Is the horsepower for crate engines rated at net or gross?

 

Gross at flywheel....at least ones I've seen advertised..

 

 

It always has to be gross at flywheel. They have no way of knowing what car the engine will be installed.

 

true

 

So, let me see if I got this straight. I have a 74 stock L-48. Think the HP is 195. I've been told this is a net hp number. I'm contemplating buying a ZZ4 that puts out 355 hp. Are you telling me that once I get the new engine in the car, it's going to be less than 355? Something like 80% of the gross number.......284??? If true, then I'll keep my 4 grand and buy bolt-ons for 2 grand to get up to the 284 hp. Let me know if I'm understanding this correctly.

 

 

You are most likely correct.....for the singel number of HP. However, you need to look at the broader picture of low end torque, etc to get something that gives you the "scalded dog" feeling you're probably looking for.

 

That beign said, the ZZ4 won't make your 'vette a scalded dog. The ZZ4 Fast-burn 385, now that's a different story...

 

How does a Fast Burn 385 (only 20 more HP net) make it that much more of a scalded dog?

As for the original question - all HP is always measured at the flywheel (nowadays).

For example - a 2005 ZO6 is 405 HP gross, but when you measure it at the rear wheels, it is somewhat less.

Not sure on the C5 numbers, but I remember for a C4 the drivetrain loss for a ZF6 was somewhere around 17-18%.

Hope this helps.

 

The heads used on the Fast burn ZZ4 are much better, and I've installed both. There is a bigger difference than you would think. I was never impressed with the base ZZ4, I think the h.p. numbers are optomistic. One thing you can't do with these engines is dog 'em down with lazy rear gears....

 

sorry, doesn't help! You are adding to the confusion.
When you buy a car today, hp is given as NET. A C6 ZO6 (is that 2005?) is now 505 NET hp. The 2003 ZO6 was 405 NET hp.

Back to the original question: Most crate engines are listed as gross hp. So the ZZ502 is 502 gross hp, and the ZZ4 is gross hp. These are crate engines that were never installed in new cars.

But there is an exception!! I have noticed that many original equipment engines are also available as crate engines. The LS6 (2004 ZO6 engine) is available as a crate engine. It is still listed as 405 hp, which is the net rating of the engine installed in a new ZO6.

So at this point I am pretty sure that there is a distinct difference between how crate engines are rated, depending on whether the engine is also used as original equipment (in which case it may be rated net hp).

If we need to review the differences between, gross, net, and rwhp someone go for it, I'm not gonna do it.


So the LS6 crate engine rated at 405 hp, which we know is the NET rating of a 2004 ZO6, is probably putting out more hp than a crate 454 engine rated at 425 hp, which is a GROSS rating.

 

Hmmmmm....I am not sure.

Isnt "NET" what is left over after all drivetrain losses?

Just like a "NET" gain or loss after taxes when talking about financial transactions?

The 405 on a LS6 is at the flywheel. NET to me would be more in tune with RWHP.

Although.....now that I think about it.....

GROSS should be what a bare engine is without all the extra accessories (AC, Alternator, Power Steering)

NET maybe is what it is at the flywheel for an engine with accessories.

RWHP is measured on a chassis dyno and adds in the drivetrain and potential full restrictive exhaust losses.

Seriously not trying to confuse people. Although you now got me confused.

 

Yes, you got it straightened out at the end of your post. We have had many discussions on this topic, but my additonal .02 which the discussion does not often get to, is that although the typical crate engine is rated gross hp (because noone knows how it will be used and what accessories it will be hooked up to) I have noticed that when LS6 or LS2 or LT1 engines are sold in crate form they are listed as the same hp that they are advertised when they come in a car, which is net hp. I have added my notes to your quote below:

 

he's from jersey