Turbine question

[mwinkle353]

Ok, I've tried to search for this information. I have not seen any difinitive answer, so I'm starting a new thread.

Question:

I'm expecting a bit of boost creep from my turbo, when I install it. I'm trying to counteract this by opening up the hole for the internal wastegate. But I don't think that will completely erase the issue.

I have an idea, but don't know how it will end up. And this is why I ask others who may know. I know that a larger turbine housing will allow for greater flow in the upper rpms with a slight sacrafice to initial spoolup of the unit. I also know that a larger stage turbine wheel will also allow for better flow. But how do the two differ on any certain application? Should I look for a larger turbine housing for the T3 I'm thinking of using? Or should I be looking for a larger turbine wheel and matching housing of same A/R I currently have?

I guess what I'm asking is....

... will a larger turbine housing or a larger turbine trim help me with this?

[Phreakish]

clipping the turbine wheel is for those that can't afford the bigger housing, or are in need of certain other aspects of the turbo.

Short answer: the larger housing will help, the increase in flow will definitely get rid of the boost creep, and so long as you have a good free-flowing exhaust it should spool nearly as quickly.

[mwinkle353]

3" exhaust is going on with the turbo. Out to the rear with cat and no muffler.

Clipping the turbine is not an option. I don't wish to reduce the turbine's effeciency at all. Just reduce the boost creep.

[Moparbishi]

yeah as long as there is no backpressure to prevent spooling then you should not have boost creep.

btw how is the progress coming been awhiel since i have talked to you?

[moparzrule]

What turbo is being used here? If it's atleast a T2 you shouldn't have problems with creep unless you have way more mods than a T2 turbo can support.

[Ondonti]

Quote:

Originally Posted by moparzrule What turbo is being used here? If it's atleast a T2 you shouldn't have problems with creep unless you have way more mods than a T2 turbo can support.

He has 6 cylinders

[moparzrule]

OK well if someone would list the setup of this it would help alot! You can't just make a post and expect people to know your setup!
Is this a 3.0? Or is this a slant 6 project? or other? Either way, a stock T2 turbo is way too small to support even 2.5+ liters at any reasonable HP level unless all you want is like 200 or something. With a 6 cylinder you will spool the .63 housing like the .48 housing on a 2.2L, full boost by atleast 2500 RPM if not sooner especially with 3'' exhaust. The .48 turbine is way too choked on a 6 cylinder, period.

[mwinkle353]

This was a hypathetical question. I just wanted the general rule on how the differences between the housing and turbine sized reacted.

But if it matters...

- 3.0L motor
- Ported intake (upper plenum ported with center divider removed, lower ported to match)
- 52mm TB
- CAI with K&N filter
- 3" exhaust with cat and no muffler

Planned mods are...

- Custom exhaust manifolds
- Turbo (T3/T4, T04B V-trim compressor mated to T3 Turbine) <---- what the question is for

I'm trying to decide if I would be better off with a Stage I turbine in a .82 A/R housing or a Stage III turbine in a .63 A/R housing.

[moparzrule]

Stage 3 in the .63 will flow way more. The stage 1 wheel is a major restriction, in any housing. The stage 2 .63 may even flow more than an .82 stage 1.
You may have creep with the .82 stage 1 because the wheel backing up the exhaust. But you will not have a problem with the .63 stage 3.

[mwinkle353]

Sounds good. Thanks


Wink

[TurboMinivan]

Quote:

Originally Posted by moparzrule Stage 3 in the .63 will flow way more. The stage 1 wheel is a major restriction, in any housing. The stage 2 .63 may even flow more than an .82 stage 1. You may have creep with the .82 stage 1 because the wheel backing up the exhaust. But you will not have a problem with the .63 stage 3.

I don't know how much experience moparzrule has with these exact turbine wheels, but I know I have none. (My personal experience is with the Turbonetics T3 .63 StageII.) Still, I'd love to help you make an informed decision.

Turning through my Turbonetics catalog, I can find exact size specs for the T3 turbine wheels: the StageI has a 1.918" exducer whereas the StageIII has a 2.229" exducer. On the surface, this seems to validate moparzrule's claim. After all, the StageIII clearly offers more flow than the StageI, and more turbine flow ought to counteract boost creep quite nicely.

But it's not as simple as that. You aren't just comparing stages of wheels; you're crossing between different a/r ratios. When stepping up to a larger a/r, you're gaining area in the turbine's scroll housing. This greater area will significantly reduce the turbine housing's restriction, and that in itself will therefore directly correlate to a significant reduction in (potential) boost creep. Furthermore, when comparing to a .82 a/r turbine, the biggest cork in a .63 turbine isn't going to be the turbine wheel--it's going to be the scroll housing itself.

Food for thought: a large number of turbo Dodge guys (myself included) have experienced boost creep with a Mitsu turbo on a 2.5L engine after we opened up the exhaust. Why did it happen? Because once the exhaust flows freely, the turbine itself is the biggest cork in the system. Now that the exhaust pipe lets the turbine kick out all the air it can, the tiny wastegate passage cannot divert enough of the exhaust air to keep the boost in check. Okay, so what can we do about it? Well, a number of guys simply ported out the wastegate passage and reported an elimination of the creep. Other people (like me) just tossed the Mitsu and replaced it with a stock T2 Garrett--this eliminated the boost creep even though I never ported the Garrett's passage.

Final suggestion: talk directly to Turbonetics. (805) 581-0333 Tell them the exact two a/r+stage combinations you are considering, and mention your concern about boost creep. They will be able to tell you with authority which combo flows more. They can probably also build you a turbo with a wastegate passage which is already ported; the as-cast passageway leaves a lot of room for expansion! Have a chat with them and see what they recommend.

[turbovanman]

Quote:

Originally Posted by TurboMinivan Final suggestion: talk directly to Turbonetics. (805) 581-0333 Tell them the exact two a/r+stage combinations you are considering, and mention your concern about boost creep. They will be able to tell you with authority which combo flows more. They can probably also build you a turbo with a wastegate passage which is already ported; the as-cast passageway leaves a lot of room for expansion! Have a chat with them and see what they recommend.

Or run an external wastegate, might be better for packaging concerns in your car?

[moparzrule]

Quote:

Originally Posted by TurboMinivan . Furthermore, when comparing to a .82 a/r turbine, the biggest cork in a .63 turbine isn't going to be the turbine wheel--it's going to be the scroll housing itself.

I'm well aware of that fact. However, the .63 stage 3 has been used 400-500 HP applications, I think it flows enough.
Another example is the stock .48 housing on our 2.2's. No matter what wheel you stuff in the .48 it's not going to be able to produce any more power because the actual housing is the restriction. The .63 stage 1 will flow more than a .48 stage 3, because of this fact. The exact opposite occurs in this case with the .82 stage 1 VS the .63 stage 3, the wheel is the restriction even if you put a 1.15 A/R housing on it. But, in this particular case it does not apply because the .63 stage 3 has the ability to flow for his needs and/or wants.
Comparing what you did with the mitsu to the garrett swap as far as creep is like apples and oranges to this comparison.

[TurboMinivan]

Quote:

Originally Posted by moparzrule However, the .63 stage 3 has been used 400-500 HP applications, I think it flows enough.

Certainly.

Quote:

Originally Posted by moparzrule the .63 stage 3 has the ability to flow for his needs and/or wants.

That was the impression I got as well. In fact, I doubt creep would be an issue with any .63 housing, even with the comparatively lousy StageI wheel. Still, I thought asking Turbonetics about it might be a way for him to put any and all fears to rest... which is why I suggested it.

[moparzrule]

Gotcha.