Crossover pipe of Rotax 912 Carbys

[skippydiesel]

24 minutes ago, Blueadventures said:

Flywheel balance is linked as the pipe effect is to reduce vibration, comments welcomed.  What's needs to reduce is the doubters that keep asking to verify (especially they almost never verify their stuff.)

Here we go again - more claims to pursue (strategy of distraction), rather than addressing the reasonable questions, arising from the first  claim- .

 

"The larger balance tube does give a better idle performance...... "

 

"Please quantify - what is "better" about the idle AND what is the operational advantage of this improvement, over the OM design?"

 

Until you either substantiate your claims, answear some fair questions, I have to assume this is just a load of BS and I advise others to be just as sceptical😈

[skippydiesel]

On 16/01/2026 at 1:35 PM, Moneybox said:

If you want a foolproof balance between manifolds use a Slack Tube Manometer.

 

The only thing I did wrong was that I started using green coolant in the tube. It was too light with the balance well out all the fluid went up one tube. Fortunately it had a shutoff preventing the fluid entering the manifold.

Once I filled the tube with Mercury it worked perfectly. Disconnect the crossover and attach one tube from the Manometer to the LH manifold and the other tube to the RH manifold. When you have balance the Mercury will be balanced.

The next mistake I made was leaving the Mercury in the plastic tube. It's now badly stained. I already had one so I didn't have to buy it but this is a very cheap accurate and long life device.

Hi Moneybox,

I can see how the U tube might work but how do you remove the effcets of manifold pulsing?😈

 

[facthunter]

Have an adjustable shut off valve in the middle. Nev

[turboplanner]

........more complications. 

Standard engines produced to do a job for a long life with basic  maintenance and adjustments usually have one carburettor and a rough cast manifold that allows gas to pass, and complete with sprags, bulges and other imperfections.

Where I come from is taking that engine and modifying it to produce double or more power.

This involves throwing away the shared manifold and replacing it with, sometimes, stand-alone cylinder processing of gases to take advantage of pulsing, as Skippy mentions.

The key process is to have tube lengths to optimise sonic wave directions.

Joining the stand-alone manifolds would interrupt the sonic waves, lowering power.

 I tried to make the point before that the Rotax pedigree comes from light weight/high power engine applications wit some degree of development above the standard engine class.....

Just how far developed it is, I haven't researched, but if it is using fuel packing design at all joining the stand alone environments may result in less power.  Power being more important than the very short time an aircraft engine is idling. Since so far no one has come up with precise figures or explanations, I'd be wary.   So far no one has come up with any real figures.

[Arron25]

2 hours ago, skippydiesel said:

 

Nothing to do with the topic, Just a comment

Ignoring upsets the flow of a 'conversation' BUT as 'Fly Tornado' (former name?) was the most ignored member Is skippy trying to re-emulate the 'record'

[skippydiesel]

12 hours ago, Arron25 said:

Nothing to do with the topic, Just a comment

Ignoring upsets the flow of a 'conversation' BUT as 'Fly Tornado' (former name?) was the most ignored member Is skippy trying to re-emulate the 'record'

Hi Arron25,

 

Aside from the core topic, its quite interesting how some people, can make a claim, with little or no supporting evidence and expect it to be accepted without challenge.

When asked for the evidence, the claimant may ignore the questions, becomes defensive and aggressive. The latter often manifesting as, strident references to their own expertees, combined with personal attacks on the questioner.

This is irrational - the sensible person would either admit that the claim is speculative or provide the evidence and the questioner(s) move on.

Its a sort of bullying tactic, by the claimant, that does nothing posative for the Forum, the topic at hand or their credibility.

""There's nowt so strange as folk". 

😈

[FlyBoy1960]

I just love it !    There are only about 10 people left on this forum, and now you are all fighting amongst yourselves!

 

This resource is slowly self-destructing.

[skippydiesel]

48 minutes ago, FlyBoy1960 said:

I just love it !    There are only about 10 people left on this forum, and now you are all fighting amongst yourselves!

 

This resource is slowly self-destructing.

Hi FlyBoy1960,

 

I would realy enjoy discussing what you have just postulated  but not within this already very shattered thread.

 

I suggest you start another thread on the matter (general discussion?)  - I will respond. 😈