Friday, January 6, 2017

Small Engine Ratings

Princess Auto has changed the way that they rate their small engine offerings, and not for the better to my mind.

It used to be that they gave a horsepower (hp) figure for a given engine; now they're giving only a displacement figure in cubic centimetres (cc). I don't find that helpful. I don't understand the thinking behind the move, and I see nothing on Princess Auto's website by way of explanation. I sent them the following email about it:

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"Please reconsider your policy of rating engines only by their metric cubic displacement. I don't find it helpful, and I'm sure I'm not alone in that.

A horsepower rating for me is a useful benchmark for gauging an engine's suitability for a purpose. If you must go metric (which I don't consider to be 'progress'), then at least give a power rating in watts. A wattage rating is readily convertible to horsepower."

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Here's the reply I got:

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"Good Morning Tom,

We thank you for your feedbacks.[sic] I will forward your suggestions to our Leaders and Buyers Team.

Best Wishes"

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Hmmm. I won't hold my breath waiting for them to bring back horsepower ratings.

Something that I find almost amusing about Princess Auto's move is the utter inconsistency of their engine descriptions. You can see an example here.

The engine is listed by its metric displacement, 163 cc. So you'd think that this is part and parcel of an overall move toward metric measures only, right? Wrong. In the 'details' section of the ad, there's a torque figure in ft-lbs. Bore and stroke are given in inches. One might expect a power rating in watts to go with the metric displacement figure, but no power rating in any kind of unit is to be had.

To be blunt, I think that this move on Princess Auto's part is an ill-considered one made by someone who knows just enough to be dangerous. Princess Auto needs to give its head a shake, and ask itself just what on earth it thinks it's accomplishing with this.

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Metric Displacement To Horsepower Conversion (Four-Stroke Engines)

Anyway, in the interest of being a little more helpful here than Princess Auto is, I found a cc-to-hp converter on the web. The converter is based on an assumption that 32.5 cc of engine displacement yields one horsepower. It's a reasonable assumption that appears to give a pretty good ballpark figure. I tried it on my lawnmower's 148 cc engine, and got an answer of 4.55 hp. The lawnmower engine's label rating is 4.5 hp, so that's close -- good enough to go with when trying to judge an engine's suitability for a purpose.

I can't be the only one who finds Princess Auto's move to be unhelpful. It will be interesting to see where, if anywhere, Princess Auto goes with this.

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