Homemade boost controller

F

First Fox

Well-known member
Thought some of you guys might find this useful. I needed a boost controller for my car and am just too cheap to pony up the cash for one and figured I could make one since they are very simple in design. After a Google search I found that a few people have indeed made them including our own beloved Linc's 200. 8)

I will include a few links to the one I made which cost a grand total of 8 bucks, and everything was available at my local hardware store. It was a matter of drilling and tapping 1 hole, and assembling the handful of parts. By far the easiest part of the turbocharger upgrade.

You will need:

1 1/4" brass "T" fitting.
2 1/4" brass hose barbs
1 1/4" brass cap (this is the part that gets drilled and tapped for the adjusting bolt)
1 1/4" ball bearing
1 spring (I have an assortment of these and found one that worked)

That's it. You drill and tap the 1/4" cap/plug to accept the bolt fine thread is better, trust me. Assemble it as shown in the pics and plumb it inline between your wastegate and boost source. Any compression on the spring will delay the boost signal to the wastegate and thus open it at a higher boost level but obviously will only be adjustable to INCREASE boost. In other words, if you have a 5 psi spring in the wastegte, this type of controller will only control boost at 5 psi and above. It can be placed in the cockpit with long enough hose, but I kept mine under the hood as I never intended to adjust it often. :beer:

Parts
http://i127.photobucket.com/albums/p146 ... uazj17.jpg

Assembled
http://i127.photobucket.com/albums/p146 ... q1fjgz.jpg

Installed
http://i127.photobucket.com/albums/p146 ... xllxdw.jpg

Installed 2
http://i127.photobucket.com/albums/p146 ... k6cirn.jpg
 
'Hobbs' would be proud, I'm still working on boost-referenced PV's and that gives me an idea ... . What's your final calibrated [sic] ? boost pressure / wastegate relief pressure with controller ? .

also: was wondering is your blow-thru carb hat/plenum welded steel or alum ?.

have fun
 
When i get this fueling issue resolved, i will turn the boost up but for now, I have it set to about 8 psi. This controller however has the capability of being adjusted until the wastegate doesn't open at all and there are connecting rods lying all over the road. 8) With the fine thread bolt it is pretty finely adjustable and a coarse thread would be too touchy I think.

I made my carb hat out of sheet metal and exhaust scraps and hit it with aluminum paint as i did the rest of the intercooler piping. There are a few pics of the carb hat as I was building it if you flip through my photo bucket pics. :beer:

I would have liked to make it taller for better airflow, but hood clearance wouldn't allow for it.
 
That's a really nice setup there. (y)
I just put my Fairmont into a garage and out of the snow.
And your build is quite inspirational, I may follow where you have led here.
Is that a Holley 1946 carb in there?
 
Did you try adjusting the actuator arm on the internal wastegate? I set changed mine from 8 psi to 5 psi. You should be able to adjust it up to 20 psi.
 
Thanks JackFish. :beer:

Yes it is the original Holley 1946 that I have had apart so many time that I have considered modifying it to come off the engine using a zipper or Velcro. It is a great carb and I believe it plays a big role in keeping my mileage at over 30 mpg. It is a bit difficult to work on, but it is doable.

And 59Orphan, I am unaware of any way to change boost with the actuator rod, would love to hear the idea behind it though. :beer: I did install mine after clocking the housings to give a small bit of preload on the gate arm.
 
Thanks for the link! Yes, this is the procedure I used to set my wastegate tension, but my understanding is that by setting it with said preload will make for less lag as the gate will not be cracked open at all during spool up. I can't see how it would allow the gate to open at a higher boost level. I can see it maybe raising pressure one psi or two if you REALLY preload it as the boost would have to compress the stretched spring before compressing it, but i cant see this being a 15 psi increase.

Have you personally tried this? You have me curious. 8)
 
We use our leak down tester to check all of our pressure sensors and to check wastegate adjustments.

Make an adapter using a fitting (or something quick and easy) to attach the leakdown tester to the black line going into the wastegate.
Make sure the pressure regulator on the tester is off before attaching the tester to the air compressor. High pressure will damage the wastegate.
Slowly adjust the air regulator on the tester until the wastegate begins to open and note the pressure reading on the testers pressure gauge.

Then make your linkage adjustments on the wastegate and retest to see what the new pressure level is to open the wastegate.
You will be able to see the operating range of the wastegate.

First Fox, Have you tried your new controller yet.
The reason why I'm asking is it usually requires a 2 port actuator to regulate boost over a selected range.

The way it looks now there will be boost until it reaches the 8 lbs you have the spring set at in the "T" fitting.
The 8 lbs will enter the actuator and snap the gate wide open because the actuator spring may be set at 5 lbs.
The turbo will spool down but the gate will remain open as there is no way to release the 8 pounds in the actuator and now there is very little boost.
Am I seeing this correctly or is there something I'm missing.

This is a great puzzle to work with but no matter how you slice it, a single port wastegate will only regulate at it's spring pressure setting.
Hence the creation of the 2 port wastegate giving you access to the spring side of the diaphragm.
 
Your "T" design can still work if you do something similar to how a leakdown tester works.
On the hose barb or inlet side of the "T", make it so you can screw in a carburetor main jet.

On the other side of the "T" where the screw adjustment was, make it so another main jet can be screwed in with a jet needle that can be adjusted into the jet.
Maybe you can use parts from an old carb.

The bottom of the "T" will go to the wastegate as it did before.
No ball and spring. The pressure relationships must be linear.

When the needle is screwed all the way into the jet, the air pressure is blocked from exiting and the pressure going into the wastegaste is the same as the turbo outlet pressure. The wastegate will operate one to one or a 5 lb spring setting controls 5 lbs of boost.

As you screw the needle out it dumps pressure and the pressure seen by the wastegate is less than the turbo outlet pressure.
The relationship between the inlet pressure and the outlet or wastegate pressure is linear.
The adjustment screw acts as a variable divider between those 2 pressures.
The "T" assembly becomes a linear variable feedback network.
And here we thought it was just going to be a boost controller

Example: If the needle is set to bleed off half the pressure and the wastegate's internal spring is set for 5 pounds,
it will take 10 lbs of turbo pressure before there is 5 lbs of pressure at the wastegate to open the gate and begin controlling boost.

As an option you may want to put a one-way valve in line to prevent a leak when the intake manifold is operating under vacuum.

Just my 2 cents
 
Oh yes I have used the controller and it works well. When you mentioned the controller not releasing the wastegate that reminded me that there was indeed another step that I failed to outline in the construction of the controller that should address the problem you describe. I don't have any pics of it now, but there needs to be a small 1/16" hole drilled in the middle of the "t" to allow pressure to escape after the controller ball checks or else the wastegate will remain open like you stated. I am sorry about that guys. When I get home I will snap another pic of the vent and post the link so it is clear.

The controller may be acting on the ball spring alone I don't know and it does make sense the way you describe it but I don't see the kind of symptoms you are describing with the wastegate relieving too much boost at all. It may be due to the afformentioned vent orifice, but it works quite well for the boost levels I am seeing.

Thanks for your insight on it though! :beer:
 
First Fox":2xzpn6d8 said:
Oh yes I have used the controller and it works well. When you mentioned the controller not releasing the wastegate that reminded me that there was indeed another step that I failed to outline in the construction of the controller that should address the problem you describe. I don't have any pics of it now, but there needs to be a small 1/16" hole drilled in the middle of the "t" to allow pressure to escape after the controller ball checks or else the wastegate will remain open like you stated. I am sorry about that guys. When I get home I will snap another pic of the vent and post the link so it is clear.

The controller may be acting on the ball spring alone I don't know and it does make sense the way you describe it but I don't see the kind of symptoms you are describing with the wastegate relieving too much boost at all. It may be due to the afformentioned vent orifice, but it works quite well for the boost levels I am seeing.

Thanks for your insight on it though! :beer:
Click to expand...

Now you tell me about the 1/16" hole. LOL
That solves the problem and you have a system similar to the one I described.

I actually like yours better because there isn't any air escaping until the pressure gets to the point of regulation.
No vacuum leaks.

On your system if the ball and spring is set for 8 lbs and the spring in the wastegate is set at 5 lbs,
when the pressure gets to 8 lbs the ball and spring will allow air to pass and pressurize the wastegate.
Once the pressure in the wastgate gets to 5 lbs the gate will begin to open regulating the turbocharger in return.
The pressure in the wastegate is then maintained at 5 lbs while the pressure at the ball and spring is regulated at 8 lbs with the 1/16" hole bleeding off the 3 lbs difference.

I learned something from this. Thanks. :beer:
 
Researching turbo vacuum controls options, found a site on building "Grainger Switch" or Mead Valve-mod which is similar construction with similar idea and nice graphics (slow to load) , didn't see it referenced in discussion:


boost controller that incorporates quick spool up, minimal spikes, and minimal hassle ...
graingervent.gif


http://www.gusmahon.org/html/boostcontrol.htm

also adds solenoid for switch selectable boost levels.

have fun
 
yeah i was wondering about that too, i remember putting something like this together for a buddy's eclipse turbo a few years ago but i've had a few beers since then and couldn't remember how we did it.

i do remember having machined several parts, i think being engineers we opted for the $50 solution to a $5 problem... there was an actual shuttle valve type thing involved and we had to change a wastegate spring.... i think we were using intake pressure to pilot it open before the direct-acting wastegate spring cracked.

the other advantage that bears mentioning is that this will hold your wastegate under acceleration so you can reach higher pressure in the exhaust before you build pressure on the intake side. i think, or at least it should if its done right. The point being that you can spool up faster without breaking open the wastegate, then it will open once high pressure is reached on the intake side.

i'm not sure if the valve you guys are talking about is accomplishing that, but if i remember correctly that was the main reason we were doing this to my friends car.
 
Until the wastegate opens there is more exhaust pressure on the turbo side of the gate holding it shut.
The boost pressure usually has to overshoot slightly to get the gate open.
Our data loggers always seemed to show this.

We connected the wastegate boost reference line to the intake manifold also.
Since there is a pressure drop across the intercooler we wanted to control the boost level at the intake manifold.

$50 solutions for $5 problems is definitely a habit here also.
We are looking things over for the next race season and replacing some stuff that was way over thought with simple.
 
The McLaren Mustang teamed Ford Design with McLaren Performance of Formula One racing fame. Planned production was just 250 examples. Power was again provided by the turbo-four, but it was newly fortified with a variable boost control having a range of 5 psi (0.3 bar)-11 psi (0.8 bar) vs. the regular engine's fixed 5 psi (0.3 bar). Rated output was 175 horsepower (130 kW) at 10 psi (0.7 bar), a big jump over the 132 horsepower (98 kW) stock mill. A $25,000 price tag and virtual hand construction limited McLaren production to just 10 units (including the prototype)
Click to expand...



I've seen many, many photos of the seven 1980 M81 McLaren Mustang's they made, but no detail on the Horsepower screw. From other information, the boost variance was more like 5.5 to 12 psi. What is being suggested was probably what was used what was used on the M81 to get the 5 or 6.5 psi boost variance, depending on whose info you use. I've been told 132 hp stock at 5200 rpm with the factory standard 5.5, then 175 hp at 7 psi, and 190hp at 12 psi.

 
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