BlackOperative

Ok, unfortunatly my first post as an Evo owner, had to be of something I honestly cant figure out. I hate the threads which dont contain a clear problem or description, so I vow to try and explain myself clearly.

I have a 2003 Evo VIII with moderate bolt-ons. I am self tuned running E85 on the Tephra Mod, and after a recent tune-up (thicker head gasket, ARP head studs, Gates racing timing belt, ported and polished head, manifold, and turbo), I was looking forward to running more boost, around 30psi. I got the car back together, and its been driving perfect for 2 weeks. I started tuning the WGA to run around 25psi without the boost controller connected, and noticed that i had a rich condition i couldnt tune out. I pulled the car into the shop, did a boost leak test, and found the BOV to be leaking air past the valve. Its a Forge diverter valve, and I had the medium spring installed with one of the supplied shims. I replaced that combo with the harder spring and no shims, put it back in and went for a tune. I immediately noticed that on decel with the clutch in the car would ALMOST die, battery light would come on and then recover slightly, with the idle somewhere around 650... a little low. After a few seconds the car would return to normal. It does this everytime, and then noticed that even when im sitting there, and rev the car a little, it will do the same thing. Now, ive tried tuning it out, played with the ignition and fuel, and nothing cures nor helps this issue.

I am quite mechanically sound, and know how the entire engine operates as I used to design and sell Megasquirt ECU's for Hayabusas, and I just cant seem to figure out why changing a spring in the BOV would affect the way my Evo returns to idle. If I was venting to atmosphere, different story. But i am recirculating and the ONLY thing i changed was the spring. I did another boost leak test and not one single leak was found. I raised the pressure in the system until my boost gauge in the car read 29, so I know I had enough pressure to properly test everything. Any input is very greatly appreciated. I did search this but all i can find are people running there BOV to atmosphere with these problems. I will list what I have on the car, not sure its needed but, never know.

Buschur TBE
Buschur Intercooler Piping
Buschur Intake
Mishimoto 3" Intercooler
Forge WGA
Forge BOV (recirc)
Stock ported turbo
Stock ported exhaust mani
Ported and polished head
Ported Intake mani
Cometic Head Gasket
ARP head studs
Gates racing timing belt
HKS 264/264 Cams
Aeromotive 340lph stealth fp
Aeromotive 1000-6 FPR
Aeromotive billet fuel rail
1000cc injectors

BlackOperative

Bump

Im going to try installing the softer spring today... if the problem still exists, then its just coincidence that something else went wrong at the same exact time the BOV spring was changed. If it fixes the issue... well then i am completely stumped...

Any ideas out there? The car acts as though it has an intake leak, the AFR's are leaner than usual and adding fuel doesnt seem to help.


The AFR's are leaner at idle only, didnt seem to affect anything while driving. The shifts are a bit harsher under very low boost, but this was expected due to the BOV not opening as much with a stiffer spring installed.

wjamyers

bump

thedru13

iTrader: (24)

Did the POsition of your maf change? I had issue when mine was tilted to much.

LCS

iTrader: (9)

Like upside-down?

dastallion951

Well heres what happens the spring rate of the bov will dictate the decel to idle drivability, if the spring is too stiff, then what happens is upon decel a small amount of air when letting off throttle should be released and the air should be recirculated back into the intake pipe, with too stiff of a bov spring the diaphragm wont open and the air wont recirculate, therefore causing a rich condition, that will sputter out and in some instances stall out the car. Now does your bov come with adjustability or do you have to swap springs in. I know my greddy type rs did that for a while, took a bunch of tests, a bunch of quick decels back to idle and adjusting my spring hex bolt to find a happy medium of holding boost, and not bogging down. Try swapping with a friends evos bov and see if the rich condition subsides, or if you have bov spring adjustability try softening it up a turn or two.
Good luck