High idle fuel usage

[billmoocow]

Trying to figure out how much the 8v71 uses at high idle? I have not had a chance to work my advanced technology stick to dip in tank.

[luvrbus]

At a 1000 rpm and a average 145 hp on high idle .482 lbs x 145= 69.89 divide by 8 the weight per gal of diesel = 8.74 gals per hr and that should be pretty close for a 8v71N/A with 60 or 65 injectors same engine @ 296 hp at 2000 rpm will be 15 gals per hour @ .403 usage hope this helps

good luck

[billmoocow]

Oh boy. That looked like Greek to me. Fuel here is $3.70 gal X 15 in an hour? Not that i would sit there and idle for that long but i do occasionally go out and rev the @^#T@@ out of it for about twenty minutes. 

[RJ Long]

Oh boy. That looked like Greek to me. Fuel here is $3.70 gal X 15 in an hour? Not that i would sit there and idle for that long but i do occasionally go out and rev the @^#T@@ out of it for about twenty minutes.

Bill -

Far better to drive the coach (i.e. put the engine under load) than to go out and rev the @^#T@@ out of it for about twenty minutes.

A half-hour to an hour drive does wonders for all involved.   

FWIW & HTH. . .

 

[FAST FRED]

Any engines fuel use depends on the LOAD the engine is under.

High idle , not humping the ancient air cond (40-80 hp), is almost zero load .
A smart marine 3 or 4 stage regulator working with your alt is also minor.

Figure 1 GPH per hour of idleing  .

However idleing is not good for your engine , tho it may be required for a couple of min to air up , it should never be used instead of a road run.

100mi , 2 hours every month, will keep your engine , and all the rest of the systems happy , and help not loose your road skills.

FF

[luvrbus]

  A gal of fuel a hr at 900 to 1000 rpm with a 8v71 dream on the cooling fan,alternator and air compressor take close to 50 hp alone

[belfert]

I have no idea where Clifford came up with 15 gallons an hour at 2000 RPM to just idle.  Perhaps he meant 1.5 gallons.  It would usually take less than 15 gallons to drive an hour at 60 MPH!  2000 RPM seems like an awfully fast idle RPM to me.

[billmoocow]

Fred, you are right about i should not let it idle but need to air up once in a while to move bus. Still got crap all over the place in there and need to tidy up before i take it on a good run. The factory air has been taken out so no load there. Was just trying to get an idea of what the fuel consumption was whenever i did have it on high idle. Actually higher than high idle since i hold my foot on gas pedal. The high idle solenoid needs to be replaced so my foot is the high idle LOL. Luvrbus, thanks for the math.

[luvrbus]

I get it straight from the DD fuel chart I wasn't talking about idle at 2000 rpm but producing 296 hp at 2000 rpm it is in the manual in black and white if the 8v71 was in a boat producing 296 hp could you cover 60 miles in a hr ? and fast idle on a  stroke is 900 to 1000 rpm some go as high as 1200 rpm where your series 60 are usually set at 750 rpm

When I test run the 8V71 series and 8v92 a 1.5 gals won't hardly prime one lol

[pvcces]

I have yet to see a graph from Detroit that takes into consideration the load at any given RPM other than at full load. This makes it very hard to figure out how to set them up for best fuel economy. I do agree that Detroit does provide fuel curves, just not for partial loads.

That has led me to try to figure fuel use by experimenting. I've had a few successes, but it's time consuming.

Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska

[FAST FRED]

A simple rule of thumb is operating at 60% power or above a 2 stroke DD will create 16 HP for each gallon of fuel burned.

Spinning an engine  is  cheap with no external loads (an alt will take few HP for 50-100A@12v  ) AND MANY FANS ARE oil temp thermostated , so will not even come on at idle.

Go on one of the truckers boards , there may still be enough old folks that will remember ideling all night , to assure you of the burn.

Yes it waisted fuel, and caused the early death of the engine , but for most it was the companies truck, so "what me worry?".

FF

[luvrbus]

Tom it is done by hp and rpm the engine produces hp at any speed loaded or unloaded the next time you stop by I will give you a copy of the chart they use for marine and industrial engines 

A simple test use a 1 gal jug turn the 8v71 at 1000 rpm and see how long it last it won't be anywhere close to a hr or find someone with a DDEC 6v92 and DD software it will tell you no guessing there and FF the fan on a MCI turns all the time it takes hp

good luck

[buswarrior]

Others can chime in on the physics involved, but those of us with functioning shutters and damper doors enjoy a reduced fan load when the cooling fans are choked off when engine temps are cool enough.

Removed, the fan consumes HP all the time.

happy coaching!
buswarrior

[lostagain]

BW, I can picture the fans trying to suck air against the closed shutters like a vacuum cleaner working harder with the curtain stuck in the nozzle. Would those squirrel cages work harder, or are they just spinning air without strain? Has the HP draw of those rad fans with shutters open and closed actually been measured? Just curious.

JC

[billmoocow]

This could get interesting!