White94RX

Okay, I have done many searches and read almost every topic I could find on the subject of low boost from the secondary. I got my car about 5 months ago, 70k, Mazda reman. engine, stock, 5-speed. Everything worked fine until about a month and a half ago. I'm only getting about 6 psi from the secondary. My boost pattern is 10-8-(4~7).

Vacuum chamber is new, check valve is okay. I also checked the other check valve, and the other pressure tank next to the alternator. The I & J solenoids have been replaced (broke a vac nipple), and boost was the same before and after. They are hooked up correctly. I even swapped them and got the same boost pattern.

One of the troubleshooting pages said to unhook them completely and you should get a solid 7 psi. I got 7 psi from the primary, and about 4 from the secondary. I hooked them back up, and got the usual 10-8-6.

I checked the charge control actuator. With the engine on, the rod is pulled in, with it off, the rod is out. I also checked the crv. With vacuum applied, it was open. Without vacuum, the airbox end was able to hold plenty of vacuum from the vacuum pump, wich tells me the valve was closed, so it's working right. Correct me if I'm wrong.

I thought about maybe something with the wastegate, and turbo precontrollers. The original lines with the pills are still in place. If perhaps the hose was wider than the pill, this might cause a loss of boost. From what I read, though, this would affect the primary boost too. Can I just pull the pills out, put them in a new vac hose and put it back on?

I've pretty much eliminated any regular boost leaks (like the Y-pipe) because why would I still get 10 psi from the primary? What about the O-ring that connects the secondary outlet to the primary? If that leaked, it'd affect the primary boost too, right?

I've read about possibly a clogged pre-cat. I know a loss of boost in higher RPMs is associated. If it was my cat clogged, would there be any other symptoms? How could I check it? I don't want to have to buy a downpipe for nothing. Anyway, thanks in advance for the help.

White94RX

Someone help please!

White94RX

Why is it that no one replies to my thread, but I see stupid threads like "I think my car is the fastest" and the whole RX-7 community replies.

Every other post I have seen about someone having a boost problem, there's always several responses from the experts telling them what to check, what to do, and a suggestion on what might be messed up. Why don't I have a single response!!! HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

You know if you were having the problem, you'd want someone to help you.

Bucrx7

It could either be your precat or main cat. Check the coupler on the cross over tube from your y pipe to your intercooler hose. Most likely a clogged cat.

gzon

I have got a similar problem. I also got som pretty bad boost spikes so I installed a manual BC on the wastegate, no I get 10 psi spikes and 7psi after spike, and my secondary boost is depends on the cars mood and is between 4psi to 10 psi. Usually its 7psi.
My mods are 3" downpipe and "poor mans cold air intake".

My theory is that the spikes and the low boost at high sec. turbo is realated.

technonovice

Keep this in mind while I review your thread:

A downpipe is NEVER a waste of money. It is the best $300 yoy can spend to increase reliability.

technonovice

You need at least 15" of vacuum from the vac chamber and 7.5 PSI pressure from the pressure chamber.

Have you tested them for these numbers yet? Do you know how?

These forces are required to force open the Turbo Control Actuator fully. It could only be opening partially/sluggishly.

technonovice

Are you able to get full boost past 4500 rpm by letting off the gas and getting back on it?

White94RX

I haven't checked for 15" and 7.5 psi, and I'm not sure how. All I did was check the vacuum tank and check valve for leaks with the vac pump.

No, even if I get off the gas, and back on, it still won't get more than 6 psi above 4500.

You're right about the downpipe, but I just gotta come up with some cash. Are there any other symptoms that only a clogged cat would give?

P'cola FD

You need to do more than just seeing if the CCA and CRV are getting vacuum at idle. If you have a boost gauge then "T" into the vacuum lines going to the charge relief valve and the charge control actuator. If you don't have a boost gauge, by a cheap auto parts store gauge. Drive through the whole rev band and watch what happens in these hoses. There should be vacuum in both until 4,500 rpm at which time they will become pressurized. If that checks out fine, then move on to the turbo control actuator. I can never remember which side is vacuum and which side is pressure on that, so go to this site http://home.istar.ca/~dvandit/rx7stuff.shtml
It's extremely helpful and will help you better understand your problems. Also, if you want to check for a clogged cat or precat, you can pick up a little deal from most hardware stores that will let you check this: it has threads on one end, and a little ribbed nipple on the other(like for the hoses in high school chemistry class). You can put it in place of your O2 sensor and hook a boost gauge up to it. There shouldn't be more than like 4 psi of backpressure. Hope this helps.

spooledUP7

Well, you asked for my help and here it is. Turbo control solenoid, vacuum side. P'cola pretty much hit it on the nail. If you have test his test, then the next logical test will be to remove the TC solenoid on the ACV under the UIM. This is easy to see, since it is the only solenoid that is different than the others on the rack. Pull it off, and test for continuity using a multimeter at room temp, then run it under hot water (without getting the terminals wet) and watch for the resistance to disaper. If it is bad, when heated it will fail. Normal ohms should be 33-37 ohms.

If you want to see the results of having a working solenoid on your car before buying a new one, you could do this: https://www.rx7club.com/forum/showth...threadid=54737

White94RX

Okay, thanks guys. Looks like I've got a bit of testing to do tomorrow. I'll get back to you when I check the CRV, and CCV for vac/boost, and the cat converter check. I'm sure those will most likely check out, except maybe the precat. Then it will be on to the testing the TCA.

The Turbo Control solenoid probably is bad, but $60 isn't too bad compared to some of the other parts that could **** up. I'll post back again tomorrow.

Thanks a lot!

White94RX

Okay, I teed into the line going into the CRV and got no vacuum, and no boost. The silicone line I think was stretched and leaked around the tee fitting. I teed into the CCA and got the proper vacuum before 4500 and boost after that. So I then used the tee fitting to put this vac line on the CRV as well. It didn't help anything though. Is there a solenoid in the rack that controls the CRV? this could be bad in addition to the turbo control solenoid. Any ideas?

technonovice

The CRV solenoid is item H in the Vacuum diagram.

gzon

I just located my slow sec. boost due to a hose popping off at the pressure chamber, now I got boost even at first gear!!!!

technonovice

Any progress?

P'cola FD

White94, there is a solenoid that runs vacuum or pressure to the CRV. It is on the top of the rack and easily accessed. There are a few hoses to check along with the solenoid itself. Make sure all the hoses are connected and pay extra attention to where the hoses pass through the LIM. if there are a few hoses switched it will mess everything up. The CRV not getting any vacuum or boost will bleed off some boost when it gets high enough, which is bad. But at low boost it might not bleed much off, which will lead to compressor surge, also bad. Let us know what's up.

technonovice

The solenoid for the CRV is item H in the vacuum/TCS diagram. It uses vacuum only as far as I know.

White94RX

Okay, today the car was acting kinda weird at first. I would get maybe 1-2 psi, then it might slowly build up to 5-7. It wasn't too consistent either. One time the boost went up to about 5, and then fell to 0 by 6000 RPM.

Then, later tonight, it went back to the normal 10-8-5. It's not exactly consistent every time either. It could be like 10-7-4, etc.

I went to Birmingham over the weekend, and I was kinda thinking the pre-cat is getting clogged and restricted the boost. Maybe then it the crap got shaken or moved around, and I'm getting regular boost again. Any suggestions? I'm gonna do some more work tomorrow.

RecKleSs

I didn't feel like reading all these post. Actually, I didn't even finish reading your post, lol, it's just way too long for me. I suggest getting rid of your cat and get yourself a downpipe. Your cat might be a little clogged. Also, the downpipe is an awesome reliability mod and it will increase your hp. Also, check your Y-Pipe and ic hoses for any cracks.

technonovice

Do you always get 10 psi on the primary until the transition?

White94RX

I used to ALWAYS get 10 psi on the primary. Like I said above, yesterday, it started acting kinda weird. It won't build any boost for awhile, then slowly it will start to make more boost, and eventually I get the usual 10 psi on the primary, then the drop at the transition. I think I need to put on a downpipe and see what happens. Any other ideas?

technonovice

Get the downpipe. You need it anyway and it may solve your problem saving you a LOT of time, work and maybe money.

P'cola FD

You should get the downpipe, but I doubt it will fix your problems. Start troubleshooting the control system.

White94RX

Ok. as of today, it's doing the same ****. For the first 10-15 minutes, I get almost no psi. Then after awhile, it will make 10 psi on the primary, but boost builds slowly, and hits 10 psi closer to 3500 RPM. It feels like something is restricting the flow, that's why I think it could be the pre-cat. Any other ideas?