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Electric Fuel Pumps

J

jim miller

Well Known Member
Geico266 and Gasman

On your RV3's that had or will have only two electric fuel pumps and no engine driven pump were they wired so you could run both pumps during
take-off? Is there any problem running both, in series electric pumps at
the same time? I wanted to be able to run each pump off of either battery
but this would be more difficult if I wanted the option of running both pumps
at the same time.

Thanks
Jim Miller
 
Electric pumps (2)

I havent read what the others are running you have refered too, but I am running two of the Fawcet electrics on my RV-4 with no engine driven pump (Lyco O320H2AD). I did this primarily because the H2 has engine driven on the top forward of the case and requires a "cowl bump" . I currently have only one battery, but going to add a back-up battery in the future. I located the "boost" pump in the tunnel per plans, and a second pump on the front of the firewall next to the gascolator. Both are in series (fluid flow) and each one is wired to a seperate switch on the panel. It runs equally well on either pump and I use both on T/O and Landing. Normally in flight I shut off the boost pump. When I wire the back-up battery in the near future, I will utilize a stand alone harness that will allow only the pumps to run from the back-up battery and be able to pull the master relay if needed removing the normal battery from the system. I may also include a B&C standby alternator on the vacuum pad to charge the back-up battery. Love to hear what the others are doing with their all electric systems.
 
Bill
Thanks for the reply. The more people I hear of running two electric pumps
the better I feel about going that route. In my case I have a RV3 that flew for 4 years by original builder and sold to me less engine. My 0235 has no
fuel pump and rather than add one I am interested in using two electric
ones and have started that mod. My initial design was to allow either pump
to be run by either battery, then realized I couldn't run both pumps at the
same time with my design. I am going to relook at it to include that option.
Do you have a fuel pressure gage? Was wondering pressure differences when
one or two pumps are running.

Thanks
Jim Miller
 
See "Frank H'

I have built two airplanes with electric pump only systems.

the RV is fuel injected and has a little over 500 hours.

Frank
 
Frank
Do you run two pumps during take-off? What size back-up battery do you
use if any? I am planning to wire both pumps in circuits that go directly
to the batteries and by-pass master switch. Each will have its own 5 amp
breaker and on-off switch.

Jim
 
jim miller said:
Frank
Do you run two pumps during take-off? What size back-up battery do you
use if any? I am planning to wire both pumps in circuits that go directly
to the batteries and by-pass master switch. Each will have its own 5 amp
breaker and on-off switch.

Jim
Click to expand...

I have been thinking about this too. I was contemplating a electrical rotary switch labelled LEFT BOTH RIGHT OFF with 90° between each switch position. Also a simple on off Andair fuel selector upstream of the Andair pumps, which draw 4.5 amps continuous 6 amps max, so an 8 or 10 amp breaker would be required for each pump. I was thinking of retaining the mechanical pump as a belt and braces. The Swiss authorities would most likely want me to do that.
 
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Wouldn't you want the electric switch to be ganged to the mechanical valve?

Or better yet, use check valves downstream of the pumps and eliminate the mechanical valve.

Seems like with both there would be a chance that the valve would be in one position and the pump selection in a different position.

Dave
 
Wouldn't you want the electric switch to be ganged to the mechanical valve?
Click to expand...

Ideally yes. But I have yet to source an appropriate valve with electrical switches. If anyone has any thoughts on this I would welcome them.


Or better yet, use check valves downstream of the pumps and eliminate the mechanical valve
Click to expand...

I would want something that would manually cut the fuel off should there be an issue with fuel flow not able to be switched off.


The valve is a two position ON OFF valve clearly indicated with the pointer in the off position when the pointer is 90? to the direction the plane is pointing. In the on position the pointer points directly forward in the direction of travel. This gives the advantage that in case of a fire the fuel can be instantly turned off, plus it is a good safety feature when working on the engine.

I have already described how I would like the electrical rotary switch to be mounted.
 
David Paule said:
What happens if you shut the valve off to a tank while the pump is running?

Dave
Click to expand...

Fuel stops flowing obviously and the pump continues to run but not deliver fuel. If your in the air, your attention is soon alerted by the lack of noise from the front end. In my opinion the fuel valve is there to be normally operated on the ground according to a check list so the situation you mention should not occur. I will be using fuel injection so the time from say shutting off the fuel valve to engine quiet is very short. With a carbed engine I could see an issue if the plane was started an abbreviated run up and a botched check was conducted and a quick departure initiated. The plane could be at 300 ft when the engine quit. However this situation could happen on a certified airplane too.
 
Last edited:
jim miller said:
Frank
Do you run two pumps during take-off? What size back-up battery do you
use if any? I am planning to wire both pumps in circuits that go directly
to the batteries and by-pass master switch. Each will have its own 5 amp
breaker and on-off switch.

Jim
Click to expand...

Hi Jim, I would set it up to act as normal as possible. The mechanical fuel pump needs no attention. so Let's make the primary electric fuel pump do the same. I will install both pumps inside with the one closest to the firewall being the primary pump. It will be wired direct to the battery with a pull breaker and controlled by a quality oil pressure switch. This pump will only run when the motor is running.

The backup pump will be installed and operated as standard in all RV's. Install a filter after the select valve and before the fuel pumps. No gascolator. The sumps is where the water is, and you want to catch the junk before the fuel pumps. On the hot side of the firewall, all you have is a nice clean line running from a steel fitting at the firewall to the carb.

In a three, there is little space behind the motor. Picture the area without a vac pump (expected), no big hot fuel pump, no gascolator and two big mags missing........ you used LSI.

I will run a backup battery due to the LSI so it will be there for the fuel pump also. My current choice for a battery is a POWER SONIC model PS 1250 5 Amp Hr. It was charged to 12.91 on Feb 16, 2011. Sitting on a shelf as of today 1/7/12 the charge is still at 12.50 volts. That is 75% of a fill charge. This battery weighs 3.5# and measures 3.5w 2.73d and 4" tall..... about $20.00. And keep in mind, batteries will get better.

I will charge my backup battery in the hangar when needed........KISS! ........... Wiring a quality system is a must.

Yes, you run both fuel pumps on takeoff. Yes, you have a fuel pressure gauge...... Just like normal. I will have a low fuel pressure alarm on my MGL also.
 
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Gasman
Thanks for the reply. I have basically came up with the same system with
very minor difference's. I have drawn a diagram I wanted to post for critique
but couldn't do it. One question I had is the filter you plan to use. Is it commonly used on Van's aircraft? I like the idea of a filter but worry about
it getting stopped up. A 5 amp hour battery is a good size. Is the battery
you mentioned a Glass mat like the oddessy or a lithium? There is currently
a big discussion on Super cub.org about possible hazards of lithium batteries
in aircraft. I certainly like their light weight and ability to hold a charge.
Whatever battery I use for back-up I too will charge it with a 110v trickle
charger on the ground. I am going to send you my e-mail address by PM
and can e-mail you what I came up with and a photo of my plane.

Jim Miller
 
islandmonkey said:
Fuel stops flowing obviously and the pump continues to run but not deliver fuel. If your in the air, your attention is soon alerted by the lack of noise from the front end. In my opinion the fuel valve is there to be normally operated on the ground according to a check list so the situation you mention should not occur. I will be using fuel injection so the time from say shutting off the fuel valve to engine quiet is very short. With a carbed engine I could see an issue if the plane was started an abbreviated run up and a botched check was conducted and a quick departure initiated. The plane could be at 300 ft when the engine quit. However this situation could happen on a certified airplane too.
Click to expand...

Sorry, I didn't express myself clearly.

Suppose that you've got one pump running and the valve set to that tank, and the engine is running fine. And for whatever reason, the other pump is on, too, but that tank is valved off. The pump is running to a blocked line.

What happens? Is the pump and the electrical system happy with that? Is there any possibility for the fuel to overheat?

Dave
 
David Paule said:
Suppose that you've got one pump running and the valve set to that tank, and the engine is running fine. And for whatever reason, the other pump is on, too, but that tank is valved off. The pump is running to a blocked line.
Click to expand...

I'm thinking Anthony intends to have his on-off valve as the final stage behind the firewall, with the output of the electric pumps going through separate check valves into a manifold or T, before the manual valve. As far as the valve is concerned, the whole fuel system is on or off. I don't think the small solid-state pumps care if they're pumping against a closed valve, although I hope some expert can confirm that. I don't know about boost pumps operating for extended periods without flow, but I've never heard of that as a potential problem.

--
Stephen
 
David Paule said:
Sorry, I didn't express myself clearly.

Suppose that you've got one pump running and the valve set to that tank, and the engine is running fine. And for whatever reason, the other pump is on, too, but that tank is valved off. The pump is running to a blocked line.

What happens? Is the pump and the electrical system happy with that? Is there any possibility for the fuel to overheat?

Dave
Click to expand...

Apologies, my turn to have not done the "express myself clearly* bit. Let me try and elaborate.

There is only one tank shut off valve. The output of the pumps are teed together before the inlet of the shutoff valve and a pipe is taken from the output of the pumps to the inlet of the single ON OFF (Not Left Right) shutoff valve. A pipe feeds fuel from the output of the shutoff valve to the fuel injection. One pump is fed from the left tank the other pump is fed from the right tank. The pumps are mounted close to the left and right wing roots to alleviate vapour locking by keep pipe runs from the tank short. Feed back of fuel through the pumps is prevented by check valves (included in Andair pumps).

It is possible for the system I have described for one or both pumps to run against a blocked line. In this case the fuel is going nowhere and the pumps continue to run. I have not done any tests but I suspect the current consumption of the pumps would rise. Overheating may happen in time but as I said your attention would be drawn to the lack of sound coming from the front end for that to be any extended length of time. Running the pump against a closed valve is less of an issue for me. I want to avoid vapour locks by pushing fuel as much as possible rather than pulling it. With proper checklist consultation on the ground with respect to turning on the fuel valve, running against a closed valve is next to impossible

I hope this is more clear now.


frankh has been running a similar system. This is not my original idea and I do not want to steal his cudos.
 
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Yes, you could run both pumps at the same time, or one at a time.

The system had two batteries. One battery was for the back up pump only and could run the pump for 1/2 hour in the event of a electrical system failure.

I sold the plane a few years ago so I am just going by memory. :eek:
 
I have an RV-6A with an O-320-H2AD with dual electric fuel pumps. I am using two Facet pumps p/n 40109 which look very close to what Van's supplies, however mine are internally checked so I can run them in parallel. When I had both pumps in series and both running the fuel pressure would go over 10psi, which is more than the 8psi max which is all the carburetor should see. Even after rebuilding my carb, it would leak past the needle & seat with both pumps on.

I have a dual battery setup, with the capability of running either pump off of either battery, (off-on-on switch). My main battery is a PC-680 and back-up battery is a B & C 7.2ah battery. The reserve in the back-up battery is more than enough to run the engine for several hours.
 
islandmonkey said:
....Running the pump against a closed valve is less of an issue for me. I want to avoid vapour locks by pushing fuel as much as possible rather than pulling it. With proper checklist consultation on the ground with respect to turning on the fuel valve, running against a closed valve is next to impossible

I hope this is more clear now.
Click to expand...

Much more clear now. Thank you very much for explaining it to me.

Dave
 
Rotary switch???

OK the design of my system has some fundamental design criteria.

1) No single point of failure..for that reason a single left/right/both switch is not acceptable to me..I use two dedicated switches on/off. Mechanical fuel selector is gone as well. Dual electrical systems..I use a single battery dual alternator system (works for IFR and an electronic panel as well).

2) Fuel pumps in the "hydralically correct" place.. I put mine in the wingroots..I could be talked into putting them both on the floor in front of the spar now..and maybe (gosh darn) use the mechaical selctor..

3) No machanical fuel pump...Its in a horrible place hydralically speaking..it sucks uphill and is on the back of a HOT engine. Worse place you could put a pump that is trying to pump a high vapour pressure liquid. You are basically hoping the fuel won't boil..which is why a lot of low wing airplanes are limited to running 100LL

4) Must run whatever is on the street corner..see 3 above, plus the compenentry must be happy on ethanol (which the mechanical pump is not).

5) bone head simple to operate...just turn both pumps on for TO and landing, then switch tanks by running the appropriate pump.

The only downside is needing to keep a reserve of fuel in each tank..5 gallons has never been an issue for me and you can go a long way in an RV on 5 gallons of fuel.

Frank
 
OH yes

The two fuel pumps are fed with dedicated circuits..as an electric only fuel system I can't have a single fuse blowing stopping the big fan.

Hence the care in making sure both pumps are electrically isolated as far as possible.

Frank
 
frankh said:
OK the design of my system has some fundamental design criteria.

1) No single point of failure..for that reason a single left/right/both switch is not acceptable to me..I use two dedicated switches on/off. Mechanical fuel selector is gone as well. Dual electrical systems..I use a single battery dual alternator system (works for IFR and an electronic panel as well).

2) Fuel pumps in the "hydralically correct" place.. I put mine in the wingroots..I could be talked into putting them both on the floor in front of the spar now..and maybe (gosh darn) use the mechaical selctor..

3) No machanical fuel pump...Its in a horrible place hydralically speaking..it sucks uphill and is on the back of a HOT engine. Worse place you could put a pump that is trying to pump a high vapour pressure liquid. You are basically hoping the fuel won't boil..which is why a lot of low wing airplanes are limited to running 100LL

4) Must run whatever is on the street corner..see 3 above, plus the compenentry must be happy on ethanol (which the mechanical pump is not).

5) bone head simple to operate...just turn both pumps on for TO and landing, then switch tanks by running the appropriate pump.

The only downside is needing to keep a reserve of fuel in each tank..5 gallons has never been an issue for me and you can go a long way in an RV on 5 gallons of fuel.

Frank
Click to expand...

Good point with the rotary switch Frank. Single points of failure are not allowed or tollerated. Two sets of selector switches will be incorperated in my system.
 
In the system I was considering I may have added too much "flexibility"
at the expencive of realibility. That is I had one switch that selected main
or back-up battery and another that selected pump 1 or 2. The thinking was
if the main pump failed why be stuck with only one, small back-up battery
when the main battery was working fine. I will relook at that.

I also have two other questions. 1. When both electric pumps (In Series) are running
during take-off is the pressure higher to the point it could be too much for
the Carb 6 to 8 lb limit? 2. What are the issues concerning vapor lock? I always
thought is was a problem with the hot engine driven pump and the in-cockpit
electric pumps were unlikely to have a problem.
 
Last edited:
Details please

Frankh,
We know your set up works well.
I know bits and pieces of how your 2 pump system is set up but not all the details.
An engine driven pump starts pumping when you crank the engine.
How about yours, do you just turn the pumps on and start cranking.
Maybe another thread but I'd like to know all the details.
 
I have decided to go with a very simple( Batt)-(breaker)- ( AN switch Off-ON)-(pump)
repeated for back-up battery and pump with both circuits independant of
each other. The back-up battery will be charged on the ground by a external
trickle charger.
I am still unsure if during takeoff when ideally both would be on if the fuel
pressure would be too high for the carb maxium of 8 lbs/sq inch. Have any RV pilots using two of these pumps in series measured the fuel pressure when both pumps are on?

Thanks
Jim Miller
 
If the pumps are in parallel with each other pressure with both pumps on will not be a problem. When the pumps are in series the pump pressures are cumlative. If the total pressure of both pumps added together are less than 8 psi it won't be an issue.
The reason the pressures increase is due to the fact that a pump will increase the pressure of the inlet by what ever the pump rating is. The inlet pressure of the first pump is zero, so the outlet pressure will be as advertised of what the pump is rated at. The pressure at the inlet of the second pump will be what ever the first pump is rated at, so the second pump will add to the inlet pressure what ever it is rated at. This may not be exact math due to efficiencies, wear, etc, but it should be close. The above is only true while both pumps are on at the same time.
 
Last edited:
Details

N427EF said:
Frankh,
We know your set up works well.
I know bits and pieces of how your 2 pump system is set up but not all the details.
An engine driven pump starts pumping when you crank the engine.
How about yours, do you just turn the pumps on and start cranking.
Maybe another thread but I'd like to know all the details.
Click to expand...

On the FI'd system

Cold start: I simply turn on one pump for 5 seconds or so..This pushes fuel thru the AFP system and primes the engine. I then turn the pump OFF and crank the engine (it will flood if you don't turn the pump off). The mixture is at full rich.

As soon as the engine is running I turn a pump back on.

For a "hot start": I open the purge valve, turn on the right pump (the purge vents back to the right tank). The I turn on the pump for maybe up to a minute on a really hot day. Then turn off the pump, close the valve and do a cold start as above.

Taxiing I run as lean as possible

Take off: mixture full rich (sea level). Both pumps run

Cruise: turn off the pump to the tank I don't want. To switch tanks I turn both pumps on then turn off the other one...It gets your attention if you turn both pumps off..:)

I normally run LOP.

Landing.. Both pumps on, miXture full rich, prop forward etc.

Shutdown: turn both pumps off an wait for the engine to die.

For the carbed airplane it ran the same except to prime the engine I had a fail closed solenoid valve that would operate from a momentry push button. with the fuel pump running it would prime.

The rest is the same.

Cheers

Frank
 
curtis said:
I have an RV-6A with an O-320-H2AD with dual electric fuel pumps. I am using two Facet pumps p/n 40109 which look very close to what Van's supplies, however mine are internally checked so I can run them in parallel. When I had both pumps in series and both running the fuel pressure would go over 10psi, which is more than the 8psi max which is all the carburetor should see.
Click to expand...

Jim, This is the way my pumps will be installed. And I will also use the Facet 40109 pumps.

It will be, fuel valve, then the filter like this one.... http://www.jegs.com/i/Aeromotive/027/12316/10002/-1 100 micron cleanable. Then Fuel flow then the fuel pumps in parallel then to firewall.
 
Mechanical fuel valve

Frank

You mention you could be talked into putti the pumps inside and using a mechanical fuel valve. Would that be a shutoff only?
 
Pumps inside

zav6a said:
Frank

You mention you could be talked into putti the pumps inside and using a mechanical fuel valve. Would that be a shutoff only?
Click to expand...

If I put the pumps inside I MIGHT go with a fuel left/right selector valve.

I say "Might" because I have really come to love the simplicity of the system..I.e without a fuel valve. The only downside with this is that you have to leave a reserve in each tank. Having done several 1000+mile cross country trips this has never been a problem in the RV with 42 US gallons of fuel.

But a fuel selector means you don't have to leave a reserve in each tank, but then there system would then be twice as complicated to operate..:)

Frank
 
Fuel valve

I do run a fuel valve currently, but it is on/off only and is only shutoff in the event of a dead stick landing.

Fourtunately I have never used it..:)

Frank
 
gasman said:
Jim, This is the way my pumps will be installed. And I will also use the Facet 40109 pumps.

It will be, fuel valve, then the filter like this one.... http://www.jegs.com/i/Aeromotive/027/12316/10002/-1 100 micron cleanable. Then Fuel flow then the fuel pumps in parallel then to firewall.
Click to expand...


Single filter = single point of failure.

I recomend running two filters...put the filter and pump in series..then put each filter/pump combo in parallel.

That way if you plug a filter you simply switch pumps.

It has been known for "worms" of proseal to plug a filter..ask me how I know!

Frank
 
frankh said:
Single filter = single point of failure.

I recomend running two filters...put the filter and pump in series..then put each filter/pump combo in parallel.

That way if you plug a filter you simply switch pumps.

It has been known for "worms" of proseal to plug a filter..ask me how I know!

Frank
Click to expand...

I have no problem with one filter ( this one has a large surface area) installed before the fuel pumps in series ( the only way it will work) to protect the pumps and carb. Van has a gascolator mounted on the firewall that will allow the boost pump to clog with junk first. In the thirty filter inspections that I Have performed on my aircraft, I have never found anything of any value in any filter or gascolator.

I will admit that poor housekeeping on a new construction could cause you some problems in your fuel system.
 
How about a single filter on the output of each tank (total 2 filters), then fuel selector, then dual electric pumps? That's the system I'm planning, wondering what the pitfalls are.
 
After relooking at the problems of series pumps and possible over pressure
I am planning on switching to the 40109 pumps and running them in parallel.
Where is a good place to buy the 40109 as neither Van's or AC Spruce carries them.

Also regarding filters. As I understand it the cube pumps are not overly sensitive to something that would be later caught by the gascolator screen.
I always do owner assisted annuals on my Colt and have never found any
significant trash at annual in gascolator.

Hopefully the 40109 pumps are carried my some major auto parts houses.
 
Poor housekeeping?

gasman said:
I have no problem with one filter ( this one has a large surface area) installed before the fuel pumps in series ( the only way it will work) to protect the pumps and carb. Van has a gascolator mounted on the firewall that will allow the boost pump to clog with junk first. In the thirty filter inspections that I Have performed on my aircraft, I have never found anything of any value in any filter or gascolator.

I will admit that poor housekeeping on a new construction could cause you some problems in your fuel system.
Click to expand...

The worm of proseal in my fuel system which plugged the tube entering my filter was about 8 inches long and broke off about 2 years after the build was complete.

There are many things to bite you in this area. and i was glad I did not have a single filter.

I think I am the only one to have suffered from this though. The problem is the proseal if it does come off does so in large blobs.

Frank
 
jim miller said:
After relooking at the problems of series pumps and possible over pressure
I am planning on switching to the 40109 pumps and running them in parallel.
Where is a good place to buy the 40109 as neither Van's or AC Spruce carries them.

Also regarding filters. As I understand it the cube pumps are not overly sensitive to something that would be later caught by the gascolator screen.
I always do owner assisted annuals on my Colt and have never found any
significant trash at annual in gascolator.

Hopefully the 40109 pumps are carried my some major auto parts houses.
Click to expand...

Here you go....... http://www.yachtsupplydepot.com/mec...tate-electric-fuel-pump-40109/prod_23417.html
 
frankh said:
The worm of proseal in my fuel system which plugged the tube entering my filter was about 8 inches long and broke off about 2 years after the build was complete.

There are many things to bite you in this area. and i was glad I did not have a single filter.

I think I am the only one to have suffered from this though. The problem is the proseal if it does come off does so in large blobs.

Frank
Click to expand...

How did that 8" worm get past the finger screen on the pick-up tube?
 
In fact

I have found a few nobs of proseal at my annuals over the years. After the 'worm" incident i turned my filters back to front. This reduces the filtered area but allows the worn into the middle of the filter basket so it can't plug the tube at the inlet to the filter.

Frank
 
gasman said:
Jim, This is the way my pumps will be installed. And I will also use the Facet 40109 pumps.

It will be, fuel valve, then the filter like this one.... http://www.jegs.com/i/Aeromotive/027/12316/10002/-1 100 micron cleanable. Then Fuel flow then the fuel pumps in parallel then to firewall.
Click to expand...



Gasman
That filter looks good. How would it work to have one in each fuel line as
they run along in front of the spar just before the tank selector valve? Would
it then be safe/advisable to get rid of gascolator?

Jim
 
Gascolator

Hmm..certainly for an injected motor the gascolator seems to have littel benefit..Jus sump the tanks.

one could argue they are a safety enhancement for a carbed motor (surface tension of water is higher then fuel which means water can get "stuck" in the jets.

Having said that, my cerbed zodiac had 700 hours on it and does not have a gascolator on it.

i live in Western oregon..lots of RAIN here..:)

Frank
 
Just a question... And why do you not want a mechanical pump? If it is just machining the accessory case for the pump and push rod, that is not an issue. :)
 
No Mchanical pump

1) Its in the wrong place hydraulicaly speaking (sucks uphill..No pump is desgined to do that well).
2) Its on the back of a hot engine.
3) it won't tolerate ethanol.


1 and 2 leads to a risk of vapour lock (very dangerous) using mogas with a higher vapour pressure..and even somewhat marginal on 100LL.

Its just a poor design, it only persisits because the certification costs for certified airplanes to go the electric pump only route are far too high.

In other words it still exists for the same reason that vacuum gyros do, even though there are much better solid state electronic instruments available these days.

Its just a bad design hydraulically speaking.

Its more of a case of "why would you want one" for me..Ok thats a little unfair. The mecahanical pump will still work in the case of total electrical failure, but there are many ways to build failure tolerant electrical systems these days.

Frank
 
1) Okay
2) My temp is not over 120 F behind the plenum at any given time in flight
3) I don't use ethanol period! :)

Just wanted to ask.




frankh said:
1) Its in the wrong place hydraulicaly speaking (sucks uphill..No pump is desgined to do that well).
2) Its on the back of a hot engine.
3) it won't tolerate ethanol.


1 and 2 leads to a risk of vapour lock (very dangerous) using mogas with a higher vapour pressure..and even somewhat marginal on 100LL.

Its just a poor design, it only persisits because the certification costs for certified airplanes to go the electric pump only route are far too high.

In other words it still exists for the same reason that vacuum gyros do, even though there are much better solid state electronic instruments available these days.

Its just a bad design hydraulically speaking.

Its more of a case of "why would you want one" for me..Ok thats a little unfair. The mecahanical pump will still work in the case of total electrical failure, but there are many ways to build failure tolerant electrical systems these days.

Frank
Click to expand...
 
Actually

LifeofReiley said:
1) Okay
2) My temp is not over 120 F behind the plenum at any given time in flight
3) I don't use ethanol period! :)

Just wanted to ask.
Click to expand...

1) Maybe not..But i wonder what the temperatur of your engine block is?..I.e the block is conducting heat directly to the fuel.

3) I believe the ethanol actually reduces the vapour pressure of mogas somewhat, therefore making a mechanical pump less evil (note i didn't "acceptable or good").

What you have in the standard system is probably a non redundant system..I,e if the elctric pump quits on take off on a very hot day with a heat soaked engine then it is possible the mechanical pump will be on the verge of vapour lock. no matter what fuel your running.

Just fortunate those electric pumps are so reliable eh?...;)

Frank
 
Maybe you took me wrong... I was in agreement with you, I just don't use entanol. :confused:

BTW, I never use an electric pump on take off... JMHC


frankh said:
1) Maybe not..But i wonder what the temperatur of your engine block is?..I.e the block is conducting heat directly to the fuel.

3) I believe the ethanol actually reduces the vapour pressure of mogas somewhat, therefore making a mechanical pump less evil (note i didn't "acceptable or good").

What you have in the standard system is probably a non redundant system..I,e if the elctric pump quits on take off on a very hot day with a heat soaked engine then it is possible the mechanical pump will be on the verge of vapour lock. no matter what fuel your running.

Just fortunate those electric pumps are so reliable eh?...;)

Frank
Click to expand...
 
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