$10 ghetto spec external wastegate

[brett_celicacoupe]

with a few spares i got for the 2JZ, i realised the EGCV would be suitable as an external wastegate.

as far as i can foresee it should work just as good as any other external gate..... thoughts?

ill be using a CT12 wastegate actuator instead of the actuator used to open it on the 2JZ.

the throat diameter is approximately 54mm so i dont think flow will be an issue. mounting will be easy(2 flanges)









results are a while away yet but ill update this thread when i get it operational

[131OWN]

I will be surprised if it seals well

[brett_celicacoupe]

i wont.................

i expect less than 1% leakage when closed

[Bored?]

Will be an interesting experiment. The relationship between actuator position and wastegate flow will be different to a regular wastegate, so it will be interesting to see if that makes boost pressure harder to control.

What is the diameter out of curiosity?

[brett_celicacoupe]

yeh its possible that it will overshoot but personally i dont think it will.

i posted the diameter in the 1st post

[YLD-16L]

as far as i can foresee it should work just as good as any other external gate..... thoughts?

Brett, attach that actuator to a pressure source and test how much pressure is required to open that butterfly you have it attached to . As far as I can see from those pics the butterfly rotates on a central axis so it's not going to work.

Both internal and external wastegates use the exhaust gas pressure, boost pressure and a spring to regulate the opening of the "gate". You have almost entirely removed (or at least significantly decreased the effect of) the effect of the exhaust gas pressure from the equation meaning for your pictured design you'd either need to lessen the spring pressure or increase the boost reference pressure to get it to even remotely work, neither of which will work out well obviously.


I could be completely wrong but that is my take on it from those pics.

[brett_celicacoupe]

i try to look at these things in the most fundamental viewpoint.

the objective is to regulate exhaust gases so that boost is limited to a desired value. we dont want 'overshoot' or instabilities either. if the final design can perform this task then what does it matter if it has a "butterfly rotates on a central axis".


i think it will be successful in regulating the maximum boost but it may have difficulties in a transient state.

the pressure feedback loop should take care of the control side of things nicely

i tested the actuator pictured with compressed air and pressure gauge.

it begins to move at 10psi and appears to continue to move linearly until 26psi where it is extended 100%

[jimmmayyy]

i don't see why it won't work, however the problem may lie in it's orientation. flow rates may be different when the butterfly is mounted at different angles.

[YLD-16L]

if the final design can perform this task then what does it matter if it has a "butterfly rotates on a central axis".

The butterfly itself can be used to bypass exhaust gasses to control boost, no doubts about that. The issue lies in how you plan to regulate it with the CT12 actuator.

As I noted in my first post, that type of actuator is carefully designed to work with a flap type internal wastegate, the spring in the actuator and the diaphragm diameter are carefully chosen to match the diameter of the internal wastegate port and produce a desired boost level and a particular boost curve.

The internal wastegate is a simple device; a hole, a flap that is attached to a small rod that has a small lever that the actuator rod attaches to. The exhaust gas pressure that forces against that wastgate flap to push it open is just as crucial a factor in regulating boost levels as the spring and diaphragm in the actuator and the reference boost pressure that acts upon that diaphragm.

Change anyone of the above and you'll affect the boost curve.

By using a butterfly that pivots on a central axis like you are using the exhaust gasses between the head and butterfly will apply to no force on the butterfly, unlike the effect on the flap of an internal wastegate or the valve face on an external wastegate.

You've noted that you get get a small amount of movement when you apply pressure of 10psi to the actuator, for interest sake let us say you plan to run 10psi.

The turbo creates 10psi, the actuator references this and extends the rod X amount opening the butterfly a little. Now as rpm increase so too does exhaust gas flow but it has little to no effect on the butterfly hence forcing more gas through the exhaust wheel. The increase in boost will increase the butterfly opening a little more via the actuator and now you're above your desired boost level anyway so it has failed to regulate. Will it open enough to bypass enough exhaust gas to regulate the boost to the desired setting? Who knows, it may be fine at one part of the rpm or load range and that would be about it.

On a conventional internal or external gate the spring in the gate or actuator is fixed at a given time, the diaphragm is fixed in diameter and the reference max pressure is set (or selected using an adjustable machanism). As rpm/load and subsequently exhaust gas volume increase none of the above change (once stable peak boost is reached). The additional movement of the internal flap or lift of the valve on an external gate to regulate the boost at the desired level is created by the exhaust gas pressure. Your design effectively has removed this from the system by using a butterfly so it won't be able to regulate boost levels effectively


Happy to discuss more, or pick my post apart either way I'm not fussed it's what the tech section is all about

[MWP]

Where is it normally located on a 2JZ car?

My bet is it wont handle the extreme heat when used as a wastegate.

[cambelt]

Its the exhaust valve in the exhaust stream so it runs pretty hot . The flap is ceramic from memory .
dave