Two Engins one carb

[madtech]

hi guys iv put together two 97cc 2stoke engines. the two engines have thier own clutches and run the same sproket which in turn turns a prop. i need to marry up the rpm of these two engins as much as possible, A to save my clutches and B to get the most efficient amount of power out of them.

altho the engins are identical the carbs are not so i was thinking of using a 200cc carb. trouble is i would have two tubes coming from the carb to the engines and the way the engins sit, they would be about nine inches long.

does any one know if there would be a problem doing this, do the carbs need to be right up close to the engine.

does any one know of another way of matching the rpms and power

please help

[StianM]

Making engines work togheter is no big sience.

If you put load on a engine the RPM will drop. If you have two engines conected to the same load they will both increase there RPM until they hit the load.

If they are not running perfectly maybe one will have 45% off the load and the other one 55%, but they will keep the same RPM.

Just try to see if you can get them identical carbs since two diferent is not ideal. I think using one carb is less ideal since the shape off the manifol would favour one engine over the other and you would not be able to get there full potential. You can see this on some multi cylinder v-engines with one carb the end cylinders on eatch bank will get less fue than the center ones. I don't think one carb on two engines is woth the effort.

You would also probartly end up with cracks in your manifoil because off the two engines wibrations on eatch there end off it.

[kenJ]

You should be able to find some tachometers that can be adapted to work on your engines. I would leave the carbs alone, use the tachs to match the rpms.

[Bergalia]

Good answers above. All I can add is 'folk lore' - carbs are usually close to the engine to pick up radiated heat to help vapourise the fuel...but that may be an old wives tale....

[StianM]

Originally Posted by Bergalia

Good answers above. All I can add is 'folk lore' - carbs are usually close to the engine to pick up radiated heat to help vapourise the fuel...but that may be an old wives tale....

I think that was some off the theory about the old updraft carbs. I don't think it has mutch relevance annymore, but I remember my old Opel had a chamber in the exhaust manifoil to store heat under the carb(this was not crosflow heads)

[Bergalia]

I'll take your word for it StianM - shows the limit of my knowledge on carbys - SU downdraughts...

[StianM]

Originally Posted by Bergalia

I'll take your word for it StianM - shows the limit of my knowledge on carbys - SU downdraughts...

Don't take my word for it. I just draw some simple conclutions from my own experience witch could turn out to be not intirely the trouth.

[Bergalia]

Originally Posted by StianM

Don't take my word for it...

Don't you argue with me young feller - If I say you're right...then you're right....

[Frosty]

Caburettors should not absorb heat, they should be as cool as possible , hence the rubber conectors on motor cycles.

AND the thick 1/4 inch thick spacers used on carbs,--heat seperator.

On early pre cross flow engines carbs had a heat shield to protect from the exhaust.

An Su downdraft I have never seen, A side draft!!

[Bergalia]

Originally Posted by jack frost

Caburettors should not absorb heat, they should be as cool as possible , hence the rubber conectors on motor cycles.

An Su downdraft I have never seen, A side draft!!

Ah ha..gotcha young Jack - how do you explain the 'pre-heat' carburettor on the Bristol 400....
But, and I hate myself for it...You're right on the SU's. They were side-draught....(my old MG TC - I still have the manual, and checked.)

[Frosty]

Bristol 400,??? jeees where do you dig this stuff up.

Pre heat carb--- dont know--probably some pre heat cold start device to start the bloody thing.

Or to run it on parrafin?

[Frosty]

Berglia --Ille let you into a secret

Dennis 1950s fire engine --petrol 6 cylinder with an SU updraft.

[Bergalia]

Originally Posted by jack frost

Bristol 400,??? jeees where do you dig this stuff up. Pre heat carb--- dont know--probably some pre heat cold start device to start the bloody thing.

I owned one Jack...but you're right. Pre-heat carb served instead of a 'choke.' You'd switch it on about a minute before firing up the engine. A buzzer would sound when it had reached the correct temperature.
Interesting old car (1947) - combination of BMW 1936 sports car body (war reperation 'loot') with a Bristol aircraft engine (cut down to size). Trouble was you needed to drive it in tandem with a petrol bowser...about 11 miles to the gallon.

[StianM]

Jack is old enough to remeber this stuff so I trust him regarding this preheater tecnolegy

[Frosty]

Yeah they were a bit of a problem those ole stuff especially when the war was on.

The second war was a doddle.