Whats up folks,

So I may have finally gotten to the root of my knock issues. Ever since I started tuning the car way back when with the utec, it always ran higher IDC's than most to get decent AFR's. Not long ago, I ditched the utec in favor of ecu+ and ecuflash. Even running on the stock, unmodified rom, I was hitting mid 10's afr up top. Added a walbro, changed the pickup screens (yes there are two, one in each side of the fuel tank) got the afr tuned to 11.5. Even at 11.5 with the walbro my IDC's were hitting 90%.

All along I have been fighting knock and was not able to run timing anywhere near what over similar evo's are running. TTP helped me tune out almost all of the knock, but that left me running only 10* advance at 7000 rpm and 200-220 load with about 21-22 psi peak dropping to 19-20 by 7000.

Last night I pulled out the plugs and took a look at the piston tops. I noticed that 1,2, and 4 were black as coal while #3 was way lighter and showed very little sign of carbon buildup. Based on this I assume #3 was weak all along and 1,2, and 4 were having to work harder than normal to maintain the afr.

I suspected the injectors all along and picked up a used set of BR680's a few months ago. I just got them back from cleaning by RC Engineering last week, so I went ahead and installed them last night. It will take a few days to get the injector scalling nailed down but the car already feels much smoother. Have not gotten into the gas yet but the trims at idel and cruize are less than + / - 10% so after a little more fine tuning this afternoon I'll head out for a logging run and see where I'm at.

Keep your fingers crossed for me peeps....

 

Let me know if you need any additional help. Your condition was a bit strange. I am glad a troubleshooter owns the car though and is willing to test different theories. Its the TTP way of doing things.

 

Well, I should know Shortly if this was the culprit or not..

And thanks again Scott for your help man. If all goes well I will be hitting you up for some cams and gears in the near future!

 

Well,

I have confirmed that replaceing the injectors solved my problem.

So far I have been able to add another 4 - 5 Degrees up top with 0 knock counts and an extra psi or 2 over the map i was running the day before. With the previous retarded map I was still getting some ugly knock counts from time to time.

Injector scaleing is almost buttoned up and AFR's are back in 11.0 - 11.2 range.

 

It sounds like #3 injector was dirty/clogged which limited fuel flow and promoted detonation in that cylinder. Is that your assessment?

 

I think there was more to it than that. The duty cycles with walbro 255 and stock injectors tuned to 11.5:1 were 90%. When I ran the stock rom for baseline logging with the walbro I was not getting any richer than 10.5:1.

Way back when I tuned my UTEC (almost two years ago) I had to add a lot of fuel to the base openloop fueling map to get my AFR's around 11.5:1, talked to txs about it and they said I should not have had to add any fuel to get the openloop fueling map to 11.0.

I suspect I had a bad injector from the factory. When I first started tuning the UTEC I only had about 10,000 miles on the car. Today I only have 30,000 and some change.

 

What fuel pump are you using?

 

his first post says walbro.

 

I had the same exact problem you did. I had counts of knock for the same reason then i was able to retune for a better feel.

 

Did you replace the injectors? Even VP 103 did not fully quench the knock in my case, that was only running 10* at 7000 rpm.

 

I don't know what Melvin is talking about. I think he is just bumping his post count.

 

Check This out Scott,

This is the ecu+ dyno software and I only use the numbers for comparison not actual dyno figures. The green plot is the best run I got before we started working on my tune. The Red is after solving the knock problem, scaling the injectors, and a few tuning passes over the last couple days, still a little more work to do smoothing things out but DAM! what a difference.



same stretch of road for both runs about the same weather conditions.

 

Very nice man! I am sure there is a little wiggle room in there. Prolly get another 10whp.