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      08-05-2007, 10:27 AM   #77
bruce.augenstein@comcast.
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Quote:
Originally Posted by swamp2 View Post
Yes, even tough I showed what I think to be a reasonable calculation the main point was simply to look at a real number, rather than crank hp or tq. Sure +/- a few percent either way depending on tranny and other losses is reasonable. So indeed the M3 may not be higher but both are darn close.
Yup - and for the first time since M-B built that 2.5 liter four cylinder to compete with the E30 M3 way back when, we're apparently gonna get ourselves a pair of pretty evenly matched cars chasing a fairly similar audience, BMW and M-B fanboys notwithstanding.

Quote:
Originally Posted by swamp2 View Post
Are you sure BER is already accounted for in SAE hp testing? Is it similarly accounted for in DIN testing?
If my understanding of BER is correct (software eliminates charging except during deceleration and idle - no hardware), it's accounted for.

Don't know all the details in regard to DIN (now called something else) test procedures, but my guess is that it is taken into account there, as well. Of course, a guess is just a guess, but the 420HP Euro rating vs 414HP SAE matches the same percentage differentials found in other engines tested with no BER. However, assuming a 110-amp alternator doing its damnest, we're still talking well under three horsepower, at max and assuming well under 100% efficiency. It's more likely we're talking less than a single pony under more real operating conditions.

SAE testing is governed by SAE Standard J1349, mildly revised in 2004 (for the first time since they went to "SAE Net" standards which went into effect for the 1971 cars). That standard calls for engine testing to be done with full intake and exhaust systems in place, all accessories in place, and with engine control software installed and operating just as it would in the vehicle out on the road. That obviously means no battery charging during the dyno run.

As an aside, J1349 was revised largely because the Japanese (among others) were taking advantage of loopholes in the 1971 standard, doing such things as using premium when regular was stipulated (with engine control software able to take advantage of the increased octane), running the engine a quart low on oil to reduce crank splash, etc. Smacked Toyota right between the eyes with that, although Honda, Mazda, et al were also embarassed.

Now, the rules are very close to air tight, and an SAE guy has to be there to witness the runs. "Trust everyone", said Ronald Reagan, "but always cut the cards."

Quote:
Originally Posted by swamp2 View Post
To multi-quote just hit reply, then copy and paste the first [...] to the begining of the second and subsequent quotes and copy the second [...] to the respective ends of each subsequent quote.
Well Duh, that was easy. Sometimes I think if I got any dumber they'd have to water me twice a week. Thanks.

Bruce

PS - Just plowed through Hawking's "Brief History" update, and got almost as big a headache as when I read the original. The difference is that the update includes a bunch of illustrations, which tend to appeal to my cartoonish mind.

His "Nutshell" book got even worse, and when he started describing "p-branes", I thought he was talking about me, and had changed the spelling so I wouldn't get it.
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