View Single Post
Old 07-02-2010, 05:38 PM   #1 (permalink)
The PRC.
Join Date: Oct 2009
Location: Elsewhere.
Posts: 5,304
Thanks: 285
Thanked 536 Times in 384 Posts
Question Friction Losses - some questions.


Friction losses isn't something I know too much about - as in I know the basic idea, the more moving parts and bearings the greater the energy required to move those parts. But I don't follow everything involved from an engineer's standpoint and probably wouldn't understand. However I started thinking about this today.

The reason this came up in my thoughts was an article in this month's Motor Sport magazine (it covers a lot of historical racing from pre WW1 to the modern era) about the Ilmore Indycar engine of 1994.

It was built to exploit a rule about engines with an OHV / Pushrod / 2 valves per cylinder layout being allowed to run more boost than race spec engines, i.e. ones with DOHC and 4 valves per cylinder. The rule itself was made to encourage more teams to compete with essentially road going engines - i.e. the Buick V6 I think.

It (the Buick) a lot of power compared to other engines because of this rule - the extra boost, but wouldn't normally last a race. The Ilmore engine had more power again purely because of the pure race design, and was reliable enough to last a full race.

The thing that caught my eye though was the explanation for the engine also being very good on fuel - the Penske cars also maintained their lead by not having to stop as often as the competition - a little like why the Audi TDI Le Mans thing wins too. The fuel efficiency was put down to the lower friction losses, partly down to the OHV layout (single cam-in-block design) and the use of roller bearings in a few places.

I know BMW is banging on about Efficient Dynamics at the moment which seems a similar kind of effort - reduce the energy wasted by the engine in just keeping itself going.

So a number of questions. Firstly apart from BMW are there accessible engines which exploit this which we can all benefit from ? I know older Honda sports cars (S600 and S800) used roller bearing cranks but not many others in mass production. Or this just down to choosing 'engineered' cars like BMW or perhaps Honda, rather than 'produced' cars lik GM, VW and so on.

Secondly are there things we can use to promote this - for example I've seen posts on people using different oils to reduce friction in engines. Does this make a big, measurable difference ?

And finally are we (outside the US perhaps) kind of wrong to giggle when people still make OHV engines in modern cars ? Are SOHC units better ?

Or am I putting 2 and 2 together and getting 22 ?

[I]So long and thanks for all the fish.[/I]
  Reply With Quote