I am returning my EVO to stock selling parts as I go and retuning as parts come off the car.

Prior to the part out my car was running like a top no knock 26psi with alchy.

I'm now sitting with the following mods:

1. Walbro 255
2. HKS 272 Cams / (-2/-2) CGs
3. Testpipe (2.5")
4. K&N Drop In.
5. ECU boost control

Everything else is stock (DP, CB, O2, ect)

My latest change was the removal of EVO9 turbo, tubular O2, and 3" downpipe.

So here's the deal. I have loaded the stock fuel and timing tables but have boost set at 22psi. No matter what I do I get KNOCK in the 5500-6500 range. Car runs clean with zero knock then wham instant 9* of knock. I've tried loading a block timing map starting at 3* and working to only 13* (like 5* less than stock or tuned) and I still see the knock at this RPM. I've even dropped boost to WG pressure and I still see the same knock count. The only thing I haven't done is tossed in race gas to see if it would patch the problem.

I have a few questions:
1. With the stock fuel map what AFR should I be seeing at 20psi?
---I can't seem to get them richer than 10.5 even with lean spool off and they are climbing to 11.5 in places. This is with a Walbro 255. I am wondering if it could be on the blink. For the last few months I've been running alchy so I have nothing to compare too.

2. Since I am running the stock downpipe and exhaust I don't think anything would be causing mechanical knock. I mean I don't see it around a shift only after 5500. As mentioned above I even deployed a very restrictive timing map with very smooth changes and still get the knock.

3. Even though I've tried 13psi is there a boost limit I should be staying below on 93 octane?

4. Is there a way to determine if the Walbro is taking a crap on me?
----My IDCs are like 14-15 at WOT

I'm attaching a log of a 13psi run with stock fuel and timing.

 

log?

 

Log attached NOW.

I will make a pull at 20psi with less timing tonight to show you how the car is responding. I'm half temped to borrow someone else's downpipe to see if the stock DP is the cause or not.

 

My very first throught is mechanical knock, it doesn't have to be your DP either.

I had a 9 knock count in only 4th gear at 3500 for a long time, thought my timing was to blame.

I've been skipping 4th gear because of it, but just the other day I found the boost solenoid bracket bolt loose. Tightened it up and voila, 4th is clean.

 

That my friend is a scary thought.

I'm hoping the cams themselves aren't creating the noise/knock at 6k.

I've been able to run to 5500 over and over without knock but as soon as I go over that I get high knock.

 

16* at 6000rpm is one assload of timing

 

Not at 13psi.

I made another blocked map and ran at 20psi. I'm getting knock with only 8* at 5500.

 

If you are still using the stock DP, cat and stock muffler, then the problem may be the HKS cams. There is a large amount of backpressure in the stock muffler. With the much greater lift of the HKS 272's and duration, you are most likely getting reversion into the cylinders due to the back pressure, and it appears to start around 5000 where the better flow effects of those cams are really starting to be seen.

This is easily checked by un bolting the stock muffler and running again. If the knock goes away, you have your answer. While you are at it, check to see if the flapper valve in the muffler is sticking partly shut, 'cos that would do this too.

The stock cams wont flow enough to run into this problem with the stock exhaust.

Milburn

 

Actually I think its the downpipe. I was running with an EVO9 turbo, SSO2, Alchy, 3" DP and TP then to the stock exhaust for almost 3 months with no issues at all. Actually the car was quiet and fast as hell. I recently pulled those go fast goodies and put the stock crap back on now I see knock.

I miss my alchy and free flowing exhaust but I'm looking to sell the car and get a NINE.

 

Less boost is the answer. Too much airflow for the stock exhaust.

 

I think Evil_EVO is right.

 

Remember its cammed, so stock timing is not going to work. I would pull more timing, like ALOT more, and see if it knocks.