Jump to content


Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse
 

Photo
- - - - -

(Crazy Idea thread) What'll happen if...


  • Please log in to reply
64 replies to this topic

#26 fbh

fbh

    USMB is life!

  • Members
  • 162 posts
  • Auckland

Posted 21 February 2006 - 02:25 AM

Drat.

Just came back from a 2-hour greasemonkeying with the car - sad to say that putting two carbs on is pointless. The ports are the same size as the manifold vent, the only limiting factor is the carb throat.

Might as well just slap a big Weber on...

#27 Phizinza

Phizinza

    Yip yip

  • Members
  • 3,867 posts
  • South Australia

Posted 21 February 2006 - 02:34 AM

yeah, thats what most people do. Theres prolly a good reason for it (I think you just found it.)
Really the only reason you would do this is because it would be super cool and almost a one of a kind. Maybe some time in the future I might do something like this just for kicks.

#28 fbh

fbh

    USMB is life!

  • Members
  • 162 posts
  • Auckland

Posted 21 February 2006 - 02:38 AM

heh, I might just still do it for kicks - just need to get the facilities, because right now it seems it's going to be too hard to make a pattern to build a new intake from.

Oh, another interesting note. Idle speed without airbox: 1700rpm. Idle speed with airbox and filter: 500rpm.......

#29 VaporTrail

VaporTrail

    Brattitude Adjustment

  • Administrator
  • 11,152 posts
  • Central Iowa

Posted 21 February 2006 - 03:21 AM

use smaller carbs, the stock carb is designed and jetted for a single carb on a 4 cyl engine, 2 carbs of that size will have great topend but suck at throttle opening and midrange. my 2 cents


exactly. I had a Holley 600 cfm 4 barrel on my '82 Brat (with built engine and exhaust). had to be extremely careful at throttle opening, or it would bog down, but once it got to about 2500 rpms, and kept it above that mark, it was awesome.

#30 Phizinza

Phizinza

    Yip yip

  • Members
  • 3,867 posts
  • South Australia

Posted 21 February 2006 - 03:26 AM

Oh, another interesting note. Idle speed without airbox: 1700rpm. Idle speed with airbox and filter: 500rpm.......


Most likely from all the sensors in the airbox making the idle lower. Or you have a really stuffed air filter. It should idle around 750 to 850 I would think. My dual carb EA81 idles at 1300 :-\ at 14 degrees before TDC.

#31 fbh

fbh

    USMB is life!

  • Members
  • 162 posts
  • Auckland

Posted 21 February 2006 - 03:41 AM

quick Q: is there anything wrong with having really long drive belts? Figured if I could somehow relocate the alternator way off to the side on the other side of the engine bay I'd be able to fit two carbs on there much easier someday.

Might need to make hood scoops for it though, they'll be moved out from under the "power bulge" on the hood and the "studs" on top might just hit the hood...


EDIT: heh, an EA82 cruising along with dual, actually effective, hood scoops... heh :)

#32 Phizinza

Phizinza

    Yip yip

  • Members
  • 3,867 posts
  • South Australia

Posted 21 February 2006 - 06:08 AM

quick A: Longer will strech more and are more likely to break. But not too much more likely. You may need to have it pulled tighter or it may slip.

HOOD SCOOOOOOOPSS!!! :D I wanted on for my ute, but never got around to making my custom airbox or addin a turbo.

#33 fbh

fbh

    USMB is life!

  • Members
  • 162 posts
  • Auckland

Posted 21 February 2006 - 06:10 AM

LoL, wonder what'd happen if you took one of those rather massive Edelbrock carbs and shoved it on an EA82...

#34 Loyale 2.7 Turbo

Loyale 2.7 Turbo

    The Mighty "BumbleBeast"

  • Members
  • 5,661 posts
  • Roatán, Honduras.

Posted 21 February 2006 - 10:55 AM

Hi Guys! :)

I think the Dual Carb question in a EA 82 is perfectly Possible, but is a Lot of Work. I know that the Performance will increase a lot over the single Hitachi carb. But first of all, you must know that the Dual Hitachis really means Dual Troubles.

I will sugest to Use the Weber 32/36 DEGV instead of a Dual Hitachi craps.

I own a EA82 since 1985 (Well my Dad, since I was Kid) and Now it´s "Weberized" and is a Whole World Appart in better Performance than the CrapTachi. But I think just only one Weber is enough. but if you still want to put dual carbs. in a EA82, I must tell ya: "Go Weber" and trow away the Hitachi.

Also, you must visit this Site:

http://ramengines.com/_wsn/page2.html


They made custom manifolds for Subaru Engines. this Pic. is for the EA81 with Dual Intake Ports and Molded Manifold. (Also: Forget the Craptachi too):


Posted Image

And this is a Dual Mikuni Carbs Subaru EA81 (Forget Hitachi Too) Maybe they can help you.

Posted Image


So, I sugest to Use Dual Webers, it would be Fantastic! but the Performance gain over just one Weber is just -only- a Little Bit. maybe dual carbs means dual troubles; but forget about it. If you want it, you must Try it. Maybe it is a good idea to the EA82.

Send us Feedback about it.

Bye... :)

#35 mbrickell

mbrickell

    USMB is life!

  • Members
  • 189 posts
  • Kansas City

Posted 21 February 2006 - 09:10 PM

Anything with dual carbs has to have the carbs synched pretty well or will run like poo

They make special tools to synch carbs, i.e. the old mercury kind, etc.

Cool idea.

#36 DJtheGOD

DJtheGOD

    USMB Regular

  • Members
  • PipPipPip
  • 56 posts
  • Raetihi,NewZealand

Posted 21 February 2006 - 10:42 PM

go with the twin carbies just BECAUSE no other reasons and while your at it put twin exhaust on it so that it breaths real easy..
My project '86 RX Ute(was one a Coupe) will have twin exhausts up the back of the cab(big rig style) and I intend to flick the turbo and install a supercharger why BECAUSE I CAN thats why no other reasons

#37 Ross

Ross

    Can't be bothered

  • Members
  • 1,865 posts
  • Christchurch, New Zealand

Posted 21 February 2006 - 10:58 PM

Something to consider:

It was mentioned above that the intake runners should be short as possible - its not quite that simple. If all you're worried about is high rpm performance, that is the case, but you will be sacrificing low end performance, something most ea81 drivers arn't willing to do.

NZers, do a google search for Sub4, they do similar stuff as ramengines (4 port dual spark heads, dual carb manifolds, injection manifolds etc) - somewhere in the North island i think.

#38 GeneralDisorder

GeneralDisorder

    Elite Master of the Subaru

  • Members
  • 20,280 posts
  • Portland

Posted 21 February 2006 - 11:06 PM

You guys should do some more research - all this has been done by Subaru, and the pics are right here on our own site:

http://ultimatesubar...trudy/rudy.html

GD

#39 Ross

Ross

    Can't be bothered

  • Members
  • 1,865 posts
  • Christchurch, New Zealand

Posted 21 February 2006 - 11:17 PM

You guys should do some more research - all this has been done by Subaru, and the pics are right here on our own site:

http://ultimatesubar...trudy/rudy.html

GD



Yes, but the chance of finding those parts (twin carb setup with no crossover) in New Zealand is almost zero.

#40 Scott in Bellingham

Scott in Bellingham

    Lets go wheelin!!

  • Members
  • 3,614 posts
  • Bellingham

Posted 21 February 2006 - 11:19 PM

Im very interested in this project , myself I have a Alluminum foundry and would like to cast a manifold with twin carbs SJR

#41 GeneralDisorder

GeneralDisorder

    Elite Master of the Subaru

  • Members
  • 20,280 posts
  • Portland

Posted 21 February 2006 - 11:26 PM

Yes, but the chance of finding those parts (twin carb setup with no crossover) in New Zealand is almost zero.


The point is that it can, and has been done. The twin carb setups are not actually all that rare, and even in NZ, I'm sure you have places that import used Japanese engines. That's where people in the US have found dual Hitachi setups.

Frankly tho, if you have any fabbing skills, it's not all that hard to cut plates for the head intakes, and carb base, and braze or weld on some tubes in-between, and nipples for the coolant cross-over. Dual carb theory is the same as it is for any of the VW flat fours, so there's plenty of reading material at your local library.

The problem is.... the head castings for the EA81/EA82 carb/spfi engine's don't flow well. This is fixed one of two ways - forced induction, or different/modified castings. If you can TIG alum. then you can do exactly what SUB4 does, and dual port the stock heads. Just bore into them, and weld in some tubes for intakes. I'll do it myself if I ever have the money for a decent TIG box.

GD

#42 fbh

fbh

    USMB is life!

  • Members
  • 162 posts
  • Auckland

Posted 21 February 2006 - 11:34 PM

I've done a fair bit of digging around under the hood - if anyone can slide me a technical drawing of the EA82 (inc. heads) and the intake manifold's carb base then I think I'll be able to draw us up a plan for a manifold, incorporating coolant, vaccuum lines, inter-carb linkages etc.

this sound like a good plan to anyone?

#43 Ross

Ross

    Can't be bothered

  • Members
  • 1,865 posts
  • Christchurch, New Zealand

Posted 21 February 2006 - 11:40 PM

The point is that it can, and has been done. The twin carb setups are not actually all that rare, and even in NZ, I'm sure you have places that import used Japanese engines. That's where people in the US have found dual Hitachi setups.

Frankly tho, if you have any fabbing skills, it's not all that hard to cut plates for the head intakes, and carb base, and braze or weld on some tubes in-between, and nipples for the coolant cross-over. Dual carb theory is the same as it is for any of the VW flat fours, so there's plenty of reading material at your local library.

The problem is.... the head castings for the EA81/EA82 carb/spfi engine's don't flow well. This is fixed one of two ways - forced induction, or different/modified castings. If you can TIG alum. then you can do exactly what SUB4 does, and dual port the stock heads. Just bore into them, and weld in some tubes for intakes. I'll do it myself if I ever have the money for a decent TIG box.

GD


Yeah i know you can easily get the standard dual carb setup, but thats not what they are talking about.

I really doubt that it would be worth modifying the standard heads to be four port - heaps of prototyping and flow bench work (unless you have access to CFD software??) would be needed to get satisfactory performance.

Sub4 offers their (proven) parts so cheap it seems a waste of time to me.

#44 Ross

Ross

    Can't be bothered

  • Members
  • 1,865 posts
  • Christchurch, New Zealand

Posted 21 February 2006 - 11:44 PM

I've done a fair bit of digging around under the hood - if anyone can slide me a technical drawing of the EA82 (inc. heads) and the intake manifold's carb base then I think I'll be able to draw us up a plan for a manifold, incorporating coolant, vaccuum lines, inter-carb linkages etc.

this sound like a good plan to anyone?



Yeah, thats the way, shouldn't take too long if you're using a 3d package like solidworks/inventor.....

Doubt you're gonna find someone with pre drawn plans tho...... You might have to get the vernier out!

#45 fbh

fbh

    USMB is life!

  • Members
  • 162 posts
  • Auckland

Posted 21 February 2006 - 11:46 PM

from taking off the manifold yesterday I saw the port in the head is pretty much adequate to feed the cylinders. Remember, only one cylinder at a time will be sucking through that hole, and unless you get some radical new cams, that hole will pretty much be sufficient.

The hole itself is about 1" to 1.5" in diameter at a guess. However, the main barrel of the Hicrappy carb is 0.75" or so - probably even less:banana: so in the end, the idea is to double-up the carb to allow the thing to run more freely - and on top of that, to just be able to say "I did this" :D

#46 fbh

fbh

    USMB is life!

  • Members
  • 162 posts
  • Auckland

Posted 21 February 2006 - 11:50 PM

Doubt you're gonna find someone with pre drawn plans tho...... You might have to get the vernier out!


Oh hell, with my in-chiropractic-progress back? gonna be murder :banghead:

very interesting thing just came to mind. At university, we have a machine that can "print" 3D shapes. Forgot what they call it, but you can basically create a 3D object straight out of Solidworks. ABS plastic. Hmm, anyone up for a plastic manifold? :grin::grin:

#47 mortimc

mortimc

    USMB Regular

  • Members
  • PipPipPip
  • 40 posts
  • Bellingham

Posted 22 February 2006 - 12:07 AM

Fused Deposition Modeling (FDM) You can use is to make a mold if you know anyone who can do sandcasting. We've used this process at the Vehicle Research Institute at WWU to make intake runners. Worked well...

Clayton
Bellingham


#48 Phizinza

Phizinza

    Yip yip

  • Members
  • 3,867 posts
  • South Australia

Posted 22 February 2006 - 12:16 AM

The point is that it can, and has been done. The twin carb setups are not actually all that rare, and even in NZ, I'm sure you have places that import used Japanese engines. That's where people in the US have found dual Hitachi setups.

GD


As said before we are not talking about a normal dual carb setup like I have. We are talking about two carbs, one of each head. If you had read all the replies it might of helped, but I forgive you. Theres so much to read on this forum it just gets nuts.


back on topic. well, not quite.
http://www.sub4.co.n...25hpengine2.jpg
if you look at that (the Sub4 dual port heads) running twin manifolds and two throttle bodies (its a EFI engine.) you may get an idea what has been done. I still think smaller, shorter manifolds would be better.

It was mentioned above that the intake runners should be short as possible - its not quite that simple. If all you're worried about is high rpm performance, that is the case, but you will be sacrificing low end performance, something most ea81 drivers arn't willing to do.


I don't see a point in going to dual carbs unless you are just after high RPM. My car is just as slow as a normal EA81 down low. It only gets into its own when I get to 3500RPM really. It might have 5 more hp then a stock one below that RPM. So that said, I think we're only after high RPM power here. (which I must say, is awfully fun when I get to 6500RPM and it keeps going easy. And the sound:slobber:....)

#49 Monte

Monte

    USMB Regular

  • Members
  • PipPipPip
  • 76 posts
  • Bellingham

Posted 22 February 2006 - 07:34 PM

I've run dualies on VW's before, not a big deal. Run the throttle cable to one carb (master) and run linkage to the other (slave). There's a tool used to balance them, basically you adjust the throttle linkage to the slave carb to open or close the throttle and get a reading on the intake air flow and make them match. There wasn't any balancing piping or anything like that. The carbs were small so the mileage didn't suffer, but you still get more flow and power.

Monte

#50 fbh

fbh

    USMB is life!

  • Members
  • 162 posts
  • Auckland

Posted 22 February 2006 - 07:51 PM

hmmm... any idea where I could get my hands on such a tool, or how I could make one myself?




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users