Let me see if I can explain what I'm thinking so it makes sense. My 5.3L is rated at 285 hp and 325 tq at the crank from the factory. You stick it in my truck with the trans., stock intake and exhaust and it dynos 20% less, let's say the numbers are 228 hp & 260 tq. If I added an intake or exhaust and the dyno now read lets say 235 hp & 270 tq, have I really increased the power of the engine over it's 285 hp and 325 tq factory rating? OR have I just reduced the 20% loss to let's say 18% by removing the factory intake or exhaust, or both? Am I making any sense? I don't see how putting on a different intake or exhaust can raise the original factory rating of 285 hp and 325 tq at the crank if that's what the engine is rated at sitting in a crate before it's installed. I see it as more of freeing of some of the 285 hp and 325 tq so more of that power is getting to the rear tires. The engine still makes 285 hp and 325 tq at the crank but it now makes more power at the rear wheels because the exhaust and intake have made it more efficient. Does this make any sense? I can see how a cam can make more power because you are changing the characteristics of the engine. So, if I add an exhaust, intake, pulleys and headers and now dyno at let's say 265 hp and 298 tq, is my crank rating 331 hp and 372 tq by adding 20%? OR is it still the original 285 hp and 325 tq and all I'm done is reduce the driveline and parasitic loss my replacing the stock parts?
Jim

 

I don't believe you've eliminated driveline loss much (maybe slightly more efficient) but you've increased the hp @ the crank. You still will need to deduct driveline loss through friction, gear drive, ect...

 

An intake exhaust or computer tuning will actually make more HP at the crank. Rated power at the crank is lost on the drivetrain and only a more effecient drivetrain will yield more HP will keeping the same HP #'s number at the crank. So to answer your question, if you add exhaust intake, pulleys and headers your numbers at the crank would go up to 331 HP or whatever horspower those mods will yield and will reflect at your wheels at about 20% loss.

 

without some kind of power adder you're still at 285 at the fly. with bolt ons you're just getting closer to the 285 which the engine makes.

or at least thats how i see it

 

That's deep!!!

Sounds like you have been thinking about this for a good while, but i understand where you are going.

You are saying that the factory rates the truck at 285, and with the intake, exhaust, and PCM tunning that they put on it, that they take away from the advertise 285? Is this right? So by adding all the aftermarket goodies like we all do only get us closer to the advertised 285 that they rated the truck at? And by changing the cam or doing something internal to the engine this is the only way to go above and beyond the advertised horse power and torque rating from the factory? This all sound pretty fair to me and I agree.

 

Bolt ons will increase hp and tq at the flywheel and at the wheels like Tiburon said. Adding intake and exhaust allows the engine to flow more air thus producing more power.

 

They rate engines with the accesories they have on them in the car/truck. Thats the standard now. Adding an intake/exhaust will add to that advertized number. That number refers to flywheel HP. Parasitic losses in the drivetrain bring the number down about 20% for RWHP.

In the 60's they rated an engine with wide open headers, no air filter, and they sometimes pressurized the dyno room with huge fans. Then add all the accesories in the car. I've heard todays LS6 (405hp) would have been rated at 500 hp back then.

 

I think your question is really just related to how the power is measured.
At the factory it's at the crank, when it leaves the factory is measured at the rear wheels unless you wanted to remove the engine from the truck again to test modifications.
When power is measured at the back wheels it's always lower than crank readings because of drive train losses.
Bottom line... if you increase rear wheel power you are also increasing
crank shaft power.


David

 

It depends on what you want to do with the dyno numbers,they can be a tool for tuning if you check or verify gains made on the dyno against modifications or tuning changes made to the truck or strickly a number to brag about to your buddies the way most people use them.A good technition can check the power curve generated by a dyno readout to tell what changes are needed in your tuning setup.I think people make to much of a fuss over peak numbers instead of looking at the complete picture.The best way to make your truck faster is to make more average power threwout the entire powerband especially on a street driven truck.

 

engines a rated SAE net HP. which is average power the motors make with all factory accesories and aircleaners and exhausts in place.(there is a plus minus for these engines w/ GM usually being fairly conservative and Ford being a little overly optimistic.)
again the delta of driveline loss is fairly costant-- to measure gains in these areas of frictional loss you need to modify things rearward of the engine these thing can be switching to all synthetic engine, trans, and differential oils and lightweight wheel and tire combos. a few magazine have done tests on this and have picked up 10-12HP by switching to all synthetics. the wheel and tire combo changes will show on a inertia dyno.
gains by switching intake, exhaust, cams power adders. you are increasing the total engine output. although some of it is in removing restrictions in the factory setups, many of the gains on intake and exhaust come at the expense of noise which performance people tend to like but the average buyer doesn't want.