People STILL don't understand fuel flow requirements !

[got...DIESEL?]

Diesel Dan...No hurry, and I respect your position. I mainly want to keep this discussion subjective without the brand wars that have ensued from this type of thread before. I think all fuel systems have their merits and demerits depending on many many variables that the owner must take into his/her own account when making a decision. Since this thread was re-visited on a different slant, I wish to keep it that way and not let it turn into a circus. So far so good. We ALL appreciate your efforts providing vendor support to the site and will not take that lightly. Nor do we expect you to involve yourself or your company in a thread for any other purpose than to relay the facts and methods as you see them. If you choose to bow out gracefully, we take no judgement. Do what youi feel is right and adequate and leave it at that.

Chris

[Superduty]

"You will note that at 2600 rpm and 260 hp it is using 15 gallons per hour at steady state."

OK... BSFC = (15 GPH x 7 lbs/gallon)/260 HP = 0.4038 lbs per HP HR.

BTW: a 325 HP 3rd gen has a BSFC of 0.390. So this ought to shut up those that say the 12V is better on fuel...

"Now if one were to extrapolate for a rising rate rpm to wot, and twin turbos, big injectors, giving some 600-1000 hp the fuel rate could indeed reach 80+ gph"

Fuel consumption has very little to do with RPM under WOT conditions. The turbos and injectors don't make much difference either. It is all related to how much power the engine is making.

I'd guess that a worst case condition would be a BSFC of about 0.50.

So GPH = 600HP x 0.50 / 7 lbs/gallon = 42.8 gallons per hour. At 1000 HP, that goes to 71.4 GPH.

"and quite possibly significantly more due to wasted fuel given that the diesel in modified form is only using some 38% of its fuel to make power, according to many research papers available on the net. The rest is cooling the motor or is wasted out the exhaust pipe."


efficiency = power out / fuel in

1 HP HR = 2546 BTUs.
Diesel fuel is 18,500 btu per pound.

So:
BSFC of 0.4 = 2546 / (0.4 x 18,500) = 34.4 %
BSFC of 0.5 = 2546 / (0.5 x 18,500) = 27.5%

NONE of these engines are getting 38% efficiency. Other engines will, but not these engines, not at WOT.

"The fuel flow requirements for 700 hp will approach 270 cubic mm/stroke."

Lets assume that is at 3000 RPM for fun.

3000 RPM x 6 cylinders/2 rev/firing x 270 mm^3/stroke/ 1million mm^3 per litre x 60 minutes per hour = 145.8 litres per hour or 38.52 GPH.

BSFC = (38.52 x 7) /700 = 0.385 !

At higher HP, a lot of fuel gets wasted as heat out the exhaust. However, the losses due to friction, etc don't climb much. So BSFC tends to stay pretty constant. If the engine is smoking a ton, it might get to 0.5.

"By anyones standards thats a hell of a lot o fuel."

Its 38.5 GPH. NO BIG DEAL !

"Given that great lenghts were made to make sure that there was very little soot, our trucks would be usin way more than this when highly modified."

BSFC **MIGHT** climb to 0.5, but that is about it.

"You will also notice he is usin a lowly Holley Black pump rated at 110 gph.
For all the naysayers on gasoline pumps - keep in mind the the carter pump on a lot o your trucks was a gas pump once upon a time ;o)"

Yeah. They had 100 micron filters and carburetors that needed 2 PSI to feed the float bowl. A Cummins needs the fuel filtered to at least 10 microns, diesel fuel is more viscous, especially when cold and the injection pumps need 15 PSI to make sure the pumping chambers are full. Carburetor pumps belong on... CARBURETORS ! Do Ford, Chev, Dodge, VW, BMW, etc put a carburetor pump on their EFI engines or do they use an EFI pump ? Guess those carburetor pumps weren't so tough after all !

"In any event, the cummins can, and is usin a lot more fuel than anyone thinks it is, especially in most instances when under power at wot."

Apparently not ! Apparently even the highly rated Sidewinder is using less than 40 GPH.

"Aeration - absolutely its there, to some degree, and in some cases, a lot. All one needs is a small leak in the return line, fuel slosh in the tank, water, etc etc etc.......to cause it."

You need to put a clear piece of hose on your feed line and tell us how much air you see. Better yet, get a digital camera and show us a movie of all this air.

Pictures or video or it doesn't happen.

[ndurbin]

Something that just hit me while reading this thread and RamRollinCoal touched on it earlier.

We see how much the engine uses fuel wise. We all know the VP uses excess fuel to cool and lubricate it. That needs to be figured into the requirements for GPH needed also. Now I don't know what amount is req'd. for cooling and lube and not exactly sure how the cooling and lube fuel is delivered. ie. wether it's split off before the fuel enters the heart of the pump or is taken from the return line or what.

[monsterB]

Originally Posted by Superduty

I don't give a darn what brand of pump they use. What riles me is that people talk like these engines need 150 or 200 GPH.

You are exactly right that it comes from word of mouth and marketing ! Don't people think ? A 200 GPH pump will empty a 30 gallon fuel tank in 9 minutes ! When was the last time you saw a truck that could drink 30 gallons of diesel in 9 minutes ?

Think, people, think.

What makes this really funny is that the FASS has the regulator at the pump body. So the injection pump gets the 20 GPH that it needs and the other 130/180 GPH gets circulated back to the tank ! Talk about a waste !

"is the 150 overkill for most? sometimes....." IT IS OVERKILL ALL THE TIME ! For everyone. 24x7. PERIOD. Show me one truck that needs anywhere near 150 GPH. All this 95/150/200 GPH talk is nothing but plain BS, through and through. How come people can't figure that out is beyond me.

On the other hand, some people still think Ford 6.0s are good engines too.

THINK PEOPLE THINK!

I LOVE IT!

YOU HAVE A BRAIN, YOU USE IT OR YOU DON'T.....................

[Glacier Diesel Power]

Originally Posted by ndurbin

Something that just hit me while reading this thread and RamRollinCoal touched on it earlier.

We see how much the engine uses fuel wise. We all know the VP uses excess fuel to cool and lubricate it. That needs to be figured into the requirements for GPH needed also. Now I don't know what amount is req'd. for cooling and lube and not exactly sure how the cooling and lube fuel is delivered. ie. wether it's split off before the fuel enters the heart of the pump or is taken from the return line or what.

From a TDR thread way back when. A user took advantage of a flow meter and found that the VP returns roughly 30 GPH regardless of throttle position or load. I'll see if I can find the old thread.

Richard

[Diesel-Dan]

http://www.turbodieselregister.com/f...t=vp44+failure

[Glacier Diesel Power]

Thanks Dan. I had the flow right but I was wrong about the throttle position. Can't win 'em all...

[Diesel-Dan]

Yeah, no prob.....Rowland sent me the link a month or two ago...i was reading on it....just had it saved.....

[Superduty]

Those of us without a membership to TDR can't read anything beyond the first page.

[seeker1056]

well your figures are nice, and I dont argue em.

GOD I LOVE GREAT DEBATE - MAKES FOR THE BEST RESULTS

If all we were doin was calculating exact necessary fuel requirements you might be entirely correct.

However, exact fueling is far far far from what we do or what goes on in any motor that most run in competition, pulls, racing or boating.

I used different calcs, from a site on diesel consumption for tractors doing various jobs - n got different figures. I cant argue for them except they used completely different calcs than you did. Quite likely they incorporated all the things some of the rest of us have posted here, and maybe some we havnt even thought of. I shoulda bookmarked the site. There was more than a few sites so lookin shouldnt be so hard.

To the last post, bypass fuel has to be taken into account in calcs for fuel supply.

It is a documented in many places on the net that a diesel motor can and does use more fuel than it needs, and with a driven pump it is, depending on the pump, exponential to wasted fuel or unburnt fuel when set up to do what we do. Your statement might be true with stock injectors and stock pumps but not with all these edm'd multi hole specials people are usin, or the pumps with half the internals modified, or left out altogether. ergo, if you can pump thru the injectors .4 - .5 lbs hr or more, its goin out the pipe, and is still fuel flow - never mind wether the motor can use it or not. There was even a site where they showed that at a certain point fuel slowed down performance in the diesel, no matter what u did to supply more air.

Again many many sites out there i have read this stuff on for diesels, all written by engineers. Either they are all wrong or ........

I dont need to take any movies - there is far more people, sites, and information that disagrees with the stance taken here that there is not air introduced in fuel in normal operation.

Your posts are the very first ones i have ever seen that disagrees with air in fuel.

I may be wrong, but it is in my experience where the many have the same information, that the "one" is usually wrong for all the right reasons, meaning their experience has not shown such to be true. That bein the case, the fact that you have not seen it, does not make it so.

In any event you are entitled to your opinion, and beliefs and so are we.

It would be interesting to put a flow meter on a well done truck and just see what the actual fuel consumption is under all conditions.

A side note it took almost twenty years for the gas guys to beleive it was possible to use 3/4 gallon in less than 5 secs. I suggest that we may find our certainties are just "not" so as well.

[ndurbin]

So it sends back 30 GPH @ WOT.........so that was extra fuel supplied and the cooling/lube fuel...........still doesn't narrow down how much is req'd. to cool and lube to me. If you know the cooling/lube requirements and you have the figure the engine needs to run then that would be howto figure out the ideal flow needed for an application.

Or am I off-base here somewhere?

[Superduty]

"If all we were doin was calculating exact necessary fuel requirements you might be entirely correct.
However, exact fueling is far far far from what we do or what goes on in any motor that most run in competition, pulls, racing or boating."

Sorry, you are wrong. Engines don't suddenly disobey the laws of physics when you hook the truck to a sled. You gave me the example of the Sidewinder at 700HP and I showed exactly what its BSFC *IS* and how much fuel it needs.

"I used different calcs, from a site on diesel consumption for tractors doing various jobs - n got different figures. I cant argue for them except they used completely different calcs than you did. Quite likely they incorporated all the things some of the rest of us have posted here, and maybe some we havnt even thought of. I shoulda bookmarked the site. There was more than a few sites so lookin shouldnt be so hard."

I'm sorry, but tractors obey the laws of physics too. I can show you numbers from Cummins and Cat and DD all day long for trucks, gensets and boats and the math is ALWAYS THE SAME.

"To the last post, bypass fuel has to be taken into account in calcs for fuel supply."

Yes. My numbers are always what the ENGINE consumes. Extra fuel is needed for pump cooling. I highly doubt the VP44 has a return flow of 30 GPH. I suspect he didn't calibrate his flow meter for diesel fuel.

"It is a documented in many places on the net that a diesel motor can and does use more fuel than it needs, and with a driven pump it is, depending on the pump, exponential to wasted fuel or unburnt fuel when set up to do what we do."

Please show me these many places. Generally diesel engines run at an exhaust temp of less than 1500F. And when they do, the fuel consumption is on a BSFC basis is about the same. As proved by the Sidewinder example.

"Your statement might be true with stock injectors and stock pumps but not with all these edm'd multi hole specials people are usin, or the pumps with half the internals modified, or left out altogether. ergo, if you can pump thru the injectors .4 - .5 lbs hr or more, its goin out the pipe, and is still fuel flow - never mind wether the motor can use it or not. There was even a site where they showed that at a certain point fuel slowed down performance in the diesel, no matter what u did to supply more air."

Well, I am pretty sure that Sidewinder has non stock parts on it. As long as the exhaust temps stay reasonable, ie less than about 1500F, the BSFC stays about the same. And even above 1500F, it doesn't go squirrelly. Some engines make a ton of black smoke, but they are also moving a ton of air to to that or the exhaust temps get out of balance real quick.

"Again many many sites out there i have read this stuff on for diesels, all written by engineers. Either they are all wrong or ........ "

Well, lets see this information. Share it with us.

"I dont need to take any movies - there is far more people, sites, and information that disagrees with the stance taken here that there is not air introduced in fuel in normal operation."

Well, lets see some concrete evidence that there is air. How much air is in a gallon of fuel ? A pound ? A few ounces ?

"Your posts are the very first ones i have ever seen that disagrees with air in fuel."

There was this guy once, he thought the world was round, instead of flat...

"I may be wrong, but it is in my experience where the many have the same information, that the "one" is usually wrong for all the right reasons, meaning their experience has not shown such to be true. That bein the case, the fact that you have not seen it, does not make it so."

I guess my truck is special. I should patent my truck for having airless diesel fuel.

Let me ask you this: how many other people have even LOOKED to see if their diesel fuel has air in it ? That would require installing a clear line...

"It would be interesting to put a flow meter on a well done truck and just see what the actual fuel consumption is under all conditions."

All you need to do is look at the valve cover on a Cummins. It states the pump volume per stroke. From that do the calculation that I did above and you will know exactly how much fuel it uses. Even the 3rd gens have a mm^3/stroke figure on them, even though they don't have a conventional plunger and barrel.