Greddy Profec Installation and Tuning

Last updated: February 17, 2002

Profec diagram

Profec diagram

Profec diagram

Profec diagram


Date: Thu, 22 Jan 1998 22:50:34 -0500
From: (Carlos Iglesias)

I may not be an elephant but my memory isn't that bad! ;-)

>> 1. Where's the fuel regulator vac hose located?

Don't bother. Just buy a vacuum T, and plumb the smaller diameter hose off of either of the nipples on the upper intake manifold. These nipples are where the stock blowoff valve and where most people connect their boost gauge to.

>> 2. Where did you mount your control box?(stepping motor?)

The manual says to mount it somewhere relatively cool, so I mounted it just in front of the cooling fan relays rack which is inside my cool air induction "space". If you'd like, I can scan a picture and send it.

>> 3. Where do the other two hoses on the control box go?

I'll call the nipple on the Profec, "Y", "E" and "G" after the letters of GReddy logo on the stepper motor which the nipples are in-line with.

The stepper motor's "E" nipple receives boost pressure from the nipple off of the primary (front) turbo's compressor outlet (the front part of the turbo "Y" pipe). What you need to do is remove the short line that's between the front turbo outlet nipple and one of the two wastegate (WG) nipples. The short hose that you need to remove is the one that contains the "wastegate orifice/pill." Connect the hose from nipple "E" (the center large diameter nipple) to front turbo's outlet nipple.

You can now remove the line that goes to the other WG actuator nipple. Put a vacuum cap in the line you just removed to keep the vacuum system from getting contaminated. Now vacuum cap off and zip cinch (or SECURELY seal off) either ONE of the two WG nipples on the actuator which you're not going to use.

The "G" nipple on the Profec gets connected to the left over WG nipple, and provide the actuating pressure to open the WG.

In summary here's how it works:

  1. The smaller diameter line provides manifold pressure info to the controller via the stepper motor (Nipple "Y").
  2. While building boost, the pressure (from the front turbo outlet nipple) being received by the unit (nipple "E") is vent out to atmosphere by the relief nipple on the bottom of the stepper motor. -> the WG remains closed.
  3. When the preset boost level approaches, the boost pressure is rerouted out to the WG actuator via nipple "G." Since the WG actuator is now open on only the nipple that goes to the Profec, the pressure in the actuator builds to the point at which it overcome the closing force applied by it's internal spring -> the actuator begins to open (about 7 lbs.). At about 10 lbs., the WG spring is fully compressed, and the WG is full open. The Profec regulates the WG to maintain the desired boost levels.

>> 4. Any other tips?

Make sure to securely zip-tie or secure all of the associated nipple and hoses. Unfortunately, if the system's pressure integrity is broken, the wastegate will not open. Long story short, the system "Fail-safes" to BUY-A-NEW-ENGINE.

Along the same line, start to program the system as if the WG ISN'T going to operate properly. By that, I mean expect the worst, just incase. After trying it out a few time, then build confidence in it. Being too aggressive off the bat, might buy you some really great performance for a few seconds, followed by a very expensive post climax.

GReddy has a great programming info page.

I've always been able to program the Profec on the first or second try while in 4th gear. In 3rd gear, it's not as easy to program. Of course, running through 7500 rpms in 4th gear can make for some really interesting highway driving. Kids, please don't try this at home ;-).


From: "Jason"
Date: Thu, 3 Dec 1998 00:10:48 -0500

PRofec B installation:

  1. Remove air box and intake piping so you can access the waste gate.

  2. remove the 4 inch piece of hose going from the turbo to the wastegate. This tubing contains the pill which you dont need now.

  3. mount the stepper motor or little black box somewhere around the headlight under the hood.

  4. run a piece of hose from the turbo to the "IN" on the black box, then from the "OUT" to the waste gate. It just acts as a bridge between the two. Then reinstall the air box and intake hoses.

  5. run the power cable coming from the black box inside the car near the drivers side kick panel. I took it through the steering wheel boot or follow through where your boost gauge hose goes into the cockpit.

  6. Mount the the Profec B somewhere where you can access the dials on it. I velcrowed it to the kick panel to the left of the clutch.

  7. Now take the vaccum tubing for the boost gauge and cut it near the back of the Profec and add a T connector. Take a small piece of tubing and go from the T connector to the back of the Profec B.

  8. Find where you want to add the power to the Profec B and there ya have it. Make sure to keep the settings all the way down at first. That would be the LOW setting. then play with it and have fun.

Hope this helps. Any questions email me at


Date: Thu, 03 Dec 1998 05:09:56 PST
From: "kyle krutilek"

You may want to add to step 2 and disconnect factory bleeder solenoid hose from the second nipple on the wastegate actuator. Plug this nipple on the actuator.

Also add that you need do nothing to the pre-control actuator. Many people have y'd the profec to both the pre-control and wastegate, not good.


Date: Tue, 13 Jul 1999 19:01:15 -0400
From: "Roadrunner" (

>I am wondering what kind of installation variations you all have on your
>3rd gen with a Profec B installed.....
>I am currently taking out the small 3" hose (contains the pill) that goes
>from the turbo to the wastegate.....  and putting the profec B inline
>there....  I am also taking off the bottom line of the wastegate and
>capping both ends....
>I am noticing that boost seems to come on much slower than the manual
>bleed valve I had hooked up....
>Is this the only way to do it??  what happends if you don't remove the
>bottom line off the wastegate?

I have it going from the actuator to the IN on the Profec and then from the OUT on the Profec to the Wastegate. Also I have capped the other side of that wastegate which allows the ECU to control boost. With this setup and the profec OFF you should get about 7psi of boost. Using the Sharp/Mild Button, that will allow you to control how fast boost comes on. Farther to the SHARP side and the quicker the response, but the less stable the boost is. More to the Mild and slower the response but more stable boost. I leave mine a few clicks off Sharp, which seems to work well for me.


Date: Tue, 13 Jul 1999 16:02:49 -1000 (HST)
From: (Richard H Thomason)

Ahaa! The great wastegate//pre-control actuator debate springs to life yet again...

I continue to posit that the only way to get big boost (ie 14/15 lbs) out of both primary and twin turbos operation with a Profec B is by regulating both the "Wastegate" and the Pre-control Actuators. If you just run the controller to the wastegate actuator, you will end up with moderate boost on the first turbo (10 lbs sustained if your lucky, depending on back pressure), perfect transition prespool, moderate boost spike and your expected big boost only after the second turbo comes on line.

If you run the Profec to both actuators, you will get near instant big boost on the primary turbo on demand at any rpm above 2,500, but will experience a more violent transition and perhaps higher spiking when the second turbo activates.

The Pre-control Actuator regulates primary turbo boost until about 4000 rpm (if you don't believe me try adjusting your pre-controller actuator rod). The amount of boost generated by the primary turbo is regulated by whatever signal is sent to the Turbo Pre-control Solenoid by either the ECU or your controller of choice. It has been said on this list that the pre-control actuator (PCA) is simply a device which opens at a preset rpm to spool the second turbo. This is not all it does. The PCA is in fact regulating boost the entire time up till near the transition point, and though it does indeed accomplish this regulation via venting excess exhaust energy to the secondary turbo to prespool it, saying that is all it does is not giving it full credit. Keep in mind that during this time, the Wastegate Actuator is functionally inoperative- all boost generated by the secondary turbo is being routed not to the intake tract but to the atmosphere via the Charge Relief Valve during this period. Simply put, there is no way that the Wastegate Actuator is regulating boost to the primary turbo before twin turbo operation, all boost is being regulated by the PCA. At the point of full twin turbo operation the PCA is switched fully open and all boost is then managed by the Wastegate Actuator.

Based upon all the above, I continue to believe that if you want to run higher than "stock" (which depends on back pressure) boost on your primary turbo you need to have your Profec control the PCA and that you cannot do this by tapping into only the "wastegate" side of the system.

Hopefully, Brooks was actually asking this question. If not, well, let the debate rage once again anyway.


Date: Wed, 14 Jul 1999 00:43:57 -0400
From: "kevin kelleher" (

From: Richard H

>Simply put, there is no way that the Wastegate
>Actuator is regulating boost to the primary turbo
>before twin turbo operation, all boost is being
>regulated by the PCA

Not true. Both the WG and PCA control primary only mode. Changing either of these pills effects the max primary boost. Just been thru this with a new total 3" exhaust. After various pill sizes, I left the PCA pill close to stock, and opened the WG pill from .063 to about .086 inch, to maintain stock boost. You can actually see a little boost drop at 3000 rpm as the PCA goes from just cracked open to substancially open, due to the sol valve's reduced venting at 3000 rpm.

I quickly learned that PCA pill changes had a big (not exclusive) effect on the primary boost and spiking, and was best left close to stock. I believe Mazda sized this control for prespool only, and used the WG vent maps that are more open in primary mode to compensate for the 'wg' effect it has on primary boost. The precontrol pill size DOES have more effect on primary boost then the WG pill, but I feel it's a very tricky way to adjust primary boost, due to increased primary overshoot/spiking.

Profec B........since you can't trim it for primary and twin modes separately, seems like you could get the remote switch, and use a relay off the turbo control solenoid wiring to switch from hi to lo settings. You could then have different boost levels, if you prefer it, for single and twin modes.

The precontrol 'WG effect' does tend to reduce primary boost a bit with normal Profec installations. Leaving the stock sol-valve vent system connected, and not plugged, would keep primary boost up, but may have more overshoot than desired. Anyone try this?


Date: Fri, 16 Jul 1999 12:22:53 -1000 (HST)
From: (Richard H Thomason)

>The function of the solenoid valve venting
>pressure built up in the actuator diaphram
>chamber of the WGA during primary turbo
>operation is specifically to keep the WGA
>spring non operational on a stock car.

Example: If you send via either an electronic controller of via a modded ECU a signal to the duty solenoid valve a signal that says to permit 6 psi to vent through the duty valve you would need at least 13 psi of turbo boost to compress the 7 lb spring. So, if you are only boosting 11 lbs on the primary turbo, with stock pills, the "wastegate" would never open till swichover. This is what I mean by "inoperative." Changing the pill size will alter this relationship as will changing the duty signal. Now, I understand it to be that on the stock car (with stock pills of course) the signal sent to the duty solenoid until about 4k rpm is 95%, which means that the duty valve can and will vent as much as 8 psi. This means that the primary turbo would need to be boosting at least 15 lbs before the wastegate spring would start to open. If I am incorrect about the duty % on a stock car and it is at any time lower during this rpm period then perhaps the WG is becoming operational a bit here and there and you are correct. I will not defend the 95% duty figure with my life since I have never personaly tried to verify it. If I am wrong then kudos to Kevin for adding to list wisdom. Kevin, you did say that you spent some time checking the signal. What did you find with stock and modded pills?

Any way. Even if I am wrong on this issue (sob, snif), my original point was to "defend" the functions of the Pre-control Actuator. No matter who is correct on the issue of whether the WG does anything at all up till 4k or so, the PCA clearly plays a major role in regulating boost on the primary turbo, thus I continue to believe that the PCA must be dealt with if you intend to coax your primary turbo into actually generating a sustained, semi reliable plus 14/15 lbs of boost. Clearly, you can do this by fiddlin with the pills with an ECU with removed boost limits. I managed to get 16/16 lbs then 15/15 lbs of sustained boost this way but the boost was erratic and prone to fluctuate greatly depending on weather conditions (heck, my car ran high 11s this way). If you try this with a stock ECU, all you get is a big boost spike which subsides in higher gears. If you hook up a boost controller to modify the duty signal you can modulate when the WG opens, but even if you tell it to stay closed 'till 15 lbs of boost is present, you still want to regulate the PCA somehow to keep it from switching to far open 'till you want it to in order to allow that much boost to even reach the WGA during primary turbo operation.

It's sure good to get a healthy debate about this, "mumbo, jumbo" or not.

Anyway, to those who asked, I've double checked and it was just a simple to hook up the Profec B to regulate both the PCA and WGA as I remembered. All I did was hook up the controller side of the Profec to both actuators via a T connection, then plug the other nipples on each actuator. This is precisely what some have said NOT to do, but my car was most happy this way with near instant sustained 14.5 lbs boost on primary and twin turbo operation. The downside was a boost spike on transition. No one has posted to me claiming they got this much sustained boost on both single and twin operation via hooking up only to the WGA. You either get less on primary and 14.5 twin, or you get 14.5 primary and too much twin. I would love it if some others would give this a test to nail down the issue once and for all, but only do it if you give a hoot about running this much boost.


Date: Thu, 08 Jul 1999 22:24:45 -0500
From: brad barber (

> Does anyone know which Dip Switch setting is best on a Profec B
> to minimize spiking? Also, where are most people setting the Balance
> knob? Mine boost seems to "bounce" if I raise the balance much above
> Mild, although I thought that the Sharp setting would make reduce lag and
> hold more steady??

Dip switches...
1 ON
3 ON

Looking at the unit .. Set the balance at 4 o'clock, the low at 2 o'clock, and the high at 10 o'clock. You can tune from there to get the boost you want. This works great on my car and Kyle Krutilek's. I have to credit Kyle with beta testing these settings, BTW.

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