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Discussion Starter #1
As many of you probably already know, Im having boost creep issues with my new 2.2 gen III... Im running a 1.06 A/R GT35/40... with a 38mm Tial gate.

My current setup looks like this:




Now.. Ive relocated the wastegate to its current position.. as close as possible to the turbine entry, Its coming off at a 90 degree angle that curves into the manifold to try and increase flow.

The pipe used between the manifold and gate is 38mm ID.. should be heaps for a 38mm valve.

The gate is also venting to atmosphere for maximum flow

This is how its currently behaving:
3rd gear pull... Ive got a 10psi spring and it holds 10psi from 3800rpm to around 4500rpm. then it begins to creep. By the time I reach 8000rpm, creep has pushed boost to around 20psi

My concerns are currently:

1) the vent pipe is 1.5" ID (38mm)... and is approx 1 metre long. I wonder if I would get significantly more flow if I used 2" pipework or whether the main restriction is going to be the wastegate/valve itself?

I am considering giving it a boost without the pipe (venting into the engine bay.. eek).. as a test of this theory if I cant get any answers...

2) the gas needs to hook a 180 degree bend in order to vent out of the manifold.. but regardless of which way the gate is pointing, it will always have to curve 90 into the gate and another 90 out of the gate.. so I dont think this is an issue? 180 degrees is 180 degrees as far as I see it


Options Im NOT considering at the moment

1) I know I would get heaps of flow if I cut into the turbine housing and welded the wastegate on there.. seen it done before and its great, but Im not willing to chop my turbine housing.

2) a bigger gate. Ive met my budget and Im not going to buy a bigger gate in the next few months.

3) restricting the exhaust to increase backpressure, reduce engine efficiency and increase wastegate flow. NO. Yes, it works well but Im not willing to do this to solve boost creep. Why make such a beautiful motor only to handicap it? :)

4) increasing turbine housing A/R even more. I cant! Ive gone from 0.63 - 1.06 and I cant realisitically go bigger.. and dont want to if I could.



So.. any thoughts? Or perhaps any ideas for modifying the Tial gate for more flow? Any ideas at all?

Thanks all,

-Tristan
 

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I had a similar problem to what is happening to you. I have a 2.2 stroker and 38 mm wastegate. I was getting boost creep above 5000 rpm's. Kris at KO changed the pipe from the adapter to the wastegate from 1.5 to 1.75 and will now hold 10 psi if boost controller is turned off. Hope this helps. John
 

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Discussion Starter #4
jsantesson said:
I had a similar problem to what is happening to you. I have a 2.2 stroker and 38 mm wastegate. I was getting boost creep above 5000 rpm's. Kris at KO changed the pipe from the adapter to the wastegate from 1.5 to 1.75 and will now hold 10 psi if boost controller is turned off. Hope this helps. John
Man thats the worst answer you could give me hehe. I just pulled the manifold off to weld this new pipe in.... that would mean I have to do it AGAIN.

Thanks heaps for the input :)

-Tristan
 

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You could make a it flare from 1.85 to 1.5, that way give the WG a little breathing room when it opens.

T
 

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The 1.5" piping after the WG is more restrictive than the 1.5" piping before the WG because the pressure is lower and the velocity is higher. I'd fab up something temporary and make a test run.
 

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Discussion Starter #8
twoina2 said:
The 1.5" piping after the WG is more restrictive than the 1.5" piping before the WG because the pressure is lower and the velocity is higher. I'd fab up something temporary and make a test run.

Doesnt lower pressure = lower expansion = Lower velocity, not higher?

That aside.. yep, my next step is to run an open outlet on the WG and see if it really is a restriction

Thanks
 

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I personally dont think the outlet of the wastegate is the restriction, I think its the inlet. But its a free worthwhile test, so do it and get back to us.
 

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Discussion Starter #11
Yeah I know it will :) But I always like to optimise what Ive got before blowing money on something bigger that might not be necessary

Id far sooner rip my manifold off and start cutting and welding for increased flow... than blow $$s on a new gate.

There are other advantages too.. the smaller the gate, the more precise the boost control. with my profec B spec II, I have logged my boost on the dyno and at higher boost levels, it was holding so utterly dead steady.. less than 1psi variation all the way to redline.

..Ive never seen such precision before with any other setup

-Tristan
 

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who is selling a 44mm for $250?

Also, who cares how accurate you boost level is if the motor is not detonating?
 

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Discussion Starter #14
"Also, who cares how accurate you boost level is if the motor is not detonating?"

Its nice. I like it. :) Come on Im trying to justify not spending money hehe
 

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Cheapest I've seen the 44mm wastegates is about $340 or so, but why chance it with some flaky vendor that wants to drop ship something he doesn't even have to sell you... I think it's worth the extra $20-$30 to get one from a legitimate seller...

As for my comment Tristan, it's true, I've never understoof the fascination people have with having such accurate boost levels, and I've had arguments/discussions with several road-racing people about the subject. I stand firm on the argument that a few psi here and there is sort of a moot point. BUT, in your case the boost creep is severe, so I totally understand trying to fix a bonafide problem that exists, it's just the idea of 15.000psi+/- 0.001psi that seems kinda unnecessary...
 

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Lay the WG back so the outlet is almost pointing up and gradually merge the WG pipe with the collector, instead of the 90 angle you have now. That way the inlet pipe to the WG will be basically aiming back at the ex. valves. A nise small "scoop" inside the pipe to aim a little exhaust @ the WG might help too. Limiting the length of the dump tube, and enlarging it may help with getting the exhaust gasses out as well.

* optional* Then run the outlet from the WG straight up with a sweet flapper on top to keep the rain out ;-)
 

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Discussion Starter #18
ATS_Scott said:
Lay the WG back so the outlet is almost pointing up and gradually merge the WG pipe with the collector, instead of the 90 angle you have now. That way the inlet pipe to the WG will be basically aiming back at the ex. valves. A nise small "scoop" inside the pipe to aim a little exhaust @ the WG might help too. Limiting the length of the dump tube, and enlarging it may help with getting the exhaust gasses out as well.

* optional* Then run the outlet from the WG straight up with a sweet flapper on top to keep the rain out ;-)

I wanted to lay it back like you suggest but the turbine housing is way big (the head of the gate is almost pressed against it)... and I cannot mount the WG higher else it'll hit the engine lid... and if I made the gate plumb in further back along the collector to get the 'lay back' then it would only be taking flow from two runners due to the internal design (very similar to the collector of the full race manifold if you want to visualise it)

All the other tips taken on board.. thanks.... except for that flapper thing :p

-Tristan
 
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