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05-07-2016, 12:57 PM
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#1
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Senior Member
Monaco Owners Club
Join Date: May 2012
Location: DFW, Tex-US
Posts: 6,196
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Was wondering about engine brake and fuel usage
Makes sense to me that use of the brake when Ira really not needed uses more fuel by slowing u down and having to throttle up to recover.
But does the fuel still flow when the brake is engaged ?
I use the cruise 99% of the time so the steady throttle doesn't allow the brake to engage but like the extra braking when in an emergency stop.
And the thing about emergency stops is that you don't know until it's happening, so not having to find the brake switch in a hurry is a good thing
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05-07-2016, 01:54 PM
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#2
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Senior Member
Join Date: Apr 2014
Location: On the Road
Posts: 1,608
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Gasoline engines use fuel on deceleration but diesels do not to the best of my knowledge.
2007 Monaco Executive 45' 525 ISX
__________________
2012 Nu Wa 363RSBDA
2016 Ford F-350 Dually 6.7
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05-07-2016, 02:05 PM
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#3
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Senior Member
Join Date: Dec 2014
Posts: 1,666
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Quote:
Originally Posted by Duoglide1
Gasoline engines use fuel on deceleration but diesels do not to the best of my knowledge.
2007 Monaco Executive 45' 525 ISX
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Gasoline engines have used fuel cut-off during deceleration at least as far back as the 1980s. It's easy to implement on anything with electronic fuel injection.
__________________
Mike
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05-07-2016, 10:35 PM
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#4
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Senior Member
Join Date: Aug 2001
Location: North America somewhere
Posts: 30,982
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Quote:
Originally Posted by JohnBoyToo
Makes sense to me that use of the brake when Ira really not needed uses more fuel by slowing u down and having to throttle up to recover.
But does the fuel still flow when the brake is engaged ?
I use the cruise 99% of the time so the steady throttle doesn't allow the brake to engage but like the extra braking when in an emergency stop.
And the thing about emergency stops is that you don't know until it's happening, so not having to find the brake switch in a hurry is a good thing
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Yes, enough fuel is still flowing to maintain low idle, which for most Cummins engines is 700 RPM. The only was to totally stop fuel flow is turn off the fuel solenoid.
__________________
2000 Winnebago Ultimate Freedom USQ40JD , ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA. " My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy
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05-08-2016, 05:13 PM
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#5
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Senior Member
Join Date: Nov 2011
Posts: 884
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Was wondering about engine brake and fuel usage
Quote:
Originally Posted by Ray,IN
Yes, enough fuel is still flowing to maintain low idle, which for most Cummins engines is 700 RPM. The only was to totally stop fuel flow is turn off the fuel solenoid.
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I'm sorry, but that is not correct. When you are off the throttle and the coach is moving at speed, there is no fuel flow at all.
I monitor fuel flow in gallons per hour with Silverleaf on a laptop computer. When coasting, the fuel flow shows zero gpm. As the coach slows to a stop, that fuel flow will slowly ramp up to maintain the 800 rpm idle. Fuel flow at idle is about 1.2 gpm.
I have the Jake Brake in our coach programmed so it does not downshift when I engage it. I use it 95% of the time. It is very helpful and my service brakes will last 200,000 miles.
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05-08-2016, 05:18 PM
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#6
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Senior Member
Join Date: Oct 2006
Location: Rochester NY
Posts: 2,706
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Quote:
Originally Posted by Rich-n-Linda
I'm sorry, but that is not correct. When you are off the throttle and the coach is moving at speed, there is no fuel flow at all.
I monitor fuel flow in gallons per hour with Silverleaf on a laptop computer. When coasting, the fuel flow shows zero gpm. As the coach slows to a stop, that fuel flow will slowly ramp up to maintain the 800 rpm idle. Fuel flow at idle is about 1.2 gpm.
I have the Jake Brake in our coach programmed so it does not downshift when I engage it. I use it 95% of the time. It is very helpful and my service brakes will last 200,000 miles.
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Rich-n-Linda are correct. No fuel usage when using the engine or exhaust brake on a diesel.
__________________
Don
'07 Winnebago Journey 34H - CAT C7, Koni's, MCU's, SS Bell Crank, Safe-T-Plus
'07 HHR Toad, SMI AFO, Blue OX
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05-08-2016, 11:10 PM
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#7
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Senior Member
Join Date: Aug 2001
Location: North America somewhere
Posts: 30,982
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Quote:
Originally Posted by Rich-n-Linda
I'm sorry, but that is not correct. When you are off the throttle and the coach is moving at speed, there is no fuel flow at all.
I monitor fuel flow in gallons per hour with Silverleaf on a laptop computer. When coasting, the fuel flow shows zero gpm. As the coach slows to a stop, that fuel flow will slowly ramp up to maintain the 800 rpm idle. Fuel flow at idle is about 1.2 gpm.
I have the Jake Brake in our coach programmed so it does not downshift when I engage it. I use it 95% of the time. It is very helpful and my service brakes will last 200,000 miles.
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Can you verify your silverleaf is accurate? I do not think you are correct. How does your silverleaf determine the fuel solenoid is closed when the ignition key is on?
__________________
2000 Winnebago Ultimate Freedom USQ40JD , ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG 11B5MX,Infantry retired;Good Sam Life member,FMCA. " My fellow Americans, ask not what your country can do for you, ask what you can do for your country. John F. Kennedy
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05-09-2016, 01:34 PM
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#8
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Senior Member
Join Date: Nov 2011
Posts: 884
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Was wondering about engine brake and fuel usage
Ray, it is standard procedure in diesels that when coasting, there is no fuel flow. Fuel is shut off in that performance scenario.
Silverleaf monitors a fuel flow sensor that determines the actual fuel flow in gallons per hour. That data is sent over the J1939 data line with all the other performance parameters that Silverleaf can monitor. When coasting (Jake brake on or off) the fuel flow is zero gallons per hour (GPH). No fuel is being injected into the cylinders. The fuel flow on the Silverleaf shows zero GPH.
As the coach slows to about 5 mph, that fuel flow begins to ramp up until when stopped and idling, the fuel flow is just over 1 GPH at the 800 rpm idle speed. At full throttle, fuel flow is up in the 18-20 GPM area, depending on RPM.
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05-09-2016, 10:23 PM
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#9
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Senior Member
Country Coach Owners Club Solo Rvers Club iRV2 No Limits Club
Join Date: May 2011
Location: Vancouver, WA
Posts: 37,725
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Quote:
Originally Posted by Rich-n-Linda
Fuel flow at idle is about 1.2 gpm.
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gpm = Gallons Per Minute? Pretty high fuel usage IMHO!!
__________________
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft, HWH Active Air
Charter Good Sam Lifetime Member, FMCA,
RV'ing since 1957, NRA Benefactor Life, towing '21 Jeep JLU Rubicon Ecodiesel
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