The AUSubaru.com.au Forums

Just a thought I had on the way home the other night..
What would it take to make a Subaru engine accept diesel? Come on all you pocket engineers. I know it's probably not possible without a HUGE injection of funds but..
So far I've come up with the following..
You'd definitely need to strengthen the bottom end to accept the greater compression ratio at the top end.
A way of increasing said ratio at the top end whilst still allowing valve clearance without weakening the piston crown so therefore major reworking of the head would be the order of the day (as I said, would not be cheap)..
What else?

drop a small diesel engine in there from another make, adapt to the subaru gearbox, you have a diesel brumby.

your never going to turn an EA81 into a diesel

Shhh!! Don't be practical. I'm talking pie in the sky.. if you wished upon a falling star... how would it be done.

Perkins make some little turbodiesel 3 pots, surely one of them could be made to fit.

I thought about it once. For about 5 seconds.

You could always wait a few years for the real Subaru diesel engine.

I'd like to know what diesels might fit.

I know on USMB they're always talking wishes about fitting a vw rabbit diesel into a subaru, but I don't think anyone's actually done it yet.

Western Washington College were modifing an ea81 for diesel in the late 80's, dunno how far they got, but it was a project.

Wait another year or so.
Apparently,.. subaru are designing a diesel boxer as we speak, to unvieled at a motor show mid this year in the new impreza.

The motor is likely to be a common rail 2ltr, 4cly boxer, one timing chain DOHC with the turbo mounted below the engine close to the exhaust ports (it will have a scavanging pump for the oil) It also has variable intake lenght and a tmic.

Google it, it is very interesting

hang on... what are the basics of a diesel? However improbable it sounds, to convert an idea into reality you'd use logic to base everything on. List what makes a diesel engine, compare it to an EA81, find the differences and apply them to the EA81.

In theory, it should work. Practicality... thrown out the window when 'diesel' and 'conversion' is mentioned.

For starter you need to up the comp ratio to about 20-1, you most probably need to inject the desiel into the combustion chamber. So what do we need,
1/ high comp piston
2/ low lift cam and timing to suit ( for clearance )
3/ rework the heads for the injectors
4/ maybe beef up the rods
5/ common rail fuel lie and electronics for the injectors
That is about it, give me a call next week when it is finished
Cheers Thierry

I've heard of deisels down to 15:1 and even heard of 8-9ish:1 petrol engines running on deisel, not well but they did run.

If you wanted to go injection you could put the injectors inplace of the spark plugs but I think you could get away with retuning the carb to suit.

I would say you'll also need a copper and/or o-ringed head gasket to handle the compression, and re-inforce the bores with deisels sleeves.

Jordan.

good pick up never thought o using the plug holes

just buy a hilux or something similar it would be lot easier...

easier? wheres the challenge in that?

Hilux = $$$$$
Subaru = $$

trying to convert a subaru engine to diesel =$$$$$$$$ and still probably wouldnt work...

Its not a question of monetary concerns, nor is it a question of reliability or any other reason but the following: Converting an EA81 or similar older-model boxer engine would be only to say that it's been done.

see, I never meant it to be a question of practicality. I was just curious how much work would need to be done. Personally I was thinking that you'd have to shave the block to increase the compression. For that, you'd need to organise pistons that had indentations in the crown to allow for valve lift. Or you could try increasing the valve diameter but there will always be the question of not making the walls to thin. The injector rail could be fed through the spark plug hole. Find somewhere for a mechanical injector to sit. And I think maybe the bottom end would have to be beefed up. A stronger crankshaft and bearings to cope. That would be the REALLY expensive part as we all know specialised crankshafts are not cheap.

Have you ever pulled a motor apart?
Have a look at a piston from a petrol motor. the rings are only mm apart. In a diesel, they are cm apart & the rings are wide.
The pistons obviously are forged to cope with the high compression & although I've now heard of alloy blocks, the clamping force on the head studs are huge. Not sure about how high, but they use a 3m extension on a 1" thick breaker bar for the trucks at work.

The block will need to be machined to accept diesel liners (BYB-01 has these in his EJ20 to handle the boost).
Unless you want crappy performance from having manifold injection, you'll need to get access into the combustion chambers with the injectors. While you could use the spark plug holes for this, don't forget you need to get glow plug in there too.
Then you'll need to organise the fuelling system. Modern electronic injection might be easier, but the older mechanical injection pumps are huge.

As an idea, the Toyota in my sig is a factory east-west engined turbo diesel.
The motor arrangement is backwards from the petrol version, ie the inlet manifold is on the front & exhaust (and turbo) on the back so that the injection pump has room to fit.

Interesting project, but there's a reason why diesel motors run diesel, & petrol motors run petrol.

Bringing back a thread from the stone age here. Now that we have boxer diesels, how hard would this project be now?

You'd want to start with a complete diesel writeoff. rear munted or rolled

The biggest problem now is going to be the gear ratios. Diesel ratios are very different to the petrol ones, and the diesel box isn't a dual range.
Probably something that someone with a bit of time could fix by mix & matching parts, but unknown until someone does it.
I've only driven a diesel Forester (manual) once, and found the ratios weren't well suited at all.