Fuel Consumption at Idle, Diesel

Submitted: Tuesday, May 30, 2006 at 18:03
ThreadID: 34422 Views:5503 Replies:7 FollowUps:1
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Does anyone have some actual fuel consumption values for the amount of fuel used by an idling diesel engine? I am asking this in the context of battery charging. Will it be much greater than that used by a petrol generator?
Many new vehicles have trip computers which display the fuel used so it should be easy to measure this under real conditions.

Phil I
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Reply By: Exploder - Tuesday, May 30, 2006 at 19:02

Tuesday, May 30, 2006 at 19:02
Just guessing as it would a depend on the size of the engine who makes it and blar blar blar< But i would say around 1-2 litres per Hour, wouldn’t recommend idling it for that long but.
AnswerID: 175690

Reply By: trolute - Tuesday, May 30, 2006 at 19:17

Tuesday, May 30, 2006 at 19:17
Hi there,

Pretty sure that your alternator is not going to put out much current at idle.

As for the fuel, i dont really know, but even though the motor would not be working hard, it is still using drawing a large volume, and you can't run them too lean, so im guessing it would not be a small amount.

AnswerID: 175697

Follow Up By: Member- Rox (WA) - Tuesday, May 30, 2006 at 23:59

Tuesday, May 30, 2006 at 23:59
My multi meter doesn't change with speed. Still get 13.4 vts
Each 1 diff I supose.
FollowupID: 431851

Reply By: Peter 2 - Tuesday, May 30, 2006 at 19:44

Tuesday, May 30, 2006 at 19:44
You would typically need the best part of 2k revs to get a decent charge out of the alternator.
Some of the high output alternators need even more. I can remember spending hours in a traffic jam years ago in a diesel troopy with an aftermarket voltmeter connected to both batteries and slowly watching the voltage drop as there was never enough revs to charge them up with headlights on.
AnswerID: 175708

Reply By: Member - Marquis - Tuesday, May 30, 2006 at 20:09

Tuesday, May 30, 2006 at 20:09
Do not idle newer diesels for more than about 20 minutes else your engine will die quicker than normal, first sign of idling your engine too long is a slightly rough idle.

AnswerID: 175715

Reply By: Member - Hugh (WA) - Tuesday, May 30, 2006 at 20:12

Tuesday, May 30, 2006 at 20:12
Hi Phil,

All things being equal, at idle the diesel engine will have better brake specific fuel consumption because it will run unthrottled and therefore not suffer the pumping losses of a throttled petrol engine.

I don't think we've got BSFC test data on small genset diesels but we did do a test last year for a customer evaluating a diesel genset running on heated palm oil. I'm pretty sure we did a diesel baseline. We didn't measure BSFC, as used the inbuilt generator for load as opposed to driving a dyno, but fuel consumption was recorded.

AnswerID: 175716

Reply By: V8Diesel - Tuesday, May 30, 2006 at 21:56

Tuesday, May 30, 2006 at 21:56
A diesel will glaze up if idled too long.
AnswerID: 175749

Reply By: Member - Hugh (WA) - Wednesday, May 31, 2006 at 19:35

Wednesday, May 31, 2006 at 19:35
Hi Phil,

Further to comments on testing of genset - found the report and points as follows:
1. Unfortunately didn't measure fuel consumption on diesel but did on palm oil (heated to 70'C to keep it liquid)
2. No idle but test done per EMA (engine manuf assoc) for this application (2.2 kVA genset), with cycle comprising 1hr 100% load, 1hr 95% load, 1/2hr 25% load and 1/2hr no load, repeated 5 times for blocks of 15hrs (total test 200 hrs). At no load the throttle is adjusted to meet manuf recommended curb idle (this is higher than std idle to avoid fouling issues as others have raised).
3. Engine speed governed ~ 3000rpm (varying from 3100 rpm to 3300 rpm as load reduced), with load varied by PLC controlled light banks.

Power output on palm oil less than on diesel (different calorific value ~ 8% plus comnbustion). Palm oil fuel consumption ~ 10 kg/15hrs (0.6L/hr) for the test cycle - suspect you'll get similar on diesel.

Anyhow, I hope this gives you a rough ball park for fuel consumption for a 2.2kVA genset, which seems to be about what your considering. For ref, test engine was a Yanmar L48 Genset. Yanmar info on L48 engine


AnswerID: 175974

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