aerated fuel

We are returning all of our returns to a manifold attached to the fuel shut off[hi speed,idle return,&pump saver]. From the end of that manifold we plan to use a #8 line to return everthing to [here's my question].if we plumb the #8 line to the bottom of our pump,or to the aluminum line supplying the pump-will that aerate our fuel?I've seen alot of guys using the same return system,but never payed attention how it was tied back to either the tank,pump,or supply line.Hope i wrote this so it makes sense?

 

For the way you describe it, I would run it back to the tank.

The problem comes in if one or more of the poppets don't open on the burnout and allow air to the pump inlet.

 

what is your application? what fuel system are you running? hat, stack, blown. i have seen some guys run returned fuel to a manifold before the pump inlet with no problems.
frank

 

i use this return style on small blocks....space issues.....main return+hispd+shut-off on a aluminum connection before pump......worked.....never had a problem.....

blown fuel small mopar, 727, fed chassis....

 

A lot of people do the return to the inlet thing and get along fine...or do they?
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On the flow bench it gets real obvious when this doesn't work. The right combination of pump, returns, etc to the inlet side of the pump will make the pump and my bench go into tire shake. It really gets my attention when it happens.
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I am an advocate of returning either to the tank (preferred) or a log at least a foot in front of the pump for the above reason. A foot in front gives things enough time to settle down plus it just eliminates the question all together.
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The only thing that vibrates worse than this scenario is that little gold water pump used on the toilets and it doesn't need a return to do it!
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Funny cars, altereds and promods. No reason not to go to the tank.
REDs: A log is used effectively.
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Dave Koehler
www.koehlerinjection.com

 

Thanks guys. Definitely the info I needed. Helped change my train of thought for the better.

 

Thanks Dave, I was waiting for a someone that flowed fuel systems to answer this question, I have always run my lines to the tank as I thought supplying the low pressure side of the pump with a higher pressure feed would reduce the efficiency of the pump and I have never asked the question.

 

where can a tee and poppet set up be bought to be used to return fuel back to the tank coming off the fuel shut off?

 

eli
InsideTopAlcohol.com Pro Join Date: Dec 2005
Location: lake ariel Pa.
Posts: 423

Quote:
Originally Posted by Funny_Winne
Hello Folks,
I am part of the only Funnycar team in Belgium, surely you have seen Danny from Belgium here on the forum, he's the owner and driver of the team.
I am normally responsible for the fuel system of the engine, and the data logging, since I am professionally involved with software.
We purchased an Autometer Data logging system, and we also changed from a Enderle pump to a waterman red pump, also the engine is an other one then last year, actually, only the blower (PSI) and hat are the same.
The Autometer data system has a few pressure sensors and also a flow meter. Allthough I still have to figure out how to connect all that (there is a frequency converter in the package that I cannot even find back on Autometer's website, and of which I don't know what it is used for...). As you can see, it is a used system we bought, we are budget racers with no sponsoring at all...
So the questions I have are the following, we used to run separate return lines from the barrel valve back to the tank for the main jet, for the high speed and for the pump saver. There was no pump sizer used in the system (with the Enderle 1000 pump)
Now that we have the Waterman pump, are we going to need a pump sizer? We have seen many collegues running their return lines to a junction block and back to the inlet port of the pump, is that a good idea? (aeration?)
What would be a good setup to do for logging the data of the fuel to the logger, where do I place the flow meter, and where do I place the pressure sensors for best and useable data? We use an enderle fuel barrel valve, hat and port nozzles, pretty standard stuff I guess...
Any help would be greatly appreciated!
Greetings from Belgium!
Erwin

Danny Lui colloqui divertenti

All kidding aside, if you were a plummer, and you conected 3 -4 in pipes into a manafold going into 1 -4 in pipe woulden`t you think that the 3 -4 in pipes would start to back up and you would be flooding or restricting the flow of said pipes??? I know everyone dose it,but I have to wonder what the beenifit to this is, I would think that if you ran a # 10 line back to the tank and manifold the # 6 lines to it, it would flow better and not interfear with the flow of the pump, think about it, you got a pump loop ,a hi speed, (if used) and low speed, all forcing its way into the flow of the pump suction, sideways no less, don`t you think it will afect the flow of the pump?? plus when the car is going down the track and gets into a little tire shake that pump is shaking too and the poppets are coming off there seat, then it goes into more tire shake cuz you just ran out of more fuel.back in the 60s there was no such thing as tire shake, all the lines went back to the tank, oh gee a little more weight, but no shake.One other thing all the poppet holders should be inbetween two hoses to insalate them from any tire shake, not mounted solid as they are now.

 

I'm not up on the tire shake thing being caused by where the fuel return line is but if you return to the tank you will areate the fuel. Think about it. The return line doesn't dribble back to the tank, it's under pressure. After you start the motor and do a burn out the fuel level is not full to the top of the tank. When the returned fuel is pressure fed back to the tank it's like spraying a garden hose into a bucket. It mixes air and fuel which then goes to the pump and nozzels. You may not even see the air bubbles but thet are there. If you return the fuel back to the main line 1 to 2 feet from the pump at an angle towards the pump it shouldn't disrupt the flow and there isn't any air in the line. Just my 2 cents..

 

Slayer: The tire shake thing was just an analogy. In review, the right combination returned to the inlet of the pump will vibrate the snot out of the bench due to cavitation. The issue also shows up in erratic flow and pressure but the vibration is a dead giveaway.

Fuel return to tank: It is assumed that the return will be spraying across the tank above the fuel level and not down into the fuel. This gives it settling time. A built in baffle is also helpful. I have not seen a problem doing it this way.

I have a clear tank that I use to flow some particular items. The returns spray across the top and while bubbles can be seen on the surface of the fuel at times they are gone in a blink of the eye.
I use methanol for testing and cannot attest to what water does as far as bubbles are concerned in this scenario.

The bubble thing working it's way down at the fuel tank outlet when the returns spray above and across the fuel level: Could be....maybe...might be..just haven't seen it.
As stated the 1 or 2 foot return in front of the pump works fine also.

 

I can't be more specific since I never wrote down any of the details and because it doesn't happen every day. It was a combination of pump size, nozzles and the amount of return flow that sets it off. By itself a sizer was never in the equation as I recall. All the items..pump etc. were fine by themselves.

I did not give it a lot of thought when it happens because it is what it is..not good. When I run into it I make changes and move on. Since the subject has come up I will keep notes next time.

 

We had a similar system with all 4 returns going into a baffeled/separator/reservoir and then back to the pump inlet line 24 in. ahead of pump inlet. WE had tried it with clear line to look for air--none. On Mandolinis dyno we made 15 more horsepower putting lines back to the tank. Over 9000 rpm pump supply did wierd stuff and as Fred said--dyno doesn't lie. We stopped popping belts in the lights for no reason by doing this. Fred convinced us not to play with something shaky if you can't afford to blow it up.