I, too have reservations about JaguarJoe's suggestion of the pressurized tank.

The fuel needs to be kept separated from the air, as in a fuel bladder. Might be OK if the tank were initially pressurized with nitrogen or CO2, as neither would present a hazard.

You might use a spring- or gas-loaded small stainless steel hydraulic cylinder.

 

Our fuel rate is 20cc / min. I just found this information for you.

Numbers do us little good in our case, because a lot of variables are un needed. The two variables we are trying to change are current consumption and PSI, thats it. All fuel pumps are rated for a certain given flow rate, PSI, and current. If the problem was going out and buying a fuel pump with just the basic information one can find anywhere, I would not have bothered asking a question here. Fuel flow is of very little concern to us as it is so low.

The fact is, our problem is a little bit more complex than looking at the numbers. We need a solution that seems to work in theory, then we will test that theory. We are working on an application that is severely current limited. Its not a regular car that can have an alternator and essentially limitless power. This car is fuel economy. Ever heard of the super mileage competition? Last year's winners did 3000 miles per gallon. Every milliamp counts to us. Every single load on the engine counts to us (alternator).

I will be having a design discussion with one of my guys over the weekend, and I will bring these issues up with him. This is good information.

 

Bit of info from a Ford EFI cousre may be of some help. Personaly i would be looking at Motorbike wreckers for a pump & reg then PWM the pump if necessary.

 

I gues if you want min load go back to a carby with an ajustable main jet you can lean it out with. There is always a trade of with realy lean mixtures such as burnt piston. Just curious if you are woried about a fuel pump current draw. Then how are you powering the ignition & the driving of the injector & its computer?

 

What about raising the tank above the engine and letting gravity do some work?

 

http://www.flightworksinc.com/products/pump/Product Datasheet, 2012-C03V-SSBBYZ.pdf

 

Interesting find, G.D.I.
Source for that PDF was this page: http://shopping.netsuite.com/s.nl/c.ACCT103531/sc.14/category.435/.f
3rd line down in the table.
That particular pump was designed for use with kerosene, diesel, etc. - fuels that would provide some lubrication and cooling to the pump. Not sure how well the standard configuration would work with gasoline. Might have to opt for the ___B-SP__ZZ configuration, which isn't a standard item. Be sure to specify the fuel you are using in your RFQ.

One thing that's virtually certain - these pumps won't be cheap.

 

What about raising the tank above the engine and letting gravity do some work

Model T fords did that - they had to back up hills.

For safety reasons, you really do not want a pressurized tank in the system that will spray gasoline after an accident. There are pretty spectacular under hood fires cause by fuel line connector failures.

Some cars have switched that kill power to the fuel pump in the event of an impact.

 

I tend to agree that the best option is to use variable speed on the pump. If pressure lag would be a problem on heavy acceleration, an accumulator would help to reduce that effect.

 

If electric load is a problem then use mechanical fuel pumps. I have one on an '86 toyota SR2 pickup. 1986 was the last year you could buy them with the 22R engine WITHOUT any engine control computer and related <SNIP>. Just a 4 cyl motor, distributor with points, carb, fuel pump, water pump, radiator and brakes. Standard 4 speed transmission, not automatic. A basic 4 wheel transport.

Didn't need no stinking electric fuel pump, or anti lock brakes. I changed out the radiator and water pump in 4 hours and only needed a 10mm, 12mm and 15mm wrench on 12 different bolts.

Try getting a radiator replaced on a toyota nowadays. $$$ take out a loan $$$

 

Holey cow.. If I am interpreting that graph correctly, the maximum current draw for that pump is 0.2 amps? How in gods name did they accomplish that one at even up to 50PSI? The only thing I can think of is a massive magnet.

Interesting find. Money is not a problem for us. We have a budget that is through the roof. We will try and buy some of those.

We have looked at mechanical pumps as well, but with our configuration, we think that such a pump would not be sufficient. The PSI on mechanical pumps is fairly low.

Thanks

 

Are you limited only to gasoline engines? Average efficiency is less then 20%. IIRC 50% has been reached but on huge engines on ships, not small 1cyl. Look into using a '6 stroke'. http://en.wikipedia.org/wiki/Six-stroke_engine "Reduces fuel consumption by 40%". Also their is water/alcohol injection available as kits. They are mostly used by racers but I can see it being used in every day driving.

 

it's not special, merely sizing the load. The same concept should be employed when sizing the engine to the load. Ideally, the engine should run against a fixed load, at it's highest efficiency operating conditions.

I hope JaguarJoe hasn't lost interest in the thread. Even though I couldn't support his suggestion, it does bring up a query. If the OP thought it was a good suggestion, that must mean that addition energy sources must be allowed, yet restricts the pump thing to a limited battery consumption (no voltage mentioned). That same volume of compressed air could be used to drive a fuel pump, or at least assist.

The PSI on mechanical pumps is fairly low.

On the contrary, it will be the highest, limited by your prime mover, which is typically your engine. Think Diesel.

 

Ah... Yes, I understand that now with mechanical pumps.. That was a dumb comment for me to say. Anyhow, what JaquarJoe suggested, we thought was a good idea; however, as people have mentioned, there are safety issues. I just put in a request for quote on those pumps that GDI found. Those pumps will be our best option, if the numbers really do pan out. It is also the simplest option as it would be a standard fuel pump assembly. We have an extremely low flow engine (20cc/min), a minimum PSI rating we must achieve (~40PSI), and a current consumption to look at. Those pumps fit the bill to the dime. I am almost ecstatically happy about you finding those pumps, because a 40psi pump that runs on as little as <200 ma is unheard of to me.

In regards to the engine, I believe that we have to use the engine that the competition says to use. It is a briggs and stratton 3.5hp 4 stroke engine. We already have bought a few of these engines for testing purposes. As far as I know, every team uses them at the competition.

 

Commercial off-the-shelf parts are the way to go; particularly if you can find something that close to your specifications.

You did mention in your RFQ that you were planning on using gasoline with it, correct?

I'd be interested to know what they have to say - and also what they are charging for them.

 

Well in the RFQ section they have an option for gasoline. So I basically said that. I also asked if their numbers were accurate lol. The current seems unreal for the specifications.

If you take a look at their higher power pumps, they are charging ~150$ for them. If that's the case for some of the lower power pumps that we want, its is extremely affordable and within our budget.

 

It is a briggs and stratton 3.5hp 4 stroke engine.

... I'll take that back for now.

Had spouted off about fuel consumption, but in double checking it was unfounded.

 

Frankly, the post should be pulled. You will basically be building a bomb.

Aw, come on. If Nasa can strap 7 guys to 550,000 gallons of LH2/LO2 and stick a match under them, we can level out a few ounces of fuel at 40psi.

Here's more accumulator stuff, a little spring loaded unit would work well:

http://www.hydraulicspneumatics.com/200/eBooks/Article/True/66530/