2.5 subaru, what size turbo for aircraft use?

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slociviccoupe

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So everyone knows that the stock subaru automotive turbo is inadequate of the continuous duty use in an aircraft, but what size compressor, turbine, and what ar housings would be suited for a 2.5 subaru? Ive read everything from a 60-1 from garrett or precision, to the gt28rs, the gt35r, the gt42, and a few others. Noticed few have used turbonetics turbo's i prefer to stay away from them as they are unreliable and not a true dual ball bearing turbo. Most likely going to stick to garrett, airesearch, precision, or borg warner.
things like stainless steel exhaust housings, water/oil cooled center cartridges, billet compressor wheels, and inconel exhaust wheels. there should be a turbo that will be sized correctly for aircraft use. I can look at compressor maps and size one but i don't know what altitude and lower density air does and how it affects the compressor map.

here is the last honda my friend david and I built making some really good hp. turbo is a borg warner sc372. 72mm compressor on a 2.0 liter honda @35 psi of boost. Tuned by CMB tuning out of central florida.
http://www.youtube.com/watch?v=CjMBolbo1UA
I know how to make good power with boost and fuel, but now have to learn and scale it back for continuous duty and for altitude correction.


just in need of some insight and hopefully get the sizing of the turbo right for an ej25 sohc subaru. and about only 10psi of boost for takeoff and boost in cruise at altitude for compensation. boost will be regulated by an electronic boost controller through the ecu and an external wastegate.
 

MacPara

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Did you ever solve this problem? I am around the same stage in determining what would be a good turbo for this continuous, light boost application with the very same 2.5l/SOHC EJ257 configuration.
 

rv6ejguy

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Did you ever solve this problem? I am around the same stage in determining what would be a good turbo for this continuous, light boost application with the very same 2.5l/SOHC EJ257 configuration.
We've used a Garrett TO4E, -50 compressor trim, Stage 3 T3 turbine with .82 A/R, integral wastegate on 3 different turbo Subes. All worked very well.
 

mcrae0104

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Did you ever solve this problem? I am around the same stage in determining what would be a good turbo for this continuous, light boost application with the very same 2.5l/SOHC EJ257 configuration.
Is there a SOHC version of the EJ257?
 

slociviccoupe

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Bringing back old dead post. With newer modern turbo's it looks like the garrett gtx3076r is the replacement for the old 60-1 that was mentioned before. New stainless steel v band exhaust housings available from tial also in .82ar. Seems like the perfect turbo for application with billet compressor wheel and deal ball bearing center section, oil lube and water cooled center section.

There is also a borg warner efr turbo that is equivalent i just dont know what it is right at the moment. But the borg warner efr turbo's are offered with internal wastegate.
 

slociviccoupe

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Dont have my hands on one yet as its an 1800$ turbo. But the weight should be prety standard and maybe a little lighter with tial stainless v band turbine housing. Can look up the turbo anywhere and get the shipping weight for a rough estimate.
 

pictsidhe

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Optimum turbo for aircraft use has a much bigger hot side than for car use. Turbos from things like generators and hydraulic machines are a better match off the shelf.
 

slociviccoupe

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How so, this turbo has same specs as the one rv6ejguy speced that works well. One he soeced is the old "60-1" the replacement turbo for a 60-1. The equivalent is a gtx3076r. And a .82 ar housing is rather big for a 4 cylinder so the housing will flow. You dont need a big exhaust wheel. Only need a big turbine wheel for a big compressor wheel.

The next size turbo is the gtx35(76,82,84)

Not sourcing this turbo for performance or from car application. Sourcing it because it medts the specs of a turbo that works but with much newer technology. Billet compressor whedl, new upgraded to4e compressor cover, dual ball bearing.

Also stationary generators yes run at constant speed dont have billet wheels and they are old outdated journal bearing turbo's usually garrets or holsets. Oh and they are on the ground and not sized for altitude. And last i know i dont know of any 2.5l generators
 

pictsidhe

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Car turbos have their hot side sized so that they produce decent boost at low rpm. The penalty for doing that is that the majority of the exhaust flows through the wastegate at high rpm. That means a much higher pressure ratio across the turbine. That means less hp per inch of manifold pressure. Aircraft don't need low rpm torque, so a bigger hot side can be used. Resulting in a cooler, more powerful and economical engine. Yes, a car turbo will work. No, you don't 'need' a big wheel, unless you want to maximise power and BSFC... But if you are buying a turbo, it could be a much better match if aimed at aircraft use instead of for a car. Generator/hydraulic turbos are closer to what we want than car turbos if you want an off the shelf unit. They do come in small sizes, I've seen much smaller ones than a Subaru would need.

There is way too much hype in the performance world. Trust me, all engine manufacturers appreciate efficient units. It makes their power targets easier to hit.
 

slociviccoupe

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So more looking through the internet and holset hx35, hx35/40 hybrids and straight hx40 seem good candidates also.

Cant find much info on the "stage 3" turbine wheel mentioned before other than possibly the 60-1 turbo had a p trim t4 wheel that was 76/74mm. So a t4 turbine in a t3 housing.
With a 60mm inducer/82mm exducer in a to4s compressor housing.

Still looking for actual specs on compressor inducer/exducer, compressor cover (to4e, to4s) , turbine size not just trim, and turbine housing ar. Seems .82 is desirable for good flow.

Now id assume open housing, but could a large twin scroll be used to isolate exhaust pulses from eachother. Easier to fabricate each side also.
 

Chris Matheny

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What power range are you looking at for takeoff and cruise? This would go a long ways to narrow it down. 10 psi from a T28 vs 10 psi from a borg SX300 would be big difference in HP.
 

slociviccoupe

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I wouldnt think 200hp at takeoff is unreasonable. Since im a car guy i dont even know what amount of boost is acceptable in an aircraft. It does seem 10psi is safe for take off and 6-8psi for cruise. I am planning on in flight electric adjustable prop.

My next question is the manifold. Build out of the stainless weld els that are pipe dimensions or build from apropriate sized 321 stainless u bends that are tube size? Incorporating slip joints for expansion.

Exhaust housing, stainless steel and with v band or bolted inlet and outlet?
Or should go with cast iron? The stainless housing saves some weight .

Flanges? Ive found some very nice flanges that are investment cast stainless steel. Also found some that are machined stainless steel. Im asuming i should be looking atvyhings in a weight perspective and shat will get the job done. But any diffefence in longetivity between investment cast stainless steel vs machined from bar stock stainless steel? And any isdues with 304 flanges welded to 321 tubing?
Use 321 filler?

Muffler, even though turbo makes a really nice resonator thoughts on one off the 3" race mufflers in the downpipe to help with some of the sound.

Turbo placement. Behind engine up near firewall. Or below engine up in front of cowling? Below will require turbo to have small sump and scavenge pump to return oil to the sump or tank.

All these questions are for my own personal conversion but may help others in their own conversions or possibly get conversion parts made for sale to the public without having to buy a whole 30k package.
 

pictsidhe

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To properly size the turbo, you need to know airflow rate and pressure ratio. To size the turbine, we also need to know the EGT. Do this at multiple altitudes so all the requirements will size the turbo. You may find you'll want to trade a psi here, for three psi there.

A poorly matched latest tech turbo will not work as well as a well matched 40 year old one. Gaining 3% compressor efficiency is pointless if it costs you a 10% loss due to poor turbine matching. Size first, fancy features later.

Ross knows more about aero EJs than the rest of us put together. You should take his advice on what power levels are safe.
 

slociviccoupe

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So this is what im trying to do. Not really wanting to buy a turbo more than once unless its for maintenance or a rebuild. More than likely ill be using the same turbo ross has used and reccommend. Now its just getting down to the other factors.

Working on the engine build and firewall forward package i dont have ability to get egt numbers, drive pressure, or any other data at this point.
And as per posts ive dumbed down the modern day turbo to the plane jane journal bearing 50 trim garrett ross has reccommended.
 

TFF

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An airplane engine is throttled around 5% of its use. Acceleration of the engine just needs to be clean. Quick is unimportant. Most running is at a set rpm. A stationary generator is closer to how an airplane engine is used; it is just at altitude. The closest similar turbo setup for a car would be a Bonneville speed car. Especially long course.
 
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