Impreza engine Query

[ianbott]

Can anyone tell me if it would be possible to skip the fuel injection on a scooby engine and convert it to run carbs, if so would there be any benefits or downfalls to this?
Thanks Ian.

[MadV]

Its possible but you would need an ignition ecu to run the coils/crank sensor/knock sensor and would have to be mapped on a rolling road. Twin downdraft 44's or 48's would do it. Not sure about the pro's and cons.

[ElusiveStranger]

Can anyone tell me if it would be possible to skip the fuel injection on a scooby engine and convert it to run carbs, if so would there be any benefits or downfalls to this?
Thanks Ian.

Why would you want to?

[MadV]

Why would you want to?

Why not?.

[the darkside]

down drafts in a van would be interesting:D

[ElusiveStranger]

Why not?.

Retrograde step really, isn't it?

[ricola]

it is possible to adapt a distributor from some particular older subaru version I believe but why bother, you will get infinitely better drivability and likely more power using what's there already...
Rich

[ianbott]

It was just a quick thought really, i wondered if it might be an easier conversion with less wiring but by the sounds of it, it'd be harder.
Oh and i really like carbs too!

[gingerbeetle]

you could go for something more in between like a weber alpha kit. i might be wrong, ive only read a lil on them

[wedgedout]

it's doable, but it's pointless.

You'd need to make a dissy of sorts, probably using old subaru stuff.. machine bits, fuck around with making manifolds etc.

For you bother, you'd get decreased fuel consumption, loss of drivablily, more restrictive air flow and you'd look a tool to anyone who can read a wiring diagram

You'd probably make less power too.

[ianbott]

Thanks wedgeout. thought there'd be a reason why it hadn't already be done.

[wedgedout]

Thanks wedgeout. thought there'd be a reason why it hadn't already be done.

No worries.

People are looking into doing it anyway, because some VW owners would rather stick with what they know... i.e. carbs and a distributor..

:confused:

Wiring and FI scares some folks, because they can't get their head around how sensors feeding back can effect things like fuel mixture.. once you understand what does what with FI, you can fault find as easily as with a carb/dissy car.. (seriously)

The main difference is, you can't really repair it at the roadside or "bodge it home" like you can with mechanical setups.

But it's a LOT more rewarding in terms of drivablility, fuel economy AND increased power, torque and useable, drivable power.

Trust me, it's well worth the extra bother (or lack of).

And with FI, it's fit and forget.. no constant tweaking. :)

[ianbott]

Very true abou the fit and forget, but am i right in saying SOME engines produce more power when using carbs?

[wedgedout]

Very true abou the fit and forget, but am i right in saying SOME engines produce more power when using carbs?


I can't see how that'd be possible to be honest.

Stock FI Vs Big Carbs.. maybe.

But there's not set of carbs in the world that can flow as much as as the biggest throttle body.

FI also allows much more wild cam profiles but because it's not struggling to provide fuel.. as it uses controled pulses rather than jets, it can make it much more streetable.

Hence TB's and FI being used in motorsports cutting edge, where carbs are now all but obselete

[rjes]

Assuming we're talking naturally aspirated here, wedgeout is right. The facrory injection system will be better in just about every way on an internally standard engine.
I have no doubt that you probably could tune a carb engine to give more peak power than the factory injection system, but to do so yould probably require swapping the cams too. This would almost certainly result in a more peaky torque curve and reduced driveability and would definitely give a considerable reduction in mpg. If you then fitted a mapable injection system the engine engine in place of the carbs and had it set up correctly, you coyld probably regain most of the driveability and mpg whilst getting a further increase in power. You will probably have either non, or very crude secondary engine management systems such as cold start and idle speed control compared to a factory ECU.

[rjes]

If anyone is still determined to convert an injected engine to carbs, the '90 - '92 EJ18 engine is the key, as it has a distributor, and uses the same head design as the EJ22. The EJ22's heads are fully machined to take a distributor - just take off the blanking plate and bolt it on. I'm not sure about the other SOHC pre 2000 engine sizes. They certainly have the same head type (post 2000 ones do not), but not sure if they are machined for the distributor.
I just sold a bell housing kit to a guy in Honduras wh has uprated his EJ18 legacy to EJ22, and modified the EJ18 carb to suit, so it can be done using the EJ18 carb. He's putting another carb'd EJ22 into his bay. It'd be much more interesting to stick a pair of Dellorto 40's or 45's on though.....
I collected all the parts to try this, just out of interest, a couple of years ago. I've never dne anything with then, and it's likely to stay at the bottom of my to do list, as it's a pretty pointless exercise really (even though I'd find it interesting!)

[rjes]

If anyone reading this is scared of the electrics in a Subaru conversion, then you may want consider the following before converting one to carbs:

The Subaru engine management system parts will cost almost nothing extra on top of the engine cost, especially if it;s an older engine.

I can do all the wiring work for you from about £230 for the simplest engines, and can make the harness 'plug and play' for T25's. Pre T25 VW's need about 10 wires connecting, and all our converted harnesses are supplied with full instructions. Assuming you want some decent carbs, then unless you already have the carb parts, and make the manifolds yourself, then retaining the engine management will almost certainly be cheaper too.

All injected Subaru's have a very useful self diagnosis system built in. No tools are needed to use it, and it usually points you straight to whatever is wrong. All you have to do is plug two connectors together and count the flashes oin a light.
Also - don't let anyone tell you that diagnostics cannot be retained in a VW conversion, as this is simply not true. If you have been told this, then either the person telling you so does not know how, or they are trying to hide the fact that they know that their harness work creates error codes, and they remove the system so the customer can't see them. What other possible reason could there be for removing such a useful system?