Fuel Pump Controllers

[John@Outfront]

What that article doesn’t say is how large the vent should be. Just stating bigger than stock. They mention stock fuel tanks I assume in a stock car. Sure. Those vents are like 1/4”. Looking at lots of aftermarket tank manufactures they have #10 outlet, #8 returns and #6 vents as standard. 

 

[Kevin]

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[Rockwood]

Fuel pressure referenced PWM controllers have been used by Ford for 20 ish years now.  They do have some additional problems compared to regular fuel systems, but the benefit on pump life and other factors makes it worth it.

One thing to keep in mind with these systems: the fuel pump must be isolated from ground.  

 

[Fullthrottleguy]

What that article doesn’t say is how large the vent should be. Just stating bigger than stock. They mention stock fuel tanks I assume in a stock car. Sure. Those vents are like 1/4”. Looking at lots of aftermarket tank manufactures they have #10 outlet, #8 returns and #6 vents as standard. 

They state  - you can never go too big

I think thats a pretty good recommendation - Holley, Aeromotive,  AEM all recommend a vent the same size  as the outlet.   That seems reasonable - I Not sure how it hurts to make a bigger vent and be certain you will not have issues rather than being stubborn and bucking the trend just to do it - although I know people like to do that.

Real world experience has shown me you are asking for problems or spending more $$ with too small a vent  - maybe not on day one but over time. Unless you sell fuel pumps and regulators  and need more business, I think its a good idea going with the recommendations  FWIW

Here is an example...

 

[John@Outfront]

They state  - you can never go too big

I think thats a pretty good recommendation - Holley, Aeromotive,  AEM all recommend a vent the same size  as the outlet.   That seems reasonable - I Not sure how it hurts to make a bigger vent and be certain you will not have issues rather than being stubborn and bucking the trend just to do it - although I know people like to do that.

Real world experience has shown me you are asking for problems or spending more $$ with too small a vent  - maybe not on day one but over time. Unless you sell fuel pumps and regulators  and need more business, I think its a good idea going with the recommendations  FWIW

Here is an example...

View attachment 30290

well that example above doesnt work for our argument, the pump in this example is "in the tank" so the suction side of this pump is unknown and  could be equivalent  to a -10 but its unknown. but if it was an effective -8 or -10 then the return and vents are smaller which boost my position.

but it would be nice to know the minimum and then go up if you want.  You could never have too much rebar in your slab like putting it 6"OC but at least it would be nice to know the min. who wants to spend or install more than needed, i suppose more is better.    i know what you are saying and sure a bigger vent cant hurt but there is no science behind it, im mean i could run -12 fuel lines to my motor cause bigger cant hurt but if a -8 works and calculates out,  then i would like to run -8--no need for bigger

 

[Fullthrottleguy]

well that example above doesnt work for our argument, the pump in this example is "in the tank" so the suction side of this pump is unknown and  could be equivalent  to a -10 but its unknown. but if it was an effective -8 or -10 then the return and vents are smaller which boost my position.

but it would be nice to know the minimum and then go up if you want.  You could never have too much rebar in your slab like putting it 6"OC but at least it would be nice to know the min. who wants to spend or install more than needed, i suppose more is better.    i know what you are saying and sure a bigger vent cant hurt but there is no science behind it, im mean i could run -12 fuel lines to my motor cause bigger cant hurt but if a -8 works and calculates out,  then i would like to run -8--no need for bigger

I do think it works as an example of vent = outlet size.

I am not saying I have bothered to calculate the exact vent size for each situation, but following the recommendation pretty much guarantees no issues  and is easy to do  While going with a tiny vent has been demonstrated to cause trouble.  So why not just take the easy route and use a big vent - thats What I do and what works for me and nearly every racer.  You can use a pin hole and if it works for you .... cool ...Its just air...

Regarding the feed line discussion actually you are incorrect.  You can use too big an outlet and it will cause problems.  That may not be completely true on the pre - pump  gravity feed if the system is designed correctly but read below and see why that can be a problems too  - here is why "science stuff"

1.  Pressure and volume have a direct relationship - You may not be able to maintain the correct pressure in a bigger volume situation like a huge fuel line -   as the pump likely will not be able to fill that volume at that pressure - every pump chart assumes a certain pressure at a certain volume  - keeping the line full seems like an easy chore - if this was a Hydraulic system - but fuel systems are Not Hydraulic systems  and using a regulator is not an exact  "bleed"  so its a worst case scenario

2. If you manage to fill the big pipe  - you need a regulator and return to bleed off all the fuel you will be wasting trying to keep the pressure up on such a big pipe - that means heating the fuel aerating and and causing more fumes for your tiny vent to exhaust  - its just not practical

3. You will likely starve the engine on hard acceleration - thats due to the "weight/Mass" of the fuel - that will actually work against the pressure  - this is VERY common on drag cars. The hard acceleration actually pushes against the pump and cars loser pressure.  The fix is always to go with a smaller.

You can learn about arteries and blood pressure this way as well and why you pass out from high G's ( and why you have "check valves" in your circulatory system  (that how we learn how to engineer thinmgs - we mnostly learn from nature as yoiu know ...)

This also happens with poorly designed wet sumps and remote filters and coolers mostly on cornering - a dry sump is not just for the oil and in the pan but the oil in lines as well - that is a much better closed system with check valves

That science I actually understabd

 

[John@Outfront]

I do think it works as an example of vent = outlet size.

I am not saying I have bothered to calculate the exact vent size for each situation, but following the recommendation pretty much guarantees no issues  and is easy to do  While going with a tiny vent has been demonstrated to cause trouble.  So why not just take the easy route and use a big vent - thats What I do and what works for me and nearly every racer.  You can use a pin hole and if it works for you .... cool ...Its just air...

Regarding the feed line discussion actually you are incorrect.  You can use too big an outlet and it will cause problems.  That may not be completely true on the pre - pump  gravity feed if the system is designed correctly but read below and see why that can be a problems too  - here is why "science stuff"

1.  Pressure and volume have a direct relationship - You may not be able to maintain the correct pressure in a bigger volume situation like a huge fuel line -   as the pump likely will not be able to fill that volume at that pressure - every pump chart assumes a certain pressure at a certain volume  - keeping the line full seems like an easy chore - if this was a Hydraulic system - but fuel systems are Not Hydraulic systems  and using a regulator is not an exact  "bleed"  so its a worst case scenario

2. If you manage to fill the big pipe  - you need a regulator and return to bleed off all the fuel you will be wasting trying to keep the pressure up on such a big pipe - that means heating the fuel aerating and and causing more fumes for your tiny vent to exhaust  - its just not practical

3. You will likely starve the engine on hard acceleration - thats due to the "weight/Mass" of the fuel - that will actually work against the pressure  - this is VERY common on drag cars. The hard acceleration actually pushes against the pump and cars loser pressure.  The fix is always to go with a smaller.

You can learn about arteries and blood pressure this way as well and why you pass out from high G's ( and why you have "check valves" in your circulatory system  (that how we learn how to engineer thinmgs - we mnostly learn from nature as yoiu know ...)

This also happens with poorly designed wet sumps and remote filters and coolers mostly on cornering - a dry sump is not just for the oil and in the pan but the oil in lines as well - that is a much better closed system with check valves

That science I actually understabd

we might be talking past each other, im not incorrect, i am "not" promoting a bigger feed line then require but to the contrary.  i clearly stated in my post that even if you could "go bigger" which most do because bigger always seems to be better as they think, on the pressure side, "i would go with the smallest line that supports my flow/pressure requirements." i am always arguing for the conservative side.

im still not seeing any science behind the actual vent size.  if there is none i will conduct one myself.  Sure i agree a huge vent could "do no harm" but your not saying how small it could be.  just saying bigger is better and "same as suction line" are not scientific no matter how many times we say it.

 

[Goatpoker]

Just did a quick sanity check on the engineering. If you are pumping out 1 gpm of fuel then you need 1 gpm of air flowing in to replace it. That's the basics. 

Fuel is ~6.8lb/gal density. Air is ~0.01lb/gal. So, ballpark... it can be a lot smaller. LOL

 

[John@Outfront]

Just did a quick sanity check on the engineering. If you are pumping out 1 gpm of fuel then you need 1 gpm of air flowing in to replace it. That's the basics. 

Fuel is ~6.8lb/gal density. Air is ~0.01lb/gal. So, ballpark... it can be a lot smaller. LOL

there we go!  so can you put that in perspective? if a common -8 (1/2" id) supply line can support 1000 hp then how small/big does the vent need to be (at a min of course)? 

 if i understand what you are saying above, is it true then in theory the vent only needs to flow 1/680th of what the -8 fuel line can flow?

 

[lincster]

Uh oh.  Actual math.........   :bangin:

 

[Rockwood]

Couple of things he said that I don't think work well for offroad (like looping the vent), but these guys have worked with some faaaaast cars.  I think the offroad standard of running it up and over the main hoop makes even more restriction.

In any case, it's a vehicle fabricated from scratch and rubber hose.  Not hard to run it and won't hurt...

 

[Goatpoker]

there we go!  so can you put that in perspective? if a common -8 (1/2" id) supply line can support 1000 hp then how small/big does the vent need to be (at a min of course)? 

 if i understand what you are saying above, is it true then in theory the vent only needs to flow 1/680th of what the -8 fuel line can flow?

Correct. As we get into the detail what we need to clarify is pressure drop and velocity. As your vent hole gets smaller the velocity will increase and the pressure drop will increase (think about the whistle from your gas can vent).  At 1/680th diameter you will have similar air pressure drop as the fuel pump suction (~3-5psi).  If you pull 3psi vacuum on the fuel cell that would be bad... and impact the suction on the pump.

Some math: 2 gpm = 0.26cfm

3 feet of 1/4" tube will flow 6.7 cfm of air at 1psi. 1 psi is a lot of vacuum, so lets drop the tank vacuum to like 5inH2O (0.18psig) and see what flow we get... that drops it to 6.55cfm. 

Now, drop the tube diameter until you get 0.26cfm @ 5inH2O pressure and your result is ~1/32" tube to keep up with 2gpm fuel out flow. 

 

[John@Outfront]

Correct. As we get into the detail what we need to clarify is pressure drop and velocity. As your vent hole gets smaller the velocity will increase and the pressure drop will increase (think about the whistle from your gas can vent).  At 1/680th diameter you will have similar air pressure drop as the fuel pump suction (~3-5psi).  If you pull 3psi vacuum on the fuel cell that would be bad... and impact the suction on the pump.

Some math: 2 gpm = 0.26cfm

3 feet of 1/4" tube will flow 6.7 cfm of air at 1psi. 1 psi is a lot of vacuum, so lets drop the tank vacuum to like 5inH2O (0.18psig) and see what flow we get... that drops it to 6.55cfm. 

Now, drop the tube diameter until you get 0.26cfm @ 5inH2O pressure and your result is ~1/32" tube to keep up with 2gpm fuel out flow. 

wow so my -6 vent "super huge" compared to what i would need, out of curiosity sake how much more in % does 3' of 3/8" hose flow compared to 1/32" hose?

so i typed in how much fuel required for 800hp on e85 and this is what i got:

Remember, if you are running E85 or Methanol be sure to use those BSFC values in your formula as well as the appropriate lb/gal conversion value for your chosen fuel.. To calculate peak fuel consumption for an 800 hp E-85 engine we can use a BSFC of.70 and a lb/gal of 6.59. 800 hp x.70 = 560 lbs/hr 560 lbs/hr / 6.59 lbs/gal = 84.98 gph

So.....84.98 gallons per hour is  1.42 gallons per minuet at peak fuel consumption for making 800 hp on E85! 2 gallons a minuet on e85 supports 1136 HP in your example of 2 gallons per min on E85!  all with a theoretical vent size of 1/32"

 

[Dustinp]

Does anyone run one? I have a Weldon pump on my car now and it’s extremely loud. The pump is on the higher side of volume and I know it’s overkill for my setup even with the turbo.  The last Weldon I had lasted 20 years without a controller and was only replaced because I sucked at diagnosing a fuel issue. 
 

Does anyone run one and if so why?

The Weldon pump is a great pump. To cut back on the noise it has to be mounted with rubber isolaters. Probably reduced the noise by 70 percent. 

 

[ChasingSand]

The Weldon pump is a great pump. To cut back on the noise it has to be mounted with rubber isolaters. Probably reduced the noise by 70 percent. 

View attachment 35523

I never thought about doing that! No issues with flex or movement when duning?

 

[Dustinp]

I never thought about doing that! No issues with flex or movement when duning?

Does anyone run one? I have a Weldon pump on my car now and it’s extremely loud. The pump is on the higher side of volume and I know it’s overkill for my setup even with the turbo.  The last Weldon I had lasted 20 years without a controller and was only replaced because I sucked at diagnosing a fuel issue. 
 

Does anyone run one and if so why?

The Weldon pump is a great pump. To cut back on the noise it has to be mounted with rubber isolaters. Probably reduced the noise by 70 percent. 

 

[Dustinp]

No it's been good so far. For a test just unbolt it from your frame amd put a thick towel between the frame and pump and that will give you a idea of you quiet it should be. The frame works like a tuning fork when it's bolted directly. I tried just putting 1/2 thick neoprene between the frame and pump with the 4 bolts through the frame and it only helped a little. The rubber isolaters with studs on both sides worked the best. I used a jam nuts on the bottom of the pump. I added one up top to stabilize it. Its been running it like that for 3 years now. The pump used to be louder than my subaru engine. It was terrible.