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93' W124 E36 AMG ; 71' Cadillac Eldorado ; 07' S211 280 CDI
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1,022 Posts
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In Poland dyno operators won't pull cars with automatic gearbox. They say that automatic cannot be controlled well throughout the RPM-band and the graph will not show the actual performance of the engine. Also - after the engine has reached maximum RPM they need to go to neutral gear to measure the drag - so that the engine HP is known - and that's not healthy for automatics. How do You Guys cope with that issue in the USA?
 

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2001 E320; 2002 ML500
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2,001 Posts
I see no reason to put my car through a dyno. It's 14 years old and it has 222K miles. I know it's not powerful nor do I care.
 

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99-C43, 05-G55K, 71-280SL, 94-E320 CAB
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2,286 Posts
In Poland dyno operators won't pull cars with automatic gearbox. They say that automatic cannot be controlled well throughout the RPM-band and the graph will not show the actual performance of the engine. Also - after the engine has reached maximum RPM they need to go to neutral gear to measure the drag - so that the engine HP is known - and that's not healthy for automatics. How do You Guys cope with that issue in the USA?
Automatic cars can be dyno with same accuracy as manual transmission.
Dyno does not know what i driving the rear wheels and only cares if the rollers are turning.

Best type of dyno for accuracy is load dyno which applies load to rollers against rear wheels.
Inertia type dyno has rollers that spin freely which wheels drive.

Usually best to dyno in gear that gives 1:1 transmossion ratio.

I find that on M103-12V with 722.3 auto best to dyno in third gear.
This allows max rpm without turning tires to 140+ mph.

Dyno operator starts car then accelerates to max RPM.
He starts dyno read about 2500-3000RPM.
No need to go to neutral as dyno reads torque real time as wheels turn rollers.
Horsepower is then mathematically calculated by dyno based on torque

This is my automatic twin turbo on dyno.
This pull gave RWP torque of 302. which equates to about 390 torque at the crank.
Baseline pull prior to TT install gave 145 torque against published 188 torque for a 30% drive train loss.

Click on picture to watch pull

 

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W124 400E, W126 500SE
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971 Posts
D->N is no problem for automatic transmission as long as the engine is running. This is not the same as towing - you can tow a car with automatic transmission in any speed for any range as long as the engine is running and pumping oi through the tranny. Towing without engine running it lethal however... (btw shouldn't by on properly working tranny because of the secondary oil pump at the transmission - but manual says otherwise :)
 
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