Mfanto

I have a 93 Rx-7, and im experiencing a boost issue. I replaced my boost control selenoid about a week ago. Now in first, and only sometimes second, I cant get my second turbo to boost. The first turbo gives me 10lbs all the way through every gear, but the secondary turbo only kicks in from 3rd gear to 5th gear. What should I do?? Is this normal, are you not supposed to use the secondary turbo in first gear?? HElp me out

reelbigfx

Do you have a Y-pipe, because before I bought my car the seller was having a problem just like that and the shop he brought it to was taking their time so he took matters into his own hands. Turns out the CCV Actuator was sticking and it wasn't boosting correctly, so he replaced the pipe.

Mfanto

I have the stock y pipe I beleive

Mfanto

I have a HKS downpipe, k&n filtered cooled air box w/hard pipes, greddy stock mount intercooler w/greddy hard elbow, apexi pfc, greddy exhaust. Someone knows what is going on here help me out!! or do you think it is the y pipe?

LAracer

Welcome to te wonderful world of turbo troubleshooting. Here's your best resource:

http://www.autosportracetech.com/RX-7/rx7stuff.htm

A quote from this site

"The Turbo Control Solenoid / Actuator is one of the more complicated actuators as it requires both vacuum and pressure to operate properly. This actuator is controlled by two solenoids, (both are wired together to the one ECU output) one solenoid applies pressure to one side of the actuator and the other applies vacuum to the other side of the actuator. With pressure on one side and a vacuum on the other side of the actuator, the speed of the actuator is improved. A typical problem is loss of Secondary boost in 1st or 2nd gear at 4,500 RPM, but reliable operation in other gears. This points to one side of the Turbo Control Actuator not getting it's pressure/vacuum, so it will still operate but not quickly enough."

Have fun!

Mfanto

so you think it is the selenoid that was just replaced?

Mfanto

could it possibly be a loose intercooler coupler?

Mahjik

iTrader: (1)

Mfanto,

Which solenoid did you replace? The Turbo Control solenoid?

http://scuderiaciriani.com/rx7/vacuum_hose_diagram2.jpg

What was happening that you needed to replace the solenoid?

Mfanto

yes the turbo control selonoid...i replaced it caust my secondary turbo would only boost to about 5psi every gear

Mahjik

iTrader: (1)

Ok, the next thing to check would be the Turbo Control Actuator and the one-way check valves.

Mfanto

do you think they need replaced or just fixed up?

Mahjik

iTrader: (1)

If you look at the vacuum diagram, you'll notice there are two Turbo Control solenoids. Both of them work together to control the Turbo Control Actuator.

Which one did you replace? Chances are, whichever one you replaced, the other one is also having a problem (which is causing the actuator to not respond fast enough for the quick gears).

Mfanto

im not sure which one we replaced, I was not aware that there were 2 or I would have just replced both of them..

Mfanto

does it hurt the car to drive it like this?

Mahjik

iTrader: (1)

If you look at the diagram, one is mounted to the ACV, the other is on the lower part of the solenoid rack (next to the charge control solenoid if I remember correctly).

Mahjik

iTrader: (1)

I doubt it. You aren't overspooling the turbos or anything so it just makes your 1st and 2nd gear not as fast as it should be.

Mfanto

it is still really fast with out the secondary in first, and second.. So you dont think I will mess anything up if I drive it for a little while untill I get it fixed up

Mahjik

iTrader: (1)

Nope. It would be different if you had some huge leak in your IC piping venting all your boost. In that case, your turbos would be working overtime trying to provide boost. However, that's not the case in what you are seeing. It's most likely the TCA not being able to respond fast enough in the first two gears due to the solenoid that you didn't replace also having a problem.

cruiser

Mine does the same thing. Atm it doesnt bother me enough to rip the UIM off. I haven't done it before and am afraid of braking something that didnt need fixing

But I notice there are no check valves included in this problem after looking at:
http://scuderiaciriani.com/rx7/vacuum_hose_diagram2.jpg
and reading
http://www.autosportracetech.com/RX-...erOverview.htm

Am I right ?

Then it could be either:
- turbo control solenoid
- wastegate solenoid
- turbo precontrol solenoid
- charge relief solenoid

Reading onwards...
At 4,500 RPM

At this time, the Secondary Turbo is at full preliminary rotation speed, the Turbo Control is opening, Charge Releif closes causing the Secondary Turbo to surge for a short time. The Charge Control then allows Secondary boost to be added to the Primary boost.

This is where I suppose you also get low transition boost - like 5-7psi, right ?
Mine does that. From that I can only see that Charge Relief doesnt close fast enough (i.e. venting too long) - pointing to Charge Relief Solenoid.

Am I right in my thinking ? I will need to order solenoids from the States and dont want to order the ones I dont need.

I know, I know... I need a Mighty Vac... but that one is also almost double the price overhere

Mahjik

iTrader: (1)

Are you getting low transition or what Mfanto is having which is no secondary boost in 1st & 2nd gear?

Mfanto

I wish I new witch selenoids I need to fix, cause they are tricky to find the part numbers for.

Mahjik

iTrader: (1)

Mfanto, as long as you know the name of the part, just call Ray at Malloy Mazda and he can get it ordered for you:

Malloy Mazda
1-888-533-3400
Talk to Ray Crowe

The first thing you need to do is figure out which Turbo Control solenoid you already replaced. Then you can just check the other one.

cruiser

Mahjik, I'm getting both (but not regulary). Low transition AND sometimes no 2ndary boost in 1st and 2nd gear (if I floor it from like 10mph).

I went on reading a bit because I'm bored and look what I found:

The Turbo Control Solenoid / Actuator is one of the more complicated actuators as it requires both vacuum and pressure to operate properly. This actuator is controlled by two solenoids, (both are wired together to the one ECU output) one solenoid applies pressure to one side of the actuator and the other applies vacuum to the other side of the actuator. With pressure on one side and a vacuum on the other side of the actuator, the speed of the actuator is improved. A typical problem is loss of Secondary boost in 1st or 2nd gear at 4,500 RPM, but reliable operation in other gears. This points to one side of the Turbo Control Actuator not getting it's pressure/vacuum, so it will still operate but not quickly enough.

No vacuum to the Turbo Control Solenoid / Actuator is a common failure. This is typically caused by the one-way valve that supplies vacuum to the Turbo Control Solenoid / Actuator through the Vacuum Chamber. The one-way valve will leak, allowing manifold pressure to leak into the vacuum while under boost.


This is the check valve I'm going to pull out coming weekend. Can you try blowing through it to verify its operation or do you need mityvac pump to do the job ?

If this one way check valve is bad I think it can be the culprit for both above mentioned problems.

What do you think ?

Mahjik

iTrader: (1)

It's worth a shot!

I don't know the specs of the check valves. Typically, if you can blow through it both directions, it's bad. If you can only blow through one direction, it's ok. You could always go to a local auto store and get one of their cheapo check valves to replace it for a test.