Increasing the compression ratio on EA82?

the engines normal compression ratio sounds like the most pump fuel will handle. the increase in cr you're talking about would likely require premium. unless perth is wildly different to the rest of aus, basic unleaded is 91(ish) ron, premium is 96, and the 'special' premium blends are generally 98.

Charlie

To a degree, but not extensively.

I've played around with the EA82's a bit, and the older EA81's as well, and found them to be a pretty good little engine that are quite robust (if you can stand the noise they make :)

I'd suggest that if you're going to go to the trouble of milling the heads to raise the compression ratio half a point, you won't make any significant gains in either power or economy, and the exercise may not be worth the trouble. You'll no doubt get *some* gains, sure, but the net effect won't be great, and on a bangs-per-buck scale it will be an expensive endeavour.

I remember looking into this when I did the engine in the wife's suby a couple of years ago, and although I can't recall the specs now, I do know that I concluded that it wasn't worth my trouble. You'd need more than 20 thou to pick up half a point I would expect, and Subaru engines *don't* lend themselves well to lots of metal being removed from the head gasket face.

The aviation stuff (and other custom Suby engines) I've seen all used custom made inlet manifolds, and in this instance you can get away with taking as much metal off the heads as the engine will stand. However, if you're going to use the *factory* inlet manifold, then you can run into serious trouble in a big hurry with head machining, as the manifold bolt locations are fairly tight straight out of the box.

Put very simply, take more than a *moderate* amount of metal off the heads and you may very well find that you can't get the manifold to bolt on anymore, and slotting the manifold bolt holes to accommodate a narrower bolt spacing isn't a good idea in my humble opinion.

You'd be *much* better off with a pair of efi heads. As well as a different combustion chamber shape, they also have a slightly different porting & valve arrangement that makes them flow a tad better than the carburetted ones.

Regards, Noddy.

how would the ecu tell?

Charlie

Didn't he say it was a carb engine?

-- Marco Spaccavento snipped-for-privacy@iprimus.com.au

What ECU? the EA82 is a carb'd engine...

One of the more popular mods to get some more power out of the EA81 is to change the carb to a weber. Never done it myself, but they seem to talk about that option a lot on the Ultimate Subaru board whenever people ask about increasing power for reasonable cost.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

Hi Noddy,

That sounds like good advice. To be honest, I hadn't considered the effect on the intake manifold.

Can I use the efi heads with the carby intake setup? I'm not interested in spending the $$$ and time it takes to convert the thing to efi.

Thanks for your help, Alex.

I guess you'd have to tell it, since it ain't plugged in to the carby ;)

Ta for the octance advice, the MPEFI versions must have been tuned for Jap fuel.

Cheers, Alex.

A bit off topic, but I will comment that I have had (and still have for that matter) several mid '80s GLs with the EA81 power plant. One of these, an '83 FWD 5spd wagon, came with an odd carb arrangement; a Carter-Weber carb with a primitive fuel feedback loop that employs an on-carb fuel enrichment (I assume) circuit, and an O2 sensor. I have never seen any documentation on this arrangement, and dread the day that it stops working, as I'm sure I'll never find parts for it, but it makes _substantially_ more power than the other "normal" EA81s, and gets better mileage as well. 240K miles, and still goin' strong, tho! Don't suppose anyone can tell me anything more about this setup? AFAIK it was bought new locally (Colorado Springs CO); I got it from one of my grad students who was the original owner.

ByeBye! S.

Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101

Bill,

Do they suggest anything for getting a little more power out of the non-carbed non-turbo EA82? My Loyale needs all the help it can get. . *g*

Just curious. .

--Decimal Cat

I know it's a totally different engine, but I put a Weber on my 1977 Toyota pickup (20R) and it made a world of difference.

I'm pretty sure you can, but you'd have to check first as it's been a while since I've done anything with them.

If they do actually fit, then they'd be a much better deal....

Regards, Noddy.

timing can tell an engines had it's cr raised? crikees, they do make em smart these days... :) :)

Charlie

I don't recall - perhaps a weber can be fitted to that too. Or convert to turbo, but many would recommend finding a car like you want rather than radical upgrades (unless you have access to a donor car with the harnesses, computers, engine, etc.).

You might try posting there yourself and getting a variety of options with the pluses and minuses as far as benefits, cost, difficulty, etc. Part of it depends on your use and type of driving.

Bill Putney (to reply by e-mail, replace the last letter of the alphabet in my address with "x")

S wrote: : A bit off topic, but I will comment that I have had (and still have : for that matter) several mid '80s GLs with the EA81 power plant. One : of these, an '83 FWD 5spd wagon, came with an odd carb arrangement; a : Carter-Weber carb with a primitive fuel feedback loop that employs an : on-carb fuel enrichment (I assume) circuit, and an O2 sensor. I have : never seen any documentation on this arrangement, and dread the day : that it stops working, as I'm sure I'll never find parts for it, but : it makes _substantially_ more power than the other "normal" EA81s, and : gets better mileage as well. 240K miles, and still goin' strong, tho! : Don't suppose anyone can tell me anything more about this setup? AFAIK : it was bought new locally (Colorado Springs CO); I got it from one of : my grad students who was the original owner.

I've got an '85 GL Hatch with the EA-81, carb'd. What you are describing is a "feedback carb." It was the predacessor to the SPFI, and according to most people worked well when it worked. What it does it sense the O2 and do a pulse-width modulation on a duty cycle solenoid that allows a small (controlled) amount of ambient pressure air into the fuel metering jet. That raises the absolute pressure (decreases the vacuum) and reduces the amount of fuel that goes through the jet to the engine. This leans the mixture for highway, steady-state, closed-loop mode, while allowing for normal carb power enrichment and a relatively benign failure mode. If the ECU or solenoid craps out, it runs a little rich, but still goes. That's why many people didn't like them because they'd get *worst* mileage than a stock carb if the system either broke or was intentionally disabled. Remember that this was the time when U.S. folks were buying new cars and ripping the emission stuff off them for performance and mileage.

I wish I had one of those, since I do most of my in-town driving at 2100', and long-distance driving over the plains when I could pull the (non-existent) big red knob back and go from 29-31 mpg to probably almost

1. Oh well... maybe someday I'll buy an EFI car for my rolling hangar... :)

-Cory

--

• The prime directive of Linux: *

• - learn what you don't know, *

• - teach what you do. *

• (Just my 20 USm$) *

Thanx for the nfo! I'll print it out and stuff it in my Chiltons. Any idea if I can still get service parts for it; gasket kit and such? The (more or less worthless) local Subaru dealership denies that such a thing even exists :-P Hope I decoded your email correctly!

ByeBye! S.

Steve Jernigan KG0MB Laboratory Manager Microelectronics Research University of Colorado (719) 262-3101