Outer Limits 4x4 Board

Few questions for the turbo guru's

How much boost can a standard CT26 handle?

Does highflowing them make that much of a difference?

What would be a good replacement turbo for performance that will still come on boost below 1500rpm?

And how much boost can a 12ht handle depending on turbo?

If i wind the boost up in mine any more than 14 pound...the red light comes on in my tacho!!!!

Red light is a overboost light, from what I understand it is only hooked upto a pressure switch, doesnt do anything.

It will only hurt the turbo in the long run wont it?

Read somewhere about someone running 20 pound in a 12ht with a different turbo setup.

brendan rooke wrote:It will only hurt the turbo in the long run wont it?

Read somewhere about someone running 20 pound in a 12ht with a different turbo setup.

14psi is the boost limit that Toyota set for the "overboost" light. As mentioned, its only a pressure switch, so its only telling you that the turbo is boosting over 14psi. Mines set at 13.5psi, and does so all day long, and quite happily. Performance is pretty good. I have 3" straight through exhaust too. From memory I hit full boost at about 1900rpm. I dont want to go any higher because I dont really have the need, mines setup as a tourer so at the moment, its fine.

IIRC anything over 15psi with the CT26 and they become inefficient, so 15psi is pretty much the max I'd go with a stocko. I do know people run them as high as 18psi, but they were setup professionally and followed a thorough inspection of the engine and injection mechanicals.

I dont think over 14psi that the light turns on "hurts" the turbo. Its more that the higher the boost after around that the more inefficient it becomes. I know of a bloke running supra internals in his CT26. tweaked to 21psi boost.

Thanks fellas.

Still learning about these 12ht's.

A bloke told me today that some supras run a ct26 and have set boost as much as 32 pound.

stumpyGU wrote:

brendan rooke wrote:It will only hurt the turbo in the long run wont it?

Read somewhere about someone running 20 pound in a 12ht with a different turbo setup.

14psi is the boost limit that Toyota set for the "overboost" light. As mentioned, its only a pressure switch, so its only telling you that the turbo is boosting over 14psi. Mines set at 13.5psi, and does so all day long, and quite happily. Performance is pretty good. I have 3" straight through exhaust too. From memory I hit full boost at about 1900rpm. I dont want to go any higher because I dont really have the need, mines setup as a tourer so at the moment, its fine.

IIRC anything over 15psi with the CT26 and they become inefficient, so 15psi is pretty much the max I'd go with a stocko. I do know people run them as high as 18psi, but they were setup professionally and followed a thorough inspection of the engine and injection mechanicals.

Mines making full boost (13 psi) at about 2200 rpm.

I did have it set at 14 and on a descent hill it would go just over 14 and the light would come on so i turned it back a turn as i was unsure about the red light.

Im going to run a front mount on it soon, i cant screw any fuel into it at the moment as the exhaust temp is already 550 on a descent hill.

Brendan, what sort of clutch are you running behind your 12HT? I wound my boost up to 13PSI and turned the fuel up to match (not that high though, no black smoke at all) and now when accelerating in 3rd of 4th my clutch starts to slip... but it goes quite well. (rebuilt engine, 3" exhaust and 3.5" dump pipe) I got a top mount to go on it, and also a hybrid supra cruiser CT26 I‘m going to fit shortly. Have heard the safari tough clutchs are very good, but also very noisy/rattley.

flyology wrote:Brendan, what sort of clutch are you running behind your 12HT? I wound my boost up to 13PSI and turned the fuel up to match (not that high though, no black smoke at all) and now when accelerating in 3rd of 4th my clutch starts to slip... but it goes quite well. (rebuilt engine, 3" exhaust and 3.5" dump pipe) I got a top mount to go on it, and also a hybrid supra cruiser CT26 I‘m going to fit shortly. Have heard the safari tough clutchs are very good, but also very noisy/rattley.

Hey mate,

Im not expecting my clutch to last very long as its only a daiken (spell)

It was a brand new kit but it was sitting in the shed for years so i thought that would save a few dollars at the time.

When i find a really good g/box ill put a new clutch in at the same time.

What clutch are you running and how old is it?

Not sure what clutch is currently in mine, I did an auto to manual conversion about 6 years ago, think I just used a standard 2H (not at 12HT) clutch. Mine has just recently started to shudder a bit when reversing up the driveway, should have replaced it when I rebuilt the engine a few years back.... doh.

Thats a good run from a clutch in a 12ht.

If i get a year out of mine ill be happy.

Its a 2h clutch aswell but a new one.



Off to work now then a big weekend on the cruiser

Gotta take the good with the bad.