GsrSol

10-5-7

I get full boost on the first turbo, about 5psi in the transition, and 7psi on the second turbo. Sometimes it will hit 10psi on the second turbo but quickly drop to 7 as of Wednesday. I haven't touched anything on the car in weeks.

I did the search and all I could find regarded the pills. I changed some of the vacuum hoses a while back and none of them had pills in them and still saw 10psi after the change. Turbos were replaced 11/99.

No boost controller.

Any ideas of what I should check?

REDLINE

I have a similar problem. I get 10-5-10, then all of a sudden it drops down to around 7psi until redline. Also when I shift gears real quick, it almost seems to forget to boost. It would stick around 3psi then suddenly around 3500rpm jump to 10-5-10 all the way down to 7psi. As far as not finding pills, I had my turbos replaced in '95. '95 and up turbos don't come with pills. Instead, they have a restrictive nipple that doubles as a pill.

pistonsuck

I have the same problem I wish I had a fast easy fix. I have spent hours tracing hoses and checking solenoids. I have not been able to check the turbo control actuator, because I didn't have a vacuum and pressure to check it at the same time, I will check it soon. I will let you know if that was my problem. My pattern is 10-5-9 in 3rd gear, but is 10-5-7 in 1st and 2nd. Is your pattern like 10-5-7 in all gears?

GsrSol

I only checked 1st, 2nd, and 3rd.

It was running fine when I raced a Mustang Wednesday, I then went to race someone else and it was just not boosting at all.
Now it boosts, but not all the way.

Tim Benton

iTrader: (1)

I assume you guys have replaced the pre-cat. It seems like you all know about these cars, but I was just throwing out the basic flow restrictions that tend to limit flow on the top end. Precat could be partially blocked, it its replaced with a down pipe, check the main cat.

Tim Benton

maxpesce

The actuator needs 8psi to transition the secondary - this is supplied by the black pressure tank on top of the engine if the tank or any the hoses leading to/from it are leaking you won't get proper staging on the second turbo - I think there is also a Check valve to maintain pressure in the tank - if it's bad that could also cause prob. - Clogged cats will cause loss of boost also

GsrSol

I have checked the black box and there is presure in it and the vacuum lines to it are fine. However, I do think my main cat is clogged. Yes I have a downpipe.

pistonsuck

I know this is a bad idea in general to keep the pre-cat in, ie more heat in the engine compartment and the pre-cat easily being clogged. I run the pre-cat because I run the car in SS at autocross events. I will not be able to run this class if I run a downpipe, at least I believe that it would be the case. I really like racing this 996 that shows up in the SS class at the autocross races around here. But my car runs a 10-5-9 in third gear, so I was thinking it was more or less a turbo control issue. Any ideas? I would really like to keep running in the SS class.

MattRX7

I've had a similar problem for months now. I'm going to replace my precat with a downpipe, once I find someone to install it for me. Hopefully that will fix it.
Look at the 3rd gen archive, I started a post on this subject a while back called "Low Boost". Since I have no mechanical skills I haven't been able to fully diagnose the problem. However, I got a lot of good replies in there. They may help.

Matt

REDLINE

If its a clogged cat, how much are they to replace? Is there an alternative to them? I know that a precat alone costs around $1200!!!!

Nameless

Get a hi-flow cat from rx7.com It costs way less, and I've heard good things about it. It is the Bonez hi-flow cat.

potatobbq

anyone know exactly where to find this check valve? i'm getting something like 10-7-9...

maxpesce

with a 10-7-9 boost pattern I don"t think you have a control system problem. when boost is building after transition it shows that the second turbo is staging ok - most likley high back pressure (clogged Cat/PreCat) or Ignition problems (Plugs/Wires) -
Poor combustion = less exhaust energy = Less Boost

REDLINE

Do they sell something similar to the stock main cat in terms of back pressure and sound level? I'm kinda trying to keep mine stock...kinda hard to do though

Swamp RX-7

I had a 10-5-7 boost problem. It turned out to be the hose connecting the CRV to the second turbo, it was dry-rotted, I replaced it and now I get 10-8-10. This hose would seem to be a major spot for leaks, when you look at it, it seems fine, you have grab it. If it's hard it's no good. The location of the hose(being above and close to the turbos)makes this a high failure rate part. I also have the bonez high flow cat, and it works great.

REDLINE

Still wondering. Anyone know the answer to this?

GsrSol

I took of the hose connecting the bov to the Y-pipe and noticed a big crack in the hose where it connects to the y pipe, the crack was underneath the clamp and the hose was rock hard. I replaced the hose and now the bov is louder and I'm seeing 8psi instead of 7....still have another leak somewhere

REDLINE

Hmmmm...cracked hose at y-pipe huh? I'm gonna have to check mine out too!!

REDLINE

Actally a friend of mine said he used to have a similar problem. With him, it was the blow off valve or the bypass valve. It would sometimes get stcuk open or something. Is this possible?