Hi,

Got a new problem just starting to manifest itself on the FD. I get good strong boost up until the transition point, the car then just suddenly looses power, not gradually, but almost instantly, like its run into something (but that is probably more a perception of loosing the acceleration, of course!). No noises or backfiring etc. (The car is standard, by the way, no mods).
Now because this happens at the transition point, its obviously something to do with the 2nd turbo coming online - but from the description, does it sound like anything in particular? Just wanted to ask before I start stripping things out, and see if it is an obvious issue to someone here. Any pointers would be appreciated!

Thanks!
A.

 

does it make any different sounds?

 

try looking through here http://www.autosportracetech.com/RX-7/rx7stuff.htm

 

I had a similar issue on my car. After double checking all the solonoids vacume lines, actuators, etc, I finally found that the main cat on the exhaust was clogged (BAD).
I had a good 10 pounds till transition, then my boost went to 0. I losened the bolts between the precat and the cat to let some exauhst through the gap, BINGO! full boost. Didn't sound very good till I replaced the cat though.

 

What is your boost level at the transition point?

 

Check all of your vacuum lines, solenoids, actuators and check valves. Could be Charge Relief not closing as Charge Control opens. . .that would dump all your boost out of system right at transiiton. I've also seen similar behavior when Charge Control doesn't open, but it wouldn't go to "O" boost. But it could be many things, probably not major if it started all of a sudden. You just have to find it!
--Jeff

 

Thanks for the replies!


Its only just started to do this, and I have tried not to drive through the transition point, for fear of doing any damage - but on the couple of times it has happened, I haven't noticed any out of the ordinary sounds.

Thanks for the link - I've been there before and it is a very useful resource.

Thanks for the pointer!

From memory it was a good 10psi+, but that is something I will have a look at when I take the car out next time.

I had the turbos off last year, so I suspect something I put back together again has come loose. The car has run fine for several months after the turbos went back on, but a pipe may have worked loose I guess. As you say, the long hard road of finding it. I was thinking Chrage Relief/Control, as it does sound a very likely suspect, esp since it happens right at transition.


Thanks!

A.

 

Max boost pressure is a number which should be consistent. 10psi is not the minimum required - it's the maximum allowed.

If you've added mods that improve airflow through the engine, you will eventually see the boost level rise beyond the programmed level in the ECU. If that level reaches 12psi (give or take a little bit) the ECU will cut fuel, giving symptoms as you describe. This is a dangerous situation.

On your next boost test, watch the boost level closely at transition. (Also check that your gauge zeros exactly at zero when the car is off).

Dave

 

Here is a chart showing at what boost levels fuel cut will occur:

Dave

 

I had a similar issue with a bad ECU. I would get a code for the fuel pump relay, but everything checked out ok. Stock ECU's are very cheap. Might be worthwhile to swap yours out.