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MG Midget and Sprite Technical - Boost pressure

Rob (or anyone else who have an idea) how do you regulate your max boost with a switch?

I understood that you can run at say 10 psi of boost then flick a switch and run at 18. How is that done?
Robert (Bob) Midget Turbo

Bob you need a electrical soleniod switch that has a valve, you can only have it open(fully vented to air) or closed(no air), so if you have a bleed valve do away with that and run the pipe to the solenoid, then adjust your actuator to run at what ever boost you require for normal driving (say 10 psi)then when you flick your switch the pipe vents totaly to air an gives you max boost and you blow away most Gti's at the lights !!
The trick to this is not to have your normal driving boost set too high because when you flick your switch you are on max boost, this will be lower if your normal driving boost is lower.
Hope this make sense, I can take picture of the solenoid if you get stuck
Rob.
Rob Newt

Hi Rob I figured that but if you were to vent all the feedback to the actuator then you would get full boost at something that does not bear thinking about. I wondered if you could simply have the actuator set at 10 psi say and then a switch to a bleed valve to bleed of some feedback and increase the boost beyond 10 psi.

Have very limite experience with bleed valve how accurate can they be?

Robert (Bob) Midget Turbo

IIRC MG Metro used a solenoid vent on the inlet manifold to prevent run-on after ignition switched off that could be used. Quite a step between 10psi and 18... you could have fun choosing the text on panel below the switch... A
Anthony Cutler

At the moment Ant I have my actuator set at about 21 to 22 psi and so once the engine is asked to work a little harder I tend to be at max boost but with little throttle opening. It would be nice to use about 6 or 7 psi for normal use with a switch to about 22 psi for blowing away K series cars. LOL.
Robert (Bob) Midget Turbo

Bob

If you are concerned about going too far when on high boost, how about 2 dump valve instead of just the one?
One at low pressure, one at high pressure. Vent the lower pressure valve via the solenoid so the dump path can be blanked of when activated, leaving the high boost valve to take over.
Paul Walbran

Bob
Perhaps I did not make myself very clear, if I set my actuator at 10 psi (solenoid closed)when I vent fully to air it runs at approx 15 psi
If I set my actuator at 15 psi (solenoid closed)when I then vent to air it shoots above 20 psi (I have only tried this once)
It all depends on other things intercooler,compression ratio etc to what boost you can achieve not just the actuator.

Regarding the bleed valve, it seems most of the mini boys use these instead of a solenoid fitted in the car for adjustment, the only advantage is you can control the boost in between min and max by the amount of air you are venting,you could just use a fish tank valve as it does the same job.
Rob Newt

You can buy very cheaply a spring valve with an adjuster of the spring pre-tension for controlling boost levels very accurately - about $30AU on Ebay last time I looked. If you want to combine this with a switch for a low boost setting then use a 2 way solenoid to switch the line to the actuator, between straight through (low boost setting - whatever you set the actuator at) and through the valve (high boost setting - whatever you set the valve at).

Robs setup sounds like it is blowing the wastegate open due to pressure from the exhaust on the high boost setting, rather than regulating based on boost pressure.

Alternatively you can spend a large sum of money on an electronic device that will ultimately do exactly the same thing...
AndrewF

Hi gents

Yes I do not understand how Robs is working?
If I were to disconnect the feedback to the dump valve god knows how much pressure on boost I would get? it would certainly be well over 2 bar (30psi+) At the moment my dump valve is controlling the boost pressure at about 21/22 psi and is generally immediately in use as soon as the throttle is pressed a tad! :)
The only issue I have with a needle vent valve is I don't think they work very well and tend to be all or nothing.

Paul You are ofcourse bang on with having 2 dump actuators the engineering required to achieve that however in the space available would be cute to say the least. A dual stage dump actuator would be the answer does such a thing exist?

Andrew seems to be on to something and I will look more closely into that. A 2 way solenoid is not a problem for me. :)
Bob Turbo Midget England

I am on the case now. On the web you can find a ball and spring regulator that acts like the needle valve only more accurately.

I need a 2 way solenoid (or hand operated valve, the above mentioned boost controller and my original dump valve actuator refitting to control the boost at about 8 psi in normal driving and via the boost controller when want full chat. :)

Thanks
Robert (Bob) Midget Turbo

Yep, the ball and spring regulator is what I was referring to, and the setup you're describing is what I was talking about.

I believe Robs idea is working purely by the pressure in the exhaust forcing the dump valve open - not an ideal way to control boost pressure. The reason that his boost skyrockets with the actuator set higher is that more exhaust pressure is required to overcome the dump valve and force it open.
AndrewF

hey robert...

Bill young introduced me to these.. perhaps this might help


http://www.controlandpower.com/catalog/PDFs/Humphrey/Humphrey%20Valves%20-%20Solenoid%20310-410.pdf

you may have to remove the 20% or do a copy paste to the browser bar

Prop
Prop

hmmm,

well thats not going to work

try going to...

controlandpower.com

click the humphreys link on the left side of the page

scroll down to the various pdf files

click on (310 - 410) pdf file

its a 2-3 way electric selinod valve for both vacume and pressure for 12 to 24 volt electrical sources... which is vary cool, and Im finding new uses for this stuff all the time

control and power website is a great time killer website, it really inspires alot of imagination ideas

Agian it was Bill Young that introduced me to this stuff

Prop
Prop

Bob
The secret is to have a restrictor in the supply line before your actuator and other pressure adjusting devices
This allows your actuator to monitor the pressure in the hose still, but stops whatever you use as a relief being overcome by excess flow of air

I ran a similar setup as what you are after on my Mazda
The actuator operates at 7lb
Then I put a T in the line with an electric solenoid valve then an adjustable tapered needle valve relief set to give 12lb
Also in the line between the solenoid and the adjusting needle I had a small reservoir about 1 1/2" dia. and about 2 1/2" long that makes a bit of a delay in boost control-- it works great
When you hook into the throttle it goes up to about 15lb for about 3-4 seconds and then settles back to 12lb
It makes it feel a lot stronger and responsive with the can in there but it takes a lot of fiddling about to get the can size correct to suit whatever size restrictor you have back in the line and how long you want your engine to get the extra boost for
Have fun
Cheers Willy
William Revit

The restrictor needs to be right back at the start of your pressure hose
William Revit

This thread was discussed between 07/06/2011 and 09/06/2011

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