UK93RX7

I have had my rx7 for about two months now and it hasn't given me any problems yet. It is a 93 with 54k miles and a few mods including downpipe, catback exhaust and a modified air box. The other day I noticed that it was only boosting to 8 psi on "lo" boost. (I have the greddy profec 2 boost controller) When I originally got the car, lo boost was set at 10 psi (stock) and hi boost was set at 12 psi. I decided to turn off the boost controller to see if that would solve the problem, but the car still only boosted to about 8 psi. From my understanding, the car should be boosting atleast to stock boost levels, if not higher with the mods that I have. After turning the boost controller back on, and adjusting the settings, I was able to get the lo boost back up to 10 psi and hi back to 12 psi. My question is, shouldn't the car boost over the stock 10 psi if the ecb is turned off? What could be causing this low boost problem?

BoostFrenzy

no, yer on wastegate spring boost with controller off, that is normal

XSTransAm

the car is should boost 10 psi, since that is what it ran stock...

but if you have the ebc you probably have the stock pills removed which will cause your boost to be dependant on the ebc.

Im not aquainted with the profec, but boost will be lower in the heat because of the less dense charge of air, which could account for the loss of boost in your setup

lastly running over 10psi on the stock ecu is asking for trouble.

UK93RX7

I know. I also have a pettit ecu among other mods. I'm just trying to understand why it would only boost 8 psi with the controller off. I have messed with the settings on the profec and with lo boost set at 24% i get about 10 psi. I get 12 psi on hi boost when it is set at 28%. But from what the manual says, when the boost is set to 0%, it should just be boosting the stock boost (10 psi). Could someone that understands the greddy profect boost controller better than I do explain things to me.

rynberg

With the controller off, there is no manipulation of the pressure reaching the wastegate actuator. The actuator is designed to open at 7 psi of pressure, therefore, with no restrictor pills or with the boost controller off, you should be getting ~7 psi of boost.

The stock boost level is ~10 psi of boost, this is achieved by the use of a restrictor pill in the vacuum line running to the wastegate actuator, which acts to change the boost that the actuator sees. In essence, this is what the Greddy EBC is doing, except electronically -- changing the boost that the actuator actually sees.

Most cars are set up to run at the wastegate actuator (or spring) pressure from the factory to simplify the setup. However, this will tend to increase lag and reduce boost response. Mazda set up the car this way to get good response and reduced lag.

XSTransAm

the stock wastegate has pills in the vaccum line to restrict the air flow so it will boost 10psi.

when the profec was installed the pills were removed and the profecs boost solenoid was placed their instead. when turned off the car will only boost as high as the wastegate allows (8psi) because the restrictive "10psi" pills have been removed

clear?

edit: nm rynberg beat me to it.

UK93RX7

Thanks a lot guys. I understand it all now.