Street King

I'am finally getting perfect boost after I "RE-GUTTED" the main cat a 2nd time as some **** came loose and clogged it. I get 11-8-11, then right around 6600 rpms it starts to drop to around 7 psi.

I know it is supposed to do this but I didn't think it happened that early in the power band. Thought it was supposed to hold boost to around 7200 rpm's. Do you think a line is collapsing under the pressure? I wan't to get this working right before I venture the Non-Seq. route. Any help guys?

I'am so glad to get full boost back just at the end it drops off a little too soon.

rynberg

With a cat-back and downpipe, I am getting a similar boost pattern.

11-8-10 then at 6300-6500 rpm, it drops almost immediately to 7 and holds there to redline. It's almost like a switch -- it's not a gradual reduction at all. It's as if the wastegate is going full open and staying there.

I have been searching boost issue posts and haven't come up with anything yet.

Street King

Yup happens like a switch. Drops really fast till 7psi and stays there. If you find anything let me know and vice versa.

gohorns

Currently I'm geting a similar pattern 11-8-11 till 6000 then drops to abt 6psi till redline. This is in 3rd but in 4th the secondary turbo hits abt 7psi. till redline - what you mentioned about your boost dropping back to 7 psi is normal when the engine is not fully loaded. It is very hard to keep a full load on a turbo rotary at redline unless you are in 5th gear or climbing a
grade. Basicly HP climbs steeply with RPM but load remains fairly constant (except at very high speed where aerodynamic drag factors in). HP exceeds
load and boost drops. Again in 5th or climbing a hill load will be high enough to maintain boost. However in my case the stock ECU is probably responsible for most of the drop in boost at redline.

maxpesce

It probably is doing that - the stock Boost control on the fd is not a feedback system (ie not a function of the pressure measured by the MAP sensor) but rather the waste gate selonoid is duty cycle controlled as a mapped function of throttle position and RPM - MAZDA decided the ECU was not fast enouch to do feedback boost control. I am guessing that the duty cycle goes to 100% at 6300RPM & WOT.

Street King

So is there any way to cure this 7 psi around 6300rpm's to redline?

P'cola FD

Get a boost controller.

Street King

Read my sig.

P'cola FD

I missed that. Here's a thought, maybe it's ignition related. Do you have new plugs. Maybe an ignition amp would help.

Street King

I did the plugs recently, and it's not running overly rich nor has it ever flooded. Maybe it is the ignition, but somehow I doubt that.

X-factorRX-7

get a boost controller to maintain boost with out cats. apexi or blitz check them out online

Street King

Sorry man, it say's boost controller in my sig, it was told to P-Cola also that I have a boost controller.

I know it's hooked up right on the Profec-B because when I turn it off it's at 7psi through all rpm's.

rynberg

Damn, I didn't notice you have a boost controller either. That makes me wonder. I have thought about getting a boost controller but now wonder if it's going to help or not.

My cat only has 60k on it and there's been a downpipe on the car for atleast 20k, so I don't think that's it. Especially with the consistent and immediate drop to 7 psi. Still made 240 rwhp on the dyno though. Wonder what I'll get if I can fix this little problem?

DamonB

I am stumped. I though with a boost controller you would hold boost to redline? Your pattern is correct for stock and gohorns is right about the load, but apparently I misunderstand how a boost controller actually interfaces electrically with the car. What signals are fed to your controller?