Crossover pipe of Rotax 912 Carbys

[skippydiesel]

58 minutes ago, BrendAn said:

912is  does away with all this drama

The origional carby one will do me nicely. 

 

As I understand, the injected varient of the 912 has two advantageous over the same carburettor engine;

• Better fuel econamy
• Greater (total?)  resistance to inlet ice.

The disadvantages are significant;

• Much more expensive to purchase.
• Greater complexity - almost impossible for the average home mechanic to do anything with the fuel delivery throttle system. Potential to be very costly if goes wrong.

Repeating what I have read-

 

The 912is fuel savings;

• Could take the average owner/ pilot near 20 years to equal the greater purchase cost.
• Are possibly attractive to flight schools/hire operators (fast hour accumulation), assuming the sale of high time engine is attractive to 2nd hand purchasers.

😈

[Blueadventures]

1 hour ago, BrendAn said:

912is  does away with all this drama

I'm happy with carbs, don't want the expense of 'is' diagnostic gear, programs and the headache of chasing fault codes. UL & ULS; the parts, maintenance and associated costs suit me and I pretty much know the critters inside out. 

 

I'd be happy still with cars of the 70's and 80's with the upgrade of points to electronic ignition, and stop there.  (Don't miss bonnet up in the rain attending to the needs of the points. It was character building.)

Edited yesterday at 04:56 AM by Blueadventures

[skippydiesel]

 

Hi Blueadventures - Second attempt to get a bit more information

 

• The above statement, (now a few back) mentions mechanical carby balance, what of the pneumatic balance???😈

[FlyBoy1960]

whatever happened to the lever system that was being developed by Kyle Communications ?    you would set up this system once and it would seem to me to be able to stay in balance for just about forever, then you don't have any issues with cables because there is only one cable going from his system to the pilot hands.  Using pushrods or hard connections for the throttle seems a no-brainer to me because there is nothing to stretch or go out of adjustment

[facthunter]

"Pneumatic" DOES throw me off. Do you Mean EVEN MP?  A MANY times bigger area will improve that But I've presented adverse Possibilities  that Only ONE person acknowledged that SHOULD be considered.. Nev 

[FlyBoy1960]

the pneumatic ones made by Carbtune are really good, they used brass rods and didn't bounce around like gauges. I have also used a digital balancer from Aircraft Spruce called the carb mate  https://www.aircraftspruce.com.au/catalog/eppages/ts111kitcarbmate.php    it seemed to work really well also

 

[skippydiesel]

44 minutes ago, FlyBoy1960 said:

the pneumatic ones made by Carbtune are really good, they used brass rods and didn't bounce around like gauges. I have also used a digital balancer from Aircraft Spruce called the carb mate  https://www.aircraftspruce.com.au/catalog/eppages/ts111kitcarbmate.php    it seemed to work really well also

 

I have used a pair of cheap (Asian made) twin carb motorcycle vacuum gauges, for about 15 years now. They are excellent!

Come with a little adjustable valve for each tube, so that the needle pulse fliker/bounce, can be "removed".

The "face"/ needle, can be zeroed if needs be.

I had to purchase longer vacuum hose, so that I can have the gauges in the cockpit, while engine running.

I always swop tubes, to assess consistence of reading - so far no discrepancy.

Can't understand why people go and purchase expensive digital/electronic stuff ($500++?) when something like this is all the owner maintainer will need.

 

($21-$51) 😈

 

 

Edited yesterday at 06:11 AM by skippydiesel

[BrendAn]

1 hour ago, Blueadventures said:

I'm happy with carbs, don't want the expense of 'is' diagnostic gear, programs and the headache of chasing fault codes. UL & ULS; the parts, maintenance and associated costs suit me and I pretty much know the critters inside out. 

 

I'd be happy still with cars of the 70's and 80's with the upgrade of points to electronic ignition, and stop there.  (Don't miss bonnet up in the rain attending to the needs of the points. It was character building.)

It's pretty rare for efi to give much trouble these days. In saying that, if you seen the Birdsnest of wiring and crap on my hks engine you would never put it on an aircraft. 

[skippydiesel]

Hi Blueadventures - Third attempt to get a bit more information

 

• The above statement, (now further back) mentions mechanical carby balance, what of the pneumatic balance???

Common Mate what's the big secret? 

 

Do you follow, as per Rotax advice, your mechanical carby balance, with a pneumatic balance?

 

If not, why not?😈

[Blueadventures]

59 minutes ago, facthunter said:

"Pneumatic" DOES throw me off. Do you Mean EVEN MP?  A MANY times bigger area will improve that But I've presented adverse Possibilities  that Only ONE person acknowledged that SHOULD be considered.. Nev 

 

I have the Synchromate and also a tube unit.

[facthunter]

Problems are often Hard to diagnose. Sometimes only done by swapping items till the faut is corrected.. Self testing built into the system can be done.  Nev

[Blueadventures]

8 minutes ago, BrendAn said:

It's pretty rare for efi to give much trouble these days. In saying that, if you seen the Birdsnest of wiring and crap on my hks engine you would never put it on an aircraft. 

Agree, however I'm happy with life on my little Carby island surrounded by water.  Have to be careful of the crocs, sharks and 'R is' gremlins (on the rare occasion they show their heads) and associated costs.🙃

[facthunter]

A U tube connected to both sides would do that or a simple flow indicator that works in both directions.  The thing you need is for the settings to remain where they are when set. Nev

[skippydiesel]

Hi Blueadventures,

 

"I have the Synchromate and also a tube unit."

 

Is this, a sort of answer to my "Do you follow, as per Rotax advice, your mechanical carby balance, with a pneumatic balance?"

 ie you have the gear, so am I to assume, you have used it?

 

I Googled Synchromate carburettor balancer to try & get a handle on the equipment you may be using to do a pneumatic carby balance - nothing!

 

Well not nothing, Google always gives something;

 

Synchromate refers to a veterinary injectable medication containing the synthetic hormone cloprostenol, primarily used in livestock (cattle, horses, sheep) for reproductive management like synchronizing heat cycles, inducing ovulation, terminating pregnancies, or inducing labour.

 

There is a more likly contender;

 TecMate SynchroMate (TS-101), for synchronizing carburetors or throttle bodies - is this it?

 

There was also something called a SynchroKing, which may be similar to your TecMate - all pretty pricey.

 

For what its worth; The Rotax Owners Forum technical advisors have opined, that the above type devises, are not as good as a simple vacuum gauge, for balancing carburettors.😈

 

 

[Kiwi]

I use a twin-engine manifold pressure gauge.
I first connect  it to one manifold to make sure they read the same, then connect the left to the left and right to right and sit in the aircraft and check at various rpm's

[Kyle Communications]

I dont know why there is so much text on this matter. You set the mechanical side of the carbs up with idle stops etc then just do the carb balance with either gauges or a carbmate. Problem done. Except of course that the pneumatic balance will shift over time and thats because most rotax installs...that use carbs use the stupid bowden cables that can change their length then your balance goes out.

The larger balance tube does give a better idle performance once everything is setup correctly. I have tested this and 3 or 4 of us locals have it done and yes it makes a difference. But you still have to do a carb balance with the vacuum and check the bowden cables..There are other things you can do to make it easier but thats another story

 

[skippydiesel]

Hi Kyle,

 

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

 

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

[Kyle Communications]

The idle sounds and feels better...cant quantify it any better than that.

 

 

[skippydiesel]

Ho Kiwi,

 

Your twin engine manifold pressure/vacuum  gauge is a great idea - wish I had one.

 

I guess its likly to use two Bourden tubes to deliver the readings, so not so diffrent from my two gauge motorcycle carby balancer, just more compact.😈

[skippydiesel]

2 minutes ago, Kyle Communications said:

The idle sounds and feels better...cant quantify it any better than that.

 

 

Thats great for those who value such.

 

Without empirical evidence AND most importantly, a clear engine operational benefit, it strikes me as being a faith based investment.

 

This concept has been vigorously debated, in the Rotax Owners Forum, over about an 8 year period.

• No empirical evidence has ever been presented.
• No improvement to normal engine management has been shown, bearing in mind that most Rotax 9s spend every little of their operational life at idle (purported to be the main area of improvement).

 

https://www.rotax-owner.com/en/general-tech-discussion/6709-polishing-intake-manifolds

 

Given the simplicity & potentially low cost of this concept, why has Rotax not adopted it as a standard fit or offered it, as an after purchase, performance enhancer?

 

😈

[facthunter]

Still needs restrictors to stop the Pulses. Please explain How a substantial FIXED Length pipe doesn't get stressed when the Engine  changes temperature and why the Response to a rapid Power increase  say when going around, would not be More compromised .Mixture wise. A plenum between the throttle and the Intake valve is never a good thing. Nev

[Moneybox]

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.

[Moneybox]

3 hours ago, facthunter said:

Still needs restrictors to stop the Pulses. Please explain How a substantial FIXED Length pipe doesn't get stressed when the Engine  changes temperature and why the Response to a rapid Power increase  say when going around, would not be More compromised .Mixture wise. A plenum between the throttle and the Intake valve is never a good thing. Nev

 

I thought the same thing when I saw the tube ends welded but on a closer look I realised there are a couple of vertical rubber hoses connecting to the manifold. These would allow for expansion and contraction.

[facthunter]

I didn't see that .Many exhaust  AND some Inlet systems have a slide joint with packers but they can All Leak. The  increase in the volume creates the Mixture issue. I wonder if anyone has checked the engine in a quick response situation. The standard set Up seems to be satisfactory. Nev