Engines struggling (labouring)

[djones]

I've alwyas been of the opinion that your better revving an engine that it been under load and 'labouring'.

I was thinking about this and wondered what actually happens whan an engine is struggling? Also why is it bad for it?

Thanks

[zac510]

It's probably mostly a bit of an old wive's tale. Modern engines are very good and very durable!

But if you think about it, if it's struggling/labouring it might potentially misfire wasting fuel and wetting the plugs. at the lower revs you might also suffer a drop in oil pressure at the same time you are trying to demand a high bmep from the engine which may damage bearings.

[Carlos]

We used to call it 'lugging the engine' ...the motor is running at very low RPM and you open up the throttle and the motor bogs down, bucking and lurching ... it puts stress on the engine as the internal parts hammer away at each other.

[Belatti]

I can tell you what I do with my car:

Lets say a 1.6L street modern engine has a range of use of 5100rpm (from 900 to 6000)

- I never start in another gear thats not 1st gear.
- In 2nd gear never let the car drop under 1000rmp, if you are between 1000 and 1500rpm (lets say you have passed a corner) and you have to accelerate, dont push the pedal hard, make it go up slowly, the car noise will tell you how to do it, as you can actually notice if it is ´lugging´.
- In 3rd gear never drop from 1500rpm
- 4th and 5th never drop from 2000rpm (in 5th accel. slowly from there, if not reduce to 3rd or 4th)
- Try to work with torque, from 2000 to 3500 rpm, you´ll have max power maybe at 5500rpm but I dont recomend you run that high all time.

Torque curve is an opposed mirror to specific fuel consumption, so if you use max. Torque rpm there you have got less fuel burning per HP used

[Ray]

Just don't hit it with a big load of nitrous when it's loaded like that! I have 'souvenirs' from my Dads' machine shop to see what it does. Not good.