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I'm having a vocabulary problem. I'm troubleshooting why when my secondary turbo comes on I lose all boost down to 3lbs. I'm following a guide and it refers to an "extension manifold." What is that? I haven't been able to identify if it's the LIM or something else. Please expand my mind with new information. Thanks!
Ah yes, that too. I tried using the context clues when it referenced the crv and y pipe made the most sense. I'm not sure why you would be measuring boost pressure at the lim honestly. If you wanted to troubleshoot the y pipe then you want to measure boost on both sides of it. If the primary is boosting as it should and then everything falls off at cross over then it's likely there's a y pipe or maybe an actuator problem. I wouldn't bet on any solenoids since the cross over is happening to begin with.
So I just went out for a drive. I had my boost gauge teed into the vacuum line on my CRV. After 4500rpm it would get up to 6.5-7.1psi but that is it. I'm leaking boost I think. Pressure tank is good, going to check the vacuum tank.
Okay, I'm an idiot, how do I find it? I tapped the vacuum line coming from the Y-pipe to the charge control actuator and it makes boost until 4500rpm just like before and then loses it. Maybe the vacuum tank? Thanks!
There's a few ways to go about it. Keep moving that vacuum line to different sources until you find where you're getting almost nothing. That will put you in the area of the leak.
you could also pressure test your pipes and find it
you could run the car and spray carb cleaner at places until the idle surges
So I just did the KOKO test and the actuator for the secondary turbo opens when I go WOT but didn't during the KOKO part. What does this mean? I thought it wouldn't open at all if there was a vacuum leak. Can you help decode my results?
You should start by describing your actual symptoms rather than some random test from another forum.
The primary turbo needs to build ~10 psi boost for anything to happen. You also need a bit of vacuum pulled (like an abrupt throttle close) to help transition. This charges the pressure and vac tanks.
First, thanks for the help! My symptoms are after 4500rpm my boost drops down to about 3psi. I capped the CRV and went for a drive, still lost boost. I tried the KOKO test on the page you linked and that is where my question comes from. I took a video of my results but for whatever reason it won't upload. I thought it was my vacuum tank but I just pulled off the hose and heard it hiss. Maybe I need to recharge it and try again at the actuator? Thanks again!
Was the car boosting properly and stopped or has it always been like this for your ownership?
What is primary boost at?
You capped the outlet of the CRV? How about the hose going to the CRV... no cracks in it?
There is also the charge control butterfly to test (CCV).
If the cold side control is good, then there is also the hot side... TCA, precontrol and wastegate.
Have you checked turbo control actuator down below the turbos? There is a KOKO test for that as well.
How about the wastegate... is the rod connected to the turbos or did it pop off?
Precontrol should be good since you have good primary boost.
One other option... collapsing turbo inlet hose. Presents at higher revs. I had that happen and went to re-inforced inlet hose from mcmaster-carr. Actual cause was a restricted intake from failed ducting.
It may still have vacuum going to it which will make it open up. I believe the solenoid switches between vacuum and atmospheric pressure - vacuum at low RPM before transition, atmospheric pressure to close it after transition (high RPM).
Dale, you're a heartbreaker. I thought I had found my issue. I removed the vacuum line, heard a hiss, and the valve was closed. I assume this is the normal operation for it. If so the search continues for my missing boost. I hear a definite whooshing sound after 4500rpm and really thought this was it. Oh well, stiff upper lip old chap.
Okay Alexdimen, I think I got all of your questions answered. Here's the full story:
The car used to work just fine, so I made it better! Now it doesn't work. I have just finished putting in a V-mount, intake, upgraded oil coolers, exhaust, removed air pump, and PFC. We took the car out to tune it and it was running great! Then the low level coolant light came on. An old radiator hose had developed a very small leak. Tuning over. I replaced all the hoses. Went out to tune again. The car was again running great. All we were doing was cleaning up the fuel on the top end when all of a sudden we stopped getting boost after the transition. No loud pop or boom. No indication. 10psi off the primary, dip to 8 for the transition, then at 4500rpm boost goes to 2-5psi and the sound of air being vented under the hood. Whoosh!! We thought the CRV died so we zip tied a cap over the CRV. It didn't help. So we zip tied the TCV open so the second turbo wasn't closed off. No change. I've been hunting ever since.
I did find a crack under the clamp on the CRV hose but I taped over that while I waited for a new one. It didn't help and didn't blow a hole in the tape. I put my phone under the car to record the KOKO test and I think it failed. The none of the rods/valves moved during the KOKO test but they do move if I rev the car. I don't know what that means so that was the question I had. The wastegate rod is connected. The pressure tank and vacuum tank hiss if you remove the lines.
I would love some ideas about what to do next. I'll be reading so I can hopefully understand you answers.
Thanks again!
Originally Posted by alexdimen
Was the car boosting properly and stopped or has it always been like this for your ownership?
What is primary boost at?
You capped the outlet of the CRV? How about the hose going to the CRV... no cracks in it?
There is also the charge control butterfly to test (CCV).
If the cold side control is good, then there is also the hot side... TCA, precontrol and wastegate.
Have you checked turbo control actuator down below the turbos? There is a KOKO test for that as well.
How about the wastegate... is the rod connected to the turbos or did it pop off?
Precontrol should be good since you have good primary boost.
One other option... collapsing turbo inlet hose. Presents at higher revs. I had that happen and went to re-inforced inlet hose from mcmaster-carr. Actual cause was a restricted intake from failed ducting.
When my intake hose was collapsing I heard a semi-truck spooling sound in higher revs. Basically the inlet to my air box was restricted and was causing my intake hoses to close up.
The fact that you are hearing air escape after 4500 rpm would lead me to think something on the secondary side is leaking.
You said you wired open the TCV... are you sure it was the turbo control valve (big actuator under the car on the exh manifold and has a vacuum and pressure line going to it) or the charge control valve (above the turbos on the y-pipe)?
I have hard pipe intakes, CXRacing, so I'm sure they aren't collapsing. You are right, we tied the Charge Control Valve open(on the Y-pipe) not the turbo control valve.
I've found something, the back of my wastegate control actuator is open. The pre-control actuator is sealed with a white gasket. Is this my problem? I've never looked at it before as so don't know if this is how it's supposed to look. You can't tell in the picture but you can look right in and the metal is reflective. Is this where my boost is escaping? See the difference in the green circles.
Originally Posted by alexdimen
When my intake hose was collapsing I heard a semi-truck spooling sound in higher revs. Basically the inlet to my air box was restricted and was causing my intake hoses to close up.
The fact that you are hearing air escape after 4500 rpm would lead me to think something on the secondary side is leaking.
You said you wired open the TCV... are you sure it was the turbo control valve (big actuator under the car on the exh manifold and has a vacuum and pressure line going to it) or the charge control valve (above the turbos on the y-pipe)?
I think the ones I have seen are open there too. It wouldn't leak from that area unless the diaphragm had torn. There is a spring and then a diaphragm that boost pressure acts against in each actuator. Besides, if you had a leaky wastegate diaphragm you would be over boosting because pressure wouldn't build up enough to overcome the spring and make it open.
You never mentioned how you are controlling boost... MBC, stock ecu, PFC?
Oh, and if you wired open the charge control valve, capped the CRV and still had good primary boost... then I would suspect a wastegate or TCV issue. And not just the actuators themselves, but the solenoid controlling them.
Would be VERY hard for the actuator to be stuck open. There's a LOT of spring pressure in there. You should be able to grab the rod and move it towards the back of the car as a test.
Really sounds like something is up with the turbo control system. There's a flapper door in the exhaust manifold that blocks off exhaust gasses to the second turbo and a large actuator with 2 vacuum lines bolted to the manifold that make it operate. One line sees boost pressure and the other sees vacuum to make it move. This is the reason for the vacuum and pressure tanks.
There are 2 solenoids that operate the valve. If either solenoid is stuck or if the diaphragm in the valve is torn you will not have good secondary boost. You can T your boost gauge into the 2 lines feeding the valve (one at a time) and see if it is getting pressure/vacuum at the time of transition. Should be 0 (atmospheric) at low RPM and either vacuum or boost depending on what side you are looking at after the transition.
03-22-19, 11:19 AM
