CT26 Actuator Pressure Ports - Free Boosting

[pauljones1976]

Hi ppl,

I just bought myself a new toy which I hope to have time to put up on here soon. It's an RA23 with a 3TGTE + CT26 and a set of forgies. The guy I bought it off was happy to run up to 20psi but I'm planning on getting a bit more milage out of her and want to drop the pressure to about 14/16psi. It has an electronic Blitz Dual Solenoid Boost Controller but no matter how I set it (even OFF - std actuator pressure) it just keeps free boosting. I don't know if it stops or not as I'm not game to run it past 15psi (the Autometer analogue guage only goes up to 20psi anyway). It does this on ANY gain setting. What I do know is that the PEAK boost this thing has had through it is 22psi (taken from the memory of the electronic boost controller) which from what I have researched is about the MAX pressure a CT26 will create. Since when I select OFF it still boosts past 7psi I assumed maybe I had a stuck wastegate.

I took the actuator arm off and found that the wastegate was fine. I removed the exhaust to check what was going on with the wastegate and checked the impeller which has a TINY TINY amount of play in-out. So now I'm looking at the actuator and boost controller.
I suspect the boost controller is probably ok but can't be sure.

I was going to plumb the thing back up to standard to see if the actuator opens the gate at 7psi but I've had a look at the actuator and it has two pressure pipes (!) that go into the diaphragm - i've never seen this before! Anyway, one is blocked (capped) off and one runs to the intake pressure outlet of the turbo (via the boost controller of course).

Some people on the net are saying the two inputs are the same - just block one off and use the other. Some people are saying that they are different, one is for pressure to drive the diaphragm -> arm -> wastegate, the other a pressure reference point for a boost solenoid. These people have also noted that they behave differently.

Here is an extract from 'AnnoyingRob' posted on Ghettobaby:
>> There are two ports on the wastegate, one closest to the actuator arm, and one further away. The far one is the boost line, and the close one is a pressure reference port.

So what I'm thinking now is that maybe my actuator has been plumbed up incorrectly. And if it is, checking factory pressure into the wrong input won't open the wastegate either. On mine, there are two inputs for the actuator. The actuator is mounted horizontally with the arm pushing the wastegate open towards the rear of the car. Looking at the actuator from the front of the car, toward the back, the two inputs are spaced equally from the centre of the diaphragm cover, one above the centre, one below.

My questions are:
1. Are these inputs in-fact different?
2. If they are, which one should be capped off, and which one should be used for the boost controller?

Any help would be much appreciated!
Cheers,
-Paul.

[wilbo666]

You don't have to have the car running to check the wastegate actuator

If you have a look at the below pic that is the port on the wastegate actuator I'd suggest will be the controlling port...

I suggest removing the hose that comes from the boost controller (On the wastegate actuator) and applying some pressure (A plastic syringe works well ) to check that the actuator moves, T in a boost gauge to check what pressure is required to make the actuator rod start to move...!

This is for a MA70 CT26, but shows what I mean...


Cheers
Wilbo

[pauljones1976]

Thanks wilbo,
Lucky for me I have been involved with go-kart racing for some time now and bought one of those pressure guage pumps to check the pop-off pressure on walbro carbies. Goes to 15psi! Nice.

Anyways, just checked the actuator and no movement. The diaphragm is not holding pressure - the guage gets to about 0.5psi and falls rapidly back to 0. Both inlets behave the same. I checked the cap on the other inlet and it's holding pressure. Same for the line I ran from the test equipment to the actuator.

So this means my actuator diaphragm is stuffed right?!

If so, what would cause the diaphragm to rupture? And what can be done to repair it? Or do I just replace it?
Cheers,
-Paul.

[wilbo666]

If so, what would cause the diaphragm to rupture? And what can be done to repair it? Or do I just replace it?
Cheers,
-Paul.

I'm not sure what the cause of the diaphram rupture was; I would suspect massive boost would be required to kill a diaphram...

Some other things that I can think of are, age, heat, contamination (oil, petrol)? Or a mixture of the above?

The best option would be to replace it I think! Good luck! (If you can't find a second hand one, aftermarket is an option...)

Cheers
Wilbo

[pauljones1976]

Thanks wilbo, you've been more than helpful. Any idea where to look for aftermarket ones? Do you know how they bolt-up? How do they configure the rod? I've tried calling a few places already and nothing second-hand about at this stage.

Cheers, -Paul.

[wilbo666]

Thanks wilbo, you've been more than helpful. Any idea where to look for aftermarket ones? Do you know how they bolt-up? How do they configure the rod? I've tried calling a few places already and nothing second-hand about at this stage.

Cheers, -Paul.

The first thing that I would try is putting up a wanted thread on Toymods!

Other than that I'd rip the yellow pages out...

(btw have you identified the version of CT26 that you have?)

Cheers
Wilbo

[pauljones1976]

Wilbo,

I was going to put up a wanted ad but I think I need more rep to do that.

I'm pretty sure I have a 7MGTE CT26. It has the single round internal wastegate flapper. All the MR2 ones seem to look different to mine on the exhaust side.
Not too sure what it has had done to it apart from I believe it was high-flowed. Shouldn't affect the actuator though?

Was going to try Mike Vine tomorrow (it is ekka holiday in the redlands today) and see if he has any ideas.

Otherwise I guess I'll be dredging through the forums looking for clues.

Thanks heaps anyway!

Cheers,
-Paul.

[thechuckster]

Was going to try Mike Vine tomorrow (it is ekka holiday in the redlands today) and see if he has any ideas.

just get a quote before committing to any purchases.....



you could also try some of the speed shops in Moss St (underwood) - yes it's bogan territorty, but ...


edit, i have a stock 7mgte dump pipe at home somewhere - i can bring over to compare bolt patterns if needed.

[pauljones1976]

Thanks Charles,

I have had a couple of people pm through but no-one with just the actuator yet. I wonder if it can be rebuilt although I suspect the cause of the problem is that it has been run up to 20psi and the diaphragm simply cannot handle that pressure. I'm not sure if it could be rebuilt to withstand even the 16psi I'm planning on running. Worst come worst I guess I'll need to go external wastegate.

Cheers,
-Paul.

[thechuckster]

you can probably adapt an actuator from another /similar toyota turbo ?

most people have to relocate them if they've clocked a turbo - you might be able to get a replacement (or something that's similar and requires some minor mods) from <shudders> autobarn as they sell povo performance gear at most stores now.

[pauljones1976]

Hi Charles,
Yes I was considering stealing and modifying the one on my 1GGTE but I'm a bit hesitant because then I'll have trouble selling the 1G complete. If I can find an actuator which will just bolt-on that'll be a whole lot easier.
Cheers,
-Paul.

[pauljones1976]

Thanks Wilbo,

Looks like thanks to your help I've tracked down a couple of actuators. Couldn't have done it without you!

Cheers mate!
-Paul.

[pauljones1976]

Oh, BTW guys,

In regards to the question I asked about the two pressure line inputs into the diaphrahm cover for the actuator:

After pressure testing I have deduced that they are the same. In other words you could use either one if you cap off the other.

Hope this helps someone out in the future!

Cheers,
-Paul.

[wilbo666]

Thanks Wilbo,

Looks like thanks to your help I've tracked down a couple of actuators. Couldn't have done it without you!

Cheers mate!
-Paul.

Great to hear!

btw no need to thank me, thank Toymods instead

Cheers
Wilbo