how i did my fuel return

[damo99]

i was going to use the cb performance fuel return fitting.
but decided against it due to a worry about fuel not cooling.
so i pulled my tank and tapped a fitting into the fller neck .
can anyone see anything wrong with doing it this way
photo is at
http://i768.photobucket.com/albums/xx32 ... ga5rmb.jpg

[Clonebug]

Some say you will get fuel aeration from it splashing in the tank.

About the same chance as the fuel warming if you use a tee on the bottom.....

I use the tee and have for over 7000 miles now. I just tapped the inside of my tank outlet with a 1/4 NPT tap and then used a Brass Tee.
I haven't seen any issues with it so far.

I did it that way because it was easy and cheap.....of which I prefer over complicated and expensive.

My Buggy is a daily driver when weather permits....it's not a race car and therefore I might get away with things others don't, can't or won't risk.

The end result is it's your car and you build it your way after weighing all the possibilities and risks.

[aircooledtechguy]

I hear this said all the time around these forums that if you use the "T" the fuel will "heat up in the loop and cause issues" to the user. . . I have to say that I'm calling B.S. on this. I have yet to know of anyone who has actually had real temp readings that verify that (a) the fuel is getting "hot" (and what is the definition of "hot") and (b) it's hot enough to actually cause an issue with how the motor and injection system works. I've known MANY, MANY folks who have used the "T" and never suffered a single issue that could ever be traced back to hot fuel. N/A, turboed even SCed; no hot fuel issues. . .

You have a constant flow through nearly 20ft of tubing; tubing that acts as a heat sync to shed heat outside the engine compartment. Conversely it can also transfer heat to the fuel in the engine compartment, however, most folks run a rubber hose in the engine compartment which is a poor heat conductor for the fuel. You also have a constant influx of new fuel coming into the stream. I think most folks "fear" this "may" have an impact because of what others have "parroted" on forums but there's no real evidence of an issue because of it.

So does anyone have ACTUAL EVIDENCE to prove and actually experienced these issues first-hand and were able to definitively point to hot fuel as the cause, or it this just another in a long list of "forum urban legends"??

Believe it or not, I am open-minded about it and would love to be proven wrong, it's just that over the years, all I've ever heard offered up as "evidence" is things like, "I've heard. . .", "He said. . .", "It's been written that. . .", or "They say that. . ." Sorry, but that doesn't cut it.

[Chip Birks]

You guys have enough fuel in the lines post injectors to actually return to the tank? Time to make a little more power me thinks
I have never run the t, mostly just cuz I don't like it. Call me prejudice if you want. OEMs don't do T's. My current setup didn't even need any welding to have a separate outlet and return.

[Steve Arndt]

People with flex fuel sensors (Chip, Eric) have fuel temperature data. Maybe they can give some information.

[Chip Birks]

I wish I had the temp data. My current sensor seems to be a bit glitchy, I haven't ever gotten solid data from it. I need to figure out how to setup the temp stuff, and smooth the noise out of the alcohol %. One of these days I'll care enough to fix it. For now it's not a big concern.

Also, neither Eric nor I can offer comparative data, we both return to the tank. I do have an in tank pump arrangement though vs. his inline external.

[damo99]

You have a constant flow through nearly 20ft of tubing; tubing that acts as a heat sync to shed heat outside the engine compartment.
Believe it or not, I am open-minded about it and would love to be proven wrong, it's just that over the years, all I've ever heard offered up as "evidence" is things like, "I've heard. . .", "He said. . .", "It's been written that. . .", or "They say that. . ." Sorry, but that doesn't cut it.

i hear what you are saying,,,, but being in a split i only have about 2ft of tubing to the tank not 20,
i have only read about the hot fuel issue but i thought i wouldn't take a chance .
it was also easy to do it this way while the motor was out (fuel tank is right behind it ).
i did make a T peice for the for the outlet of the tank (like CB one)but wasn't really happy with it (someone modified the outlet of the fuel tank to screw in fittings)
as the outlet hole to the T peice was only about 4mm in diameter

[raygreenwood]

I have posted lots of posts on this subject. Years ago when I lived in Dallas...think really hot weather.....and worked at a plant with a really good lab and intruments......I went crazy over a 2-3 year period doing experiments on my cars simply because I could.... and I needed the info to trouble shoot mysteries in the running of my 411 and 412.

All in all I drove for at least 6 months with thermocouples hooked into my fuel system running to a fluke meter in the front seat.

The gist of it is...more precisely what I found out (and your results may vary). .....is that in hot weather in places like Texas where pavement temps range EASILY to 150°F in summer......your gas tank will heat up from heat reflected off the pavement. How much will depend on the design of your car, how close to the pavement, how much airflow, what color the tank is etc.

I mention that last detail just so you know that I bench marked the stable spring, summer and fall fuel temps....and yes they were significantly different....but in all climate situations.....the fuel temps in the tank on a sustained drive....reach an equilibrium that is related to ambient temps....and not engine temps.

This changes....I found at least on my car.....as the tank drops below about 1/2 full. The fuel temp still stayed stable.....but dropped a noticable amount most probably due to reduced fuel mass and reduced ability to bank heat....and fuel sloshing,around with air on a larger surface area of metal.

Does the trip through the fuel loop add heat to the fuel? Well...yes.....unless you ignore physics. If there is heat in the metal lines above the fuel temp there will be heat absorption. BUT.....the ability of fuel or any other liquid to absorb or shed heat is a TIME RELATED FUNCTION....not JUST a differential temp equation.
Also.....the fuel in most ACVW efi set ups spends far more time in portions of the fuel loop running through cooler non heated areas outside the engine compartment. ..than it does running through a decidedly warmer engine fuel loop. It has the potential to lose more heat than it takes in.

From my findings.....the cumulative heat rise to fuel imparted by the fuel line loop on my car....which would also be nearly identical to a type 3 and pretty damn close to a superbeetle ......was insignificant to non-existent.

You need to bear in mind.....that each small charge of fuel that traverses the roller cell chamber and passes the outlet check valve into the fuel loop.......to be pushed through the loop by incoming fuel behind it at a volume rate of between .6 to 1.0 liters per minute at pressure......spends at best .....between 7-10 seconds in the fuel loop (depending on length and volume per foot) before re-entering the fuel tank junction....depending on pump volume and engine usage.....which is only a few percent of what is actually pumped each minute or hour.

At an average of 28 feet of fuel line in a type 4 car (only anbout half of it metal)..... thats between 2.8 and 4.0 feet of travel per second. There is very little time to absorb much heat in the engine compartment. ...and even more time available to lose just as much heat in metal lines running through the tunnel.

The idea being proffered that the pump itself puts out 200-500 watts or more of heat.....is true.....but only a small portion of that is imparted to the fuel....and again....time in pump in important (and very small).....and surface area for loss between pump outlet and tank inlet IS HUGE.

By my findings....heat rise to fuel from engine and pump on ACVW systems is quite insignificant. Almost beyond ability to measure....even cumulatively ....because both heat rise and heat LOSS are cumulative. With other car and tank configuration and pump systems. ...your results may vary......but I would doubt by much. Ray

[aircooledtechguy]

Thanks for chiming in Ray. I trust your experiences since I know you've been doing these kinds of tests for years and years for your own learning. This is pretty much exactly what I had expected. I always hear people speak philosophically about this type of stuff with no first-hand experience to back up their claims. Such is the nature of the internet I guess. I still think the absolute biggest fraud is the debate over engine tin COLOR and it's effect on engine cooling. . . Sheesh!! Pure idiocy.

This was in no way intended as a negative toward our original poster. But rather on the other forces which "guided" him to his decision based on false info that's everywhere.

One of the reasons I started my website over 15 years ago was to ensure that there was at least one place that had info that could be trusted (see #3 on my main page). I always found it frustrating when I as starting out with my bus on the internet that everyone "knew how it should be done and what needed to be done" yet it became clear quickly that when I attempted the same modifications, lots of VERY important and key pieces of info were non-existent. When I would ask about these things half way through,. . . silence. . . Crickets. . . Because no one had actually done any of it themselves and I had been talking to the "parrots" again. . .

[damo99]

thanks for the info ray ,
intresting reading

[raygreenwood]

Thanks for chiming in Ray. I trust your experiences since I know you've been doing these kinds of tests for years and years for your own learning. This is pretty much exactly what I had expected. I always hear people speak philosophically about this type of stuff with no first-hand experience to back up their claims. Such is the nature of the internet I guess. I still think the absolute biggest fraud is the debate over engine tin COLOR and it's effect on engine cooling. . . Sheesh!! Pure idiocy.

This was in no way intended as a negative toward our original poster. But rather on the other forces which "guided" him to his decision based on false info that's everywhere.

One of the reasons I started my website over 15 years ago was to ensure that there was at least one place that had info that could be trusted (see #3 on my main page). I always found it frustrating when I as starting out with my bus on the internet that everyone "knew how it should be done and what needed to be done" yet it became clear quickly that when I attempted the same modifications, lots of VERY important and key pieces of info were non-existent. When I would ask about these things half way through,. . . silence. . . Crickets. . . Because no one had actually done any of it themselves and I had been talking to the "parrots" again. . .

While its quite true that black surfaces ....especially matt black surfacws....are incapable of reflecting away huge parts of the light spectrum.......including infrared (rafiant heat is primarily infrared light).... (this is the actual technical reason why black surfaces get much hotter than light colored and highly reflective suraces).......haviny black or white fooling tin will not make your car run any hotter.

The black tin itself will get hotter because it will absorb more heat. With cooling air flowing between it and the cylinders its likely not going to concuct, convect or radiate any significant heat into the engine.

However.....black outer cylinder coating with no insulating fillers will most certainly allow measurably better heat draw from the cylinders. I have written a pile about the testing I did on that back in about the same era.

The flat black, gloss black, flat white and gloss white colored steel plate test with a uniform heat source is one of the teaching tools i carry during my consulting gigs when training industrial shops for color theory.

Blows people's mind that four identical steel plates placed under the exact same energy/light/heat source for the same amount of time...can have surface temps that range from nearly hot enough to boil water (flat black) to just above body temperature (gloss white).

Ray

[volksbugly]

This is cool, but also pricy:
https://www.designengineering.com//cate ... ing-system

[aircooledtechguy]

This is cool, but also pricy:
https://www.designengineering.com//cate ... ing-system

Well, there's nothing better than adding complexity, weight and blowing through 4 bills to solve a problem that doesn't exist. . . Sign me up!!

[volksbugly]

This is cool, but also pricy:
https://www.designengineering.com//cate ... ing-system

Well, there's nothing better than adding complexity, weight and blowing through 4 bills to solve a problem that doesn't exist. . . Sign me up!!

But its soooo cooooooool.

[Piledriver]

My flex sensor reports my fuel gets pretty warm from recirculation after running awhile (+20-30F), and that's with a feeder and sump setup with a 044, return to sump.

In the peak of summer the fuel gets over 130F, well above the boiling point for gasoline.

A larger feeder would probably help matters, as would a small oil cooler in the loop.

It hasn't been an issue for me, but my setup gives the boiled off vapor a way out other than the injectors.

If there was a way to seriously preheat fuel (without creating problems) before it got injected I'd run it as it would mix far more uniformly.

The chilled fuel setups seem like a "parody of rice", but are actually like NA intercooling, and work well for drag racing.
An ice chilled intercooler would be even more effective, but any temp reduction increases air density.

That has been done in many forms since folks started racing things with engines..