Aux fuel pump

[grevaly]

Would it be usefull to have a small electric fuel (boost)pump installed to help restore fuel flow in the event of fuel burp?
I will be using an aerocarb. I am sure this has been disscussed but I do not know the pros and cons or if it would even
work at all.

[achesos]

Hi Mark,

I've wondered the same thing, and I already had a pump from another project laying here. I haven't weighed it, but it doesn't seem too heavy to add the potential level of safety it could provide if integrated properly with appropriate considerations.
IF the burps I've been reading about but have yet to experience myself (still assembling) are caused by the fuel temperature increase as it passes too closely to the exhaust (as in boiling the fuel and creating air bubbles), it seems that adding pressure to the fuel line upstream of the injector would raise the boiling point - might help the burp thing then, right? Also seems likely that it would be useful during unusual attitudes once properly tuned??
BUT,
There might be some funky stuff to consider if the pump failed on tuning as well though if the pressure change does affect the tuning as delivered in the throttle body - does it even flow fuel when switched to OFF?, etc. I haven't thought it through too extensively, but we need to work through failure modes and effects when planning this stuff out - the NASA guys do it for the folks getting the ride, but in this case, we are both design engineer and test pilot...
I'm disappointed that you haven't gotten any feedback on this besides my cent and a half.

Sean

[MichaelFarley56]

I may be wrong, but I believe the AeroInjector isn't really designed for the added fuel pressure that an inline pump would provide and you may have issues with it. People have tried it and generally not liked the results.

Your better bet is to keep the fuel flowing by gravity only and keep the fuel cool, which could mean removing the gascolator (if you'd like) as well as insulating the fuel lines in the engine compartment. Most people can reduce or eliminate any burping by simply wrapping fuel lines in insulation.

[fastj22]

In order to use a fuel pump with the Aerocarb, you would also need to provide a pressure regulator that will simulate the pressure of a gravity fed system on the carb side. Too much pressure and the carb will flood. Too little and it will lean. I think it would be difficult to find that sweet spot.

The Bing uses a float bowl to shut off flow when its full to give a constant flow to the carb jets.

The Rotec TBI has a regulator built in. It works like a SCUBA regulator and draws only what it needs independent of the input pressure. Rotec claims it operates on anything from .5PSI to 10PSI. I'm currently running mine with just gravity feed and its working fine. I'll probably install an electric pump and return line later.

In any of these systems, you could provide a return line of smaller diameter to the tank to circulate the fuel while providing higher pressure to the carb/regulator.

[radfordc]

Having once had a bad case of the burps I understand you wanting to avoid them!

I don't think adding a fuel pump alone will work due to the Aero Injector not working well with high pressure fuel delivery. However, if you incorporate a pump with a return line that may work. The return line idea has been discussed here before as a cure for the burps. The return line should be connected to the fuel system as close to the carb as possible and run back to the top of the tank and should be at least as large a diameter as the fuel line or even a little larger. The pump will keep a constant flow of cool fuel through the lines.

[merle reppert]

Ok --I will chime in here again---The Aero Injector does not like a pump---
My solution is to add what I call a Burp Tube---I ,and several others locally and maybe others have it on there's --With the Aero Injectors--NO ONE has had Burps since--
It is simply a T fitting at the inlet of the TBI with the side outlet pointing up---
A fuel line is run from the T outlet up to the TOP of the tank--T'd in to the tank vent--
(This tube will have fuel in it at the level of the tank )---The way it works is any of the Vapors
go up this tube to the tank where they condense and NOT INTO THE AERO INJECTOR
Try it you will like it -----No Pucker factor from Burps---
Merle Reppert

[achesos]

I'm glad to hear some people are having success eliminating burps... my AeroVee isn't flying yet, but I've wondered if I will suffer this startling event in flight myself.

But, I'm a root cause analysis kind of guy, so I have a bit of a problem with the tee-pipe-return-line solution mentioned above. Not trying to make enemies - this is only my opinion - so here is my interpretation of how this solution may be making an improvement: This modification only seems to only address the symptom of the problem by allowing air bubbles to escape the fuel line just prior to entering the TB - this might make engines not temporarily starve for fuel (most of the time?), but it makes me wonder where these bubbles are being created in the first place? The heat source of fuel line crossing exhaust pipe seems to be a likely candidate for boiling fuel and inducing air bubbles. So, this makes me think wrapped headers and / or a heat shield is a better preventive solution to the random burp. Heating fuel should be avoided anyway, right? I hope this makes sense to someone besides me? And yes, I've wrapped my header pipes as part of my heat control strategy.

Sean

[Onex107]

Here is my experience. I started flying my Onex with a solid fuel line from the tank to the fire wall through fitting. The through wall fitting connected to the back side of a gascolator with flexible fuel line to the Aeroinjector. In 80 degree weather I began to experience the burps after landing and beginning to taxi. Everything was getting heat soaked. On advice from a Sonex friend I wrapped the exhaust pipes and insulated the flexible line with foam water pipe insulation. That worked until I had flown for about an hour then the burps started again. It's difficult to insulate the gascolator mounted on the fire wall. The burps are nothing to fool with. It's very scary when your engine quits and restarts about every 10 seconds. I didn't like the idea of running another fuel line to the height of the top of the tank, plugged or not, and I was determined to make the Aeroinjector work.
The end result is I removed the gascolator, recommended by Sonex, and heavily insulated the flexible fuel line from the fire wall through fitting to the Aeroinjector and the problem has not recurred, even in 90 degree weather. An inline filter is not a bad idea, in addition to the one at the main shutoff, but I have not done that. 81 hours and counting, flying very well on needle #3 in central Illinois. If you want to talk about needles I have a lot of experience, from research making needles, to get the optmum design, to eliminate multible mixture changes during a flight.

[Doron]

If you want to talk about needles I have a lot of experience, from research making needles, to get the optmum design, to eliminate multible mixture changes during a flight.

Yes, I really curious to hear about your experience with needles, i am struggling for long time with my needles trying to rich my Jab 3300 at WOT
Doron