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Discussion Starter · #1 ·
I know the difference between bhp, gross, net, and rwhp but when did the advertised hp numbers like the 405 for the 2002 Z06 Corvette end up as net. I had read in the past (don't remember when) that new car makers hp readings were taken at the rear wheels after 1972. I even think there is a blurb about this in Chiltons.

I remember reading the drop from 365 to 275 in the 454 Corvette wasn't only from lower compression and polution equipment but that the HP rating was now at the rear wheeels.

Well, I was in a discussion the other day and after I had my hat handed to me in a handbasket about the Z06 405 HP being at the rear wheels, I did some research and my research it showed to be SAE net, although one source listed it as bhp.

So when did it all change back? and where was I when I missed this boat?

Mytmouse




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67 SS396 350HP 4 sp 3:55 Posi Butternut Yellow w/Black Vinyl
68 RS Z/28 302 350+Hp? 4sp 4:10 Posi, Euro Red on Black
70 SS396 350HP 4 sp 3:55 Posi, Black on Black

Mytmouse A.K.A. Robert Stacho
ACES Member # 04359
 

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I may be all wet too, but I've always heard net beginning in early 70's up until present. I did have a 90 ZR1 and a 90 Callaway at the same time in the early 90's and these cars were never described in terms of RWHP in anything I recall reading. In the case of the old 454 Corvettes, I always thought the 365 HP rating in 71 was still BHP and the lowering to 270 in 72 was the result of some other minor changes, but mostly the change to the net rating system. These cars (72 - 74 454 Corvettes) were such pigs they could hardly pull themselves from one gas pump to the next, so the assigned horsepower rating seemed overly optimistic to me. I sure wouldn't think they had 270 at the rear wheels. I've never heard anything about rear wheel HP ratings from a manufacturer. I wonder of some of the confusion doesn't come from some of the "experts" on TV and printed media that road test the cars but don't know a lot about what they're talking about. I'm not stating any of this as fact, rather just opinion, 'cause I ain't no "expert" either. I've just always gone by the "seat of the pants" rating. That's why I love those old solid lifter big blocks.........strong SOP rating.
 

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Discussion Starter · #4 ·
Below is a blurb I pulled off the the net. So if everything after 1972 was net then am I to assume that everything before was gross or bhp?? And if so, then the 350 HP on both my 396's rating in todays net ratings would probably be much closer to 300-325?? And the factories never rated at the rear wheels?

I think maybe my confusion was my interpretation of "net". I think maybe I always assumed that net meant what really went to the rear wheels and but that really rwhp is, is net - (minus) the loss through the drive train (from flywheel back which can only be measured on a chasis dyno.

I think 2blueLs6's probably has it right...SOP is probably the best anyway
Unfortunately I was made to look foolish because of my error. It wasn't the first and surely won't be the last


In today’s modern engines, horsepower is calculated electronically on an engine dynamometer, or dyno. Four specific classifications need to be mentioned, as they are often confusing:

Brake Horsepower (bhp): Prior to electronic bench testing, horsepower was quantified as the amount of resistance against a flywheel brake. Although the method is no longer used, the term remains an industry standard.

Gross Horsepower: Absolute maximum horsepower at the flywheel, with no load or drag from auxiliary systems, such as the alternator, water pump, etc. Created in an ideal environment with precisely controlled intake and exhaust flow characteristics, this category is of little practical use.

Net Horsepower: Maximum horsepower at the flywheel, with intake and exhaust systems in place and accounting for load from auxiliary systems. This is what most automotive manufacturers publish as SAE net horsepower.

Real-wheel Horsepower: Measured on a chassis dyno, the maximum horsepower transferred to the ground by the rear wheels. It can be affected by gearing, with lower (numerically higher) gearing tending to indicate a lower torque peak. Considered the most practical measurement of usable horsepower, it is the standard used in all 4WD vehicle tests whenever possible


Mytmouse


------------------
67 SS396 350HP 4 sp 3:55 Posi Butternut Yellow w/Black Vinyl
68 RS Z/28 302 350+Hp? 4sp 4:10 Posi, Euro Red on Black
70 SS396 350HP 4 sp 3:55 Posi, Black on Black

Mytmouse A.K.A. Robert Stacho
ACES Member # 04359
 

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Factories NEVER rated HP at the rear wheels. There are too many variables for the same engine (auto or manual trans, type of rear axle, 2WD vs 4WD, etc.). Net and Gross ratings were always and continue to be a rating of the power available at the flywheel.
 

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Mighty, my take on these forums is that they're for sharing information and sometimes thinking outloud. If a misunderstanding is the benchmark for looking foolish around here, I'm in deep trouble. If you read my post on the 350HP stuff there were several errors that I knew off the top of my head after I read back through it. So don't feel foolish. On most any subject we throw up here somebody's gonna come foward with a lot of knowledge and that's what makes it great. (now if I could just find that majic subject that I'm an expert on)
 

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Discussion Starter · #7 ·
2Blue,

Sorry, about the confusion. I understand what you said and don't mind looking the "fool" around here. The help that is given around here generally... is well, exactly that, and advice given to educate. I certainly understand that.

But my foolishness on the subject of HP ratings came up in another format on the net and this punk handed me my hat in a handbasket and contunued to ridicule me from my job to my worthless life (that he absolutely has no idea about either) that got under my skin a little bit. I did some research and found out my mistake and even e-mailed this idiot and indicated that "I stand corrected". What I got back was "it is better to look the fool and keep you mouth shut than to open it and remove all doubt". It must be nice to have that holier than thou attitiude at the ripe old age of 24. Geesh.........takes all kind.

Thanks for the feedback

Mytmouse


------------------
67 SS396 350HP 4 sp 3:55 Posi Butternut Yellow w/Black Vinyl
68 RS Z/28 302 350+Hp? 4sp 4:10 Posi, Euro Red on Black
70 SS396 350HP 4 sp 3:55 Posi, Black on Black

Mytmouse A.K.A. Robert Stacho
ACES Member # 04359
 
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