So I've heard that the hemi's only get about 240 rwhp. I also heard that the tranny is the culprit. Can anyone tell me why this is? What about the tranny makes it so inefficient, and what else(if any) contributes to a 100hp loss form the flywheel to the wheels?

 

I don't think it's a 100rwhp loss. some people have dynoed in the 270 range. some are a bit higher, some lower. a good part of the problem is the torque convertor. I think I saw somewhere that about %14 is lost due to the TC. If that is true, we got one of the crappiest TCs in existence.

read this

 

Where are you seeing bone stock dyno's in the 270 range? I've personally seen about a half dozen being performed on 3rd Gen Hemi trucks and have yet to see one break 250, and the only 2500 truck I've seen done was in the 230s!

Yes, it's mainly the torque converter.

Torque converters typically include impeller assemblies that are operatively connected for rotation with the torque input from an internal combustion engine, a turbine assembly that is fluidly connected in driven relationship with the impeller assembly and a stator or reactor assembly. These assemblies together form a substantially toroidal flow passage for kinetic fluid in the torque converter. Each assembly includes a plurality of blades or vanes that act to convert mechanical energy to hydrokinetic energy and back to mechanical energy. The stator assembly of a conventional torque converter is locked against rotation in one direction but is free to spin about an axis in the direction of rotation of the impeller assembly and turbine assembly. When the stator assembly is locked against rotation, the torque is multiplied by the torque converter. During torque multiplication, the output torque is greater than the input torque for the torque converter. However, when there is no torque multiplication, the torque converter becomes a fluid coupling. Fluid couplings have inherent slip. Torque converter slip exists when the speed ratio is less than 1.0 (RPM input>than RPM output of the torque converter). The inherent slip reduces the efficiency of the torque converter. While torque converters provide a smooth coupling between the engine and the transmission, the slippage of the torque converter results in a parasitic loss, thereby decreasing the efficiency of the entire powertrain. Further, the torque converter itself requires pressurized hydraulic fluid in addition to any pressurized fluid requirements for the actuation of the gear shifting operations. This means that an automatic transmission must have a large capacity pump to provide the necessary hydraulic pressure for both converter engagement and shift changes. The power required to drive the pump and pressurize the fluid introduces additional parasitic losses of efficiency in the automatic transmission.



So, you want less parasitic loss from the crank to the ground, then get you a better torque converter...




(oops) sorry 'Feej, I didn't catch your Wikipedia link till after I pasted this excerpt from the U.S. patent office. Kinda explained the same thing twice...

 

Hammer,You explained everything but where to get the replacement TC.

You posted a link a while back to rebuilt auto trannys and TC's, You don't happen to have that link do you? Also have you seen any numbers with a tc replacmed for the 1500's?

 

Will the new TC make a difference for the cost, and what about the warrenty issues

 

you got a big *** sponsor ad right on top, SunCoast. also a link on the right. I think they're a little on the expensive side though.

 

I don't rmr where I saw 270. that isn't from personal experience though, someone mentioned it on this site.

 

I was wondering when someone would be bright enough to notice it...

and don't believe everything you read on the internet...

 

so i was thinking about this anyone know if its any good

http://www.compperformancegroupstore...ct_Code=141276

 

K&N's dyno for the hemi in an 03 states about 270 hp stock http://www.kandn.com/dynocharts/63-1533_dyno.pdf which is about a 20% loss. How does the power loss compare between manuals and automatics? Is it any more beneficial power wise to have a manual?