Ok so first off let me start by saying that i have search, and search and still have no luck. i have also followed multiple links with no luck at this time. here are the links i already looked at to get them out of the way.

https://www.rx7club.com/3rd-generati...ow-psi-864920/
Mazda RX-7 3rd Gen Primary Turbocharger Leak Diagram
Symptoms
Troubleshooting
https://www.rx7club.com/3rd-generati...-gears-685555/
Boost Test

So now here is my situation:

1995 rx7 pep
HKS downpipe- wrapped
stock midpipe
Apexi gt spec axle back
apexi power FC with base map
K&N drop in air filter with stock air box.
everything else is stock

3rd gear wot boost will not even hit 5-7 psi until 3500+ rpm. then after 4500 it starts dropping and by red line i'm lucky if i have ever 3psi.

I have no Check engine light on in my dash, as in, the light doesnt even exist.

1) Double throttle vac hose at idle does not have vacuum.

2)Vac at idle is 16-18 inHg

3) WOT in neutral i only get 1psi on gauge

4) Engine off, remove vac line from the pressure tank and i can hear air rush out.

5) Checked intercooler pipes and clamps and they are sealed tight. Couple at y-pipe also sealed tight, tried pulling on it and did not see any holes.

Also i took a screen shot of my commander after about 20 min of hard driving. Different gears, tried to do WOT pulls through as many gears as possible. The screen shows the max for the sensor i chose to monitor.



boost was +.48- about 7psi
air temp 70
water 85
injector duty 73.3

Can someone point me in what direction to go? Iv contacted Dale about buying new check valves and he told me that he will not have any for another 2 weeks. Also during that time I want to do all the vac lines. While im waiting for check valves i was going to tear everything apart but would like ideas on what to check and how.

Any help would be greatly appreciated!

 

edit

 

Can you hear and leaks or "whooshing" sounds while driving?

I had the same problem, and turns out one of the couplers for the stock intercooler was ripped.
It was on the bottom so I couldn't see at first, and everything felt tight and OK. You might want to double check all of those.

Also, I have 2 of dales check valves brand new. I bought 4 from him, but when I replaced all of my vac lines over the winter, I decided to get rid of all the emissions so I only needed 2. If you are going that route as well and want these, I can ship them out tomorrow.

Happy boost leak searching!

 

I didn't physically take the pipes off or the coupler. Just pulled on them and used a inspection mirror. Also the only noise I hear is the normal turbos sucking in air. I am going to boost leak test it. Also will be doing the vac lines and removing all emissions. Can you pm me with PayPal info and how much you want for the 2 valves?

 

Do you get 10 psi on your primary turbo before the transition? Verify that first.

 

Regardless if you had the light there or not, I don't think check engine light works anymore when you have PFC.

 

No. Like stated, primary lags a lot, primary hits about 6psi at 3500rpm. Then transition happens after 4500 and then boost starts dropping.

 

That was kinda what I was thinking also. But no one could ever verify that for me or not. Everyone always just said to ignore it because they don't tell you anything anyway.

 

Do you have an external boost controller or is the PFC controlling boost? If the PFC is controlling boost, can you verify/post your boost settings int he PFC?

Settings > Boost

 

Do a boost leak test it'll help narrow down if not completely help solve your low boost. Aside from that you can test all the check valves with a handheld vacuum pump to see if they are bad.

Also the pfc eliminates the CEL light so not having a CEL light is normal.

 

No MBC installed PFC controls boost, but was curious to see what would happen if I did put one in. I can post the settings later when I get home. But I haven't touched any settings, car already had the PFC when I bought it and i haven't touched it.

I was also wondering if I should just disconnect battery, de-energize system, and then reconnect and see if that makes any difference. Maybe there is a fault that is limiting boost?

 

I would check the crossover pipe for cracking. Also check to make sure all your vac hoses are good and connected properly.

I've not had sequential twins for around 4 years, so my trouble shooting on them is rusty... I do remember that if your primary turbo is NOT making over 7psi of boost by/at transition then you're not likely to actually transition to the secondary turbo. So it sounds like you're only running on one turbo, which would explain why you're falling down to 3.5psi by the end of your rpm range...

Have you confirmed that all your solenoids are working properly and hooked up correctly?

 

Have not checked operation of solenoids at this time. Will be doing that once I get silicone vacation lines and redoing everything.

Will be trying to do a boost leak testate tonight. Hopefully that finds something.

 

In theory the second turbo will never even come online unless you can make at least 7psi on the first turbo.

so, it sounds to me like your probably only operating on the first turbo as boost drops off so much by redline.
You need to get the first turbo working properly before you can diagnose the second one.

Is this car new to you?
oh and i dont think you can build boost in neutral...

 

Yes it is newish to me. I had it since February and the problem just started happening last week.

Also according to one of the websites, in neutral at wot it should build about 4psi. If someone would like to confirm that, that would be great!

 

Ok cool, so the first time it started happening what were you doing? Did it fall on its face after a hard run? or did it run fine, then next time you turned the car on it had the issue? Or did the issue gradually appear?

Im off to lunch soon so ill stab the gas in neutral and have an answer for you real soon..im confident we shall see no boost though
cheers

 

Honestly I couldn't tell you. I used to only drive the car on weekends beat the **** out of it as much as possible. then I got into a accident with my daily so I started driving the fd to work. 33ish miles one way, 90% highway. About a hour commute with traffic. One random day I noticed the low boost. Next day it was fine. Then low boost and back to normal. At first I thought I was just heat soaking intercooler in traffic. After a few days, I noticed it was normal first thing in the morning and as I drove it would get worse and worse. Now it is just always bad.

In traffic I made damn sure that the water temp never went over 95c. I'm really starting to think maybe I should do a compression check. But I took my friend for a ride and he said it felt great... but could clearly see the low boost on the gauge and apexi also read low.

Also, I wasn't able to get anything done or check tonight. Ran out of time and I can't be loud after 9pm due to association, sick of paying the stupid fine!

 

Checked boost in neutral, zero
Pretty much instantly goes to 0psi and stops.

Sounds like a check valve or solenoid may be sticking to me. I had a similar problem where It would sometimes make boost and sometimes not.

One of the check valves from either the pressure tank or the vacuum chamber (I forget which it was) literally fell apart when I tried to pull the hose off.
Replaced a bunch of check valves with Dale Clark’s ones (which I highly recommend) and problem solved.

Replace all vacuum hoses & check valves and you will probably be good

Get that UIM off

 

Ya wanna do the check vales buy dale said 2-3 weeks till they even come in. Fellow member is going to be sending me 1 extra he has.

Also, figured I would mention this also. When I first bought the car, I took it to the drag strip. Had a boost issue in 2nd gear. Here is how my runs went down.

Launch at 2500-3k rpm.
First gear- all normal. Shift at 7500rpm
Second gear- 6psi from the time I shifted into gear until about 6k rpm.
3rd gear- all normal again.

That boost problem was also weird because after getting to know the car I found that if I shifted at 7500rpm I would have a boost issue going into 2nd gear, but if I shifted at 8k rpm it would be perfectly fine at 10psi.

Never got around to figure out why or even looked at it, I just started red lining before I shifted...

 

Well good news. Finally got time to actually look at it and take stuff apart. Found that the coupler WAS actually torn on the bottom facing the intake manifold.

Quick stop to PEP Boys, got one of those Spectrum 3 in couplers and installed. test drove and car feels even better then before! Coupler was only $9.00, cheapest fix ever!

thank you to all that helped and gave any kind of advice.

 

damn, wishing my fix was that easy.

 

Glad to hear you got it fixed!

Check valve is in the mail btw

 

Cool. Thanks. Wanna redo the hoses anyway.

 

So the pep boys silicone hose already ripped and started leaking. Went to a local speed shop and bought a reinforced silicon hose and we will see how that works. New hose was $13. Also stopped by the dealer and with my discount the oem part is $38.

 

Bill got a bunch of high quality 4 ply silicone couplers, get a couple from him and never have to worry about it again.