I recently purchased a '94 FD with a Blitz boost controller hooked up. The car had good compression, so I didn't worry about it having been beaten on. However....

The boost controller must not be set up correctly, as I am getting more boost than stock. I set it up the controller to be a pass through (no additional boost), but it still will overboost. 1st, 2nd, and 3rd gears don't seem to be much over stock (though I want it down to stock again), but 4th and 5th are really bad.

In 5th gear crusing on the highway (maybe 3,000 RPM), the digital readout shows that I can hit 10 PSI at maybe 20-30% throttle. If I try and give it more throttle, the boost continues to climb (very very quickly) and will hit fuel cut (I think) at 15 PSI. I haven't tried this more than a few times, as I was worried for the sake of my engine!

Should I be hitting these high boost levels at only 3,000 RPM? How do people drive on the highway if they can't floor it in 5th? Is it possible that the Blitz readout is wrong? There is no calibration option I see available. If so, what would be causing the fuel cut? Would the Blitz controller do that?

Confused by boost....
David

 

Mods to your car?

 

First off, what mods are done to the car? What ECU is in the car?

Next thing I would look at is how the boost controller is hooked up. If it's still using part of the factory boost control you can easily overboost. With a properly hooked up boost controller you should have about 7-8 psi of boost with the controller turned off.

There are 2 actuators on the turbo for boost control - the wastegate and the precontrol. There are 2 different methods people use to hook it up, I prefer hooking up so it's controlling both the wastegate and the precontrol. This totally eliminates the factory boost control solenoids and the wastegate "pills".

If need be, post pics up of the vacuum line routing to the boost control solenoid, I'd be happy to look at it.

Dale

 

Thanks for the replies.

The only mods I know of to the engine are the boost controller and a high-flow cat. Stock ECU, stock injectors, etc. I haven't actually verified the high flow cat, this was just what the previous owner said. I was under the car recently and it looks like the rest of the exhaust is stock, save for the extra sheet metal I welded on the muffler to close the holes that almost caught the car on fire. I kept wondering why the car filled with smoke when I accelerated....

I know that the controller is still using at least some parts of the stock setup, because those lines still remain in the system and are hooked up places. I won't be able to get a photo of the system for a little while, but as soon as I can I will post it.

The stock turbos will really make 15+ PSI of boost at 3,000 RPM? That seems really high. My work on turbo motorcycle motors seems to say that if the turbo can do this, it isn't sized very well for this application.

David

 

I'm almost wondering if there's something REALLY wrong with the boost controller install, like a line came off and the wastegates are just staying closed.

I'd pull the airbox and get looking around pronto. Something is way not right there.

Dale

 

It's normal for the car to make full boost easily in 5th/3k. What's not normal is the lack of regulation.

I agree with Dale - inspect the lines and look for a vacuum line leak between the boost controller, wastegate actuator, and the turbos. Also grab the metal connection and make sure it's not working loose at the compressor housing.

If that all seems secure and you're concerned about the boost controller, try removing the hose from the boost controller to the wastegate actuator and plugging it (a golf tee + zip tie works very well) so air can't escape the wastegate. This should ensure you get no more than 8psi.

David

 

I have the same problem. Have you tried to give it full throttle in third under 3k rpms? My guess is your like me and anywhere under 3k rpm your boost will go until fuel cut. I can sometimes get away with it in fourth (3.5-4k) starting but there is no way i could do it in 5th. Im using an HKS Evc which is pretty much the same as your Blitz.

 

So, I finally was reunited with my car and got a chance to look at the boost setup.

The blitz controller is set up such that the "in" side of the valve is routed to the exit of the front turbo. The "out" side of the valve controller goes to a T, and then is hooked to both the wastegate and precontroller on the passenger side ports. The driver side ports of these two actuators are plugged off, though the plug on the bottom one (precontroller) is badly cracked and probably leaking like crazy.

From what I can tell, my setup looks like this:
https://www.rx7club.com/attachment.p...1&d=1208733342 With one change. Where this setup says that I have two lines going to the intake line, I actually only have one.

So, would this cracked plug on the precontroller be causing my problem? How should my controller be set up? Does wide open (0 %) on the controller mean boost, or the opposite? I currently have it set up as a pass through.

David

 

Well, I looked up how the system worked and figured out that any leak would give me basically max boost. I fixed the leaking plug and the system now works great! I set it up so full throttle gives me 10.5 PSI of boost, which is what I have heard is pretty safe.

Thanks for input from those who helped.

David

 

^ with stock intake and exhaust, that should be ok. Just don't add any bolt on intake/exhaust mods except maybe a ss downpipe instead of the stock on.