Crossover pipe of Rotax 912 Carbys

[Moneybox]

39 minutes ago, facthunter said:

This Obviously WORKS is NOT the answer. That's confirmed by the Bolt instead of a spring  and extra inspections which Indicates excess pressure in the Bowl which has predictable consequences. It's NOT negativity to  investigate  and comment on such things no Matter What brand of Jigger it is ON. That particular Carburettor is a Pretty cheap and Nasty thing to have on a modern (and expensive) engine in an aeroplane. It's way out of date. There's infinitely Better stull on good ride on Lawnmowers with one throat to each individual cylinder. nev

I hope Rotax take your criticism on board and start producing a reliable product. That cheap nasty carburettor seems to manage ok. Of course we know fuel injection has the answer to your stated faults but those cheap and nasty carburettors keep it simple, no electronics, reasonable performance and economy, easily maintained and a good long service life. The float chamber retaining bolt is common place on small carburettors and hardly a sign of pressurised float chamber. More likely a little easier to remove and replace in situ than those little spring retainers.

[facthunter]

They would have to be aware of the shortcomings. They are NOT idiots but at the end of the day it's about  $$$s and a relatively Low rate of production As compared to the MASS Production unit cost. ANY experienced Race engine tuner Knows the fundamentals of all this. Carburettors should not be on the top of an aeroengine. Fuel lines too are in a bad Place and heat rises after an engine is shut down. it seems you only read what suites your case which is Basically it's Rotax so don't you dare criticise anything about it which is illogical. I evaluate ALL engines I have to deal with and Plenty of so  called good (and expensive) ones have Basic obvious weaknesses that let them down.  Nev

[T510]

Everything is built to a price Nev and the Rotax 914 has proven itself to be a reliable package when maintained properly. Sure efi would be better, direct injection would be better again, but it would also increase the cost considerably and the Bing on the 914 is designed for forced induction with appropriate design changes to suit it's purpose. There are lots of things I don't like about lots of different production engines but we have to use what is available and affordable

 

The way your posts are written does come across as negative which I find detracts from some of the good points you make. 

Not knowing you personally, and only being able to base my opinion on what you write, it does appear your have a great dislike for Rotax engines.

 

 

[Thruster88]

A little bored atm so i thought why not calculate the maximum force on the carb bowl of a Rotax 914, 6 years in development and now 29 years in production, unchanged, i would call that a succsess.

 

So standard 912 80hp carb inlet pressure at sea level = 15psi. 115/80 x 15 = 21.5 psi approx required to make 115hp.

 

This engine has a critical altitude of 16,000 feet.  At 16,000 feet atmo pressure is 7.96psi. So 21.5 - 7.96 = 13.54 psi pressure differential.

 

Carb bowl is approx 2.25 x 2.5 inches = 5.625 sq in x 13.54 psi = 76lb or 34.5kg.

 

Feel free to point out anywhere i have gone wrong. I did this in imperial units for skippy's enjoyment.

From above posts, the boost pressure is in both the carb throat and bowl area so flow thru the jets is not affected as one might think.

 

[Blueadventures]

For info this is a gauge tool

to check 914 carb bowl is not warped bent, showing pins ate vertical.

[facthunter]

I'm very careful around  aircraft and not likely to change at this stage and I've not scratched a Plane or injured a passenger. The situation where you can't say a word about Rotax that isn't praise is JUST not Logical. You're Paying a considerable price and expect it to be good. All things CAN fail. .I Pick on all Motors Non are perfect, Even the Merlin never had a TBO above 650 Hours. and that's got RR in front of it. Nev

[facthunter]

 Hey you guys who want Bigger cross over pipes than Rotax do, Reconcile that with your Blind faith that Rotax Knows best?  Nev

[Blueadventures]

A lady fitted a washer to the merlin a number of years back and it performed better, development and refinement is a good thing, innovation.

[facthunter]

I'm not against Innovation at all and don't suggest that I am. She fixed an existing Problem without much help  from the USUAL Knockers, who wouldn't do anything about it. Nev

[T510]

30 minutes ago, facthunter said:

 Hey you guys who want Bigger cross over pipes than Rotax do, Reconcile that with your Blind faith that Rotax Knows best?  Nev

I haven't seen anyone say "Rotax Knows best"

 

I have not seen anyone say you can't say a word about Rotax that isn't praise 

 

The fact that people are modifying and refining the Rotax says we recognise they are not perfect

 

How many aircraft engines have you designed, prototyped, manufactured and successfully brought to market (and had that design copied by other manufacturers)?

[BrendAn]

I think the problem is nev. You keep bringing up all the faults you think the 9 series have but all the pilots on here that fly those engines don't have any of the issues you think they should have.  They are a fantastic reliable and economical engine proven time and time again

 

[facthunter]

I am JUST discussing things & If you don't like it don't bother reading it. I NEVER SAY sell it. Don't tell me the carburettors haven't given concerns, Take the drowning floats as an example, they have been known to stick with the dashpot wide open. No-one could really argue they are Located in  a place that could be better. A float Carby sitting there is BS really. Its a fire risk and hard to keep the fuel lines cool. That's why you have to have that silly fuel return  bleed thing which adds fuel to one tank and mucks up any fuel flow measurement and may cause Low fuel Pressure which is NOT safe. Lets not kid ourselves. A lot of other set ups are not as finicky. Nev

[BrendAn]

26 minutes ago, facthunter said:

I am JUST discussing things & If you don't like it don't bother reading it. I NEVER SAY sell it. Don't tell me the carburettors haven't given concerns, Take the drowning floats as an example, they have been known to stick with the dashpot wide open. No-one could really argue they are Located in  a place that could be better. A float Carby sitting there is BS really. Its a fire risk and hard to keep the fuel lines cool. That's why you have to have that silly fuel return  bleed thing which adds fuel to one tank and mucks up any fuel flow measurement and may cause Low fuel Pressure which is NOT safe. Lets not kid ourselves. A lot of other set ups are not as finicky. Nev

why so agressive. i simply said they are a reliable engine no matter how many faults you assume they have.

[facthunter]

Only responding. You wrote a lot more than you requote. Just a few FACTS which could not be refuted and you chose to ignore. Nothing assumed. Nothing personal. Unlike your comments, which I feel get very Personal though you May not realise it.. Play the Ball and not the Man, please. Nev