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Weber/OER carbs conversion to E85?

General engine tech -- Drag Racing to Circle Track

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KnightEngines
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Weber/OER carbs conversion to E85?

Post by KnightEngines »

No-one I talk to seems to know much about this, some of it is pretty straight forward, but I'm stumped on a few things coz I really don't know shit about weber type carbs.

Got a motor going on the dyno in the next couple of weeks, it wears a pair of OER 47 DCOE carbs - which take all the same tuning parts as a weber 48 DCOE other than chokes, they have a couple of nice features than make them slightly more tunable than webers.
So I gotta get a base tune into the carbs to get it fired up & break in done, they are currently out the box for normal petrol.
I'll be switching out the factory 40mm chokes for 42mm.
Motor is a 2.3L 4 cyl that *should* make 250-260hp @ 7000rpm or thereabouts.

I figure I gotta bump the main jets up about 30% in area & switch to larger needles & seats.

But what about the idle jets, emulsion tubes & air corrector? - one guy has advised F2 emulsion tubes.

Currently they have:

160 main jet
200 air corrector
Nothing on the emulsion tube
50 idle jet

Any recommendations for a base tune?
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Re: Weber/OER carbs conversion to E85?

Post by modok »

"Nothing on them"......
Post a pic of it and measure the OD

Switching to ethanol MAY require smaller OD emulsion tube and/or larger needle and seat, but other than that all that should be required is proportionally larger main and idle jets.
KnightEngines
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Re: Weber/OER carbs conversion to E85?

Post by KnightEngines »

Will do, but I got hold of a guy I know that's played with 45 DCOE's with 42mm chokes on E85, he said as a base tune:

200 main
200 air correction
60 idle
F2 emulsion
3mm needle & seats
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Re: Weber/OER carbs conversion to E85?

Post by Geoff2 »

Never heard of 47 DCOEs. The Weber sizes [ some ] were 42-45-48-50-55-58.

Congrats on being able to work on such fine carbs. They are really very simple in operation, but I think the vast array of E tubes & jetting combinations scare some people.

Some tips on basic tuning.

- If one carb barrel per cyl [ IR, isolated runner ], the main jet needs to be considerably smaller than if one barrel feeds two or more cyls.
- a good starting point for the m/jet is 4 times the choke diam for petrol for one bbl per cyl.
- fuel level is critical with Webers & should use rubber isolaters to minimise carb movement on 4/6 cyl in line engines
- There is no way of knowing which E tube is correct for THAT engine unless the same exact combo was built previously.
- the F2 E tube is a good all round tube & comes std in a few Weber carbs.
- out of the dozens of E tubes originally made by Weber, only a handful are still available now. Hope you have a steady had & are good with a drill!!
- the original Weber tuning manual is excellent, & so is the Haynes Weber manual, ISBN 1 85010 061 6. Pretty sure the Automotive Book Shop in Sydney has both of them
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Re: Weber/OER carbs conversion to E85?

Post by KnightEngines »

The 47's are OER, they don't make a 48. They had a 50mm, but have stopped producing them, now you've got a choice of 45 or 47.

They have an adjustable accelerator pump & adjustable float level - which webers don't have, other than that they are pretty much a weber & take all weber parts (except the 47's need specific OER 47mm chokes).
They are made in japan by the company that made the Mikuni/Solex carbs, just updated to use more commonly available weber parts.

Plan is to switch in the E85 base tune & take along the original bits & a set of jet drills, if anything needs to be smaller we can drill the originals.
For dyno work I'm enlisting a guy with 40 years experience tuning - including webers on methanol. I don't know shit, but he sure does!

Looking forward to seeing how they perform.
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Re: Weber/OER carbs conversion to E85?

Post by enigma57 »

Its going to take some experimentation as you know. Increasing jet size 60% for E-85 as a rough rule of thumb over what should work on pure gas for a 2.3 redlined at 7,000 RPMs...... Try this with your 47mm carbs......

40mm chokes * Consider 38mm if you need more torque coming off the corners * I think 42s will be too large to allow for precise fuel metering with 47mm throttle bores (can these be overbored to 50mm and fitted with 50mm throttle blades (might allow for 42mm chokes?)
4.5 aux. venturi
F2 emulsion tubes
230 main jets
180 air corerctors
95f9 idle (slow running) jets
65 pump jets (70s if 65s unavailable)
3.0 needles and seats
10mm fuel fitting and hoses / 3 PSI fuel pressure using pressure regulator as pressure relief valve sending excess fuel back to tank

Should be close enough to fire her up (a bit rich) and work from there.

Best regards,

Harry
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Re: Weber/OER carbs conversion to E85?

Post by chimpvalet »

Hey mate, how did this work out?

Steve
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Re: Weber/OER carbs conversion to E85?

Post by enigma57 »

:D Roger that! Inquiring minds want to know!

Best regards,

Harry
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Re: Weber/OER carbs conversion to E85?

Post by jarmoyp »

enigma57 wrote: Tue Oct 01, 2019 4:45 am
40mm chokes * Consider 38mm if you need more torque coming off the corners * I think 42s will be too large to allow for precise fuel metering with
Motor is a 2.3L 4 cyl that *should* make 250-260hp @ 7000rpm or thereabouts.


With 38 or 40 chokes, very hard to get 250-260 hp.

Fuel injection is the best choice for e85.
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Re: Weber/OER carbs conversion to E85?

Post by BLSTIC »

I raced against a speedway guy with a "260+ hp" 2.3 Pinto (?) engine in his Sierra. This was 2018 though, and he had mechanical fuel injection at the time. I can't remember what fuel he was running, but it was either e85 or methanol. Think his name was Weir. His brother/teammate had a similarly powered Escort that wasn't quite as wild.

Wasn't one of those two engines was it? I can't imagine too many 2.3's being built in Australia around this time. If it was, you did a good job. Those things kicked ass royally.
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Re: Weber/OER carbs conversion to E85?

Post by enigma57 »

Agreed. 2.87 HP per cu. in. displacement naturally aspirated held to 7,000 RPMs redline is quite an acheivement.

My concern is the relationship of 47mm throttle bore to choke (main venturi) size vis a vis proper fuel metering. I can see a maximum of 40mm choke size allowing for proper fuel metering ('just'), but 42mm chokes seem a bit much with that throttle bore size unless this is a WOT event only and all else is off the table. With 42mm chokes, I would expect a minimum throttle bore size of 50mm and ideally, 52.5mm .

Best regards to all,

Harry
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Re: Weber/OER carbs conversion to E85?

Post by chimpvalet »

A local owner had a Triumph TR-7 with 2 litre 16V Dolomite Sprint 4 banger, factory grade rally build with 48DCOE's and 42mm chokes. Drove it on the street and he was altogether delighted with the car and the engine including carburetion.
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Re: Weber/OER carbs conversion to E85?

Post by Geoff2 »

D. Vizard has some good info on Weber choke sizing in one of his books. From memory, optimum choke size is 72-80% of bore size, with 80% optimum for atomisation & flow. Using bigger chokes because the carbs are too small hurts power, as does trying to choke down carbs that are too big.
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Re: Weber/OER carbs conversion to E85?

Post by jarmoyp »

chimpvalet wrote: Wed Jan 06, 2021 1:52 am A local owner had a Triumph TR-7 with 2 litre 16V Dolomite Sprint 4 banger, factory grade rally build with 48DCOE's and 42mm chokes. Drove it on the street and he was altogether delighted with the car and the engine including carburetion.
Weber 48 has original 42 mm chokes.
50 weber has 46 mm choke original.
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Re: Weber/OER carbs conversion to E85?

Post by blown265 »

Quote:
"Agreed. 2.87 HP per cu. in. displacement naturally aspirated held to 7,000 RPMs redline is quite an acheivement"

Likely a typo, but 2.3lt/140ci and 260hp is 1.86hp/ci. Still a very impressive endurance engine!!!
Regards
Paul
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