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Two questions about fuel injection system

AX-O

AX-O

Well Known Member
Can you please post pictures of your remote purge valve installation? I am having a tough time finding a location where to install my purge valve on my RV-4. The engine plenum is not helping me either.

Also, this is not a final configuration or anything, just playing around but are hard lines allowed between the spider and the purge valve?

CIMG3689.JPG
 
I got my AFP at Superior during the build school. When I opened the box, the spider already had the purge valve attached as in the picture of that purple (purple?) engine in the thread linked above. If you don't have the bracket, you can get it from Don; AFP has great customer service.

As for the hard line, I'd avoid it.
 
Fire!

Axel,

Please don't use a hard line to the purge valve. It is subject to fatigue failure and would cause immediate engine stoppage and a real possibility of an engine fire at the same time! Yikes!:eek:
 
ronschreck said:
Axel,

Please don't use a hard line to the purge valve. It is subject to fatigue failure and would cause immediate engine stoppage and a real possibility of an engine fire at the same time! Yikes!:eek:
Click to expand...

Thanks. That was my initial thought. I was just sitting in the garage trying to figure something out. The positions shown on the other thread don't work for my set up. I have to figure something out. One of the problems is caused by my narrow deck engine. In order to have enough clearance for the spider, I need a very long spacer. That puts the spider further away from the engine block and reduces my options.
 
The illustration in this thread won't work because that exposed piece of aluminum tubing is not a section that will see fresh fuel with the purge valve doing its thing. The line is exposed to top engine heat after shutdown and that heat will cause vapor in the line. You need to get the purge valve as close as possible to the flow divider.

I would seriously consider installing the the system as per AFP and modifying the cowl to accommodate it.
 
I would definitely not use the hard line as shown in your picture - even though both ends of the line are affixed to equipment that is bolted to the same engine block and they should not move relative to each other, there will be harmonics and standing waves set up in the hard line that will cause it to vibrate and you'll put yourself at substantial risk of stress cracking, with very bad results on that particular line if it does fail.
 
David-aviator said:
The illustration in this thread won't work because that exposed piece of aluminum tubing is not a section that will see fresh fuel with the purge valve doing its thing. The line is exposed to top engine heat after shutdown and that heat will cause vapor in the line. You need to get the purge valve as close as possible to the flow divider.

I would seriously consider installing the the system as per AFP and modifying the cowl to accommodate it.
Click to expand...

I respectfully disagree with David. Once the purge valve is opened cool fuel will flow from the selected tank, through the fuel controller, through that exposed piece of tubing, through the purge valve and back to one of the fuel tanks. It may take a bit longer since the purge valve is remote to the divider, but it will get there. I still maintain that a flexible line from the divider to the purge valve is the safest way to connect the two.
 
David-aviator said:
The illustration in this thread won't work because that exposed piece of aluminum tubing is not a section that will see fresh fuel with the purge valve doing its thing. The line is exposed to top engine heat after shutdown and that heat will cause vapor in the line. You need to get the purge valve as close as possible to the flow divider.

I would seriously consider installing the the system as per AFP and modifying the cowl to accommodate it.
Click to expand...

I spoke with Don at airflow regarding this about 3 months ago. He is the one that told me to remote mount the purge valve and that an 8 to 9 inch line would not affect functionality. After reading the operations manual, it said to cut the engine off using the purge valve vice the mixture. Would that not burn all the fuel on the lines after the purge valve?

Will not use the hard line. Thanks.
 
AX-O said:
I spoke with Don at airflow regarding this about 3 months ago. He is the one that told me to remote mount the purge valve and that an 8 to 9 inch line would not affect functionality. After reading the operations manual, it said to cut the engine off using the purge valve vice the mixture. Would that not burn all the fuel on the lines after the purge valve?

Will not use the hard line. Thanks.
Click to expand...
The purge valve will dump the fuel pressure as soon as you open it and the engine will stop immediately. And I mean RIGHT NOW! Nothing in the lines will burn as there will be no pressure to deliver it to the combustion chambers.
 
ronschreck said:
The purge valve will dump the fuel pressure as soon as you open it and the engine will stop immediately. And I mean RIGHT NOW! Nothing in the lines will burn as there will be no pressure to deliver it to the combustion chambers.
Click to expand...

Thanks Ron. Did not know the internal operation.
 
I am still trying to figure out a good location. Will post a pic once I am happy with the location.
 
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