duehuynh

Searching the forums on hybrid turbo upgrade revealed lots of conflicting information and at times, noise (my turbo is better than your turbo..)

Reading this month’s Sport Compact articles regarding turbo selection made me more confused.

So, I started this thread in order to summarize what has been discussed hopefully to come up with a hybrid answer “most” can live with. Please avoid the “noise.”

Note: I opted for a hybrid solution because I am looking for a MILD upgrade without heavy expenses or work (also taking into consideration of engine and tranny life). It means:

1) No more than 250 rwhp
2) No more than 10psi of boost
3) Want to reuse TMIC
4) Want to reuse stock manifold, stock turbo intake tube, stock mount, etc…

The SC article recommends:

1) larger trim compressor and/or turbine wheel ONLY IF from the same family/frame size.
2) switching the turbine housing to a larger a/r in the same frame size.
3) use a larger compressor wheel with its matching housing. However, it also indicates that you must avoid pairing too large of a compressor wheel with a small turbine wheel. The ratio of compressor wheel to turbine wheel it recommends is 1.1 to 1.25. Anything greater reduces turbine efficiency.
4) The SC article indicates that you must avoid clipping turbine wheel. It may increases flow, but efficiency drop-off is greater than any gain in flow.
5) The SC article indicates that you must avoid “boring out” stock housing for larger wheels. Doing so kills compressor efficiency, mess up internal aerodynamics, increase intake charge temperature, and lag.

Typical hybrid setup I have read:

T-04B (H3, 60-1) wheel/backplate/housing/dynamic seal
Modified thrust bearing, 360 degree thrust package
Reuse stock turbine.

FEDREX setup:

Milled compressor housing w/ TO4E-46 wheel (milled 1mm).
Milled turbine housing w/ Stage III wheel (milled 1mm, with 8 deg clip).
Installed used over-sized bearing housing with new bearings and new seals.

Here are the problems I noted:

A 60-1 Hi Fi T04B compressor is probably the largest you can bolt on that won't present fitment issues when bolting on the turbo (Compressor housing hitting the lower intake manifold). Even then, it requires “clocking” or rotating the compressor housing to fit.

With a T04B housing, the stock wastegate actuator will have to have one of it's mounting holes on the bracket notched or enlarged in order to mount on the back of the compressor housing (spacing is different).

With a T04B housing, you may need to install a nipple either on the compressor housing or the aluminum pipe (One that the BOV connects to) for the wastegate hose to connect to (compressor housing doesn't have a fitting on it)

With a T04B housing, you'll need to do the TID mod since the turbo inlet is larger on the TO4 than the stock Hitachi (4” or 2.75” for Hi Flow version vs 2.35”)

In other words, a T04B still requires lots of modifications that I am not familiar with/may not want to do.

Fedrex milled the housings and installed larger wheels. This is not what the article recommends. What’s your take on this issue?

Some clipped the turbine wheel. This is also not what the article recommends. What’s your take on this issue?

What is the stock wheel size? Is the stock Hitachi compressor housing a T3 size? If yes, then the biggest compressor wheel I can use is the super 60? The chart I made shows that the best you may get out of this is 250hp.

What size is the stock Hitachi turbine wheel and housing?? (stock housing is 1.00 a/r?)

What’s the deal with T3 high flow, 0 trim, 69 trim, and P trim?

I also included another chart comparing the T04B wheels for your viewing pleasure.

Thanks,

dewey

duehuynh

nm

BLUE TII

iTrader: (9)

I personally went w/ a '89+ turbo and manifold upgraded to T04B housing w/ 60-1 and had the turbine modified to "O" trim and threw in some extras like 360 deg thrust bearing and manifold port match/polish. I wanted to avoid all those hybrid issues that SCC mentioned and avoid boost creep as much as possible. The price difference between clipping the turbine and replacing it wasn't that much; I decided to do it the right way (in my opinion.) I don't have my set-up anywhere near together, but I will post here when it is done- of course. Ian

RacerXtreme7

iTrader: (2)

I agree with BLUE TII 100%!! Exact same set up I'm going for! It avoids all those issues like stated. Should be reliable and good for 300 hp. I'll also be modding the rear exit of turbine with a defuser and separating the wastegate and turbin exits and merging them smoothly into the downpipe. Also going to ceramic coat turbin housing and exhaust manifold.

RETed

My experiences with compressor upgrades...
http://fc3s-pro.com/TECH/MODS/TURBO/compup.htm

Turbine wheel clipping info...
http://fc3s-pro.com/TECH/MODS/TURBO/clip.htm

I would recommend a V-trim compressor upgrade.&nbsp This has really quick spool-up, and it should hit your 250hp mark with relative ease.&nbsp Some turbo shops should be able to place a V-trim wheel inside your stock Hitachi compressor housing (machined, of course), so that takes care of the TID issue.




-Ted

BLUE TII

iTrader: (9)

Yeah, I plan on cutting up my SS downpipe and incorporating a wastegate relief like RacerX... said. I am trying to take precautions against boost creep; I want to be able to boost flat out in 5th without worrying.

RacerXtreme7

iTrader: (2)

"Turbine wheel clipping is actually used to decrease turbo efficiency and prevent boost creep due to an inferior wastegate that can't keep up with large gains in turbo exhaust flow. It also boosts turbo spool-up just a tiny bit due to the slight weight drop from the original turbine wheel. "

For the most part this statement is true, except "It also boosts turbo spool-up just a tiny bit due to the slight weight drop from the original turbine wheel. " is completely wrong. Yes it does DECREASE turbine efficiency and prevent boost creep by increasing flow, but it DECREASES SPOOL also. I forget the exact numbers but a 2% loss in turbine efficiency is equal to 25% gain in mass. So that loss in efficiency due to the clip will NEVER make up in spool rate due to the tiny weight loss. I'll correct these #'s after I find my info on it, or if someone else does.