Subaru 2.5 Carbed???

[dae]

Does anyone know somebody producing a carbed intake manifold for the 2.5 Subaru? Thanks, David Eiland

[KenSandyEggo]

Do the old RAF carb manifolds for the 2.2 fit the 2.5 or are they different animals?

[mceagle]

The standard Subaru multipoint injection and ignition system is worth about 20 hp over a carby and distributor. (and is far more reliable). Why would you want to step backwards?
When RAF changed from their home made manifold with carby to a fuel injection system, they claimed that they had gained an extra 15 hp. In fact all that they had done was to bring the engine back to the origonal hp that it had before they had tampered with it.

[Aussie_Paul]

Tim, when I changed my first Raf, to ecu driven m/point Fuel and ignition, I picked up between 80 to 100 engine rpm. I had not changed anything else. How many HP would that be I wonder? :confused:

That, with a 20% decrease in fuel consumption without carby ice problems, was a win, win, win situation. :D

Aussie Paul. :)

[dae]

I appreciate all the info but I have been flying an 2.5 EFI engine and I have specific reasons for going to a carb. So.... I still want to find out if someone makes a manifold for it. Ken the 2.2 manifold is more narrow than the 2.5.
I believe there is NO way you get 20hp going to the EFI engine. The advantage is fuel savings but I believe there are a heap of disadvantages to. I have had 2.2's carbed and EFI and just like Paul says the difference is about 100 rpm at best.

[mceagle]

The only disadvantage that I can think of with EFI is the initial set-up cost. Often this is minimised if the origional computer is purchased with the engine. I have heard of a few unhappy customers but without exception it is a result of poor installation and set-up.
You only have to set up an exhaust gas oxygen sensor and a readout to find out the reason why EFI is more efficient and delivers more power than a carby. (100 rpm at the top end certainly equates to considerably more power). Purely by design, it is impossible for a carby to deliver the correct air-fuel ratio all the time.

[Aussie_Paul]

That's the way I see it too Tim. 100 rpm is considerable at that end of the scale.

Aussie Paul.:)

[Russell]

Some people just like the simplistic of the carb / distributor set up.
I agree the FI is the way to go until you have a problem with it. A gyro is a little different that a car as some sensors are not connected. I.E speed sensor. ect.
Russ :D

[Harry_S.]

David:

Might I suggest you contact Maxie Wilde or Curtiss Patten; ref. carb. manifold.

[dae]

Will do Harry. Thanks! David

[jos]

Hello,

An ej22 with a 2.25 reduction drive producing 130hp at 5300 rpm,produces 137.8 hp at 5400 rpm.
The last 100 rpm give in this senario 7.8 hp.
The finer tuning of the efi systems is not responsable for the extra 7.8 hp.
The efi systems go at max engine load rpm combination into a richer adjustment regardles the oxigen sensor.
This is to protect the engine.
A carburetor setup can easily be set to the same values.
The main difference is the better airflow in the manifolds for the injection system.
If one puts the same effort in the manifold design as the engine maufacturer did the engine puts out the same power.
If one puts the correct effort in the manifold to design it to fly a gyro the engine 'll put out more power.
Power only comes from the combination fuel air not from electronics.
If you want more power you need more oxigen or air.


JOS

[mceagle]

JOS,
You are right about the the increased air flow as being a big factor in the increased hp. However the fuel mixture also plays a big part (assuming that it is properly set up).
EFI can be set to deliver a stoichiometric mixture of 14.7 to 1, at all RPM and load settings, something that a carb cannot do. It is the principle of the carby where it falls short. It must have a comparitively small throat, partially restricted by a venturi, to create enough reduction in pressure to "draw" the fuel out through the discharge tube. Though the mixture can be set for max efficiency at a certain RPM, it will still not approach 14.7 to 1 because they have to be set too rich to compensate for many of the other variables that can not "programmed" into a carby.
I have got to admit though that a good carby does a good job of making engines run as well as they do.
Even going from throttle-body injection to multi-point injection delivers a worthwile increase in power.

[automan1223]

The new generation 2.5 sohc engine has ports that are considerably larger than the earlier ej engines. NO ONE currently makes one for a 2.5. I building one for my engine. I will let you know how it works out.

I have a raf intake manifold. It is not a max effort design and is built to be compact and inexpensive. It does not have a smooth path to flow to the intake ports of the head. Since it is a low profile manifold the air has to make a sharp bend to enter the cyl head. Maxie and others have made taller manifolds with smoother bends. While this aids airflow 100 rpm can be blamed on fuel tuning, ignition timing and air cleaner placement. The efi is a much better setup if you are going to fight cold mornings. then plan on long warm up times and poor driveability. The simplicity of a carb cannot be beat. But it DOES REQUIRE proper set up.

After I spoke with RAF their usual suggested jetting of the carbs was off by 5 jet sizes when I finally had mine dialed in. You must put in the time to set your engine combo up or you will blow it up or have poor performance.

Jonathan