So I just got my car up and running again and I have a few kinks to get out. One of which is a boost problem. The car has no issue boosting through the power band when accelerating, but after I've accelerated pass 4.5k ish rpms, if I slow down the primary turbo will not spool unless I've bring the rpms under 3K. Basically I get major turbo lag between the rpms of 3k and till the secondary spools.

incase it helps with the assessment my set-up is Apex intake, 99 spec turbos, down pipe, mid pipe, Apex exhust and Power FC.

can anyone assist? Thanks for any input.

 

Check the turbo control solenoids. They may be sticking.

 

This is from a forum member where he describes the same issue you are going through (in fact me too but I have yet to look in to it. ) http://rx7.voodoobox.net/howto/solen...oid_check.html

In his case it was the turbo control solenoid.

 

Unless I'm misunderstanding what's going on, I think this is just the proper way the sequential turbo system works. After 4.5k rpms, the ccv (I think that's the one) opens, and then it doesn't close again, keeping the turbos in parallel mode, until the rpm's drop below 3k.

If you have a power fc, you can go into the settings and change the transitions points to reduce that as much as possible.

 

I beleive bencb44 is correct i used to beleive this was a problem, i swapped in upgraded solenoids and everything and its still the same. The car goes into twin mode at 4250 rpm it wont switch back to just one turbo until the rpm drops below 3000 rpm.

bencb44 i have a quick question for you,, i know you can alter the settings on the power FC , if it was up to me id have the turbo system change back to single at say 4000 rpm,, has anyone ever done this and does it have any bad effects? why did mazda make the change back to single mode so low?

 

The whole purpose of the the sequential mode was to help you from a stop, giving you boost quickly at low rpm to get a quick launch, then once up to speed on a track or twisty road, the sequential mode gets locked out and you get the response and predictability of a single.

I would have to say that the car could be a handful, if it where to jump in and out of parallel mode at higher rpms. Many people find out the hard way how tail happy the FD can get if that second turbo comes online right as you are powering through a corner.

Once you're up to speed, you want to be running on both turbo's as much as possible anyway. Two is better than one!

 

tiger18, I know some people have messed with the transition times. Mostly though, I think they do it to make the transition smoother rather than to increase response. I have also heard about people lowering the transition as a way of testing out whether or not they want to go parallel twins.

The Powerfc section would be a good place to ask about this.