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-   -   Lugging the engine - good or bad for economy? (

landspeed 06-18-2008 09:16 AM

Lugging the engine - good or bad for economy?
I was just reading another thread on here, where the final drive ratio was being discussed, and several people said that lugging the engine is bad, and will cause a drop in MPG.

What do people here think? Is Lugging the engine a useful tool for hypermiling or not?

dcb 06-18-2008 09:31 AM

lower rpm is good from an internal friction and lower stress point of view, but if it is run too low where the engine is bucking then that isn't so good :) I don't think hypermilers lug their engines.

PaleMelanesian 06-18-2008 09:52 AM

Anything above the jerky-jerky point is ok, if you're gentle on the throttle. Realize that there's not much power available and act accordingly. I'll run mine as low as 30mph in 5th (1700 rpm) and there's still enough for some gentle acceleration.

From a dead stop, low rpm (just above lugging) and gentle throttle is the best way to get up to speed.

landspeed 06-18-2008 10:12 AM

I have to say that lugging is very underrated among most hypermilers. I can't wait to get a manual car and start lugging again. I got 240% above EPA by using lugging and engine-off coasting in my last car :)

Daox 06-18-2008 10:32 AM

Your engine is not running at its best efficiency when it is lugging. You'll see better results from higher rpms. Take a look at this thread for more info on why this is.

dcb 06-18-2008 10:54 AM

I think we have to get our terms straight.

Landspeed, when you say "Lugging", I think many people are thinking of that mode of operation where the engine is literally bouncing back and forth because the rpm is too low for the given load. I suspect that isn't what you are talking about.

ebacherville 06-18-2008 12:35 PM

lugging is hard on the motor.. low rpm thats smooth isnt lugging..

landspeed 06-18-2008 01:02 PM


When I say Lugging, I mean high load, low RPMs, at the highest possible load to avoid the engine shaking / struggling. I was using about full throttle between 600 and 1200rpm in 5th gear (!), then lifting off to 65% throttle between 1200 and 1500rpm, then going to 40% or so throttle between 1500rpm and 1800rpm, before EOCing and coasting for a long time. (I was lifting off the throttle to avoid fuel mixture enrichment).

I think it may have been because my engine was low compression that it let me do this 'lugging' (although importantly it wasn't 'shaking', it was quite smooth). It started shaking below 600rpm.

Using this technique together with EOCing, I got about 54mpg over a whole tank which was around 240% of EPA IIRC, so about 140% above EPA (the car was a low-compression 1.8 petrol turbo with no aerodynamics at all, and it weighed about 1300kg (2860 lbs). No other method got better economy - and I was EOCing for up to 66% of the whole journey :)

johnpr 06-18-2008 03:53 PM

yep lugging is when when youre engine is "jerking" or working harder.

i usually drive in a "higher" gear than many people i know, for instance about 1000rpm 4th gear 25 mph.

th eimportant point is that if it seems like it is hard for your vehicle to do the work it is probably not good (i.e. no accel power, jerking engine, hard to maintain speed etc) but it is good to keep the rpms low and the engine running smoothly. i mostly drive in the city and get pretty decent gas mileage with this technique

Bror Jace 06-18-2008 07:59 PM

Lugging is more of a term of art than science ... so defining it as folks have done above helps.

Traditionally, Europeans think lugging is letting the RPMs go below 3,000. A friend of a friend ate up his Porsche's flat six driving like that ... because his mechanic told him to do it. :rolleyes:

I tend to drive at a very low RPM ... just above where the engine would struggle. My minimum speeds in gears for my stock '06 Civic are as follows (from memory):

5th 36mph
4th 24mph
3rd 13mph
2nd 7mph

I'll have to see where the RPMs are in these speeds 'n gears.

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