Testing wastegate opening pressures

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oldn64
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Re: Testing wastegate opening pressures

Post by oldn64 »

The Frankenwastegate will work tops!!

Essentially you have built a boost reference gate. This will keep the pressure equalised until you want it to open. Because the spring is only 7psi (as Delco stated normal for 12psi) you will have a on off tap.

To answer your original question the gate should remain closed at start with a boost pressure of 2psi as it is not go enough to overcome the spring pressure yet.

We used to test with a air pressure value and gauge to see the tension of the spring. Often when playing with the older turbo cars (read sigma and torana) you would find the spring would loose pressure over time and thus the boost would drop off. this would give us a clear understanding that as to whether the gate was at fault or there was another problem.

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Holden202T
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Re: Testing wastegate opening pressures

Post by Holden202T »

the main issue with this current setup is that the exhaust manifold needs more pressure in it than the inlet side .... so im going to see if i can get another regulator or a second air compressor on it - wife has a small craft air compressor with reg so it might be perfect, that way i can get more accurate results
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Re: Testing wastegate opening pressures

Post by oldn64 »

Holden202T wrote:the main issue with this current setup is that the exhaust manifold needs more pressure in it than the inlet side .... so im going to see if i can get another regulator or a second air compressor on it - wife has a small craft air compressor with reg so it might be perfect, that way i can get more accurate results
Yep just go up one pound each time to get ball park. this will show you the opening pressure.

The gates I have modified did not rely on the exhaust pressure but had this sealed off from the spring seat and boost pressure hat, that way a simple tap into the lower section and pressurise with boost pressure kept the spring neutral. Then when you reached the required boost pressure the solenoid would remove the pressure from underneath the spring (vent to atmo) and the gate would open. Simple principle but very effective, as you can use whatever spring and it will always open at the right stage seeing that the reference is what controls the valve not the spring.

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Holden202T
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Re: Testing wastegate opening pressures

Post by Holden202T »

yeah i plan to run 14psi spring in mine and then use the solenoid to go up to 25psi, that way i can add / remove as needed.
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Holden202T
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Re: Testing wastegate opening pressures

Post by Holden202T »

Ok so i've modified the rig, and with the use of the wifes craft compressor (which is not allowed to smell like fuel or have grease or dirt on it) :wtf: :lol: i've been able to use it for simulating manifold pressure, and lets be honest, it doesn't have the cfm for much more than that anyways ... it maxed out at 280kpa on the delco log :P
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So i removed the air brush and found some suitable fittings to make a little manifold for my wastegate/solenoid feed and the map sensor.
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This thing is pretty cool, it has easy adjustment down to about 120kpa (map sensor reading) much below that and it starts cutting on and off and gets a bit pulsy ... it also seems the guage is not quite accurate at low pressures, but the map sensor is there for monitoring that stuff anyways.
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So i used my boost gauge to go onto the exhaust manifold, and i have a 18cfm i think air compressor on it, its got enough flow to put the manifold pressure to well over 30psi so i've got plenty of room to adjust there.
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So im going to go off some logs i got from VL400 as he is measuring exhaust and inlet manifold pressures, so this should give me as good idea what pressure ratio we are going to see.

I just need to connect up the boost solenoid now and i can start playing, but with adjusting the wifes air compressor i can easily open the wastegate :)

this video is cool, cause we all know how it works, you just never get to see it in action!

[youtube]https://www.youtube.com/watch?v=zwh5MFHic-8[/youtube]
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Re: Testing wastegate opening pressures

Post by Holden202T »

so this has progressed a bit, i used my fuel pressure sender for the FX to plumb into the exhaust manifold, this gave me a PSI reading in tunerpro logs, and was then able to see what changes i got in the exhaust from changing the inlet pressure on either side of the gate.

the end result is, i can see pressure changes and i can see the actual wastegate valve opening and closing but i think it really needs a flow meter on the outlet of the wastegate to see how much air is going through it, i've also found while the craft compressor is able to provide the pressure needed to simulate the inlet pressure, i dont think its moving enough air to open and close the gate quickly enough, ie. i move the duty cycle of the solenoid from 10-15% and then the gate slowly opens more over a few seconds.

unfortunately theres not too much i can do, however it did give me a good idea of how much DC% it took to make the gate do stuff, and also at what point the DC% really makes no difference.

i'll probably get a few more logs of some things just so i have the data but i think i'll pack it up after that.

I've also worked out that with no inlet pressure on the gate to open it, it barely cracks at all till its spring pressure, so its more than likely that using it to try and build more boost on the start line is possibly not going to make a lot of difference until exhaust pressure is over the spring pressure.
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Re: Testing wastegate opening pressures

Post by oldn64 »

Holden202T wrote:so this has progressed a bit, i used my fuel pressure sender for the FX to plumb into the exhaust manifold, this gave me a PSI reading in tunerpro logs, and was then able to see what changes i got in the exhaust from changing the inlet pressure on either side of the gate.

the end result is, i can see pressure changes and i can see the actual wastegate valve opening and closing but i think it really needs a flow meter on the outlet of the wastegate to see how much air is going through it, i've also found while the craft compressor is able to provide the pressure needed to simulate the inlet pressure, i dont think its moving enough air to open and close the gate quickly enough, ie. i move the duty cycle of the solenoid from 10-15% and then the gate slowly opens more over a few seconds.

unfortunately theres not too much i can do, however it did give me a good idea of how much DC% it took to make the gate do stuff, and also at what point the DC% really makes no difference.

i'll probably get a few more logs of some things just so i have the data but i think i'll pack it up after that.

I've also worked out that with no inlet pressure on the gate to open it, it barely cracks at all till its spring pressure, so its more than likely that using it to try and build more boost on the start line is possibly not going to make a lot of difference until exhaust pressure is over the spring pressure.
Well done Holden202T,

Yes you are correct about both the airbrush compressor and the exhaust pressure. Your turbo will move more air than the compressor will provide. You need a compressor capable of 15cfm or more before you start to look at getting anywhere near close.

You would be in a far better place if you could trap the gate completely in boost pressure not boost pressure one side and exhaust pressure the other. As soon as the spring has boost both sides then you will get complete control, because the spring would only start to come into it when you bleed off the boost from the underside so that the boost on the spring then starts to become positive.

The only other option i can see is that you dont feed boost into the gate until you need to. What that would mean is if your gate does not support boost both sides that you make up a electronic tap of some description whihc you can control to send the boost to the gate thus then opening it when you give it the boost signage which you control. Either way the gate will only start to open when the boost is feed or equalisation is not met. :thumbup:

Definitely a fun project and one i am sure you will get working 100% with more playing.
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