EA81 Performance - The intake manifold

[RAD]

I have come across one really promising possibility for improving the performance of the EA81 engine.
I came across a video for an excellent example of multiple possibilities, taking lemons and making lemonade.
- This may not be an original idea, but nobody has suggested in in any of my posts for improving performance.
It is a worthwhile concept that can be done better and improved on, which makes it worthy of serious consideration.
Why? One performance mod that can have more than one performance improvement and adaptation!

Youtube Video Link:
"POV Drive 1985 Subaru Brat"

In the above video, you'll see someone taking an old, beat-up, poorly modified Brat for a drive.

A little over 5 minutes into the video, after the drive, they look at the engine and discover that the intake manifold had been modified, eliminating the coolant flow through the intake manifold.
(1) This was done to eliminate the extra heat of the hot water going through the intake manifold, and possibly other reasons.
(2) They figure this leads to the engine over-heating, and find an oil cooler under the front bumper to compensate for this.

Looks like a second-rate screw-job, doesn't it?

The guy had the right idea, but didn't take it far enough.
Instead of just bypassing or blocking that coolant flow through the intake manifold, and having to compensate elsewhere, take it and run with it! If you have to compensate, then rather than just blocking it, use it! Re-route it!
I have seen elsewhere where someone custom-fabricated adapter plate(s) at the base of the manifold, to divert the coolant flow. This can be re-routed to a small secondary radiator, possibly using an oil cooler or a transmission cooler.
Right there, two benefits - the manifold runs cooler, allowing for colder, denser air through the manifold, and also adding more cooling capability in general.
If one is going to do various things to improve performance, and is going to be running the vehicle/engine hard and hot, you might want some extra cooling anyway. There is probably more than one way to do this, maybe an easier way.
Combine this with an over-sized intake manifold, and you have something. While at it, one could also do other things, like smoothing/polishing the inside for better gas flow, there are other improvement that could also be made as well.
The intake manifold, at least the stock version, is not hard to find, not very expensive to buy a second used one, is easy to get at and change-out, being right on top of the engine.
The only issue is the modification itself, and if you are working with an inexpensive used part, time involved in modifying it somehow is not an issue.

Now that I have found this, I am a believer! This is worth doing! as inexpensive and convenient as it is, one could afford to buy more than one and feel free to experiment with more than one modification, or even making the adapter plate as one guy did.

Here is a more extreme modification of a 1.8L engine/intake manifold where he made such an adapter plate:

http://bb.bbboy.net/vwengineconversions-print?forum=8&thread=82

 

http://i148.photobucket.com/albums/s6/brentwulf/SubaruSwap005.jpg

He did this because he came up with his own way to mount dual carbs.
I may not want to mount dual carbs, but the coolant re-routing he did is key to what I am getting at.
If he could do that, the way he did, then it leaves the door wide open for a completely re-designed intake manifold, like those Webber performance Intakes I have seen, which I would guess are very hard to find, and possibly not available for the EA81, but if they are, still, they do not necessarily have the coolant re-routing.
Instead, a person could fabricate something similar, with a better design and flow of fuel, using mostly just aluminum tubing.

This has now taken priority in my thoughts of what I can do for various performance mods, because I can get more than one improvement or result from one inexpensive, small, simple, easily accessed or replaced part of the engine.

Also, to get down-right extreme about it, one could also rig up a small, separate cooling system specifically for the intake manifold using the manifold's already existent coolant passage(s) that use cool water, not the hot water from the radiator/cooling system. Yes, sounds a little complicated, but not too much, and still better than replacing half the vehicle!

 

[RAD]

The more I think about this, the more I am realizing that for the EA81 (Brat), this could be the very key to higher performance!
The intake manifold has a whole lot to do with fuel flow, air flow, etc. If one was to use Nitrous Oxide, then that also could or would be routed somehow through the intake manifold.
Making/allowing for cooler, denser airflow, polishing the inside for fuel flow, re-routing that part of the cooling system, adapting for dual carbs if wanted, adapting to use one or two super-chargers, with a customized manifold, allowing more flexibility in how and where things are mounted, how much and what would be coming up through the hood.
The intake manifold may be the very heart, overlooked and underestimated, of the engine and vehicle, and thus could be the proper focus for various performance improvements. I think I have found several of my answers in one, small, inexpensive, easily accessed, changed, experimented, or played-around with engine part! I am now re-inspired with the answers and possibilities now available to me!

[GeneralDisorder]

Besides the obvious carb icing issues in cold climates, reducing intake temps will yield performance gains that likely would not be measurable on a dyno or at most generous may show a 1 HP gain. Yes the intake gets hot, but the air flowing through it at WOT will not heat up very much as its transit time is quite short. On an engine already making 300 HP with a turbocharger (exhaust driven induction heater) this might be worth 5 HP. On an EA81 it will just cause carb icing in the winter which will reduce performance by enriching the mixture till the exhaust catches fire..... B36 bomber style.

 

GD

Edited February 26, 2017 by GeneralDisorder

[tweety]

Hi, l got an auto email about this. I no longer have my ea81 nor my trike.

 

After all the work on my ea81, fabricating a manifold and setting up a sc12 SC with dellorto carb...l wouldnt do it again

It was impossible to tune and drank fuel worse than a big block chevy.

 

Sticking to the ea81 rather than an EJ does have advantages in that its simplistic, compact, no body mods etc. So in my view the spfi manifold with the 32/36 was the best move l made and 9,5:1 CR. I dont believe twin carbs had a much greater output and my set up was simpler. If you desire greater ouutput than what my set up Delivered then go EJ.

 

THATS A COMMONSENSE VIEW

 

Cheers

[GeneralDisorder]

Yes one of my guys has a an EA81 with SPFI pistons and a Weber. It's really quite a large performance increase over stock. The area under the torque curve is a gigantic improvement. It probably makes 80-85 peak HP but the lift to the torque curve on the low end is substantial. I wouldn't be surprised if it close to doubled it.

 

More than that - get an EJ. Unless you are prepared to spend years of your life learning about forced induction. Not even kidding. And doing forced induction with a carb..... besides being a waste of time, it's a whole different critter. You'll want to lookup such things as the Maserati Biturbo.....LoL

 

GD

Edited February 26, 2017 by GeneralDisorder

[ferp420]

I modified my intake on my ea82 i used spacers under the manifold to raise it up a inch then i added a spacer under the throtle body so the fuel had a chance to mix before turnin a hard corner i opened up the intake the best i could portin both ends leaing it ruff inside if its to smooth the fuel will colect on the walls of the manifold i blocked off coolant flow to the throtle body but not the manifold if the manifold is to cold the fuel wont mix well on a multi port injection setup like the ej motors have it dosent mater because the fuel is injectwd at the head with single port or a carb the key is keepin the fuel suspended in the air till it hits the combustion chamber the more efficiant you can do that the more power you will make There are gains to be had with the intake but unless the rest of the system isent upgraded you wont see any gains so after you upgrade the intake upgrade the ignition then port the heads and fab up a custom exhaust no one mod will make a big difference but all the mods together add up to about 25% more usable power by just getting the air in and out more efficiently and burning the fuel all the way

[GeneralDisorder]

For a carb setup you want the inside of the manifold to be ROUGH not smooth. This creates turbulence which better atomizes the fuel. Smooth surfaces cause smooth flow and allow the fuel to settle on the surfaces. For fuel injection you want smooth surfaces - the atomization is handled by high pressure injection forcing the fuel through tiny holes in the injector diffuser cap. Smooth manifolds allow higher velocity airflow because the turbulence isn't working against the direction of flow.

 

GD

[ferp420]

Link to my manifold thread

http://www.ultimatesubaru.org/forum/topic/150643-intake-and-throtle-body-spacers/

[86BRATMAN]

Blocking off those two tiny coolant lines will do nothing for performance. If you look at the intake manifold design you'll notice that the coolant crossover is cast together with the air passage. To get around this you would have to build a new manifold and coolant crossover, ram engines sells a manifold base plate with AN threads for coolant. You would need to figure out where to relocate your thermostat and how to plumb that in as well.

[carfreak85]

To piggyback off what GD said above:

 

On any engine in general, carb'd or fuel injected, you want to keep the intake ports a bit rough.  Not as-cast, per say, but not polished.  This is because of the boundary layer of turbulent air right next to the port wall that keeps atomized fuel from dropping out of suspension.

 

The exhaust ports in general, regardless of fuel delivery, may be polished to expedite the flow of the exhaust gas column.

[GeneralDisorder]

Right. Any area that doesn't touch fuel can be smooth. And newer stuff that's direct injected should be smooth everywhere but all that stuff is computer modeled and likely should not be touched. You can smooth out the interior of the manifold below the throttle body, etc if it's port injected. The head intake ports should not be too smooth.

 

GD

[RAD]

Hi, l got an auto email about this. I no longer have my ea81 nor my trike.

 

After all the work on my ea81, fabricating a manifold and setting up a sc12 SC with dellorto carb...l wouldnt do it again

It was impossible to tune and drank fuel worse than a big block chevy.

 

Sticking to the ea81 rather than an EJ does have advantages in that its simplistic, compact, no body mods etc. So in my view the spfi manifold with the 32/36 was the best move l made and 9,5:1 CR. I dont believe twin carbs had a much greater output and my set up was simpler. If you desire greater ouutput than what my set up Delivered then go EJ.

 

THATS A COMMONSENSE VIEW

 

Cheers

 

That, sir, is the most helpful reply I have gotten in several posts/questions I have submitted!

At least you meet me half way.

 

As I have stated, either here, and/or in other posts, the performance of my Brat is at about 80% of what I want. That is not too bad, not hard to improve.

A few tweaks or minor modifications WILL make a noticeable difference, this I know from my own personal real-time real-life experience with 5 Brats so far.

I do not need to build a race car, I need to have just a little more power on occasion, otherwise, My Brat with its EA81 has been a JOY to drive 80% - 90% of the time.

If anything, the other replies I keep getting from people trying to shove the EJ's down my throat is only convincing me more, as they are regular reminders of the difference between having a little fun doing a little this and that, one stage at a time, vs. the EXTREME, and yes, that is what it is, of swapping an EJ is just plain ridiculous!

I may not have the expertise preferred to do such a thing myself, I cannot find a mechanic worth a damn anywhere in my area at all, much less one I would trust working on my Brat (An older Subaru), and I cannot find anyone in the area who is a Subaru Freak I feel comfortable entrusting the work to.

The sole and only exception is a guy who works at a Subie dealership who I can tell knows what he is talking about, but he has no place to do the work, I have no place to do the work, and it would cost at least $2500.00 to do.

 

No. I defy all those who scream EJ ! I am not going to screw myself because someone else thinks they are the expert, when most cannnot even manage to answer the actual question or issue in the first place.

 

Any number of things CAN make enough of a difference to be worth doing without spending enough to buy another whole damned car!

 

In fact, if I were to go to that extreme, I would rather build a cross between my Brat and an XT I may have access to, so that I could maybe adapt its gas/air suspension to the Brat.

- Yeah, I know, that would open a whole 'nother can of worms with the "Experts", lol. I don't care!

 

I have owned a total of 5 brats, 7 Subarus in all, and I know what I know. I know where I like going with this, and where I do not want to go with this.

 

However, all things considered, the WEALTH of info you provided me and the community with your Trike project is PRICELESS! and I thank you for it all!

 

 

 

 

[tweety]

Well thankyou. Uskng the spfi manifold does increase the low torque a lot. The biggest isdue is making an adapter plate on an avute angle as the spfi manifold has duch an angle on it. I had one made from alloy.

 

Bear in mind that my trans on my trike was vw automatic 3 speed circa 1970. That robbed me of 14hp.

 

I have a long hill near my place in oz. It was a good gauge as to engine output. The new vw engine would flat out climb the hill in 2nd gear at 45mph. The supercharged version of the trike ea81 in top gear at 70mph, the spfi version 60 mph top gear. With a reconditioned engine bored to 1820cc with spfi manifold ...65mph with torque to spare in normal driving.top gear.

 

That compact easy to work on ea81 is a delight when in good nick. Use good oil and that spfi manifold you'll be happy.

[GeneralDisorder]

SPFI pistons with a Weber is the biggest and easiest performance increase that is viable on an EA81.

 

GD

[bratman2]

Does the SPFI pistons bump compression ratio up to premium fuel required level?

[turbosubarubrat]

Does the SPFI pistons bump compression ratio up to premium fuel required level?

The compression ratio is the same as a spfi ea82 which is something like 9.7 or 9.5 to 1.

[ferp420]

Your best cheapest performance mod is gona be a msd type ignition then you can eficiantly burn fuel then a spacer under the carb will alow the fuel to mix before it turns the corner makin the engine more eficiant porting the manifold will give you more available air when you crack open the throtle makin the manifold longer or shorter with change your powerband longer more low end shorter gives more top end you can build a 200 hp vw motor but you will have to increase the displacement to somethin like 2.1l on a subi you cant replace the pistons and barrels like a vw so your kinda stuck with your displacement give or take a few thousands if your only lookin for %10-%20 increase you can get that through efficiency the inturnal cumbustion engine only runs at what around %60 eficancy so there is wigle room to play with but even better plugs and wires add up in price high octain gas cost a bit more to your gona pay if your gona play the reason behind the whole ej swap is to incress the displacement givening the potential for alot more power and a more efficient set up so we dont have to spend weeks porting and polishings shaving laping and studying i think read every last web page out there on porting and engine performance before i started moding engines not to mention the years of college studying automotive related stuff's and working innthe field with the old timers so to brake itnback down if you want more power ether make the engine more efficiant or stuff fuel and air down its throut with a turbo or supercharger or get a bigger engine you only get the same three options everyone else gets no mater what engine your dealin with

[RAD]

At this point, with this present Brat, I may at some point be forced to do an engine swap. Cannot do that for now, just trying to bring it back to life, keep it alive.
Sooner or later when I get my life back, I will be looking for a second brat, and that one WILL be, and remain an EA81 engine, by damn!
I love that engine/design, lol...

[DaveT]

Keeping one original, is the best way to continue the simple reliability.

[RAD]

Where my issue was and is concerned, it has never necessarily been about turning my Brat into a race car.
I have made a post about "Hot-Rodding" my Brat. which means doing those things possible to improve performance overall, without replacing half
the vehicle, and where the EA81 engine is concerned, most of what can be done one way or another involves the Intake Manifold, thus this thread.

This subect/issue figures into my post/thread about respect for EA81 and performance, see my next post there for what I was tempted to type out here, regarding the EA81 vs. EJ swap concept and what is wrong with it.

[ferp420]

Just get a spfi system it will solve alot of your issues you can simplify the wirng down to just what you need to run the rig its a bolt on setup or learn carb and learn it good any change to the engine or manifold or exhaust will create carb issues  so basicly chang anything and your gona need to rejet the carb in order to know what jets to use your gona have to learn to read spark plugs rejeting the carb usaly means rebuilding the carb so get good at it learn all the air passages learn the idle system learn the main jeting system accelerator pump system the choke system the realy nice thing about fuel injection is it addapts to whats going on the computer makes changes on the fly so if you change you exhaust / intake or what ever the computer will make the nessisary adjustments a carb cant do that and you will get better milage and power because your running more eficiant the subaru spfi system is extremely simple and i bet some one on the forum would be able to turn down a wiring harness for you so your set up would be plug and play might take some convincing though enjoy and good luck