Fuel line Configuration

[Andy R]

Im trying to finalize my fuel line configuration for return and sending with a RCI tank that has the 1 top vent and 2 bottom fittings. Here is a picture of what I currently plan on doing. Do you see a problem with running the return line back into the T to feed the pump? Would it be better to return to the other lower fitting?

To be honest, the thing I like the least about the configuration in the picture is what appears to be hard aluminum lines? I might be wrong but that is what they look like to me.

I would rather see steel braided teflon lines that will take vibration with no risk of breakage and would flex in an accident. Go to a hydrolic hose maker with your stuff you have made and have them make the new hoses from those measurements. You should be given a choice of SS or brass fittings, go with the brass unless your dealing with Methanol.

As far as the return line, what injection system are you running and on what car? The size of the "lines" in the picture will supply enough fuel for 1000+ hp! Is that a Walbro pump in the picture? Damn good fuel pump, but not good for 1000hp.

The return line should work just fine, what were your concerns over the placement? What you did is a good thing (the Home Depot fitting could be better) but it's just the return. The hose maker will fix that easily for you and incorporate it into the lines.

Welcome in Andy! Ask questions anytime, hope this helped.

Just keep in mind there are a few Engineers in here that are guru's at everything, Probably cook up a good omlet in the morning too. so don't worry about their snide comments that is just the way they are, just ask away.

Edit, please do a better job mounting the fuel pump, those gold sheet metal screws just don't hack it, we joke about them because we use them in extreme cases also, nut and bolt please or insert sheet metal, make it look clean. nobody will see it but you know what you did! And know you can do it better. (straps also)?

Edit, Do it right the 1st time! Don't be an Engineer and have everyone else fixing your, opps I forgot that part, or "yep" could have done that one better, eeeeeh yea but the techs will fix it let it go.

Mont.

[This message has been edited by Marzracing (edited January 22, 2005).]

[ddewhurst]

***Just keep in mind there are a few Engineers in here that are guru's at everything, so don't worry about their snide comments that is just the way they are, just ask away.***

***Edit, Do it right the 1st time! Don't be an Engineer and have everyone else fixing your, opps I forgot that part, or "yep" could have done that one better, eeeeeh yea but the techs will fix it let it go.***

Mont, do you have a issue with or about engineers you would like to talk about ?

What is your profession ?

David Dewhurst
CenDiv #14 ITA/7

[John Herman]

Just thinking out loud here..but would there be any issues of cavitation with the return line T-ing in like that. I think I would put a filter/small tank where your T is to act as a bit of an accumulator. Would help to solve any fuel starvation issues and/or get all the fuel out of the cell. I agree with the hard tubing comment. You'll need at a minimum some short braided sections to absorb the vibrations. Look under any street car and you'll see hard steel lines running most of the length of the car, with sections of flexible joining to the filters/tanks/pumps. It will help with assembly/disassembly as well. Nows the time to be asking the questions, not at the track. Good luck. PS, yes I'm an ejumakated injuneer.

[JohnRW]

The return line will often have lots of aeration - that's why I like to dump it back into the cell and let the bubbles go away. By making it a 'closed-loop' system, once the air checks in, it can't check out. That's the way the original designers intended for it to work.

[Andy R]

Yes, sucking air is what I was concerned about. The lines are 0.5" aluminum, with the Walbro 255 lph pump. Currently 4 450cc injectors. Those actually are nut/bolts and not sheet metal screws holding the pump down. I may try using a sump cylinder in that opening behind the cell fittings.

This is all on my 89 Honda CRX Si (heavily modified) but will not be raced in SCCA. I just plan on taking it to open events. In the near future I plan on getting another Si and running ITA. But right now i'm working on my last semester of school at Iowa State University in Electrical Engineering and will be starting in a hardware/software design position at Rockwell Collins in May. Once I am finacially stable, I will begin to invest some time and money into ITA. If anyone is curious about this CRX, you are welcome to comb through my pictures. I'm sure some may not like some of the stuff, but I am proud to have done all the work myself (painting, designing exhuast/downpipe, building engine). Intentions of this car are for a nice weekend cruiser and something I can take to the track on occasion.

http://www.public.iastate.edu/~ajross

B16a cylinder head and block. Currently building ductile iron sleaved B18 block with JE/Eagle 9.0:1. Garrett T3/T04e 0.63 a/r turbo with custom made charge pipes, downpipe, and modified Starion IC. I'm shooting to keep boost around 9-10 lbs (225 hp) on 92 pump, with the ability to run higher. I'm sure I will learn much from this, and will eventually swap out components (IC, turbo) for more efficient units.

If anyone notices anything that may compromise my safety, please let me know. I'm sure i'm going to get flak for the rear spoiler, but as you may notice in a few pictures, I am working on an electronic moveable spoiler. I've been looking at some factory and aftermarktet units for ideas and have sourced some inexpensive alternatives. I will be modifying some Toyota seat sliding Acme drive screw sets with flexible shafts connected to two GM actuators. The great thing with a variable wing is that the downforce is variable. Theoretically, I could set it up so that accelerating on the straights, the spoiler flattens out, 0 downforce, near 0 drag. Then dipping into a highspeed corner, it adds downforce, depending on the vehicle speed, to keep the back end planted.


[This message has been edited by Andy R (edited January 22, 2005).]

Just wondering? Where did the air in the return line come from?

We have flowed many systems for a lot of years and never came across that one, must be new?


Mont.

[Andy R]

I wasn't sure how constant the pressure would be and if there would be an adverse effect if the return flow was greater than the pump send flow that would require the pressure to push the gas back into the tank. If I were to use a sump, would you suggest this:
line from cell to sump end
line from opposite sump end to pump
return line into sump

And would any check valves be required?

Thanks for you help Mont

Your fuel system has a fuel pressure regulator on the fuel rail to the injectors, pressure to the pump is not a problem, infact, it will take some strain off the pump.

Your welcome, have fun with your project.


Mont.

Went and looked at some of your pictures, WOW you have a real project going on there, bet you can't wait for when it's done and rippin 10 second quarter mile times.

Looks good.

Mont

[apr67]

Return line contains fuel that is hot.

Dump it into the cell so it can cool down.

Hot fuel? How long do you think it will take for the fuel in the tank to get hot? The heat aspect is not even a variable to consider.

Keep the system the way you have it.

Mont

[apr67]

Originally posted by Marzracing:
Hot fuel? How long do you think it will take for the fuel in the tank to get hot?

Huh? It would take a while for the fuel in the tank to get hot. But if you re-feed fuel that has already been heated by its trip through the fuel rail back into the fuel rail it will be MUCH warmer than fresh fuel from the tank.

apr67,

What is your point? Fresh fuel? Warmer fuel? I just don't get where your going? Warmer as in better fuel atomization? Warmer intake air temp? Warmer for the good? Warmer for the bad?


Mont

[This message has been edited by Marzracing (edited January 23, 2005).]

[apr67]

My point is simple.

Hot fuel is bad for power.

apr67,

You have got to be kidding me! Fuel atomizes better at higher temps, better atomization
happens with hot fuel! More HP happens with more fuel atomization, cold air makes even more power/split that one Engineer!

apr67, What are you an Engineer of? Can't be automotive related is it? If it is you must work for VW! Their Engineers these days suck.

Or if you say your an Engineer that means you know everything about all things?

Just asking with a smile.


Mont

[JLawton]

Ohhhhhh boy, here we go again.


------------------
Jeff L
#74 ITB GTi

[Greg Gauper]

Okay, not a 4-year degreed engineer (just a plain associates degree in electrical engineering) but I can pass on a lesson I learned the hard way.....

I think the power difference between 'hot' fuel and 'cold' fuel is a moot point. However hot fuel, does present a different problem in that it is much easier to aerate than cold fuel. This in itself isn't a problem, but if you route your suction line too close to the return line, and the return line fuel becomes aerated for whatever reason, your Fuel Injection system will have fits.

When I first converted to Production (involved the addition of a fuel cell) and upgraded from carbs to FI, I figured I would be clever and dump my return line fuel back into my surge tank, so that the surge tank was always full. This worked great.....until the ambient temperature got over 70 deg, at which point the return line fuel in my setup became aerated. This would get sucked up into the pump, become further aerated, pass thru the regulator and dump back into the surge tank to become aerated even further, in a vicious circle.

I spent two race weekends trying to figure out what was going on (car ran great when it was cool out in morning practice, but ran crappy in the afternoon when it got warmer than 70 degrees). I got lucky and happened to peer inside the cell with a flashlight and could see the air bubbles from the return line getting sucked into the suction line, with the car idling, but running rough. I then reached into the cell with a long screwdriver and gently pushed the hose about 2 inches away from the suction line and the car instantly ran better!

The solution was to add a small baffle to the surge tank to keep the return line seperate from the suction line, and I also added a small scrap of cell foam to help break up any air bubbles.

One more comment....as I said before, the hot fuel/cold fuel issue is probably a moot point regarding power. But keep in mind that some fuel pumps rely on the fuel passing thru them for cooling purposes. So while you may or may not see a difference in power as a result of hotter fuel, you might (strictly opinion here) have reliability issues by pumping 'hot' fuel thru the pump.

FWIW - in my setup, even though I'm dumping my return line fuel into my surge tank, and it could potentially cause the fuel to get 'hot'....in reality, the way the fuel sloshes around on track and due to the design of the check valves in the surge tank, the hot fuel and cold fuel zones are pretty well mixed by the time the fuel passes thru the pump.

[This message has been edited by Greg Gauper (edited January 24, 2005).]

[apr67]

Cool fuel reduces temps, allowing a denser air charge. Our engines burn air, and the goal is more air.

[Quickshoe]

The old school (ol' skool?) way of thinking was that cooler fuel resulted in a denser fuel and therefore more fuel available to make power in a given volume. (anyone remember cool cans).

In my non-degreed engineering education in "automotive performance and design-engine and chassis theory" (college FSAE program 15 years before it existed). We learned that the greater the difference in temp between the fuel and air the greater the HP. The problem is when the fuel becomes too hot and the pump can't deliver enough (or any at all).

The problem I see with the installation is the cell and container themselves...that appears to be a rotary molded JAZ-type cell??? The edges of the container could cause some accelerated wear issues where they meet the cell as well.