Limitations of CT26 power outputs

Q&A regarding engines, turbos, and intercoolers and power upgrades

Postby furpo » Tue Sep 21, 2004 10:20 am

i have found the limit of the standard jdm spec ct26. we made 280 wheel hp with a fmic, after market ecu, exhaust and 18 psi boost. any more boost than this and too much ignition timing had to be pulled out and power was lost. at 3000 ish rpm we could run up to 24 psi with big torque gains. yaaaaa for map-able boost controllers.

i came to the conclusion that the compressor side was the limiting factor. we monitored egt's and manifold pressure and they both started going through the roof at about 265 hp.

i would like to see how the supra spec ct26 goes but have not tryed it yet. we then did a back to back test of the evo3 tdo5 which made 320 ish wheel hp on the same engine with a manifold to suit. with this turbo imo the turbine was still the restriction.

roger

ps. 320 hp was pushing the std injectors aswell.
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Postby Griffin » Tue Sep 21, 2004 2:49 pm

furpo wrote:i have found the limit of the standard jdm spec ct26. we made 280 wheel hp with a fmic, after market ecu, exhaust and 18 psi boost. any more boost than this and too much ignition timing had to be pulled out and power was lost. at 3000 ish rpm we could run up to 24 psi with big torque gains. yaaaaa for map-able boost controllers.

i came to the conclusion that the compressor side was the limiting factor. we monitored egt's and manifold pressure and they both started going through the roof at about 265 hp.

i would like to see how the supra spec ct26 goes but have not tryed it yet. we then did a back to back test of the evo3 tdo5 which made 320 ish wheel hp on the same engine with a manifold to suit. with this turbo imo the turbine was still the restriction.

roger

ps. 320 hp was pushing the std injectors aswell.


Wow that was completely unmodified? Those are some good numbers if thats the case.
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Postby furpo » Tue Sep 21, 2004 7:06 pm

the exhaust side of the turbo was matched to the manifold but nothing like a porting that would change the a/r rating. this was done because production tolarance is rather large, i have seen up to 3mm mis allignment. this exhaust housing represents the factory best case senario.

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Postby OlyST185 » Wed Sep 22, 2004 3:34 am

the best thing to do is to have an external wastegate and 18inches minimim before the wastegate's piping go to the exhaust line.
this way it will not have disturbances in the exit of the turbine.
this mean a better flow while providing a bit better low end performance with no boost.
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Postby alltracman78 » Wed Sep 22, 2004 10:17 am

mtbgael wrote:A larger trim allows exhaust to flow more freely past the turbine, making the turbo more "efficient" when large amounts of exhaust are flowing (high rpm). It will spool a little later, but it's ability to flow means it will hold power in high rpms better. Go too large though, and the turbo will never spool.

SilverGhost wrote:My point is that your engine at a certain rev rate, throttle position and boost level will always use the same amount of air regardless of turbo size, so if the standard snail can hold that kind of boost pressure why upgrade it?


It can't, that's the problem. Get an accurate boost gauge and monitor boost as you get to redline.


A lager trim would not necessarily allow more flow around it. That is the function of the ar ratio, which the turbine, or compressor wheel, has nothing to do with. It is all the housing.
If you got the turbine clipped, it would allow more flow around it however.

My 93 and 92 both held 10 psi on stock turbo to redline. My 92 now has a 50t compressor, and holds 12.5 psi to redline.
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Postby mtbgael » Wed Sep 22, 2004 12:46 pm

I knew I'd be wrong somewhere :doh: Thought I was finally getting the hang of this turbo stuff :twisted:
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Postby alltracman78 » Wed Sep 22, 2004 1:38 pm

That's cool, man. Nobodys perfect.
Even me :D


Especially me :P
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Postby gearhead313 » Wed Sep 22, 2004 1:47 pm

[quote="alltracman78A]
If you got the turbine clipped, it would allow more flow around it however.

.[/quote]

clipping a wheel is only if you want to fine tune the setup, otherwise, it won't yeild you any type of major change in performance.
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Postby Trance4c » Thu Sep 23, 2004 11:11 pm

Holly crap.. let me know how long those CT's hold up at those boost levels before the seals go! juez... poor turbo seals!! :cry:
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Postby alltracman78 » Fri Sep 24, 2004 3:12 am

gearhead313 wrote:[quote="alltracman78A]
If you got the turbine clipped, it would allow more flow around it however.

.


clipping a wheel is only if you want to fine tune the setup, otherwise, it won't yeild you any type of major change in performance.[/quote]

Understood, I was just making the point that it would increase flow.
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Postby illGT4 » Fri Sep 24, 2004 5:08 am

clipping also moves everything to the right (dyno chart). (spool, power, etc..)

IMHO, clipping the CT26 is a bad idea. Modifing the exhaust housing is an excellent idea on the other hand.

ATS is doing 20psi on their upgraded "CT27". Turbo seals are happy as long as it's taken care of proper-like.

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Postby furpo » Fri Sep 24, 2004 6:09 am

on the supject of modifying the turbine housing has anyone tryed the supra 3L ct26?
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Postby illGT4 » Fri Sep 24, 2004 7:38 am

on a st165, yeah Dave Hall and others have. It's a great turbo for a 46 or 50 trim upgrade for the ST165. BUT, it's single entry. Not twin entry like the ST185/205 and MR2 CT26. So the exhaust manifold design is also different.

The only worthy CT26 upgrade(IMHO) is one that does something with the exhaust housing.. Either replaces it or modifies it like ATS. I'm not talking about the turbine wheel, but the entire housing.
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Postby furpo » Fri Sep 24, 2004 7:48 am

i am of the same opinion about the ct26. the reason i ask about the supra ct26 is because i am in two minds at the moment. go for the supra ct26 or go for the mitsi tdo 5 big 16g off the evo 3.

the mitsi guys are making 235kws at the wheels down here on the mitsi turbo so will the supra turbo do this? also there is a guy down here coming up with a ball bearing conversion for the mitsi.

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Postby illGT4 » Fri Sep 24, 2004 7:51 am

for ST165 or ST185?
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