Maximum Torque = Maximum Efficiency?

Submitted: Sunday, Feb 05, 2006 at 11:14
ThreadID: 30442 Views:2567 Replies:3 FollowUps:1
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Hi Guys,

Just wondering if anyone can tell me with any authority, if the maximum torque RPM on a Diesel will also yield it's maximum efficiency, without taking into consideration the vehicle speed wind resistance etc. I'm just talking about the engine.

In my case the Patrol 3.0 TD produces maximum torque at 2000 RPM and the auto box always gets the engine sitting around that figure except once you get up to highway speed when it has to go over 2000. To about 2150RPM at 100km/h give or take.


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Reply By: theshadows - Sunday, Feb 05, 2006 at 11:54

Sunday, Feb 05, 2006 at 11:54
Simple answer NO

keep in mind there is Max power ,Max torque , Best efficiency.
Each motor is different ,each tune is different but best rule of thumb 1/3 about max torque and below max power.
AnswerID: 153100

Follow Up By: theshadows - Sunday, Feb 05, 2006 at 12:17

Sunday, Feb 05, 2006 at 12:17
woops that should read 1/3 above max torque / max power rev range.

FollowupID: 406996

Reply By: Member - Collyn R (WA) - Sunday, Feb 05, 2006 at 15:55

Sunday, Feb 05, 2006 at 15:55
With a typical diesel engine, the answer is generally yes - and many vehicles (the OKA is a superb example, the Nissan TD 4.2 litre is another) are geared such that keeping engine revs around the higher part of the torque curve results in optimum economy.

But this is only a generalisation. There are quite a few diesel vehicles around now that are very highly geared and where peak torque may be above realistic road speeds in top gear.

The query is interesting - but is more relevent to fixed engine-speed applications such as generators, power take offs etc.
Collyn Rivers

AnswerID: 153147

Reply By: desert - Sunday, Feb 05, 2006 at 16:40

Sunday, Feb 05, 2006 at 16:40
If maximum volumetric efficiency translates to the most energy derived from a given amount of fuel, and that point equates to maximum torque output at a given engine speed, then surely that follows?
AnswerID: 153159

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