Improving EA-81 performance

[casm]

Let me start by saying that I've read through a number of the threads regarding EA-81 performance upgrades, and they've pretty much left me thinking that trying to improve on what I've got currently in my '86 Brat may be something of a dead-end. Having said that: what I want to accomplish is better pull through the gears (particularly on long hills on the Interstate), not faster off-the-line acceleration or a higher top speed.

 

The Weber carb conversion looks like the most expedient way to (possibly) accomplish this, and by 'expedient' I mean 'bolt on'. However, having gone through some of the recent threads it sounds like it mainly improves on low-end torque - a part of the rev range I'm not exactly sitting in when I want to get back up from 60mph to 75mph in 4th gear. My federal-spec Hitachi does OK in this regard on flat ground, but forget about it on inclines.

 

Given what I want to accomplish, what are my reasonable options? The Y-pipe and cat were just replaced with stock parts and I don't want to do an EJ swap; it's a level of complexity and downtime that just isn't something I want to get into. Is the Weber swap the best bet, or are there alternatives I haven't considered yet?

 

I'd really like to graft on a small supercharger, but again: complexity and downtime.

Edited September 2, 2009 by casm

[renob123]

Have you thought about a transmission swap? I'm sure someone will come in and correct me, but if the 60-75 mph acceleration is what you want, then a shorter 4th gear from a 5-speed might help. I know on my Brat with the 4-speed, 3rd is too short, and 4th is too long around that speed.

 

Jacob

[casm]

Have you thought about a transmission swap? I'm sure someone will come in and correct me, but if the 60-75 mph acceleration is what you want, then a shorter 4th gear from a 5-speed might help. I know on my Brat with the 4-speed, 3rd is too short, and 4th is too long around that speed.

 

Thought about it, but parts availability, complexity, and downtime come into the equation again. Right now the Brat's my only running driver, and I figure I can do the Weber swap on a quiet Saturday, then tweak it Sunday and still drive it on Monday without too much hassle. Not to mention that I've got a fresh clutch and good synchros all around on my 4-speed, so there's really no reason to change it out. I do agree with you in theory, though, and the deeper low range would be nice.

[GeneralDisorder]

You aren't going to get what you are after without *more* than just a bolt-on. You might gain a little bit with the Weber and adding a free-flow muffler but you will probably be dissapointed with the cost/benefit ratio in the MPH/RPM range you are looking for extra performance in. The engine simply doesn't have it - you have 74 peak HP to work with and you aren't going to change that apprecieably with a carb swap.

 

I have a 90 HP EA82 (SPFI) in my Brat and it's like a completely different car - it's actually a bit scary how much of an increase 16 HP really is on these light body's. A Weber isn't even going to give you that - *maybe* 5 HP - but probably more like 2. Mostly people do it for the low-end throttle response - and there's a lot to be said for it - you can easily chirp the tires going into 2nd with a Weber - hard to do with the Hitachi due to the vacuum secondary. And it's done for the reliability and ease of maintenance of the Weber - which beats the stock carbs hands down every day of the week.

 

But really I don't think you are going to find what you want. You are asking too much for too little work. If you want the HP then you'll have to put a bit more time and effort into it or just buy a 2.2 Legacy wagon and park the Brat. The mileage is almost as good, the cargo room is better, and if you stop at a rest area you can actually recline the seat....

 

(not dogging the Brat - I own an '85 - but I stopped using it as anything more than a restro-project and weekend driver years ago. EA81's in large measure do not make good daily's).

 

GD

[casm]

You aren't going to get what you are after without *more* than just a bolt-on. You might gain a little bit with the Weber and adding a free-flow muffler but you will probably be dissapointed with the cost/benefit ratio in the MPH/RPM range you are looking for extra performance in. The engine simply doesn't have it - you have 74 peak HP to work with and you aren't going to change that apprecieably with a carb swap.

 

This is pretty much the conclusion I was coming to, unfortunately.

 

(not dogging the Brat - I own an '85 - but I stopped using it as anything more than a restro-project and weekend driver years ago. EA81's in large measure do not make good daily's).

 

Yep. They just don't suit modern traffic conditions well, even where I am. The third car idea is looking more and more like the way to go (or selling the Jeep and sticking to two cars, but I know that's never going to happen).

[spikedbeetle]

I heard there was a dual carb version of the ea81. I don't remember where I saw or heard about them, but supposedly the intake manifold would need to be replaced along with the carb. I also heard those engines put out closer to 100hp.

 

I will try to find this info again and post it. It shouldn't be much more difficult than a weber swap.

[spikedbeetle]

There is some info on this site if you search for it. I looked through some of it. I may not be the answer, but it wouldn't hurt to look.

[hatchsub]

I am interested in the same thing and have done enough research to agree with GD lol. The weber and the exhaust is what i have on my sedan and while it does make a bit of a difference, it really is not what you will be looking for. I gained maybe 5 horse at most with the exhaust and the weber.

 

As for the mention of the dual carb..that is a JDM motor. It had different heads, cam, and the dual carb intake. It was rated at around 105 horse or so. The intakes do come up for sale every once in awhile but the heads and cam are impossible to find. There is some debate however as to how much gains there are with those heads. I was speaking with the guy that owns Stratus engines (builds airplane motors out of EA81s) and he said that those heads are only good at the top end and in fact you will lose low end using them (surprised the hell out of me). His advice was to port the hell out of the big valve (hydro) EA81 heads and get a performance grind cam. Those and a .030 shave of the heads and you would be making good power. And yup thats what im going to be doing when i get the money. Oh and the SPFI pistons.

[SueBee2]

Yep. They just don't suit modern traffic conditions well, even where I am. The third car idea is looking more and more like the way to go (or selling the Jeep and sticking to two cars, but I know that's never going to happen).

 

I guess it depends on where you live.... I have a 2010 Forester and most days it sits in the garage and my '82 Brat is my daily driver! That's small town living...

[backinbrat]

you need to remember about that lost power as well, mine was 14 years old when it went on the dyno last year, it produced 69 hp and 100lb/s torque and only having a K&N and cherry bomb, so you just adding bits to get your power back as it was to standard, maybe trying to restore that power you could do such a thing as heads off, give them a good clean up, polish up the valves, its all somin you can do yourself, and get the heads skimmed, bring up that compression a bit, also ported as well if you fancy it.

 

then tune the weber a tad richer, and you should be away for quite a bit more

 

and as said before, get a cam grind, but then you might as well go the whole hog and do the bottom end as well, which is what i ended up doing!

 

or you could do the really expensive thing and get some dual ports thats what i ended up doing!

[casm]

you need to remember about that lost power as well, mine was 14 years old when it went on the dyno last year, it produced 69 hp and 100lb/s torque and only having a K&N and cherry bomb, so you just adding bits to get your power back as it was to standard, maybe trying to restore that power you could do such a thing as heads off, give them a good clean up, polish up the valves, its all somin you can do yourself, and get the heads skimmed, bring up that compression a bit, also ported as well if you fancy it.

 

Good point. I really don't want to go all-out on it, but rebuilding the Hitachi, replacing the coil, cap, and rotor, and running a couple of Seafoam treatments through the intake and crankcase have substantially restored the lost power. The butt dyno says it's about stock at this point, which is fine in terms of lugging it along.

 

The more I think about it, the more the 5-speed swap looks like what I need. My main issue is with the gap between 3rd and 4th - 3rd is too low on a lot of the hills around here, and 4th is too high. Dropping those two down a bit should let me maintain 70mph on the uphills, which is what I really want: getting passed by semis because I'm stuck in 3rd at 55mph on an incline is getting old.

 

I think that part of it is that my first Brat spoiled me - it was a non-US-model MV that I owned in the UK, and running 90bhp in that one vs. 73bhp in the past couple I've had here set some expectations that I know won't be met.

[backinbrat]

I think that part of it is that my first Brat spoiled me - it was a non-US-model MV that I owned in the UK, and running 90bhp in that one vs. 73bhp in the past couple I've had here set some expectations that I know won't be met.

 

ah you see, this is the thing, the UK ones i did think ran higher horsepower, like 85 standard or somin, i put it down to low octance being 95 here and high octance being at the most 99, and us is like 87-92 (i dont know, cause i dont live there!) so when i have seen factory figures saying below 100lb/s torque, its like AY?! but i got 100 and its detuned over time anyway! lol

 

put some race fuel in it, that will sort it! lmao!

[carfreak85]

and as said before, get a cam grind, but then you might as well go the whole hog and do the bottom end as well, which is what i ended up doing!

 

or you could do the really expensive thing and get some dual ports thats what i ended up doing!

 

Go on... Used aircraft parts? SUB4 perhaps?

[GeneralDisorder]

Highest HP stock EA81's were the JDM and EDM dual-carb engines - they were 108 HP - such as found in the EA81 RX coupe's and the EA81 SRX hatchback's.

 

Best in the US market was the MPFI Turbo EA81 at 95 HP.

 

GD

[backinbrat]

Go on... Used aircraft parts? SUB4 perhaps?

 

lol, errrm, maybe....cam as well, lightened flywheel perhaps, maybe some twin 40 IDF webers.....

[bobjr94]

I put an ea81 dual carb setup on a ea82 and it didnt make much difference, I would expect similar results on an ea81 unless you get better exhaust and maybe a cam regrind. It just took more work since it had a manual choke.

 

I put a 5 speed in my ea81 brat, made it seem faster. No running up hills at 4000rpm in 3rd or bogging down at 1600 in 4th. The next step is fuel injection off an ea82. People say it ads some power and they run alot better.

[spikedbeetle]

My brother and I just completed our subaru to VW swaps. His engine is an all subaru EA81 solid lifter engine. Mine is a hydraulic lifter EA81 with dual carbs and a "tuned" exhaust. (both my own setup) His feels like a good daily driver. Mine can do donuts, gives a lot harder kick in the seat, and will leave a lot more rubber on the road.

 

http://www.ultimatesubaru.org/forum/showthread.php?t=103498

[vagen]

I wonder what a set of mpfi pistons would do for the EA81 after all the EA82 MPFI has 9+:1 compression. it would have to help hill climb power.

[coxy]

You are definately on the right path regarding compression ratio,stock is old school low,this is to our advantage though.Compression ratio increase between say 7:1 and 11:1 is a range suited to street use depending on head design and propensity to detonate or pink (pre ignition)

The beauty of stock Subaru compression ratio is it is in the range of best returns.

If you increase your compression ratio from 8.5:1 to 9.5:1 the percentage change in comp is basically what you will see in torque increase.

Ten percent more comp basically relates to ten percent more torque and it is torque that makes you accelerate and lets a vehicle pull top gear useably up an incline,good also for fuel economy.

Above 11:1 the linear rate of returns drops away when increasing comp and actually slows down the ability to rev responsivley up high.

Things such as porting and camshaft swaps are all about improving cylinder filling which will increase effective compression ratio as well as giving more oxygen density to which you can add more fuel to make more power.

MPFI pistons and a light head skim will work wonders for engine response.

[backinbrat]

My brother and I just completed our subaru to VW swaps. His engine is an all subaru EA81 solid lifter engine. Mine is a hydraulic lifter EA81 with dual carbs and a "tuned" exhaust. (both my own setup) His feels like a good daily driver. Mine can do donuts, gives a lot harder kick in the seat, and will leave a lot more rubber on the road.

 

http://www.ultimatesubaru.org/forum/showthread.php?t=103498

 

This has got me very interested, i like the carb ideas, thats somin i thought of before, but what do you do with the water system, where have you put the thermostat and temperature guage sender? or did you buy somin or cut one off somin?

 

i really like this idea, lots of fuel and air, its gonna give you some more ooomph! can you put a vid on youtube? my computer went spastic over photobucket!