HELP: Unsolved Boost Problem
 

Ok, after checking all the vacuum lines, the silonoids, and the wastgate, my cousins boost leak is still unsolved, but my shop does have an idea on what the problem might be. The car only has an hks exhaust and dp, other then that its stock with about 65,000miles on it. My shop said that if we used an electronic boost controller and set boost using that, it would fix the boost leak problem. what do you guys think of this solution? Anybody run in to this same problem and solved with this action?

we did plug in a boost gauge and saw that the boost would hold at 10psi but then drop to 0psi right after 4,000rpms.

Thank you.

You have checked all the intercooler coupler connections, right? Especially the one for the Y-pipe/crossover pipe?

Yeah we did check that as well.

So your boost pattern is 10-8-0?

If so, I don't see how a boost controller is going to fix that.

Sounds like the secondary BOV (the one for the secondary turbo) is letting all the air out.

yeah me to, thats why I wanted to ask you guys because I cant see how installing a ebc will fix the problem. the max boost the car gets is 10psi which is the right boost setting but it only get it for a second then drops to 0psi at about 4,000rpms. Its been 2 months since we bought the car and I just cant find the problem. I hope its not the motor!

This sounds very interesting, has this problem accord with you?

Uh, you mean the charge relief valve...

Try venting the CRV to the atmosphere instead of the airbox, and see if you can hear it venting when your secondary boost drops. You should be able to hear it, since you're apparently losing all boost.

Thanks. Ill check it out.

ok I checked charge relief valve/bov pipe. It was fine. Do you guys think the spring in the wastgate is just worn out and cant hold boost anymore? I think we are going to try to get a ebc cheap and see what happens when we control boost with that.

If the wastegate is having problems, you either get limited to 7PSI or you have uncontrollable boost upwards of 14-15PSI (wastegate spring lowest limit is 7 PSI).

If you have anything less than 7PSI, there is a problem with the turbo system outside the wastegate.


How did you check/test the Charge Relief Valve?

Well I had the shop check it and they said it was fine, they keep telling me that the wastegates are missed up and that i need a ebc. Im about to just take the damn thing to PF.

If they really think that's the problem; tell them if it actually fixes the problem, you'll pay for it. If not, you aren't paying for the EBC or the labor.

Did you actually watch them "check it"? If so, what did they do? If the shop is telling you to buy a boost controller to solve your "problem with a wastegate", then I'd question their actual tuning and diagnosis skills.

Thanks for all your feedback and help man, its just that we have had the car for about months now and still no boost. Its frustrating knowing the power is there but we cant find it. The shop will not sell me the ebc, I need to find one my self, I dont even know which one to get. What do you recommend? Thanks

No I didnt see them do it, but I trust them, I have known them for 4 years now. They checked everything out on the car. Thats the only thing left to try.

If the shop won't purchase the EBC for you to test their theory (since they say that will fix the problem), find another shop.

They are just guessing and are just going to run down your bank account. EBC's are nice to have, however, that is AFTER the turbo system is functioning correctly.

When you have time, take a read through this page:

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

wow, thanks for that link, thats is a lot of great information! So since the boost hold to 10psi then drops right after, what do you see the problem is?

The best thing to do is follow that link and skip to the secondary turbo section and perform those tests. I believe they are in order of what is most likely to fail first.

Basically, it seems like your CRV is not closing, thus venting all your boost at/after transition.

There could be various causes:

1. Bad/damaged CRV
2. Bad/damaged Charge Relief Solenoid
3. Bad/damaged vacuum line

It sounds like the shop where the car is at, does not know what they are doing. I would recommend removing it from that shop before you waste any more money and either ask for local help or find a better shop.

1) You need a different shop
2) You probably have a failed secondary CRV, like Mahjik said. After the gate in the y-pipe opens during the secondary transition, the boost will drop to zero as it now has a path to escape through the open CRV
3) You need a different shop

Thank you everyone, from what you guys are telling me, it sounds like the CVR! Do you know where I could go on the net or this site to see a photo of this unit.

My friend introduced me to a guy in my area that owns a white 94 rx7 with a T-78 on it. I went to the guy and asked him what he thought, he showed me what he thought the problem was, he pulled out of his junk area a plastic looking unit that could fit in my hands. He said he thinks that the problem. I think he was showing me the CVR. Is this a common problem on rx7's? I cant wait to fix my cousins car. have a rx7 boosting at 0psi is no fun. thanks for all the help everyone.

George

https://www.rx7club.com/forum/attach...postid=1261370

The CRV looks just like the stock BOV. Each one has a label on it (the BOV is labeled ABV and the CRV is labeled CRV).

Simply replacing the CRV might not fix the problem. The CRV is controlled by air which is regulated by it's corresponding solenoid (Charge Relief Solenoid). I rarely hear of the actually CRV failing, but do hear of the solenoid failing often. My solenoid finally gave out last year.

...

How many solenoids are on the rx7? the shop said they checked all the solenoids. Thank you for the photo!

Take a look here:

http://www.scuderiaciriani.com/rx7/v...e_diagram2.jpg

You can see all the solenoids. If that shop thinks that no secondary boost is a wastegate problem, then they have no idea how to test the solenoids.

wow man, you know so much about this car, i wish you were in my area so i could just have you check the car out. So do you think i should just take the car to PF, because i dont think i want to take it to a mazda dealership.

I don't think Peter is messing with RX-7's anymore (or that his shop is open, I think it might be closed which was said in a recent thread).

I do think, as I said earlier, that you need to take it to a different shop.

see the problem in my area is that there are no shops i know of that work on rx7's. that is the probelm im facing. i think what im going to do is print the website you gave me and take it to the shop and show him it.

so how did you find out you had a solonid problem when your gave up last year?

:rolleyes: He probably tested the solenoid and found that it was faulty. Troubleshooting is actually testing each component to eliminate possiblities and narrow down the search to find the cause.

I know there's got to be some decent shops in that part of the country (maybe not in your "area", but not that far away). What about Malloy Mazda? Or is it just that Ray Crowe is able to get the best parts prices?

you don't need another boost controller. it will not solve your problem.

if your boost is going to zero at 4500 it can only be your wastegate and the associated control mechanisms.

i agree, as usual, w Kento. you either need to find another shop or figure it out yourself. there are plenty of resources on the web. diagnosing a wastegate control sytem problem is relatively easy.

good luck,

howard coleman

I reiterate.

Yeah the car has been taking out of the shop last week, so its not there anymore. I have read that you can change the bov to the cvr and then the cvr to the bov and test the cvr like that. I might do this myself and see the outcome.

Why go through all the trouble of switching them? Just unplug the "airbox end" of the CRV :rolleyes: and see if you hear it venting boost after 4500 rpm...

I then suggest reading up on the car as much as possible before you do any more work on it (or otherwise find a reputable shop to do the work).

Sorry about that I meant "cvr". yeah I have been reading up on the car and its motor. Its just getting to the point where we wish we never purchased an rx7. We heard rumors about the car and the problems it has but never thought we would bump in to so many. Mind you this is not the only problem we have encountered on the car since the last 3 months we have had it. I was able to fix the others but this is the last problem that needs fixing and there is no point in having a rx7 that performs like a pinto. But I know how this car SHOULD perform and thats whats keeping me going on fixing it.

I reiterate.

Possible vacuum problem. You can verify this by accelerating WOT, and after you pass the 4500 rpm, get out of the gas until you build 20 inches of Hg (check your boost gauge, or wait a second or two), then get right back on WOT. If you regain 10 psi boost after 4500 rpm by building engine vacuum through decleration, you'll know it's a vacuum problem.

Common causes for vacuum leaks are:
-cracked/broken vacuum hoses
-bad vacuum chamber check valve
-bad vacuum chamber (cracked/split)
-vacuum chamber full of oil (this was my problem)

Other common causes for secondary turbo problems (past 4500 rpm) are:
-bad turbo control actuator solenoid
-bad turbo control actuator
-bad charge control valve
-bad charge control valve actuator

Read that link thoroughly. It gives a good rundown on how to diagnose turbo control problems.

Do the simple stuff first, and work outward to the more complicated and expensive (turbo control and charge control actuators).

The solenoids and actuators are pretty stout on these cars, and your cousin's is fairly low mileage, but based on the symptoms, check the turbo control actuator solenoid, and the turbo control actuator itself (if the vacuum is fine).

Yes, the sequential turbos are a dream when they're working, but life really sucks when the turbo control system is screwed up!

Good luck!

OK, well I unplugged the cvr pipe that goes tot he intake box and we revved the motor to 6,000rpms and no air was coming out from the pipe. I then did the same for the abv pipe and air came out from it. is the cvr pipe not supposed to make air flow like it did?

Did you "drive it" or just "rev it in neutral"? You have to actually drive it to put load onto the engine to engage the turbo transition and secondary boost.

I didnt drive it, damn!!!! ok well Ill do it while Im driving. Will I be able to hear it while driving though?

Yep, it's damn annoying if you leave the CRV vented. It should close around 4000 rpms. If you keep hearing it blow after 4500 rpms, then you know it's either the CRV, the Charge Relief Solenoid, or one of the vacuum lines connecting those together.

Thanks a lot Mahjik! I will try it again.

Mahjik, I did run the test again but i did not hear any noise at all. Good news is I found a reputable shop in my area that works on strictly rx7's! I will be taking the car in tomorrow and let them have a look at it. I will keep you updated on what happens. Thank you.

So...it's been a couple of weeks...has anything happened? Is it fixed?
Was it the Charge Control System or the Turbo Control System?

I'm curious because I have a similar problem....Full boost on Primary dwindling to Zero boost just past transition.
I have a feeling that it's my Charge Relief Solenoid because the CR Valve closed nicely when I removed the vacuum line, although I do need to test it properly.

Man still no boost...

quick question,

when you hit the accelerator do you hear a noise like rushing air on the passenger side of the car??

lennie, what would that mean? PM me....

It would mean there is a leak or blow off valve opening too early. (But the stock blow off valves open into the airbox and usually can't be heard)

he is asking about the crv possibly staying open when it should close at the transiition point. i and many others have asked him about the crv and he says it is fine.