The 914 Thread

[Esser]

Lots of info on the 912 here but not as much on the 914. Because of this I thought I would start this thread where it would be easy to find all the information in one place. If you find relevant older threads we can post the link in here.

So we now have a 914 for our project and I had two questions for those who are running them.

1. How do you find cooling and do you have any special setups or operating procedures to deal with the heat?

2. Is anyone using a single throttle body instead of the dual carbs? Any experience or advice with this? I have been looking at the Rotec TBI and it is intriguing me but I don't want to sacrifice reliability for anything.

Thanks,

[foxy]

a customer is doing his 1st 25 hrs on his ...in a Zenair CH750.

I trained him on the first 5. No problem so far EXCEPT it is very hard to restart after a short stop.

It's probably too hot under the cowl and vapor locks occur.

during flight ..absolutely no problem.

[mr bill]

Can you get any pictures of the setup?

[foxy]

voilÃ*

Airmaster prop

[Esser]

Thanks for the pictures.

So nobody has an experience with a throttle body in place of the bings?

[mr bill]

I misunderstood. I thought the pictures would be of the throttle body injector setup.

[Esser]

Well my partner and I are leaning towards fuel injection and are looking at SDS in Calgary, http://www.sdsefi.com/rotax3.htm

My question for everybody with a 914 is do you find the 1 gallon header tank large enough to cool the return fuel or are you going back to the mains?

[War Eagle]

My setup just returns to the header tank. Hasn't appeared to cause me any problems.

[jrevens]

I don't want to hijack your thread, Josh, so if this post is better placed within a different thread, I understand and would appreciate someone doing that.

I have an opinion about this issue that doesn't directly address your question, but the return line issue in general. I know that there are many (probably most of the fleet) Kitfoxes that don't have a return line, as this is a relatively newly defined problem. Maybe it's just cropped up since the tighter cowls have been used. I'm still learning, & I will gladly consider other opinions, but I believe the "problem" involves two issues and both affect "hot" starts & hard starting. I'm not sure, but I believe that the issues generally don't surface during a normal run, but occur when trying to start a hot engine after it has transferred heat especially to the section of fuel line running over the top, between the fuel pump & the carburetors (could be that specific section of fuel line for fuel injected systems also - I don't know for sure). Anyway, starting out with fuel in that section of line that is as cool as possible should certainly help, but I think there may be another issue at least as important. That issue is that you have a fuel line that is basically a closed container completely filled with liquid fuel. It can't go backwards through the fuel pump, and the float valves in the carbs are closed. As the line absorbes heat, hydrostatic pressure is created that will easily force open the needle valves & possibly overfill the float bowls. Then the fuel that remains in that section of line cools off and may have pockets of fuel vapor rather than all liquid. The return line not only allows recirculation of fuel through a controlling orifice, but also (maybe at least as importantly) prevents building pressure in that section of line when the engine is shut down.

As a matter of possible interest, I've been told that RANS recommends running this "return/recirculating" line back to the gascolator only. This of course is before the engine-driven fuel pump and will allow relief of pressure in the line. At this point in time, that's what I'm planning to do.

[Esser]

Hey John,

No hijack here. Any info is good info. I was thinking with a gravity feed system, you could in theory just return to one tank if you really wanted. I will look more into this gascolator thing.