Boost Spiking on Stock Car?
 

I have a completely stock 1994 Rx-7 with 60,000 miles, which I bought 2 months ago. I installed an Autometer boost gauge because I could tell that my second turbo was not giving full boost all of the time.

When I got the gauge installed, I noticed I was getting 13 psi spikes on the first turbo, regardless of rpms. Whenever I would give it enough gas to get the turbos spooled up, it would spike to the 13psi, then it would go down to 10 psi.

I did confirm that my second turbo was only hitting 5 psi most of the time, although occasionally it would get 10psi.

I am going to replace my pre-cat with a downpipe, and hopefully correct the second turbo problem. But, I don’t want to do that with this spiking issue. I would think a freer flowing exhaust, might cause more spiking.

I haven’t found many people that have had this problem with a completely stock car. One thing that I did come across was on the troubleshooting website.

” If boost pressure is way above 10 psi, (i.e. spiking at >14 psi) then the tube between the Primary Turbo Compressor and the Wastegate Actuator has popped off.”

I haven’t tried looking at this tube, although it says >14psi, which I am not getting. Has anybody had experience with this tube coming off?

I was hoping to get some ideas of what my be wrong, so I can get it figured out without taking off and putting stuff back on the car constantly.

Thanks.

I have the same problem with a stock car at 68K miles. Look here for the thread I started . I haven't figured out the problem yet, but haven't put any time into it either. I am going to do a hose job soon, so I might just wait until then. I hope someone has some info on what hoses we should check first so we can try to pinpoint the problem. It sucks because I am too afraid to do a boost test because I let off when it hits 12psi. Can't afford a new engine right now. Somebody please help us figure this one out. Thanks.:)

Experience similar symptoms; spikes, delayed secondary turbo, weird boost patterns. Checked vacuum lines, etc. In the end I replaced the duty control solenoids that control pre-spool and wastegate, and this corrected all the problems.

Check around though, dealers quoted me $138 to $180 for the set, and none of them had it in stock. Took about 3-4 days to arrive.

The solenoid (if we're on the same page here) looks like this. You can also check/PM some of the single turbo guys and save quite a bit b/c they don't need them anymore. Just my $.02

Thanks

Jack

Thanks for the replies.

I will definetly have to look at those solenoids.

Part of the Problem sovled!
 

From looking at the troubleshooting guides, I started with something simple. I check to see if my pressure chamber was holding air, by taking off one of the hoses. When I took it off, I heard nothing.

Then, I removed the chamber and saw that the check valve was not connected. So, I connected the check valve and ran the engine, it still didn't hold air. So, I tested the check valve, and it was clogged. I then went and bought a HELP 1 Way Check Valve :eek: to see if that would cure the problem.

Now the second turbo is kicking on. However I still have my boost spiking to 13 psi. I did a 3rd gear boost test, and had the following pattern.
13-10-7-9
The car would boost up immediately to 13, fall slowly to 10, then at the transition would goto 7, and afterwards would hit 9 and stay there.

Now, I am giong to look at the Wastegate Accuator hoses and the Turbo Pre-Control Accuator Hoses, and try to test both of those solenoids to see if everything checks out.

Hopefully I can get the spiking figured out, so that I can truly enjoy my car.