Not being the brightest

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shorty

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on this site I am wondering what the transmission has to do with HP to the rear wheels. Is 30 hp actually lost running the auto tranny? Does it take 30 HP to spin all those gears? If so, why are so many drag cars going to auto?

No stone throwing please, just an answer for a curious old man. With a plastic left knee I ain't going to a clutchy type anytime soon.
 
Less friction in a manual transmission compared to an automatic transmission. There is a more technical in depth description, but that's the jist of it.
 
shorty said:
on this site I am wondering what the transmission has to do with HP to the rear wheels. Is 30 hp actually lost running the auto tranny? Does it take 30 HP to spin all those gears? If so, why are so many drag cars going to auto?

No stone throwing please, just an answer for a curious old man. With a plastic left knee I ain't going to a clutchy type anytime soon.
Click to expand...

Hello Shorty-

Until the torque converter "locks up", you are also dealing with a fluid coupling instead of a direct mechanical coupling like you have with a flywheel, pressure-plate and a clutch disc. Fluid couplings can't transfer 100% of the torque the engine is producing. So, there are some transfer of power losses in that area as well.
 
Good Morning Fellas. Ronnie is correct, Shorty. An automatic is a fluid coupler. Power is lost transferring the the rotation of the engine, through fluid, to the driveshaft. A manual transmission is a direct mechanical connection between the engine and the driveshaft.

Many drag racers prefer an automatic because they are more consistent than a human driver and because they can shift more quickly than most human can shift a manual. Once upon a time we measured the shift times of many of us RC owners and compared the results to the shift times of modern automatics. The results were interesting.
 
I remember when lock up torque converters came out. People would bitch about feeling the clutch turn off & on after going into drive. They thought something was wrong with the transmission.
 
Here's your answer Shorty. Pretty simply put, fluid drive versus direct drive.
Auto trannys have a pump, that by turning of flexplate/torque converter, build line pressure inside trans to control shifting via valve body, drums, clutches, bands, etc.
In a manual your flywheel is spinning with clutch/pressure plate attached. Attached to the clutch directly is the input shaft of the manual trans. When ckutch is released, the mating surface of flywheel and clutch mate causing a direct drive mechanically.

Basically autos lose power due to being fluid driven and not directly driven.
For racing it's a no brainer. Autos are easily repeatable in a race. Where as a manual is up to the driver. No missed shifts in an auto. They can be built to withstand much more power than a manual. Many benefits of an auto, but a manual can outlast any auto. Clutch swaps are cheaper than auto rebuilds. Manuals are better IMO for a daily driver, racer, and overall a much more fun truck/car as you have better control over powerband and application of power.
Today's newer 6-8 speed autos kinda change those rules though as the extra gears allow for the correct/efficient use of the powerband for any engine.
 
caveman said:
Good Morning Fellas. Ronnie is correct, Shorty. An automatic is a fluid coupler. Power is lost transferring the the rotation of the engine, through fluid, to the driveshaft. A manual transmission is a direct mechanical connection between the engine and the driveshaft.

Many drag racers prefer an automatic because they are more consistent than a human driver and because they can shift more quickly than most human can shift a manual. Once upon a time we measured the shift times of many of us RC owners and compared the results to the shift times of modern automatics. The results were interesting.
Click to expand...

Minor bump..

Do you remember the "clutch-flights"?

Some crafty individuals replaced the torque converter with a clutch setup in the old 727 (48RE) autos back in the day when the performance converters were really inefficient.

I'd forgotten about those until just now.
 
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rottenronnie said:
Minor bump..

Do you remember the "clutch-flights"?

Some crafty individuals replaced the torque converter with a clutch setup in the old 727 (48-RE) autos back in the day when the performance converters were really inefficient.

I'd forgotten about those until just now.
Click to expand...

Isn't that similar to what is happening inside some of the newer exotics with "twin disc" paddle shifted transmissions?
 
caveman said:
Isn't that similar to what is happening inside some of the newer exotics with "twin disc" paddle shifted transmissions?
Click to expand...

Could be, I do not know..

My 0.83 liter 3-cyl. diesel SMART car uses paddle-shifters with the "sort-of" automatic transmission.
Does it qualify as an exotic? :)
It must be because it's a total chick-magnet. ;)
 
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rottenronnie said:
Could be, I do not know..

My 0.83 liter 3-cyl. diesel SMART car uses paddle-shifters with the "sort-of" automatic transmission.
Does it qualify as an exotic? :)
It must be because it's a total chick-magnet. ;)
Click to expand...
Totally reminds me of this:

[ame]http://www.youtube.com/watch?v=9z-uYMrWTCc[/ame]
 
DYNO DAY 2005

RAW DIESEL POWER

Baseline pulls 2005 SMART fortwo.
 

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caveman said:
If thats you, you are much more feminine than I pictures... and pretty cute! :D
Click to expand...

Thanks, I'll pass that along to my daughter (it was her car at the time).:D

I was wondering if it would even turn the rollers....We didn't strap it down, I just hung onto one of the side mirrors.
 
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rottenronnie said:
I'll pass that along to my daughter (it was her car at the time).:D

I was wondering if it would even turn the rollers....We didn't strap it down, I just hung onto one of the side mirrors.
Click to expand...

That was worth a great laugh!
 
rottenronnie said:
Yes, the early ones were diesel.
It is also chipped, with exhaust...
57 HP and 85 ft. lbs. of planet-twisting torque.

"It may be slow, but it sure is ugly!"
Click to expand...

So about this much power?

[ame]http://www.youtube.com/watch?v=jnp-PKvNIZk&feature=1m38s[/ame]
 
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