Please Help : Overboosting with Greddy Profec-B
 

My car is always overboosting to 15 PSI even if my Profec-B is OFF (I heard it's supposed to be 7 PSI when the Boost Controler is OFF).

I tried to change the dip switches on the back of the unit (Overboosting mode) and same problem.

Here's how it's installed (see Version 1) :

https://www.rx7club.com/forum/attach...&postid=952472

Any idea ?
Thanks !

Bump !

Did you try turning the boost controller on and seting it for say 10psi?

What are your mods?

Not much :
New JDM RX-7 1999 Turbos, Intake, Downpipe, Catback, Double Throttle Removed, BOV, Boost Controler, Turbo Timer, Silicone Hose Job...

The thing is even if the 3 knobs (Balance, Low and High)are completely at the minimum on the Profec-B it's still going up to 15 PSI so how could I lower the PSI if the knob is already at the bottom !?

Thanks

Hate to bring up a dead thread but did you figure it out???

I am having the same problem ever since I started using the high boost setting. . . .

Justus

bump

I have the same issue, i just gave up and just let off the gas to keep it from overboosting. If there is a solution I would love to hear it.

Theres no reason to use two nipples t'd off into the stepper motor. Both nipples see the same boost/vaccum. Theres no reason to believe that restricting the boost seen by your PCA would lower your boost. It could only raise your boost. Turn up the gain on your boost controller. Low gain = low sensitivity. High gain = high sensitivity. If this does not work your profec is broke or your wastegate is broke or something is preventing one of these from seeing the correct pressure.

also,

according the profec-b (orginal) manual, you can change the switch settings from on/off/on/off for 1-4 to on/off/off/on if you are overboosting

I'd recommend the Version 2 plumbing diagram. I set up a Profec B for a friend like this - no probs, 7psi with the boost controller off, and he had no problem setting it where he wanted.

You should always see what boost you're getting with the boost controller off after an install. If you're not seeing 7psi, you have a plumbing problem.

With the #1 diagram, you'll still have the pill in there I believe. The pills are evil - if you have a good boost controller, there's no reason to use the pills. I could easily see #1 leading to overboost problems on some setups.

Also, the vacuum caps on the opposite side of the actuators have to be on VERY well. If you can't find high-temp vacuum caps, use a short piece of silicone vacuum line with a bolt stuck in it. Cheap rubber parts store caps will split and leak, and that will cause increased or out of control boost. You have to be VERY careful with the plumbing for a boost controller - clamp everything down, make sure lines don't rub or touch something hot that will make a hole in the line.

Dale

so if the vaccum cap cracks it will cause overboost? i thought that venting from the other side caused it to underboost

For anyone having this problem mine was because the fitting into the turbo for the wastgate and prespool had fallen off leting the turbo spool as much as its wants. Check vac lines all along the turbos if you can turn the unit off and still go above 7 psi

/\ sorry to resurect an old thread but im having the same problem with the greddy profec b. Only that my boost is at 25lbs no matter where i put the boost controller on/off/ low boost setting.

Originally my boost is at the low boost boosting 15lbs but when hit 25 i was like WTF? and my 550cc/1600cc were @ 91%

This is an old thread, but saw it while looking for something else. Most of the time (particularly if the boost controller has been working and then starts to overboost) it is because the cap on the other side of the wastegate actuator is leaking or missing. While counter-intuitive to many, you must build pressure in the wastegate actuator to OPEN the wastegate. No pressure = uncontrolled high boost! Approximately 7 lbs pressure opens the wastegate. The stepper motor controls the pressure to the wastegate actuator based on feedback from the EBC sensor. So for example, if you set your boost to 10psi, the stepper motor will deliver approximately 7 psi to the wastegate actuator (to open the wastegate) when the sensor reads 10 psi boost. If the cap is leaking on the other side of the actuator, the wastegate actuator will never reach 7 psi no matter how much air the stepper motor pumps in. Hope this helps. . .took me a while to get it at first.
--Jeff