Heater V Mpg

[voyager t180]

I was chatting to a mate today on the low MPG on the 180s, maybe caused partly by 1100 RPM for 6mls til the engine warms up.
He said try turning the heater off..and sure enough it works..revs drop to 650 from cold start .
I'd never have believed it.
All good if like me you dont mind the cold for 15mins.
every days a schoolday..

[Tech01]

Just wondering, when you say "try turning the heater off" - would the heater have been set to maximum? If it was on max, then the electrically-powered PCT heaters would come into operation on a cold engine (to provide quick cabin heat), and these heaters consume a large whack of alternator output. Correspondingly, the ECU ups the engine revs to provide this output.

Do the revs rise to 1100 with the heater set to just half-way (when the PCTs will not operate) between cold and hot?

Even with an idle speed of 1100rpm, the amount of fuel consumed by a diesel engine is tiny, compared to powered driving, and wouldn't have much effect on overall mpg. Wasn't the T180 just thirsty??

Chris

[voyager t180]

Just wondering, when you say "try turning the heater off" - would the heater have been set to maximum? If it was on max, then the electrically-powered PCT heaters would come into operation on a cold engine (to provide quick cabin heat), and these heaters consume a large whack of alternator output. Correspondingly, the ECU ups the engine revs to provide this output.

Do the revs rise to 1100 with the heater set to just half-way (when the PCTs will not operate) between cold and hot?

Even with an idle speed of 1100rpm, the amount of fuel consumed by a diesel engine is tiny, compared to powered driving, and wouldn't have much effect on overall mpg. Wasn't the T180 just thirsty??

Chris

No..thats with heater set to 20c..

But turned OFF completely the revs drop to 650rpm immediately,switch it back on again,back up to 1100rpm.

Once the temp guage starts to move past cold the revs drop down,usually after around 5mls.

If your outside temp is above around 12c you probably wont experience this.

I'm not saying I will turn it off,just wondered why it happened,now we know,thanks.

The T180 is thirsty on urban driving and more so in winter.(25-30mpg.

But the car comes into its own when warmed up M'way driving @ 60-70 mph and does return 35-45 mpg on cruise control.

Its a fantastic M'way driver,at 70mph you can hardly hear the engine at all..I love it.

And thanks for the great info.