Wastegate solenoid mod?

[toomanymodz]

I have searched on this and haven't found any mention of the following scenario. I'm still new to this...but here is what I am thinking:

On a 86/87 GN/T-Type, the stock wastegate solenoid (located on the passenger side valvecover behind the turbo) is designed to pulse and limit the amount of vacuum going to the turbo and wastegate actuator whenever the ECM detects that there is knock. What this does is lower the boost levels when there is a knock condition detected. Of course the ECM backs off the timing as well.

Most tuners disconnect the wastegate solenoid and instead connect an air valve which has a knob that can be turned to precisely limit the amount of air flowing through. By adjusting the knob, one can raise/lower the boost however they wish.

The problem now is if there is spark knock detected, only the timing can be backed off. Boost can no longer be lowered by the ECM.

What I would like to try is to utilize both the wastegate solenoid AND an air valve. I would basically Tee-junction into the vacuum line running from the solenoid to the Y-connector (which is a factory-installed piece that splits the vacuum line into two lines, one to the turbo and the other to the wastegate actuator).

The factory wastegate solenoid will function as it originally did and provide around 12-15 lbs of boost. Then the air valve would introduce a little bit more airflow, thus raising the boost up more. Of course the effectiveness of the solenoid to restrict airflow is somewhat diminished, but I think it still may be able to lower the boost a little.

Has anybody tried this? I think it would be a great idea to have the boost level drop automatically whenever knock is detected. As much as I have read about head-gaskets getting pushed out, any extra insurance is worth a try.

Thoughts anyone?

 

[TurboRegal84]

I think I am confused but if you are looking to increase the boost just buy an adjustable wastegate actuator. Prior to doing so be sure you have an adjustable fuel pressure regulator and the proper scantool.

 

[GNeric]

If you are talking stock computer system, that doesn't register boost. It has no idea what you are running and only backs timing down, which is why headgaskets can go away. Boost stays up and sometimes not enough timing can be pulled and detonation takes care of the rest. Cliff Wolff showed me what you are talking about back in 97 and my old 85 GN was set up this way until I got RJC boost controller for that car. Didn't worry about it after that.

 

[toomanymodz]

I think I am confused but if you are looking to increase the boost just buy an adjustable wastegate actuator. Prior to doing so be sure you have an adjustable fuel pressure regulator and the proper scantool.

It seems as though it already has an adjustable actuator. There is a threaded rod with a lock nut. I believe I read that if I lengthen the rod, that will lower the boost.?

The previous owner told me that to raise/lower boost, I just need to turn the knob on this air valve thing that he has sitting on top of the engine. This air valve is connected to the line that used to be connected to the stock wastegate solenoid.

The car came with a laptop running TurboLink. It's currently running 25# of boost with no knock retard. According to the pile of timeslips that were in the console, the car ran consistent 11.40's at around 117mph.

I'm not sure if 25# is too much for the stock shortblock and I was thinking about lowering the boost to maybe 22 or 23# for a margin of safety.

I'm running 110 octane and I know that the 02 sensor will be history in a very short time. I'd like to run 104 unleaded.

I've had the car about 2 weeks now and I have soooo much to learn. I appreciate all the patience.

 

[salvageV6]

" On a 86/87 GN/T-Type, the stock wastegate solenoid (located on the passenger side valvecover behind the turbo) is designed to pulse and limit the amount of vacuum going to the turbo and wastegate actuator whenever the ECM detects that there is knock. "

Wrong, the solenoid only raises the boost level by bleeding off air going to the wastegate actuator that would normally open the wastegate lowering boost, when that air isn't doing it's job the boost goes up.

The factory non-adjustable actuator was around 10-12 psi. with the stock chip and PWM bleeding off air to maintain around 13-14psi. boost.

Aftermarket chips could raise the boost to 17-19 or so psi.

From what I understood how it worked.

I'd start with the air valve to adjust boost if there is room in the knob to set it to the 22psi. or so you want to run on 104.

If there's not enough control then lengthen the mechanical arm setting.

 

[LOT]

solenoid

Waste gate solenoid works off pressure (boost) not vacumn. It is an electronic bleed valve controlled by the ECM. For that system to work exactly as factory intended --all the hoses (size and length) need to remain the same. That is why the orfice in the plastic tee is drill a certain size. You are right in that you can put an adjustable valve in the system and bleed pressure off the actuator to raise boost but it may or may not now function as originally intended. Let us know how this plays out.

 

[toomanymodz]

So, in theory, if I hook up the factory wastegate solenoid along with an air valve, this should work. From what I'm reading, the factory wastegate solenoid, by design, bleeds off a small amount of pressure, which would raise the boost somewhat, and the air valve would bleed off a little more pressure, thus putting the boost where it needs to be. If the ECM detects knock, it pulses the factory wastegate solenoid, thus shutting off it's airflow, which would lower the boost. Of course it probably wouldn't lower it by much, since the air valve is still there and bleeding off some pressure.

I'm not sure how I can test this theory safely. Getting into a knock condition on purpose and watching for the boost to drop will be tricky. My turbo link software isn't setup to log boost, so I would have to watch the boost gauge myself. If I can get this to work, even if it lowers boost just 3 or 4 psi during knock conditions, I think it's some worthwhile extra 'insurance'.

 

[GNeric]

Again, it does not lower boost. There is no boost reference to the computer. It only backs off timing. The MAP sensor is only for the light show on the dash. If you raise boost to say...22psi and you encounter 20 degrees of knock at full throttle and stay in it, it will back off timing and your boost will still be up too high and you can kill head gaskets, rod bearings, ring lands. The pulse action of the solenoid is to limit boost at a calculated amount, not a feedback amount. You have to run the right amount of octane for the boost amount. Alky injection is another way of running the octane you need instead of race gas in the tank all the time.

 

[mikestertwo]

Again, it does not lower boost. There is no boost reference to the computer. It only backs off timing. .

Listen to Eric. The computer has no idea how much boost the motor is making. The duty cycle on the wastegate solenoid is calculated by the computer software. The computer does not know the actual boost pressure.

 

[toomanymodz]

Again, it does not lower boost. There is no boost reference to the computer. It only backs off timing.

Hmmm, on page 26 of the book titled "1986-1987 Buick Turbo Regal Engine" by Peter Hoffman, it says:
"The wastegate solenoid, located on the passenger's side valve cover, will under certain conditions, regulate the movement of the wastegate actuator.

One of those conditions is detonation. If detected by the ECM, it will 'pulse' the wastegate solenoid which, in turn, will bleed vacuum into the atmosphere. This will allow the actuator to open slightly and the exhaust gas will exit the turbo exhaust housing through the wastegate port."

I know that there is no boost reference to the computer, however, the computer does detect knock, and it can modulate that solenoid, which does affect boost levels. I'm a noob, but this I do know. :biggrin:

 

[mikestertwo]

One of those conditions is detonation. If detected by the ECM, it will 'pulse' the wastegate solenoid which, in turn, will bleed vacuum into the atmosphere. This will allow the actuator to open slightly and the exhaust gas will exit the turbo exhaust housing through the wastegate port."
:

You better go back and look at the theory on how the boost control works. Pulsing the wastegate solenoid will "Raise" the boost. Bleeding off pressure will tend to keep the wastegate closed raising boost.

 

[toomanymodz]

You better go back and look at the theory on how the boost control works. Pulsing the wastegate solenoid will "Raise" the boost. Bleeding off pressure will tend to keep the wastegate closed raising boost.

Looks like the book is wrong then. Thanks for all the info. I may now have enough information to do the 'experiment'.

 

[Razor]

The wastegate solenoid shuts when knock is detected. And is pulsed more when 3rd gear is detected to help control boost creep.

Now even if it shuts... it may not drop boost all that much. Your only looking at a few PSI. So intead of 25 your at 22/23. But if the reason you went into knock was severe.. even 22 PSI is too high of a boost level.

Correct the computer has no ties to detect boost levels.

 

[JayC]

I dont know about these days but at one point, all the chip guys were removing the boost reduction from the chips and using knock retard at different recovery rates for engine protection.

 

[machinegun]

Just for some FYI.

There actually are 2 scalers in the chip that deal with boost as it relates to knock.

Boost - Wastegate Duty Cycle Reduction for knock

Boost - MAX ESC Retard before Lowering WG DC

These 2 functions in the stock chip will help control boost under knock.

Some chip designers have however set these so high that the function is not generally used from the chips I have seen.

The Duty cycle of the waste gate increases to increase boost.

This bleeds the boost from pushing the diaphram open on the wastegate arm.

So higher duty cycle, more boost bleed less push on the diaphram to try to open arm results in higher boost.

Moral is that your setup has been configured and appears to work very well with a manual boos controller. I would stick with that and set as need be.

I would find a good buick person to help you. Being a newbie to the turbo buick can be overwhelming at first. I would not risk damaging anything without using a methodical approach to tuning the car for the fuel you want to use.

You can contact Cal Hartline down there and I am sure he will be more than happy to help you.

 

[salvageV6]

"The wastegate solenoid, located on the passenger's side valve cover, will under certain conditions, regulate the movement of the wastegate actuator."

Of course this statement is true.

It raises the boost when the air going to the actuator is bypassed to the atmosphere.

Actuator has less movement when the solenoid is pulsed, raising the boost.

So it does regulate the movement just not in the direction you want it to go.

Check with your chip designer of choice to see how they use the stock (if at all) features.

 

[Razor]

I dont know about these days but at one point, all the chip guys were removing the boost reduction from the chips and using knock retard at different recovery rates for engine protection.

I think part of this reason would be in case of false knock which these cars can suffer from.

And as posted, contact your chip maker to see how his chip handles the WG solenoid..