Manual Boost Controller

[Steve940estate]

Thanks Andrew

I was hoping that someone else who has one would give me a few ideas. I wondered about the flow through the valve. I have an 8mm ball bearing which is a pretty good fit in the hose fitting where it seats. The amount it lifts off must be very small and the air then has to pass round the ball and through the valve.
The other problem is that once the pressure drops the small bleed hole allows the wastegate actuator to shut, this releases any pressure in the valve and line. This helps the actuator but next time the pressure increases and openes the valve the air has to pressurised, a small amount escapes from the relief hole and then the actuator opens again. There is going to be a slight delay in the actuator opening because of this.

Does your valve have a relief hole in it ?

I have a larger bore fitting but I think my biggest problem is the size of the ball. another problem is that because of the size and greater seal area more spring pressure is needed to keep the valve shut. I might give things a go with a smaller ball bearing to see if that helps as well.

I'm having a new screen fitted in the car later but I will have a go at the valve later or tomorrow. The only time my one does anything noticeable is when you really floor it after lifting off at speed. The reat of the time it seems ok. Oh and in case you were worried about offending me I haven't really got a clue what I am doing , just learning as I go along !

[typhoon]

Reducing the size of the ball is probably the way ahead for you. As you said, it will greatly reduce seat pressure on the sealng surface and allow far more air to bypass the ball.
The ball seat is just a drilled face I assume, so seating will not be an issue with a different size ball. The drilled depression will also self centre the ball.
My MBC has a bleed hole.
Here's my MBC, you can see teh body is much larger than yours:


Regards, Andrew.

[Alan M]

The bore size of the valve and pipe will not really effect the operation to much. The hose you are using is only 4mm internal bore. The hoses only shift air inside a closed system for reference and opening/closing the actuator/wastegate. The air movement is very minimal for reference and the air is compressed under boost conditions to operate the valve. The MBC usually does provide a more low down grunt because the actuator is held closed till that preset value so the power seems to come in earlier.

[Steve940estate]

Thanks for the info guys. I think I need to increase the flow through the valve by using a smaller ball.
As you said Andrew the ball seat is just a drilled hole and isn't very well finished. I will clean this up and give it a polish to help it seal.

The way the ball valves work you will always get some restricting effect I suppose it's just a case of minimising it.

I have been looking at proper pneumatic valves with diaphrams in them as a better way of doing things but haven't worked out exactly what type would work. The cheaper pressure regulators cost about the same as a car specific MBC anyway.

I will update this thread when I have come to some sort of conclusion, it will probably be that it would be far easier to just buy an MBC, but I want to know exactly how they work.

[Suterman]

Dont you need a bigger wastegate to reduce or eliminate boost spike?

A bigger hole and gate would allow pressure to be released faster as soon as the thing opens, having too much boost running though a smaller wastegate means the pressure takes some time to drop and hence the spike.

This is what I heard on TB anyway....

[typhoon]

Originally Posted by Suterman

Dont you need a bigger wastegate to reduce or eliminate boost spike?

A bigger hole and gate would allow pressure to be released faster as soon as the thing opens, having too much boost running though a smaller wastegate means the pressure takes some time to drop and hence the spike.

This is what I heard on TB anyway....

99% of people on TB are parrots, mimicing what they say to each other all day. Read up on turbos elsewhere and you'll learn a lot more!
Seriously, look at the plethora of cars there that have had $1-2k dumped on them and they're still unreliable heaps that are barely faster than stock..........
I have NO spike in my system at all. The stock wastegate and dump valve work just fine at 15psi. It is handling the same VOLUME of air, just at a higher PRESSURE.

Regards, Andrew.

[Steve940estate]

Ideally I would buy an adjuatable wastegate but they aren't cheap. They also start to open before maximum boost is reached. I could splash out on an electric boost controller.

I was really looking to give the maximum boost as soon as possible. I think the one I have made helps with this but would be better with a smaller ball fitted in itas the large one restricts the flow. I only get problems with the boost going up above the normal level if I really give it grief. The easiest way it to drive at a constant 70mph, foot off and then floor it. Not something I would normally do but it highlights a problem that is there.

I am only running about 9psi, I am pretty sure I would get better results with a higher setting because if the way the ball valve works. The biggest problem with ball valves is that you don't get full flow when the open. I have been looking at other pneumatic valves and have found a way to do it. It would involve a pilot operated valve that would open fully when the set pressure is reached. I haven't found out if the varying pressure from the turbo would operate the valve correctly.

I like to question things, just because people always do things a certain way it doesn't always make it right. I will investigate furthur, but I've got to sort out the clutch on my car now.

[Steve940estate]

Originally Posted by Suterman

Dont you need a bigger wastegate to reduce or eliminate boost spike?

A bigger hole and gate would allow pressure to be released faster as soon as the thing opens, having too much boost running though a smaller wastegate means the pressure takes some time to drop and hence the spike.

This is what I heard on TB anyway....

Thinking about this a bit more a larger waste gate would be needed if you were running really high boost pressures. The low pressure I am running shouldn't be a problem. I think the Turbo plus system gave 10psi at full throttle.
As I said my homemade boost controller isn't quite right and is acting more like a restrictor than a proper valve, hence the build up of pressure.
The car behaved better when I just spaced the actuator to increase the boost. This works the same as adjusting the actuator rod length if it's adjustable.

[typhoon]

Originally Posted by Steve940estate

Ideally I would buy an adjuatable wastegate but they aren't cheap. They also start to open before maximum boost is reached. I could splash out on an electric boost controller.

I was really looking to give the maximum boost as soon as possible. I think the one I have made helps with this but would be better with a smaller ball fitted in itas the large one restricts the flow. I only get problems with the boost going up above the normal level if I really give it grief. The easiest way it to drive at a constant 70mph, foot off and then floor it. Not something I would normally do but it highlights a problem that is there.

I am only running about 9psi, I am pretty sure I would get better results with a higher setting because if the way the ball valve works. The biggest problem with ball valves is that you don't get full flow when the open. I have been looking at other pneumatic valves and have found a way to do it. It would involve a pilot operated valve that would open fully when the set pressure is reached. I haven't found out if the varying pressure from the turbo would operate the valve correctly.

I like to question things, just because people always do things a certain way it doesn't always make it right. I will investigate furthur, but I've got to sort out the clutch on my car now.

I'm sure, if you are so inclined, an electric solenoid valve, controlled by an adjustable rpessure switch, would be the optimim. Then you could use a really large valve and control the setpoint very pecisely. Shouldn't be too expensive either. I was actually loking into this before I bought my cheapo valve, but the cheapo works so well I don't care!
For what it's worth, now I am running 14psi, I still rarely get above 10psi when driving. The car just makes so much torque now I don't need to go that far.

Regards, Andrew.

[Steve940estate]

I finally got round to fitting my new MK 2 valve today. I took the old one off and thought it would be worth testing it to see what pressure it held before releasing.
The gauge in the car showed almost 10psi when driving but checking the MBC off the car showed it would only hold about 2psi.

The way that the operation of a ball type valve works is explained is that pressure is held until the preset is reached, I wonder if any really work that well.

Part of the problem with the first one I made was that the ball was too big and restricted the air flow. I am pretty sure this was the cause of the boost spike I got. The new valve has a smaller ball. I also cleaned up the bit it seats on inside the hosetail fitting. Just for good measure I gave the ball a tap while fitted to seat it a bit better.

Before I fitted it to the car I roughly set the valve to hold about 2psi like the old one and fitted it. Driving the car I found I could wind up the pressure a bit more and have found that the spike seems to be gone.

Overall impressions are that the car doesn't seem as fast. Because the ball was restricting the flow to the wastegate I was getting more boost low down, it is smoother now though.