So every time I hit the duty cycle that's set in my boost control table the boost drops down, then hits the quick spool setting then boosts back up only to drop the boost back down again. Checked for boost leaks and as far as I can tell all couplers are good, bov is good, wastegates are not loose. I am having some intermittent vtec issues that I am chasing but don't think I am coming in and out of vtec. The only two other things I can think of is head lift or turbo is going bad. I think I cooked this one to be honest as the blades are starting to ever so slightly rub on the compressor housing and have very little shaft play. But it doenst smoke or make and funny squealing. I think head lift because the overflow was full..... but no bubbles in the rad when the car is idling. That's all I can really think of so if anyone has had this issue or can ask some questions that I have not thought about yet please feel free to comment. Here is a picture of a datalog of the exact issue Im having.

 

I would bypass the boost solenoid/ ECU control and connect the wastegate directory to the intake vacuum source, if the fluctuations go away you probably have some settings incorrect or the ECU might be failing or the solenoid could be going bad

 

^^ Co-sign

 

looks like boostcontrol. where is ur boost cut in ur boost settings?

 

My boost cut is 20lbs so its not hitting that. @ 47% duty on the EBC I hit 10lbs and keeps dropping into my quick spool feature but I will double check to make sure I didnt set it up incorrectly. You think if I had the quick spool set for a higher boost setting than in the table it would act in a similar fashion? Reasons I think it could be turbo related: (1) Didn't have this issue when I first started driving the car around, even when hitting higher boost. (2) I have a -3 oil feed line going to my turbo but I believe it called for a -4 feed but I though caution to the wind and ran the -3. (3) I did have to turn the car off suddenly, twice, due to over heating when I first started driving my freshly build engine around, not sure if I cooked the turbo when I did that and I also wasn't very cautious with letting the car idle for a few minutes after driving the car around to cool the turbo. I do have some shaft play on the turbo after recently inspecting it but not sure how much shaft play is "ok". Could the turbo be spooling up and just start falling on its face after the EBC stops feeding it 100% duty due to a cooked journal bearing?

 

A journal bearing turbo is going to have **some** shaft play, this is normal. By "some", I mean it will move a little bit, ever so slightly.. As long as it is not touching the compressor housing, you're fine. As mentioned, it sounds as if something is going on with the solenoid, maybe settings in the EBC, maybe the solenoid.. Bypass that solenoid and run it on gate without PWM control on and then log your boost and see how it does.

 

I will give this a try. I only have a 3lbs springs in my wastegates though so not sure if Ill even see much of a drop in pressure. The solenoid is new but I'm sure that doesnt mean much since things can come defective straight out of the box, although when I test my outputs while live with my ecu the solenoid does activate. Do you think the turbo could be falling on is face due to a cooked journal bearing causing it to lose spool quickly?

 

The blades are ever so slightly starting to touch, I mean BARELY. This is why I think I cooked it and maybe the blades rub when its spooled up making it drop boost. I will give this a shot, do you think Ill have much fluctuation with only running 3lbs springs?

 

May change the spring out, if you've got them, to something a bit higher. If the blades were contacting that housing at all, you'd hear it. Really loud, sharp clacking sound. Lol

 

How do you have the solenoid hooked up plumbing wise? 10 psi is about all you gain from a 3 port hook up from what I’ve been told, not sure about the 4 port. So 13 psi should be your max boost on a 3 port with a 3 lbs spring ? A larger spring is probably in order for a baseline

 

Its a MAC 4 port EBC. I got 20lbs @ 60ish duty cycle with my 3lbs spring so unsure about the 10psi max you're referring too with the 3 port. As far as the plumbing goes I used this image. I run dual 44 gates tops and bottom are ran to a T then the boost solenoid.

 

Dual 44 gates. Damn. Unless you have enough back pressure that could be way to much wastegate, I’ve heard of a pulsating boost when having to much wastegate since to much exhaust gases dump to fast and things have to fight to recover. How big is your turbo and what’s your power goals?

 

^^ What is the setup? This on a K and sidewinder?

 

Engine setup: 83mm B18b1 Benson block, 9:1 CP pistons, Eagle rods, GSR head with upgraded valve train, Edelbrock manifold, Full-race twin scroll t4 manifold with dual tial 44's.


I never thought about back pressure to be honest. I thought having too much gate would be better than too little and have boost creep issues. Its a big *** BW turbo, T4 S300SX turbo 350-800Hp range. I will admit after driving my car I knew I got too big of a turbo. The plan was just to drag race it will power goals around 650WHP but after driving it I figured I would like to drive it more that just at the track. You really think having too much gate is the issue?

 

Get a block off plate for one of the wastegates...... it’s worth a try better yet just disconnect one of them for a test run

 

Ill check back next week when parts come in.

 

So I changed a couple things since I was having the boost oscillating issue. I went ahead and blocked off one of the gates and got a t3 style turbo. The boost issue has resolved. Too much gate was this issue IMO.

 

hate you had so much trouble, but glad your on the right path now

 

Its all good. Learned something new and hopefully will help others in the future.

 

Do you remember what turbine housing you were using? Was it a T4 divided .91 A/R with a divided t4 manifold?