wakeech

hey guys and gals...

cruisin' around autoweek forums, and found this great thread:
http://chat.autoweek.com/showthread....0&pagenumber=1

to you, what's a good metric of measuring an engine's level of performance or tune?? just basic output, horsepower/lb of engine, torque/cc, hp at what rpm... which is it, and why??

...i'm glad this is a rotary forum, and we don't have to put up with the pushrod vs. OHC debate bs.

babylou

Pushrods baby!:D Just kidding. I like all good engines, even some diesels.

The metrics I like are: hp/lb/rpm. Why? Because an engine tuned for peak power at 5,000 rpm due to customers wishes for low rpm grunt may be capable of 7,000 rpm if the customer wished so. For example; the Corvette crowd seem to lean towards low rpm grunt so the LS6 engine makes peak power at around 6,000 rpm. These engines can turn 7,200 rpm all day with a cam change and titanium valve spring retainers. If the LS6 were built like this from the factory the cost increase would be about $50 but peak power would go from 405 hp to around 455 hp at 6,700 rpm. All this from an engine that weighs nearly the same as a BMW M3 engine.

Quick_lude

I would say the hp and torque curves along with the absolute numbers.. It's nice to see the torque flat from 1200rpm to 7000rpm while the hp just climbs...

wakeech

that's true, but then why do you drive a Prelude instead of a Hemi pick-up truck?? i mean, other than cost, why not go for a car with a bigger engine?? what was the reasoning there (beyond looks, "i just like it" factor)??

Quick_lude

But, what is the redline of a Hemi pickup? 5K rpm? I drive the Prelude because it's the car that I most liked and could afford at the time of my lease agreement..
So yes, I would rather be driving an S2K or Boxster S or Corvette Z06..
You asked what would be the best way to show metric for any engine.. So what I was saying is that absolute numbers don't tell the whole story.. I would need the dyno graphs WITH the max hp/tq numbers for a more accurate representation of any engine

Farsyde

i think babylou's got it. At least for straight line performance HP/pound (or pounds/HP) is pretty good. Now actual street performance has to take acount of a bunch of things that are very dependent on each other. Let's say the car made about 10lbs/HP ( i think the BMW M3 is about this much), but the suspension was garbage and the distribution was 60/40. It would fly down the dragstrip but be eaten alive in the twisties.

It really all comes down to what is the best measurement for the application you want