Manual Control of External Wastegate
Moderator: martauto
Hey peeps! Anyone got a plumbing guide for the above. Ive got a cheap ass manual controller with seperate check valve which i cant seem to get to work. It works out either fully closed or fully open i.e. max turbo pressure (25psi) or wastegate pressure (7-8psi). Has any1 any idea of how to plumb it correctly (think i have but its not working) or any suggestions for a cost efficent stand alone electronic controller. (my megasquirt has the optional output for boost control, has anyone utilised this and can verify its reliability??? (phil at extra efi has warned its still experimental)) cheers in advance
There are essentially two types of wastegate controller that may be implemented to achieve closed loop boost pressure control: One mechanical, the other electronic. Before providing you the details of either you need to be more specific with regard to your wastegate (a pic would be useful).
Most external wastegates have adjustable pre-load on the wastegate spring and hose connections to BOTH sides of the actuator diaphragm. The diaphragm is responsible for moving the wastegate poppet valve in and out. Pressurising one side of the diaphragm relative to the other will either force the poppet open or closed. This type of wastegate is compatible with either form of control. Having successfully implemented both myself I prefer mechanical for its simplicity and reliability.
If, however, your turbocharger has an internal wastegate operated by a simple one-sided (meaning that you can only connect boost pressure to one side of the diaphragm) externally mounted diaphragm actuator then your options are very limited. What you absolutely MUST understand is that a wastegate does not begin to open (thus regulating boost pressure) until such time as the pressure (over the surface are of the diaphragm) exceeds the tension in the wastegate spring. By exercising some form of electronic or mechanical control over the boost pressure that connects to the wastegate diaphragm you can ONLY (at best) raise the boost pressure at which the wastegate will open. You cannot make it open at lower boost pressure than is governed by the actuator spring. To make it open sooner (in other words, to dial down your boost pressure) you need to reduce the tension in the wastegate spring. Most external wastegates allow you to do this. You then use electronic or mechanical control to regulate the boost pressure above that defined by the basic spring tension. Wastegate actuators fitted to OEM turbochargers (pulled from donor cars) seldom provide this option.
Post up the details of your wastegate actuator and we can take it from there.
Most external wastegates have adjustable pre-load on the wastegate spring and hose connections to BOTH sides of the actuator diaphragm. The diaphragm is responsible for moving the wastegate poppet valve in and out. Pressurising one side of the diaphragm relative to the other will either force the poppet open or closed. This type of wastegate is compatible with either form of control. Having successfully implemented both myself I prefer mechanical for its simplicity and reliability.
If, however, your turbocharger has an internal wastegate operated by a simple one-sided (meaning that you can only connect boost pressure to one side of the diaphragm) externally mounted diaphragm actuator then your options are very limited. What you absolutely MUST understand is that a wastegate does not begin to open (thus regulating boost pressure) until such time as the pressure (over the surface are of the diaphragm) exceeds the tension in the wastegate spring. By exercising some form of electronic or mechanical control over the boost pressure that connects to the wastegate diaphragm you can ONLY (at best) raise the boost pressure at which the wastegate will open. You cannot make it open at lower boost pressure than is governed by the actuator spring. To make it open sooner (in other words, to dial down your boost pressure) you need to reduce the tension in the wastegate spring. Most external wastegates allow you to do this. You then use electronic or mechanical control to regulate the boost pressure above that defined by the basic spring tension. Wastegate actuators fitted to OEM turbochargers (pulled from donor cars) seldom provide this option.
Post up the details of your wastegate actuator and we can take it from there.
"It is amazing how many drivers, even at the Formula-1 level, think that brakes are for slowing the car down." - Mario Andretti
To add to the above, it just occurred to me that this is probably exactly what you have already, except you have installed a tap instead of a pressure regulator, which is why it is behaving the way you describe. Either that or your pressure regulator is rated to 10-bar or something silly.
If you install a simple tap in place of the regulator then, with the tap closed, the boost pressure will be regulated according to the tension in the spring. The instant, however, that you crack the tap even slightly open, you will lose all control over the wastegate and your boost pressure will climb dangerously.
If you install a simple tap in place of the regulator then, with the tap closed, the boost pressure will be regulated according to the tension in the spring. The instant, however, that you crack the tap even slightly open, you will lose all control over the wastegate and your boost pressure will climb dangerously.
"It is amazing how many drivers, even at the Formula-1 level, think that brakes are for slowing the car down." - Mario Andretti
bob cheers for the reply. Ive got knowledge of pneumatics and understand the preload and differential pressure between the two wastegate chambers. I'm quite happy to go down the route of manual control. the controller i'm using is similar to this
http://www.aliexpress.com/product-gs/33 ... alers.html
currently ive got the check v/v inline (like the teepeice u mentioned) and the "red" barb goes to the top port (nearest adjuster) on the pressure control. I'm guessing this is a "bleed valve" set-up??
http://www.aliexpress.com/product-gs/33 ... alers.html
currently ive got the check v/v inline (like the teepeice u mentioned) and the "red" barb goes to the top port (nearest adjuster) on the pressure control. I'm guessing this is a "bleed valve" set-up??
Hmmm, I'm not sure about that kit. Is that a pressure regulator or just a tap for bleeding pressure away from the wastegate actuator? I suspect the latter.
Probably the simplest form of boost pressure control is to insert a tee-piece into the line to a single-sided wastegate actuator (as used on most OEM turbo's). Then connect a bleed valve (a simple tap) to the third arm of the tee-piece. With the tap closed the wastegate works as normal. However, as you open the tap you bleed air away from the wastegate actuator causing the wastegate to open at ever higher boost pressure. I'm pretty sure that that is how that kit you posted is intended to work.
To make a kit like this work on your two-sided external wastegate you need to connect the tee-piece in line with the BOTTOM (not TOP) port of your external wastegate. Leave the top port open to atmospheric pressure. That is to say, pressure from your compressor (before throttle, but after intercooler) comes in at the tail of the arrow, and goes out at the head of the arrow to the underside of the actuator diaphragm. Then connect the bleed tap in line with the red barb on the side of the tee-piece.
The reason you need to connect to the underside of your external wastegate diaphragm is because (unlike a typical internal wastegate) your external waste gate will open by lifting the poppet up, not pushing it down. Check your external wastegate to be sure of this and to satisfy yourself how it works. Pressure applied to the BOTTOM of the diaphragm should lift the poppet open. Pressure on the TOP of the diaphragm will push it closed.
Also, keep in mind that this type of boost control is quite crude compared to what I described in my earlier post. If you want to implement what I described earlier (connected to both sides of the diaphragm) you will need to use a proper pressure regulator. A simple tap (in-line flow restriction) will not work in that system. The system you are implementing works by literally bleeding off pressure from the diaphragm whereas the correct way to do it is to regulate the pressure differential across the diaphragm. Since the system you are implementing works by bleeding off pressure the tee-piece includes a restriction inside it, else the compressor simply makes up for the lost pressure as fast as you can open the tap. In order to have some linear control over your boost pressure your tap needs to have a very fine pitch, else you could relieve all pressure from the diaphragm with just a few degrees of turn on the tap handle, and that’s no good.
FYI, replace the tap in your system with a PWM (pulse width modulated) solenoid valve and you have the mechanism that you require for electronic boost control.
HTH
Geoff
Probably the simplest form of boost pressure control is to insert a tee-piece into the line to a single-sided wastegate actuator (as used on most OEM turbo's). Then connect a bleed valve (a simple tap) to the third arm of the tee-piece. With the tap closed the wastegate works as normal. However, as you open the tap you bleed air away from the wastegate actuator causing the wastegate to open at ever higher boost pressure. I'm pretty sure that that is how that kit you posted is intended to work.
To make a kit like this work on your two-sided external wastegate you need to connect the tee-piece in line with the BOTTOM (not TOP) port of your external wastegate. Leave the top port open to atmospheric pressure. That is to say, pressure from your compressor (before throttle, but after intercooler) comes in at the tail of the arrow, and goes out at the head of the arrow to the underside of the actuator diaphragm. Then connect the bleed tap in line with the red barb on the side of the tee-piece.
The reason you need to connect to the underside of your external wastegate diaphragm is because (unlike a typical internal wastegate) your external waste gate will open by lifting the poppet up, not pushing it down. Check your external wastegate to be sure of this and to satisfy yourself how it works. Pressure applied to the BOTTOM of the diaphragm should lift the poppet open. Pressure on the TOP of the diaphragm will push it closed.
Also, keep in mind that this type of boost control is quite crude compared to what I described in my earlier post. If you want to implement what I described earlier (connected to both sides of the diaphragm) you will need to use a proper pressure regulator. A simple tap (in-line flow restriction) will not work in that system. The system you are implementing works by literally bleeding off pressure from the diaphragm whereas the correct way to do it is to regulate the pressure differential across the diaphragm. Since the system you are implementing works by bleeding off pressure the tee-piece includes a restriction inside it, else the compressor simply makes up for the lost pressure as fast as you can open the tap. In order to have some linear control over your boost pressure your tap needs to have a very fine pitch, else you could relieve all pressure from the diaphragm with just a few degrees of turn on the tap handle, and that’s no good.
FYI, replace the tap in your system with a PWM (pulse width modulated) solenoid valve and you have the mechanism that you require for electronic boost control.
HTH
Geoff
"It is amazing how many drivers, even at the Formula-1 level, think that brakes are for slowing the car down." - Mario Andretti
) ill get a look next time im in the lock-up.