Subaru Turbo conversion

Propane, Butane, LPG, GPL, C3H8, C4H10
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Binford
Posts: 5
Joined: Sun Jan 01, 2006 2:34 am
Location: MN

Subaru Turbo conversion

Post by Binford »

I'm looking at options for coverting to straight lpg. I have read close to every single thread here in the last few days, and have some ideas and questions. My car is a 1991 Subaru Legacy with a 2.2l turbo engine, MPFI. I have made some modifications to bring it to around 220-250 chp(160chp stock). I calculated I need 600 cfm.

For simlicity sake, I'm thinking Impco 425 and a model E, and whatever approved tank I can come up with. As an alternative to the 425, what about using a mixing ring with my exsisting throttle body? Are these for dual fuel use? Could I adapt something like this? About lpg injection, assuming I could source the correct injecters, why couldn't I just swap injecters and let my factory ecu run them like stock? Would the pulse width be that different? I'm just kicking up some possibilities. I would appreciate any advice or other ideas. Thanks.

franz
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Joined: Thu Oct 07, 2004 7:57 pm
Location: Central Texas
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Fuel systems for your Suby.

Post by franz »

You didnt discuss either a blow through or a pull through system. If it is pull through, the 425 is the best option. If it is blow through, I have seen a couple of Subaru's using the Impco 200 with a model E vaporizer run like a scalded rabbit. Lastly, use 1.68 cu ft air per hp for a pretty good rule of thumb, not the written rule.

A mixing ring (venturi) doesnt work in a blow through but would in a pull through. It would work ok in dual fuel mode.

As for injection, you would play with pressures for quite a while before you found the balance between flow rate, pressure and injector pulse width and dont even think about using liquid injection, your pockets are not deep enough. Sourcing or building a vaporizer for about 30 psig vapor pressure is your next challenge, there are no commercial units that will do what you need. Do not use your existing fuel rails for propane vapor either, you will have to fabricate every inch of your fuel system.

Franz

Binford
Posts: 5
Joined: Sun Jan 01, 2006 2:34 am
Location: MN

Post by Binford »

Here is a pic of my enginebay as it sits.

http://www.thawa.net/gallery/album99/IM000150

I was thinking blow through, but I am now reconsidering. However, as I understand it, I would have to remove my intercooler. Is this correct? I would have to remove it in a blow through setup for space reasons. I would like to keep it if at all possible.

franz
Posts: 1205
Joined: Thu Oct 07, 2004 7:57 pm
Location: Central Texas
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Hmm

Post by franz »

It seems like you may have to remove it. I would never put a pull through with an intercooler in any street application. The turbo lag would be pretty noticable and one stray spark in the intake and there is lots of pre-mixed air and fuel in the system which will want to find the quickest way back to atmosphere pressure (read as intake backfire).

Removing the intercooler may be the only solution, there is not a lot of room under that hood. The earlier ones I saw were not intercooled.

Franz

Binford
Posts: 5
Joined: Sun Jan 01, 2006 2:34 am
Location: MN

Post by Binford »

Thank you for your help so far. Nobody local can understand why I want to do this. Whenever I tell someone what I'm trying to do, all I get is a really big WHY?!?! This must be why I cannot find any parts around here. Good thing for the internet! :lol:

Anyway, using 1.68 cu ft air per hp has me needing 420 cfm. According to my research, the Impco 200 flows 345 cfm and can only handle 5psi boost pressure. Right now, I run up to 16 psi, and I plan to go up to 20 psi(possibly-turbo is out of efficiency range at that point). Is there another mixer that is up to the task? Am I understanding correctly?

What, if any, are the dangers of a draw through(besides what you stated above)? Particularly vapour running through the turbo. To me, this goes against common sense. I know that it is done, so it must be safe. I dunno. :?

As a side note....Once I get this up and running, what are the possibilities of NOS or water/methonal injection? Would this have any benifit in your opinion? Of course, my main goal is horsepower and torque, not neccisarilly efficiency. :twisted: Although, you should know, I'm cheap and poor! :wink:

franz
Posts: 1205
Joined: Thu Oct 07, 2004 7:57 pm
Location: Central Texas
Contact:

pressures

Post by franz »

The limiting factor with boost on these products is sealing. Most components have covers which are cast "pot metal", rarely more than 3/16" thick. Using a stock part for pressures more than 5 psi might invite a pressure leak. Industrial variants of these parts used heavier cast metal components, I have seen more than 20 psig on occasion. In your case, and as stated earlier in other threads, you can push more air under pressure than pull through it at atmosphere pressure.

Using water or methanol injection serves as a detonation deterrant, no matter which fuel is used.

Franz

Dylan86GL10
Posts: 44
Joined: Tue Jan 10, 2006 1:36 pm

Post by Dylan86GL10 »

I want to do basically the exact same thing with my '86 GL-10 EA82T (have a EJ22 to turbo later). I am looking to make a dual fuel vehicle and I have a megasquirt to control fuel/spark as needed and changing tables on the fly for different timing / AF requirements.

Hopefully we can source a push through LPG carb that will take more than 5psi.

Thanks!

Dylan86GL10
Posts: 44
Joined: Tue Jan 10, 2006 1:36 pm

Post by Dylan86GL10 »

Vapor through the turbo is no problem. The problem is that there is quite a good volume of "Ignitable" air once you add turbing and an intercooler. A BOV would also have to circulate back after the carb to keep A/F right. With the added octane of LPG I would concentrate on boost pressure and tuning for power as opposed to refillables such as NOS.
Binford wrote:Thank you for your help so far. Nobody local can understand why I want to do this. Whenever I tell someone what I'm trying to do, all I get is a really big WHY?!?! This must be why I cannot find any parts around here. Good thing for the internet! :lol:

Anyway, using 1.68 cu ft air per hp has me needing 420 cfm. According to my research, the Impco 200 flows 345 cfm and can only handle 5psi boost pressure. Right now, I run up to 16 psi, and I plan to go up to 20 psi(possibly-turbo is out of efficiency range at that point). Is there another mixer that is up to the task? Am I understanding correctly?

What, if any, are the dangers of a draw through(besides what you stated above)? Particularly vapour running through the turbo. To me, this goes against common sense. I know that it is done, so it must be safe. I dunno. :?

As a side note....Once I get this up and running, what are the possibilities of NOS or water/methonal injection? Would this have any benifit in your opinion? Of course, my main goal is horsepower and torque, not neccisarilly efficiency. :twisted: Although, you should know, I'm cheap and poor! :wink:

Melvin
Posts: 26
Joined: Sun Oct 16, 2005 8:33 pm
Location: Calgary Canada

Why LPG

Post by Melvin »

Binford wrote:Thank you for your help so far. Nobody local can understand why I want to do this. Whenever I tell someone what I'm trying to do, all I get is a really big WHY?!?!
Imagine the boost you can run on 105 Octane is all you have to say. Once they compare the price of race gas to propane they at least stop irritating you. I realise the numbers can't be compared directly (if only because your intake charge isn't being cooled by the liquid fuel), but they don't need to know that. :)

Dylan86GL10
Posts: 44
Joined: Tue Jan 10, 2006 1:36 pm

Post by Dylan86GL10 »

Binford:

Here's the list for my EA82T (1.8 turbo) in my GL-10 Wagon:

Impco CA200
Impco Model E
Electric lock off

Going to EJ22 swap within the year. These should be appropriately sized. Seems boost pressure is going to be an issue with all the carbs except maybe gas research grand. Franz is confident the CA200 is fine to 300+ hp boosted.

Binford
Posts: 5
Joined: Sun Jan 01, 2006 2:34 am
Location: MN

Post by Binford »

I got a wee bit side-tracked on this project and ended up installing a high flow Walbro fuel pump so I can drive again. I will be watching and doing some slow research around here. Dylan86GL10, maybe I'll let you be the guinee pig for me, as it sounds like basically the same setup I need. I would be very interested in seeing what you put together!

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