Electric Fuel Pump

[surfguitar58]

My TCS came with a Facet FAC-40178 "cube style" electronic fuel pump. Looking back over what scant documentation I can find, this pump is for cars with "about 80 HP". The output pressure is rated "2 to 3.5 psi max" and the stock twin cam mechanical fuel pump puts out 1.25 to 2.5 psi, so roughly the right pressure range, but wrong horsepower. The engine is a Fed TCS with Strombergs.

Before I swap out the fuel pump for one rated for ~120 HP, is there something I don't know that makes the existing pump the better choice?

The car seems to drive fine, but I admit I never had the opportunity to drive it hard and "give it the beans" in my brief amount of suburban driving time before I had to put it into winter storage. The knowledge base on electric fuel pumps mostly chronicles the many opportunities to mis-wire the fuel pump, and not much on pump selection. I'd appreciate the tribe's advice.

[Pfreen]

I have the Facet 40288 which is 30gph and 3-4.5 psi and 60” of lift.  I use a Holly pressure regulator set at 3 psi.  I mounted the pump to the rear shock mount bar below the luggage tray, so it is about 14” above the bottom of the tank.  So, the suction spec is important as well to lift the fuel and overcome the inlet filter restriction.

[Grumblebuns]

My TCS came with a Facet FAC-40178 "cube style" electronic fuel pump. Looking back over what scant documentation I can find, this pump is for cars with "about 80 HP". The output pressure is rated "2 to 3.5 psi max" and the stock twin cam mechanical fuel pump puts out 1.25 to 2.5 psi, so roughly the right pressure range, but wrong horsepower. The engine is a Fed TCS with Strombergs.

That particular fuel pump is rated at 15 gph. Unless you're running full throttle for an hour at a time, is it possible to use that much fuel?

[BDA]

I second what Joji said. If you're really worried about it, you can get one with a higher flow rate and you'd probably want a regulator because the pressure would probably be too high.

FYI - the Europa documentation says the fuel capacity is 15 gallons. I don't think that's quite accurate. When my car was new, I could drive 90 mph all day and get 30 mpg. One night I was in the middle of (almost) nowhere in Colorado at 2:00 am with around 415 miles on a tank when my car started sputtering. Luckily I was able to coast off the highway into a residential area where, amazingly enough, there was a work truck with a gas can in it. I splashed a gallon or so in my car and took off! I only wish there was a way I could have left him some money or at least a thank you...

[surfguitar58]

What is missing from any documentation I have found is a pressure/flow curve. They tell us flow with 0 back-pressure is 15 gph, and "typical" flow at 1 psi is about 7 gph. We can assume max pressure (3.5 psi) happens dead-headed at 0 flow. Fudging a pressure/flow curve would then look something like the graph below.

The other pic is a screen shot from a Holley video on sizing fuel pumps showing the formula for calculating gph requirements. We are told gas engines have a BSFC (brake specific fuel consumption???) of .4 to .5 pounds/hp/hour, and gas weighs 6.2 pounds per gallon. So if my twink puts out 120 HP (optimistic?) I get 10 gph needed. BUT, at our desired ~2 psi we only produce about 3 gph! And that's not enough, right??

Oh well, I'm not going to do anything about changing fuel pumps until I have a little more experience with the car, and that won't happen until spring anyway. Then I will install a fuel pump rated for 350 HP and INSTANTLY my engine will put out 350 HP! Right? (If only it worked that way...) 

[jbcollier]

Strombergs and Webers do not like high fuel pressure.  Don't go over 4 psi.  2.5 to 3 is perfect.

Some people fit high pressure pumps and then use regulators to bring the pressure down.  I have worked on a couple of dozen cars with regulators and have noticed a couple things.  One, the actual pressure never matches the markings on the regulator.  It's usually off by quite a bit.  You need to use a known good pressure gauge to check and adjust as required.  Two, they can leak, sometimes spectacularly.

Myself?  I run a low pressure diaphragm type pump (similar to an SU) with no regulator.

https://www.bpnorthwest.com/mg/mgb/fuel-system/fuel-pump-electronic-dual-polarity-banjo-mgb-65-to-80.html

Can't remember the brand but we found these units to be very reliable.

The most important thing is that you run the pump with a safety cut-off device.  Any shunt will then automatically shut off the fuel.  I used:

https://www.amazon.com/ACDelco-D1876D-Professional-Cut-Off-Switch/dp/B000C9PBXU

As always, YMMV.

[BDA]

I believe I have the same pump as you, but I can't be absolutely sure. The only numbers on my pump that I can see are Patent numbers. I got my pump from Dave Bean Engineering. They list two cube type Facet pumps. One with AN fittings built in and one with internal 1/8 NPT threads which mine have. This one appears to be the 40288 because the DBE parts book shows it to be: 3 1/2 psi, 15 gpm - good to 180 hp. Now, the parts book is pretty old and they could have stocked different versions since then and before I bought mine about 20 years ago, but I think that's unlikely since, as we know, DBE specializes in vintage Lotus and other British cars which have engines generally under 2.0 liters.

So, I have a BDA (imagine that!) with 45mm Webers that was built and dynoed by DBE. I still have my rev limiter set at 6000 and at that speed my engine generates almost 150 bhp. I don't track or even autocross my car so it is possible that in situations where I am continually using the accelerator pump that I drain the fuel bowl but I think I would have a very difficult time doing that. I have accelerated to 6000 in the lowest three gears and I've never had any problems.

Back in the '70s, those cube Facet pumps were new and some friends who raced Formula Atlantic (240+ hp 1600 BDA motors) used them without regulators. There are too many of those pumps to see if there are any rating the pressure about 2 1/2 psi (for Webers) and a higher flow rate. I'm thinking my buddies used the same pump we have. They never had any problems either.

If you are still concerned, I would recommend that you call DBE and see what they say.

BTW - You are correct, BSFC does stand for Brake Specific Fuel Consumption

For fun, I've attached the dyno sheet for my engine.

[surfguitar58]

Great advice all. JB: is that in in-tank type pump? Looks like a little more research is in order. (Not getting anything done here at work today anyway.) Love the Colorado story BDA, I have an image of a surly construction worker finding some punk kid siphoning gas out of his truck into what he would see as a prissy little foreign sports car. 
Tom

[Arizona]

BDA, lucky for you that was Colorado. We hang gas thieves in Arizona...and confiscate their cars.

[BDA]

Then I guess I'm even gladder I didn't get a ticket for speeding in Arizona when I think I drove across the entire state one night at 90 mph on my way back home!

[jbcollier]

It's not an in-tank pump.  It's a clone, but more reliable, of the common SU fuel pump.

[Certified Lotus]

RD Enterprises sells an electric pump with the proper fuel pressure without using a regulator. I have one in my Elan for the last three years and it works very well. The TC was dyno’d at 150 HP.

[surfguitar58]

Just a follow-up to this thread I started back in January. I have been driving my TCS all summer with the fuel pump rated for “about 80 HP” and never had a problem until today. Most of my driving is genteel suburban driving with the occasional blast of acceleration on a particular stretch of rarely patrolled road, but even this is a nice controlled push on the gas pedal letting the revs catch up as I accelerate. For all this driving the little fuel pump performed flawlessly.

Today I had a visit from an old high school buddy who I of course wanted to impress with the Lotus, so on my little stretch of unpatrolled road, after uttering those fateful words “watch this”, I did something I never do; I put the pedal to the floor. The car accelerated nicely up to about 4000 RPM and then started sputtering and backfiring while still accelerating. This I imagine to be incomplete combustion caused by thirsty Strombergs not getting enough fuel.

So, on the advice of Ken Gray at Dave Bean, I will be replacing my FAC-40178 pump with a larger capacity FAC-40105 (rated for 150 HP, 3 to 4.5 psi max). I looked at some of the diaphragm pumps recommended in this thread but am going with the Facet cube pump because it is a direct bolt-up replacement for what I have now. Unfortunately, the old pump I am replacing includes an integral shut-off valve, and the new pump does not, and since the pump is below the fuel tank level, I will also be installing a separate inline fuel shut-off valve.

How often will I use that extra fuel pump capacity? At least as often as old high school buddies come to visit.

Tom

[Gmg31]

When I added an electric pump I also fitted a second hand impact cut off switch from eBay. The Europa is not a car that you can get out of in a hurry. In the event of an accident I wanted to know that the fuel flow would stop

[BDA]

+!

If you have an electric fuel pump you should have a fuel pump relay switch that will turn off the pump in the event of an accident.