Boost creep problem - 3sgte

[CelicaGT8]

I have an upgraded ct26 (ct27) on my 3sgte as showen below.


Very old pic, but you get the idea...


Im using an aftermarket wastegate which i have a 8psi spring in.
However when i floor the car it just boosts to 14psi then hits boost cut (using standard computer) . If i floor it in a higher gear tho, like 3rd when im going 40km it the gate will open as normal then the boost will creep untill it reaches boost cut.


I think this is because the standard internal waste gate that im running my new waste gate from is to small or doesnt get enough flow to it, and it just cant bypass enough air????

Any idea how to fix this bloody problem?
It was fine when it was a standard turbo.
How do you get rid of the boost cut on a gen 2 3sgte?

Thanks

[JustinSpiderholden]

You external is pointless if you are feeding it from the standard internal wastegate port, as the flow will still be being restricted by the the size of the standard internal wastegate port


So you need to weld up the stock internal and have the external taking the exhuast gas away before the exhust hosuing, or have the exhuast housing modifyed so that the external waste gate take exhust gasses away directly from the housing

[levinguy]

wow how many brass t's do you have for your oil pressure sensor/s?

[Akane]

You can first try a cheaper fix by porting the internal gate, and see if it improves anything.


Or fix it properly, weld up internal gate, feed the external from the manifold, like everybody else does.

[CelicaGT8]

Sounds like a lot of effort
Basically just needs a new manifold and dump pipe, no biggy...

You would think that a turbo croud that has done tons of these would tell you that the standard waste gate will be useless after the upgrade.

Iv seen some standard waste gate ports modified with very little gain

its a lot of effort to make another dump and manifold tho, suppose i could run two pipes from each of the enterys to the turbo from the manifold and feed them into the pipe just before the after market waste gate. would there be a problem with back pressure tho?

And those cheap manifolds will be horrible to weld to.

(mr levin guy, like it says, old pic when are you going to race your ga70?)

[MR2BOY23]

Off topic: But did you get your turbo from the states?

[CelicaGT8]

no sent it down to the south island and got it upgraded.

[strx7]

what brand of wastegate is it? also how is it being controlled? where is the boost feed to the wastegate fed from? does it have a massive intercooler?

[levinguy]

what brand of wastegate is it? also how is it being controlled? where is the boost feed to the wastegate fed from? does it have a massive intercooler?

its an hks copy wastegate, been fed from straight off the compressor housing as well as the intake manifold with the same results. intercooler isn't that excessive

[Anth_555]

dont ct20b and ct26 have this problem becose the watsegate port is to small even porthing it dosnt fix it you have to set it up off the manifold

[sergei]

dont ct20b and ct26 have this problem becose the watsegate port is to small even porthing it dosnt fix it you have to set it up off the manifold

Yep.

Don't waste your time on porting. Just blank off the original ports, and weld the wastegate port on the manifold (from looking at the pic you already have custom/aftermarket manifold, hence it will be easier to do it.).

Something like this:

[CelicaGT8]

Thanks for the input guys

I was thinking of welding a pipe from the manifold on the right (in the pic) and link a feed from those two clynders to the pipe from the standard wastegate....

Will that be a problem...?

means i dont have to muk around to much, this project has gone way out of hand, was just suppose to be a 3sge

[sergei]

your manifold and turbo is twin entry. which means two pipes + either 2 wastegates or 1 wastegate with separator.

[CelicaGT8]

Yes it should be like that, but would it really matter if i did it that way, i mean it wont be a perfect system, but if it wont damage the turbo or something then why not.

It will still be bleeding some air off from the other 2 clynders through the standard waste gate ports aswell as from more from the manifold to try and get more flow to the waste gate....

Its the easyest way i can think of, but if its going to have negitive effects then i wont do it.

Also, does anyone know how to stop the factory boost cut on a 185 computer

[JustinSpiderholden]

I'm not 100% sure but doing it the way you intend would make it laggier wouldnt it? as the turboo would bleed excess exhuast gas from one side of the turbine effecting spool

Yes it will still bleed excess from the other side of the housing but the standard internal gate takes exhuast gases both side's of the housing

[Guss]

I would have thought that bleeding the air from two cylinders only would affect the backpressure of only those two so going to behave differently to other two cylinders possibly leaner due to more scavenge ?
also what happens if the two cylinders not bled provide enough exhaust to still get boost limit.

Wheres steve murch

[CelicaGT8]

Well it would be those two cylinders directly aswell as the other two through the standard wastegate ports... im not sure of any negitive eccects... but if there are any that could destroy my engine then please do tell me before i do smthing silly lol

[Anth_555]

on my st205 when i got it i put a external on. had a big hole right through the collector on the stock manifold and never had lag or boost problems at al. that was with a ct20b.

[ST205 GT4 NZ New Group A]

Havn't read the whole thread but do you have an aftermarket down pipe?

if so clearance issues with internal wast gate on downpipe
???

[Akane]

Havn't read the whole thread but do you have an aftermarket down pipe?

if so clearance issues with internal wast gate on downpipe
???

well, read the whole thread and see why that isn't an issue.