Tracy,

I must be missing a point somewhere, or we have crossed wires, as I haven't mentioned the combustion chamber. My only concern is high pressure fuel leak in flight. Don't get me wrong I like fuel injection because of the control over injection volume and performance. I only wish there was high pressure at the point of injection - only.

 

I have fuel injection on my Suzuki 1800 Motorbike and it's great, but I would hate to have to work on it, like I did on the old carbied bike.

 

I've noticed the Jabiru are running a very simple system. Their using a Honda ignition module with an altitude compensating carby - not that the system is perfect either.

George ( down under)

I think you are missing Ernest's point George.  Note the location of the injectors in the 16X.  They are NOT in the combustion chamber.

Tracy

On Sat, Sep 6, 2008 at 2:16 AM, George Lendich <lendich@optusnet.com.au> wrote:

Ernest,
Very true mate,  to me high pressure in a cowl is my concern - paint me paranoid. If we could have low pressure injection I would be most appreciative, but sadly the carby is 'old hat' now. The Bendix type systems are about 30 psi - not too bad!
Are they really going to have ceramic coatings on the side housings?
George ( down under)

George Lendich wrote:

Jim,
The biggest volume is at BDC- anything past this is compression, it's not getting high until it goes past the inlet area; but it certainly is quite high at the 12:00 O'clock position where the direct injection is taking place.
Direct Injection has to be high to atomize the fuel particles finely enough to get complete combustion. Of course it has to be high to also counter the compression pressure at this stage.
George ( down under)

But, George, "high" is a relative term.  We run our fuel system on the road anywhere from 30 to 60 psi.  That 60 seems awfully high;  but the natural gas in the portable tank that I buy from the grocery store to fire by BBQ grill comes with 300psi.  That's what it takes to make natural gas a liquid at room temperatures.  And that crazy guy, T. Boon Pickens, is trying to convince us Americans to run our cars on that same natural gas (actually, many are doing it already).  At a 10:1 compression ratio, ambient pressure is driven to 147 psi.  You still only need 60 above that to get the good atomization.  Yet, you can buy tanks from the GROCERY STORE compressed to 300.

Granted, the BBQ grill doesn't get the same sort of vibrations as a car (unless I've got the burgers REALLY flying), but that is just a matter of engineering the connectors to handle the stress.  Simple engineering that has been done a gazillion times before (see diesel engine).  I'm not saying they don't have some engineering and testing to do.  I'm just saying that they're not having to blaze new trails into unknown territory. This seems to me to be very much a small evolutionary step, and not a major revolutionary one.

--

http://www.ernest.isa-geek.org



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