How can the 7.3L produce less horse power and torque than a 6.4L and the 5.9 and the Duramax? The 7.3L has more leters how can this happen?

 

I'm sure there are engine-heads out there who can give you specifics, but the short answer is that there are many other variables. Read a bunch of posts here about how members get mega horsepower out of their 7.3's without increasing the displacement of the cylinders. Things like fuel amount (injectors), air volume, valve area, compression, the timing of it all, and I'm sure a bunch of other stuff I don't know about. Some of the experts will chime in here, in the meantime, read, read, read.

 

There were years when the 400 motor was only around 150HP... and I think even the 460 might have dipped into the 100's as well. There is a lot more to the output than just size.

The 7.3 is a completely different motor than the 6.4...

And in todays horse power race do you really think ford would have released the 6.0 and 6.4 with lesser power output than thier 7.3L predecessor? Engines are only increasing in power over the last 3 decades or so.

 

I understand the differences. But still the 7.3 is a bigger engine. And straight out of the box it has less power. I was reading some sites and finally the 6.4 out powers the Duramax. Not the dodge.

 

If you understand the differences then you would know the answer.

air flow

There is a lot to engine design, but the basic principle is air flow through the motor. The 7.3 originally does not flow as much air as efficiently as the newer motors. Head design, number of valves, intake design, exhaust, turbo placement, intercooler... .on and on as far as why an engine with less displacement can make more power than another engine of greater displacement.

 

My 65 289 motor when stock put out a little more than my 75 mercury's orig. 460 motor. This was mainly due to head design and cam profiles.

 

it also comes down to what the manufactures believe the engine is most reliable at. they could have made the 7.3l have 800 hp and 1000ftlb but it wouldn't of lasted thru the warranty. new technology allows more out put and reliability.

 

I thought the 7.3L made similar power as the 5.9L of the same era.

http://www.edmunds.com/insideline/do...rticleId=46028

1999 5.9L DIESEL
"for 1999 included increased power for the turbodiesel engine, now rated at 230 horsepower/450 ft.-lbs. of torque (manual transmission) and 215 horsepower/420 ft.-lbs. of torque (automatic transmission). "

Also found http://www.cumminsdieselspecs.com/24v.html

5.9 L ISB Specifications:


Displacement: 359 cubic inches, 5.9 liters
Configuration: Inline 6 cylinder
Compression Ratio: 16.3:1, 17.2:1 (high output version)
Bore: 4.02 inches
Stroke: 4.72 inches
Injection: Direct Injection:
Electronically controlled Bosch VP44 rotary injection pump. Bosch high pressure common rail injection introduced for 2003 model year.

Aspiration: Holset turbocharger
Valvetrain: OHV, 4 valves per cylinder, solid lifter camshaft
Oil Capacity: 10 quarts
Weight: approx. 1,150 lbs
*Horsepower: 235 - 325 HP @ 2,900 RPM
*Torque: 460 - 610 lb-ft @ 1,600 RPM

http://www.internationalpowerstroke.com/73psd.html

Displacement: 444 cubic inches, 7.3 liters
Configuration: V-8
Compression Ratio: 17.5:1
Bore: 4.11 inches
Stroke: 4.18 inches
Injection: Direct injection, HEUI (hydraulic electronic unit injection)
Aspiration: Single turbocharger
Valvetrain: OHV, 2 valves per cylinder
Oil Capacity: 12 quarts
Weight: approx. 920 lbs dry
Horsepower (peak)*: 275 HP @ 2,800 RPM
Torque (peak)*: 525 lb-ft @ 1,600 RPM

 

Very good answer. And let's not forget RPM. Thre 6.4L can just spin faster. It makes more HP because it can spin faster. The HP peak is 3000rpm whereas the 7.3s HP peak was at 2500RPM. The torque peak is also 400rpm higher in the 6.4L versus the 7.3L.

The internal parts must be lighter to a degree. A little less compression but I imagine a bit more boost...well now we're back to airflow

 

That and it has 10 years advantage in the development and technology. If the 7.3L were out today it would have a compound turbo and much bigger injectors.

 

Thanks guys, That answered my question.