Driving my Evo x on the interstate when pulling a hill makes me want to drive a car off a cliff. I own a fully built Evo 8 and that car is way smoother than this evo x. I bought the car off of an idiot and im going through trying to fix all the problems he passed onto me with out telling me. If it set the cruise on this car at 70mph it bucks and jerks when pulling a hill. The sound is vrooom ch ch ch ch chchch vroommm ch ch ch ch chchchch constantly over and over again lol. The tial is VTA and im not sure what spring is in it. I have searched and searched but no one ever seems to have a definite anwser on how to fix it or what BOV works best. The car only has mild bolt ons and was tuned at Buschurs at 25psi.

 

if its on maf i wouldnt vta the bov.. is it using ecu boost or no? id probably put my money on the bov causing the issue if its not on ecu boost.

btw been meaning to ask you - what exhaust manifold is on your evo 8? shearer?

 

yea I figured that would fix it by going to a recirculating setup but from what I've been reading people that switched to a recirculating setup still had the same issue and never did post back up to say how they fixed it. I run a stock ported manifold BTW.

 

it's not the bov...that is the turbo in a surge condition if you are on throttle

 

Sounds like its an issue at partial throttle? If so I would look into different springs for it. Also make sure the vacuum line going to it is the right size, I believe 6mm. If you want, Feel free to PM me and I can help you get the issue fixed.


-Em

 

no, i had the same issue with even a forge recirc. all it really tends to be is that the evo x's tb being electronic and the bov being too tight along with the ecu not knowing how to smoothly let off the throttle makes it buck like crazy because you're getting rid of air the car is trying to calculate for. i noticed also that the car didnt like to cruise smoothly because its able to build boost sooo easily. notice how its way smoother on the 8 because of the cable tb? you are in control and you know how to appropriate for it. the ecu is ok with you in control. the evo x has a very fast ecu on response times but cant predict air.

the turbo can surge but under high load conditions at low rpm, this is not the case here. its partial throttle with the evo x's that guys have difficulty tuning and getting rid of. if you could get the tb to open on a 1:1 ratio with the pedal without the ecu interrupting it would go away for the most part because then you could control the tb directly. try getting the response time for the throttle to be faster or smoother and it should help. also, if you drop the spring pressure down it should help also with partial throttle boost build and blow off.

 

Em, my reply wasnt directed towards you, lol you just ninja'd the heck out of me there.

 

I know its surging but it shouldn't be doing that. The driveability is terrible. The bov should be releasing the pressure a lot easier instead of it being so choppy and making the car jerk. I know how to drive these cars I've owned 4 of them and currently own 2. I thought a softer spring might help but I've read other threads where they tried it and the softer spring didn't seem to help much. People also switches to the tial qr and the problem was still there if not worse. Some people talked about other bovs that solved the problem but no one gave a definite answer on which one worked best.

 

I don't think you are understanding...the BOV isn't making the noise until the throttle is released....that cha cha cha noise is the turbo itself, the BOV has nothing to do with it at all, as in it would do the exact same thing if there was no BOV on the car.

the only way to remedy this situation is to go larger on the A/R, re-tune (might work, might not), different cam, different turbo

 

Thanks Em. I would PM you but I would rather trouble shoot the problem in this thread so other people can read this and know how to fix it.

 

Lol I know the turbo is making the sound man but the problem is the bov opening and shutting while I'm part throttle that causes the jerking. If it would slowly open and slowly close while I was part throttle the surging wouldn't be as bad.

 

no, it's not
unless the surge is causing you to pull X vacuum(spring rating), that bov is stuck shut - unless you have a leak in the line to the manifold, or the ecu chops the throttle because it's DBW

 

Think of it like this. If I set the cruise at 70mph on the interstate then start to pull a hill my car is going to accelerate to try and keep the car at 70mph. The car then keeps dropping to say 67mph bc of the hill so my car has to give it gas again till its back to 70mph. So its on and off the throttle constantly trying to keep the car at 70mph. Everytime it gets to 70mph it let's off the gas and the flutter happens. Which is the bov. The car builds boost then releases it through the bov when I get back to the set cruise speed.

 

PS not saying you're wrong. Just making sure we understand each other completely. It might be in the tune or something else. It just seems from what I've read in the other threads that it is a bov issue.

 

this is different from what you were saying in your first post, you said you were getting the surge noise while you were light throttle accelerating in a high gear

what kind of hill are we talking about here


the cruise should not be chopping the throttle when you hit 70, it should lightly apply and release to get to speed and maintain