you should have a better idea of what's going on.