Fd3BOOST

Sorry guys I haven't been paying attention here.

This link may come in usefull as well if you haven't already checked it.



**** load of info on stock twins and their related problems and how to's

P'cola FD

Have you checked to see that the precontrol rod is attached to the door, via a little c-clip?

13brv3

There's a thread on the other forum that suggested that the ECU turns down the boost at around 6k RPM. The theory states that some stock ECUs are programmed to do this, and some are not. Supposedly, if you have a normal 10-8-10 pattern, you will either get 10 all the way to redline, drop slowly as RPMs build (plugged cats or intake), or drop instantly at some point (ECU programming).



Why am I telling you this, you ask? Well, I just drove my car to see when and how my boost fell from 10 to 8. In my car, the drop is immediate, and happens at 5500 RPM. I'm starting to wonder if you have no transition, and the 5500 RPM drop is due to the ECU programming.



This is way out there as far as theories go, but something to consider maybe.



Cheers,

LAracer

Checked out ok. Thanks.

LAracer

There's a thread on the other forum that suggested that the ECU turns down the boost at around 6k RPM. The theory states that some stock ECUs are programmed to do this, and some are not. Supposedly, if you have a normal 10-8-10 pattern, you will either get 10 all the way to redline, drop slowly as RPMs build (plugged cats or intake), or drop instantly at some point (ECU programming).



Why am I telling you this, you ask? Well, I just drove my car to see when and how my boost fell from 10 to 8. In my car, the drop is immediate, and happens at 5500 RPM. I'm starting to wonder if you have no transition, and the 5500 RPM drop is due to the ECU programming.



This is way out there as far as theories go, but something to consider maybe.



Cheers,[/quote]

Interesting idea. Does make sense. I'll have to do some reading on it.

LAracer

Well, I had the car back together and everything set up to double check my 2.5psi result (the only thing that still points to precontrol). I was also going to switch the wiring on the precontrol and wastegate solenoids, just to see what happens. The car was warming up in the the garage and then...snow. Can you believe it? Maybe I need a break anyway.

LAracer

Snow didn't last so I got to run my tests. I T'd into the hose that connects the precontrol solenoid to the precontrol actuator (on the solenoid side) and also to the short hose that connects the actuator to the y-pipe. The first test was a repeat of the one I talked about before where I got 2.5psi. I got the same this time. The second test was different. I got over 10psi at around 4000rpm (easily enough to open the precontrol valve). This test is about as close to the actuator as you can get. Conclusion: the precontrol IS working.



I had thought that both of these tests should give me the same pressure (since they are in the same line), but I guess the pressure drop between the actuator and the solenoid is quite large (about 7.5psi). This is an important lesson since it applies to tests in any system. Don't assume that pressures are the same at different points in the same line.



And the lesson for anyone debugging their precontrol is - T into the hose going from the actuator to the y-pipe, not to the solenoid. The y-pipe hose is a little harder to get to, but that's the best way to do it.



Since the problem definitely not the precontrol, I think I should start another thread with a more appropriate title.



Thanks for everyone's help on this.

LAracer

For the benefit of future newbie searchers...



I am an idiot; I should have gone straight here:



http://www.rx7turboturbo.com/robrobinette/.../boost_note.htm



This has everything I needed to know about precontrol and boost control in general.