Horsepower Ratings, Net...Gross...??? Options

[Tom73]

Was wondering about the HP ratings used for the 914 engines. Are they GROSS or NET rating. I know most of the American companies changed from Gross to Net around 1972, in the middle of the 914 production. So for comparitive purposes was wondering how the engine was rated?

(did a search on this topic to see if it had been discussed before but that came up empty.)

tom...

[Jake Raby]

Net HP is what matters the most... BUT the thing that most people do not realize is that the factory engine was measuerd in DIN HP the European measurement system. Here we use SAE standards and thats why there is a difference in the power we see compared to the factory power numbers that are posted, measured in DIN...

The DIN HP of a 2 liter 914 spec engine is right at 100, but the most I have ever seen SAE on my dyno from a 100% stocker is 86HP and that was with a ton of tuning to achieve..

[Tom73]

So my '71 1.7 which is rated at 80 HP would be DIN HP? Okay, did a search on the net and found that DIN and SAE Net HP are basicly the same, so close they can be interchanged. But to nail it down you can divide DIN HP (80 in this case) by 1.0139 to arrive at SAE Net HP (or 78.9 for my 1.7).

Thanks....

tom...

[Dave_Darling]

Hmm?? I thought that DIN and SAE Net specified different testing set-ups, so you could not do a direct mathematical conversion. You can guess at it, but the actual ratings might be different.

I know that the SAE Gross ratings were a very different test indeed--no accessories running, open intake and exhaust, pretty much every "cheat" you can apply to inflate the power ratings. IIRC, the 1.7 made about 90 SAE Gross HP and the 914-6 120 SAE Gross HP.

Oh, and the US-spec 2.0 was rated at 95 DIN HP; it was the European version that was 100 DIN HP.

--DD

[Brando]

I thought gross HP ratings were when they bolted the engine itself right up to a brake and tested purely the engine's power rating. Net would be in a car, everything attached, rear-wheel testing?

[Tom73]

QUOTE (Brando @ Mar 23 2005, 12:37 PM)

I thought gross HP ratings were when they bolted the engine itself right up to a brake and tested purely the engine's power rating. Net would be in a car, everything attached, rear-wheel testing?

Gross is at the flywheel with no accessories, no air cleaner assembly, no stock exahust manifolds/mufflers (used headers with open exhaust), no emissions, no alternator, etc etc.

Net is also at the flywheel but with all stock/standard equipment in place. Stock exhaust manifolds running through stock exhaust, stock air cleaner assembly, alternator, emission equipment, etc.

The factories do not do any HP ratings at the wheels, that is a Hot Rod/aftermarket thing. All factory ratings are at the flywheel.

tom...