[DarkneSS]

I read an interesting post in a thread on here with someone asking how to get his LS3 up to 500 crank HP. Someone replied with this:

"OK, seriously?
I don't think you understand how this whole thing works.
Most mods out there will not give you horsepower.
They may free up horsepower that is robbed by the powertrain, due to entropy inherent to any mechanical system.
The LS3 itself, under ideal, laboratory conditions (which is probably with NO headers, and NO intake) is rated at 426 at the crank.
Without specifically adding power to the formula, the best you could ever hope to get, in a perfect universe without friction and entropy would be 426 RWHP. Most of these mods will not really increase your crank HP, they will simply reduce the parasitic loss, and bring your RWHP number closer to your crank HP number."

This seems to go completely against my understanding of engine mechanics.

If I add bolt ons to my engine, am I making more crank horse power? I was under the impression that I AM. I've never heard that something like headers doesn't increase crank HP. If you increase wheel horsepower are you not also increasing crank horsepower?

Hence why the LS3 in the Vette is rated at 10 more CRANK HP than a Camaro's because it basically has a cat back.

"The LS3 V-8 is the base engine for the 2010 Corvette and the new Camaro SS. In the Corvette it is rated at 430 horsepower (321 kW), or 436 horsepower (325 kW) when equipped with the optional dual-mode exhaust system (RPO NPP)."

The reason I'm asking is because people were agreeing with this person and a Google search isn't really helping my question.

[GretchenGotGrowl]

Some mods do add power others simply reduce the losses. An internal combustion engine is a pump. The more air you can get to flow through the more fuel you can add and the bigger the "explosions" you will get. Bigger explosions mean more power. Changing the exhaust manifolds allows more air to flow through and you make more power. Add an underdrive pulley and the accessories run at slower speed and take less power. No power was added to the engine, but less was robbed. In the first case you crank and wheel power went up, in the second only the wheel power went up.

Hope that helps.

[CamaroSkooter]

Well, the guy is wrong.

If you do not change the amount of air and fuel in the combustion chamber, and you don't touch the tune, then yes, the 426hp number is more or less "the number."

But adding a cold-air intake and swapping out the headers with something less restrictive will increase the efficiency of the combustion process and thusly increase the power capabilities of the motor.

And on top of that, re-tuning the computer to change any number of variables will also increase the power capabilities of the motor.

I would not consider your intake and exhaust manifold to be "parasitic losses" like he seems to think. Parasitic losses come from things attached to your motor that have absolutely nothing to do with the direct production of power. Examples of these would be the stuff attached to the front of the motor called the accessory drive (your alternator, a/c condenser, fuel pump, oil pump, etc.) and the stuff attached to the backside of your motor (your transmission and differential) called the drivetrain.

The stuff up front robs power from your motor because it creates a drag on the system. The stuff out back robs power from your motor because of efficiency losses. The drivetrain losses are something you generally just have to live with unless you want to spend some serious coin swapping big ticket items out (or tearing into those big ticket items to swap a gear here and there). And the stuff up front you can minimize with under drive pulleys if you want, but that will in turn cause a bit of stress on some parts if the pulley is sized way too small. An example of this would be not spinning the alternator fast enough to fully recharge the battery, or not spinning the oil pump fast enough to properly lubricate all parts of the engine.

But the intake, exhaust, and tuning are not part of the parasitic losses discussion because they can be tweaked and tuned all day long to force more power out of the motor. Not to mention you can go the forced induction or the nitrous route and completely alter the characteristics of the combustion process, thus increasing your motor's power output.

Okay, I just typed a whole bunch but have no idea what point I was trying to make anymore.

So...I hope that helps clear things up...maybe...

[KMPrenger]

I've seen others on here make similar arguments...overall I think its just silly talk. Some people make this way too complicated and confusing in my opinion.

Some mods are power adders, and some are parasitic loss reducers.

You can bet your butt that intakes, and headers (and other similar bolt ons) add power...which is the same as "freeing it up". Stock it will test at 426 crank, but we all know if the stock configuration came with a cold air intake and headers it would have been rated higher.

Installing a one piece, lighter drive shaft, and installing lighter rims are what help to reduce that parasitic loss at the wheels which is the other side of the equation. So maybe instead of having 16% loss, you could install a few new driveline components and only have 15 or 14% loss, thus increasing your power at the wheels.

[strych9]

Interesting take, but incorrect.

Engine mods in and of themselves don't add horsepower. However, they allow for better operating dynamics in which to create more horsepower, with tuning.

Look at the basics: an engine is essentially an air pump. There is a theoretical finite amount of air that can flow through an engine, limited only by its displacement.

Adding items like a cold air intake, headers, and cam are all working toward the same goal: allowing a greater amount of air to enter the cylinders at a higher velocity than the stock components will allow. The factory sets up the components for a good balance of durability, economy, emission control, and power.

Modders shouldn't care about economy or emission control, so when going for extra power, these items are not a major consideration. Putting those items at the back of the line frees up the ability to make more horsepower.

Back to the mod scenario. Now that we've added some items to increase air flow and velocity, properly tuning the engine computer adds the optimal amount of fuel and ignition timing control, and this combo adds more horsepower to the engine. Tuning is critical; if you add air, you MUST add fuel. Otherwise, the gains will be sub-par. Same as if we added more fuel without components: little, if any gains.

This is as simple as I could make it...

[DarkneSS]

I always think of an engine as an air pump and explain it that way to those that don't get it. Glad to know I'm not going crazy, everything you guys said was as I have understood it.

[MLL67RSSS]

Also JFTR, current SAE Net and Certified Horse Power numbers are done with all engine accessories and stock exhaust in place.

http://en.wikipedia.org/wiki/Horsepower

SAE net power

In the United States, the term bhp fell into disuse in 1971-72, as automakers began to quote power in terms of SAE net horsepower in accord with SAE standard J1349. Like SAE gross and other brake horsepower protocols, SAE Net hp is measured at the engine's crankshaft, and so does not account for transmission losses. However, the SAE net power testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold.

SAE certified power

In 2005, the SAE introduced "SAE Certified Power" with SAE J2723.[20] This test is voluntary and is in itself not a separate engine test code but a certification of either J1349 or J1995 after which the manufacturer is allowed to advertise "Certified to SAE J1349" or "Certified to SAE J1995" depending on which test standard have been followed. To attain certification the test must follow the SAE standard in question, take place in an ISO9000/9002 certified facility and be witnessed by an SAE approved third party.