Weak ct26 wastegate spring? It wont boost.

[FullNelson]

I started to up the boost, to just under fuel cut, first with a boost controller and approximately 2mm of shims (mostly to load the spring). That didnt get me the results, so I placed a few more washers in there, approx. 5-6mm of shim. It worked, While even with the manual boost controller closed all the way I wouldnt hit fuel cut, which isnt important, but it got me to the boost level I wanted.

Two days later I went to run the car again, and once more It only hits 4 and climbs to 6 and feels much weaker. Nothing was modified by me in between the results.

To me it seems like now its maybe blowing through the wastegate spring.


How can I test it? I need ideas of how to pressurize the vacuum line to such small incriments as say 5 lbs.

Can you get a new spring/wastegate just from Toyota? Cygnus did not have it listed.

 

[jdub]

Test the actuator per the TSRM.

Check for a boost leak.

 

[Doward]

Exactly 100% what I would tell you to do.

 

[Poodles]

Also, list of mods?

 

[FullNelson]

Bump.

The car is a fresh rebuild on the bottom end, everything beside shortblock is stock.

I did a pressure test and the bov will release pressure every couple seconds sparadically.
Ive also noticed compressor surge starting. so a new BOV is mandatory regardless of the lack of boost.

I did a test on the wastegate itself and it seemed to open at aout 5 psi, and definately by 10 psi, but on the leak test the wastegate failed to open even with the MBC at full open.

Would the bov alone be able to prevent another 6 to 7 psi?

 

[GrimJack]

What BOV is it? The stock one, no. An aftermarket, sure.

Chances are your wastegate spring is toast. I don't think Toyota sells them independantly, so you're likely going to have to pull the turbo, buy a new generic one, and do some work to get the new one to mount.

 

[FullNelson]

Yes its the stock one.

For the effort to adapt an aftermarket wastegate, I would believe it would be just as easy to go t4. Im not ready for that yet.

 

[GrimJack]

It's actually not that hard to adapt one... you'll need to do some work on the mounting plate, and cut & die the arm, but it can still be done in a couple hours with average tools.

 

[williamb82]

can you give me an idea of what application to get one for? i cant go over 18psi on my 57 trim anymore no matter what the bc is set to. thought it was the bov leaking but tightened it to the point of surge and still only 18psi. so its the wastegate spring.

 

[Poodles]

I've been wondering as well for a long time as even if you get the turbo rebuilt/upgraded you're still at the mercy of a 20 year old wastegate actuator...

 

[GrimJack]

Actually, when I picked up an upgraded CT, it came with a new one. I have *NO* clue how the shop got one...

A buddy of mine put a generic one on his DSM, and the mounting wasn't much different than a Supra, which is why I'm sure it can be done.

 

[jtamulis]

Sounds like the wastegate diaphram is dieing. like there is a leak in it or something. I prolly have a spare wastegate actuator around here if you wanna try it out. It could be many things, have you tried adding 5/10 psi to the diaphram and then just seeing it it stays open or if it closes?

Jeff

P.S. I don't sell aftermarket wastegates for CT turbos, but I think I could proly make one, and I bet it'd be a nice thing to add to the website...

I'll look into to doing that in the future.

 

[jdub]

Asked him to test it Jeff...didn't get much of an answer

 

[dumbo]

Sounds like the wastegate diaphram is dieing. like there is a leak in it or something. I prolly have a spare wastegate actuator around here if you wanna try it out. It could be many things, have you tried adding 5/10 psi to the diaphram and then just seeing it it stays open or if it closes?

Jeff

P.S. I don't sell aftermarket wastegates for CT turbos, but I think I could proly make one, and I bet it'd be a nice thing to add to the website...

I'll look into to doing that in the future.

If it was leaking the WG wouldn't open...:3d_frown:

 

[williamb82]

i think its the spring. as i recall my upgraded ct26 has 3 screws on the back of the actuator like they rebuilt it and made a new cover plate. i may pull it off and see if i can get a stiffer spring for it.

 

[jdub]

If it was leaking the WG wouldn't open...:3d_frown:

Small leak + enough pressure, yes it would. Just not very well.

 

[Poodles]

Aftermarket actuator that we could change springs on would ROCK!

 

[lewis15498]

Aftermarket actuator that we could change springs on would ROCK!

+1

If you passed the boost leak test, you can test the actuator buy hooking a bicycle pump with a gauge to it and watching when the arm starts to move. it should start to move at 7-9 PSI unless its shimmed in which case it would be higher

 

[jtamulis]

I can look into Adjustable CT-26 wastegate actuators when I get back from my trip.

Jeff

 

[dumbo]

Small leak + enough pressure, yes it would. Just not very well.

Then it would be overboosting


My bet is the spring, or a turbo on the way out maybe? Are you running the stock AFM or a MAP based tune?