Background:

2003 Evo VIII
1 owner car, daily driven to and from work. Never beat on, no autocrosses, etc.
81K original miles

Mods:
3" turbo back
+read below


After 80K miles, I decided that stock was enough so a few "fun" mods were justified for the evo. Initially, I went with an AEM dry flow filter and MAF adapter (did not use the intake pipe, as my DSM experience showed that metal intake pipes=crappy idle usually). Everything worked great, car was spiking around 19 psi (obviously not holding to readline) and was fun.

About 2 weeks ago, I installed my 3" catless turbo-back. Car now spikes 21 psi (stock boost selonoid setup, untouched), and holds about the same pressure as before to readline.

To keep tabs on the car, I also installed a boost gauge (actually installed quite a while ago) and an AEM wide band. At this point is when the problems start. Two nights ago, I finished up the AEM install. For a Michigan summer, it was a very (abnormally) cool night, in the 50's and very windy. I did some 3rd and 4th gear pulls and the AFR's were in the mid 12's most of the way, with a very high 11 by redline.

Today, I switched back to the stock intake and did some pulls. Today, I was hitting mid 11's by redline and a high 11 after spool up. I figured that a turbo back might lean out the stock tune a bit, but this much? However, I should say that I have no idea what AFRs my car ran at when stock, as I didn't have the wideband then.

So far, I've checked the following:
-Boost leak: Only one small one, and I fixed it.
-Idle/cruise AFR: Car runs right at 14.7 at idle, and hits right around there at a partial throttle cruise. Thus, I dont' think its an intake leak.
-Vac. line to FPR: I removed the boost gauge line and replaced it with a brand new vac. line with clamps, so no leaks here.

I was considering throwing the cat back on the car to see what it does, but that is kind of a pain and I'm trying to avoid it. Any thoughts as to why the car is doing this? The AEM wide band is brand new (maybe 50 miles on it so far, purchased new in box).

I plan on putting the AEM intake back on tomorrow when its warm out and doing some pulls to what it does.

As a back-up plan, I was considering disconnecting and re-routing the boost solenoid to have the car run at wastegate pressure for the time being to see what AFR's it hits. Any thoughts?

 

How about just getting the car tuned for the mods that you are installing = Problem Solved

 

We have had several stock fuel pumps go bad and cause lean conditions. I would start there as you will want one when you get the car tuned anyhow.


-Em

 

tune for sure.

also check for an exhaust leak

 

gsrboi, I planned on installing a few more mods (FMIC/IC piping/Cams) and then towing the car to a shop to have it tuned. It was my plan to have the car tuned, but just not yet. Also, I don't see any reason why a car couldn't handle having a turbo back on it, considering the hundreds of evos which run turbo back as a first mod without a tune.

Emery, thanks for the info on the stock pumps, I was wondering the same thing.

As for the exhaust leak, my plan is to get the car up on ramps tomorrow and check for this. I verified there was none at the o2 housing, but I'll check the rest of the connections as well.

Any more input guys? Any is appreciated!

 

As a side note, I was considering lowering the boost at the time to wastegate pressure to richen up the mixture until my logging cable gets here. Does it work or by going to the lower load cells in the ecu will I be essentially making the car run leaner than it is now?

 

had the same problem, tune will fix it easy. If you got the money, throw some mods in
it as well