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Re: [GMCnet] Horsepower and Torque Converter Efficiency [message #61534 is a reply to message #61530]

Sun, 25 October 2009 06:29

GMCWiperMan

Messages: 1248
Registered: December 2007

Karma:

Senior Member

Good information, Gary,

The Cad 500 numbers are surprising considering the enthusiastic
performance reports from those who've made the conversion. The retarded
spark must have made a BIG difference.

Don't Lug!

Thanks,

Ken H.

Gary Casey wrote:
> I was digging through some old GM test data and thought I would share the following:
>
> Olds 455 test data with an uncertain pedigree (Toro or not? Test conditions?) and it showed a torque at 2800 and below of about 398. No data below 2000, but other tests implied a peak torque at 1200 to 1600 rpm. Peak hp was 234 at 3600.
>
> Cadillac 500 EFI - peak torque 395 at 1200 and 1600 rpm. Peak hp 225 at 3600. The engine was knock limited and spark was retarded about 10 degrees from MBT at most rpms. Both of these are consistent with other big GM engines built at the time(except for the knock-limited part). Max torque was always below 2000 rpm and peak hp was never above 4000. That's not counting performance engines like the Chevy 427 or the Chrysler Hemi, of course.
>
> Olds 350 EFI (Cadillac Seville) - peak torque 290 at 1200, peak power 190 at 4400 and still rising. Not knock limited.
>
> If the Cad 500 were tested on today's fuels would it be knock-limited? Don't know.
>
> Here is some examples using a typical fixed-pitch torque converter with a 2.05 stall torque ratio:
> Stall speed, assuming 400 ft-lb input - 2253 rpm.
> The efficiency rises with increasing speed, so I picked a couple of operating conditions to look at - one was for a "high-load" cruise with 150 ft-lb input. I think actual loads might a little less for a coach without a trailer. The efficiency rises, and the torque ratio drops and reaches a peak of about 92% efficiency. Then there is a dip at the coupling point where the torque ratio becomes 1.0 and from then on the efficiency continues to rise. I haven't made a chart of this to post, so I hope you get the idea. In the cruise assumption the efficiency reaches 88% at an engine speed of 1491 and finally climbs over 92% at 1890. At 2500 it is over 96%, so at a normal cruise speed the efficiency loss is probably 4% or less. Not too bad, but not good.
>
> At full load as might be used climbing a hill I assumed an input torque of 360, not quite full throttle, but close, and on a hot day at any normal elevation that might be all there is. The converter reached 88% efficiency at 2310 engine rpm and finally climbed over 92% at 2930. What that says is that if you are running with your foot in it you want to have the rpm over 2930 or you can expect to be putting about 10% of the engine hp into the transmission oil. Really not good, unless you have a direct pipeline to a refinery and have a really big oil cooler. Better to downshift.
>
> Hopefully this data will be useful to somebody.
> Gary
>

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		Re: [GMCnet] Horsepower and Torque Converter Efficiency By: GMCWiperMan on Sun, 25 October 2009 06:29
		Re: [GMCnet] Horsepower and Torque Converter Efficiency By: Gary Casey on Sun, 25 October 2009 09:13
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		Re: [GMCnet] Horsepower and Torque Converter Efficiency By: Tin Gerbil on Sun, 25 October 2009 10:59

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