Sticking CCV cause of boost problems?
 

As I've posted in some other threads on related subjects, I'm currently chasing a problem where I get very little primary boost...sometimes. The boost gauge needle pauses just north of 0 psi on the way up...sometimes it continues as it should, others it stays there, with no real boost. In first gear, it rarely works. In second, it sometimes works. In third, it almost always works. Even when it does, there is that pause as it transitions from vacuum to boost...sometimes the pause is short or vanishes altogether, sometimes not.

While trying to figure this out and run a lot of the tests at autosportracetech.com, it seemed the CCV actuator rod wasn't always doing the same thing as I reved the car in idle....I messed around with it a bit, moving it in and out, and it seemed to move freely. I eventually gave up and decided to drive again....and it worked almost completely right, every time and in every gear.

Below 4500 the CCV actuator is supposed to be ON, rod pulled in...and that appears to be true...so this doesn't seem like a likely explanation for the problem. However, I don't think I messed with anything else enough to have any sort of effect?

Opinions? This problem is killing me, any ideas at all would be a huge help!

jds

I should add that I just had new turbos put on, and the sequential hose job. The turbos went in because the old ones were leaking oil. They did not seem to have this exact problem, although there were enough problems that I couldn't say for sure. The hose job was done to fix the problem being discussed here...which it obviously did not. At any rate, something in the turbo swap MAY have caused this, but not the hose job. C'mon somebody's had to have had and fixed this problem before!

jds

If the CCV is sticking it will definitely effect your primary boost. The CCV separates the secondary turbo side of the Y pipe from the primary turbo AND the ic input pipe.


. . . . IC
. . . . .| |
. . . .//.\\
. . . //. .\\
. . .//. . .CCV
. . //. .. . .\\
. .//. . . . . CRV=
. //. . . . . . .\\
Pri . . . . . . . Sec
Turbo . . . . .Turbo

When the CCV is closed the air flowing out of the primary turbo must go up to the IC input pipe. Because the secondary turbo prespools before the CCV door opens the secondary side of the Y needs an exit to send the air flow that the secondary turbo generates. Therefore in primary mode the CRV opens to bleed off the airflow from the secondary turbo.

. . . . IC
. . . .| |
. . . .//.\\
. . .//.. \\
. . .//. . .CCV
. .//. .. . .\\
. .//. . . . .CRV=
.//. . . . . . .\\
Pri . . . . . . . Sec
Turbo . . . . .Turbo

If the CCV AND the CRV are open at the same time the airflow generated by the primary will flow across the Y pipe, through the CCV into the secondary side and out the CRV.

. . . . IC
. . . .| |
. . . .//\\
. . . //.. \\
. . .//. . .CCV
. .//. .. . .\\
. .//. . . . .CRV=
.//. . . . . . .\\
Pri . . . . . . . Sec
Turbo . . . . .Turbo


I think you should consider replacing or testing the CCV and CCV actuator. A solenoid may be the problem, but in the 7 years that I’ve owned my car I have never had a solenoid go bad and I’ve had many boost problems. I really think the solenoids are more durable than most people believe. The CCV actuator sits right above the hot turbos, hardly an ideal location for longevity.

^^nice work on the diagrams CCarlisi

Good info, that makes sense. It seems that the car boosts a bit better after I "mess with stuff." I was manually opening and closing that valve, reving the car in idle to watch it operate, etc. In a test drive immediately following that everything worked great, however in subsequent drives its back to its same old intermittent tricks.

Somewhere I read about testing it in idle...reving the car past 4500 and watching the arm on the actuator move. It didn't always act the same way. Sometimes it kind of half came out as I revved up, but then finally came all the way out briefly as the revs fell. Other times it worked more or less as expected.

The only thing that bothers me is that at idle, it seems to be sucked in, which is correct. Since my problems are prior to transition, it seems like primary-only mode would be working in this scenario.

If this really is the problem, my primary is making boost, its just all going out the CRV, right? Where is the best (and most easily accessible :) place to T into with my boost gauge...if I see full boost there when I'm not boosting, that will be a good indicator that this is indeed what is happening.

jds

OK, I did a few experiments. If somebody could validate (or discount) my findings, it would be helpful.

I tee-d my boost gauge into the wastegate actuator line coming off the primary compressor (T was before the pill). I expected to see full boost when the car was NOT boosting, thus indicating the primary was making boost and dumping it out the CRV. That did NOT happen...when the car didn't boost, the primary really did not boost. So then I tee-d into the line coming off the back end of the Y-pipe on the secondary side. This line appears to go to the LIM, not sure what its really attached to. Anyway, when the car is boosting properly, I see the gauge show 0, and then a steady climb to max boost as the secondary prespools. When the car is not boosting, I see about 2 psi on the secondary. In the case where the car hesitates, and then boosts, I see the secondary hover about 2 psi, quickly drop to 0, and then steadily boosts to 10 psi as the secondary prespools.

What this tells me (I think!) is that during the failure mode, the secondary is spinning a bit, and I don't think it should be. However, its not a lot of prespoool. At any rate, this leads me to suspect a stick precontrol or turbo control actuator, allowing the secondary to spool up before the primary ever really gets going. Does this make sense?

TIA,

jds

Off the topic of the thread, nice ASCII art.

One more thing...one of my key assumptions is that if the primary is boosting but the pressure is getting vented past the stuck open (hypothetically) CCV and out the CRV that the pressure seen at the primary compressor nipple that goes to the wastegate will be full boost, or close to that. Mulling this over in my head I'm starting to question it. If it vents too quickly that would probably reduce the pressure, I just don't know how "wide open" the system is in that case.

This is fundamental to my investigation here, so if anybody knows for sure about this, please let me know. Way too many posts by me in this thread! :D

jds

In case anyone cares, I'm reasonably certain that the CCV is in fact the problem. More correctly, the CCV ACTUATOR is the problem. I tried to apply a vacuum with a Mityvac to the chamber that connects to the charge control solenoid and it won't hold. I think the two chambers are leaking into each other. As soon as I get a new one I'll know for sure.

jds

souds promising. GL.

I have my turbo plumbing pulled apart and was playing with my CCV on the bench. With my vacuum pump I can open the valve and it will hold vacuum for ever. It only takes about 5inHG vacuum to hold it open.

Just wire the door closed and see if you get primary boost. If so you can be certain the CCV is suspect.

Actually the CRV is between the IC and the CCV, so the correct diagram looks like this:

. . . . IC
. . . . .| |
. . . .//.\\
. . . //. .\\
. . .//. . .CRV=
. . //. .. . .\\
. .//. . . . . CCV
. //. . . . . . .\\
Pri . . . . . . . Sec
Turbo . . . . .Turbo


If the CCV is shut all primary air must go to the IC or out the CRV. If the CCV is open and the secondary is not boosting then the primary's charged air may escape back into the intake side of the secondary and then out the secondary's intake hose.

You can see in CCarlisi's diagram that if the CCV were shut there would be no way to vent primary boost as it would not be able to reach the CRV...

Damon, I think you're confusing the CRV with the air bypass valve (they look the same but work differently). The CRV is there to vent secondary pre-spool boost, not vent primary boost. In your version of the diagram there's nowhere for the pre-spool boost to go.

How about this:

. . . . IC
. . . . .| |
. . . .//.\\
. . . //. .\\
. . .//. . .CCV
. ABV .. . .\\
. .//. . . . . CRV=
. //. . . . . . .\\
Pri . . . . . . . Sec
Turbo . . . . .Turbo


But your advice to wire the CCV closed is good, that will definitly prove if that is the problem.

Thanks, Alex. I'm getting Mazda's 3 letter names confused again. I recalled Mazda calling the blow off valve the CRV and that's incorrect. The CRV vents the secondary's boost when the CCV is shut so CCarlisi's diagram is correct.

http://www.autosportracetech.com/RX-...BigPicture.htm

I was getting ready to wire that sucker shut when I did the vacuum test on the actuator, and saw that it was bad. I have another one so I'll put it in and see what happens. I'm pretty sure it will fix the problem, but I'll post again to confirm once I've proven it.

jds

bureau_c, any results yet?

Yeah...kind of. I replaced the CCV actuator...well, I actually replaced the entire back half of the Y-pipe. You can get the actuator out but it is a pain do do it on the car, and once the Y-pipe was out, it was easier to just swap them.

I'm pretty sure it fixed the problem, but...I'm having another problem right now that makes me afraid to get on it and check for sure. As soon as the primary turbo starts making boost, I hear it spooling VERY LOUDLY. Its not just a wooshing sound, more of a high-pitched zing. I must have a MAJOR boost leak, but I can't figure out where. I'm sure I've just gone and done something stupid, but I haven't found it yet.

jds

the y pipe seal? if you replaced the back half...

You know, I was wondering about that. The o-ring was still there and looked good. I got a Y-pipe from someone else with the actuator on it, but it was stock rather than the Efini piece that I have. The back half seemed to be identical, so I just swapped 'em....I wonder if that was a mistake.

jds

OK, its official...a bad CCV actuator was in fact the cause of my problem. The boost leak I had on re-assembly wasn't from the Y-pipe halves, it was from the Y-pipe/primary compressor outlet junction. One of the bolts had stripped, so the y-pipe had worked itself a bit loose. I got a longer bolt and its holding better, but I was kind of afraid to torque it down. It makes full boost but still whistles a bit...maybe I should take it back apart and use some RTV gasket maker? It would seem to seal better than that thin little metal gasket. Then again, maybe the RTV would just blow out of the seams, I don't know. Either way...the car felt great. Its been a while since it was working right I guess!

jds

Congrats on the fix and thanks for updating the thread! :bigthumb:

Congrats on the fix as well. I think the CCA may be my boost issue as well. Anyone know how much these cost from a dealer?

The shop I sometimes use wanted $150 for a used one...which seemed steep, but I don't know how much they are new. As it turns out, a friend who went single turbo still had his old Y-pipe lying in a box, so lucky me!

jds

okay here's my two cents on this one.. for one you cant pass the stuck open ccv and exit the crv because the crv comes before ccv. thought assuming your ccv is is acting properly and is closed until 4500rpm and your crv were to be failing(as in not relieving pressure under 4500rpm) all that prespool would have nowhere to go except back through your secondary turbo, then the precontrol valve, and back into the primary turbo causing it to have excessive backlash pressure and not spool correctly.

mine is having similar problems except mine closes properly above 4500rpm, but does not open quickly enough once i shift or decelerate causing similar boost problems.


p.s. the boost line off the back of the y-pipe leads to the rats nest through a bunch of shit and back into your charge control actuator.