I have a question about horsepower ratings of the powerstrokes. Automatics are rated at 250 and manuals are rated at 275 hp. Is the engine between these two really any different (other than a sensor)? Can the 250 hp be converted to the 275 by reprogramming and adding the ECT sensor?

Thanks,

Dave

 

i dont know if this is right or not but ive heard the engine is the same its just you lose more hp threw an automatic transmission. it takes more hp to work it than a manual.

 

Doesn't have to do with the 250/275 because those numbers aren't rear wheel numbers, they're engine numbers. Maybe Ford didn't have that much faith in the automatic transmission behind the 7.3.

 

The manual trannies are able to take the extra horsepower and torque better than the autos. From what I have read on here that was the reasoning behind the lower numbers on the auto.

basstardo

 

The autos have a torque converter that muliplys the torque and it might outpull or equal a stick shift.

 

I don't follow your logic. The manual was rated higher than the auto, not vice versa.

 

I think he's trying to say that the actual rear wheel HP, ie, whats put to the ground for moving the truck, gets there quite differently. The torque convertor on an auto acts like a compound gear at lower rpms..there ISNT any way to accurately comapre it to manual transmission gearing, as the trans can be slipping, and boosting the gearing at the same time. I'm not sure of the ford ratios, but here's a best guess on my part. ( I'm going to put in the same rear end ratios, too, which usually isnt the case from manual to auto, but, again, I dont know the ford ratios)

manual trans:
5:1 1st gear , 4.10 axle...20.5:1 power multiplication at all rpms.

auto trans:
3:1 1st, 4.10 axle, and a torque convertor with a peak ratio of 2.5:1, stalls ( engine & trans turn at the same speed) at 1600. this setup would have UP TO 30.75:1 (3*4.1*2.5)gearing at rpms below 1600, and 12.3: gearing above 1600 rpm.

thus, even though its got a lower rated output, the potential is there for the auto to actually put more power to the ground at select rpms. The actual convertor ratio starts low, usually peaks about mid way between idle, and stall speed, and (obviously) drops back to a 1:1 ratio as rpms approach the speed where the convertor stalls. This is also why a lot of smaller engined setups use automatics now - the convertor can make up for a lot of power, and allows the motor to rev up into the torque band a bit too.

sorry for the longish post - hope this helps clear up the murk a bit.

chris