We we discussing the differences between GROSS HP and NET HP on another thread. Here is some musing on this from Wiki:
SAE horsepower
SAE gross horsepower
Prior to the 1972 model year, American automakers rated and advertised their engines in brake horsepower (bhp), frequently referred to as SAE gross horsepower because it was measured in accord with the protocols defined in SAE standards J245 and J1995. As with other brake horsepower test protocols, SAE gross hp was measured using a blueprinted test engine running on a stand with no belt-driven accessories, air cleaner, mufflers, or emission control devices and sometimes fitted with long tube "test headers" in lieu of the OEM exhaust manifolds.The atmospheric correction standards for barometric pressure, humidity and temperature were relatively idealistic. The resulting gross power and torque figures therefore reflected a maximum, theoretical value and not the power of an installed engine in a street car. Gross horsepower figures were also subject to considerable adjustment by the manufacturer's advertising and marketing staff under the direction of product managers.The power ratings of mass-market engines were often exaggerated beyond their actual gross output, while those of the highest-performance muscle car engines often tended to be closer in actual output to their advertised, gross ratings.
No pre-1972 engine in its unaltered, production line stock form, as installed in the vehicle, has ever yielded documented, qualified third party validated power figures that equal or exceed its original gross rating.Claims that such engines were "under-rated" are therefore dubious; for example, the 1969 427 ZL1 Chevrolet, rated at 430 bhp (320.7 kW), is frequently cited as an "under-rated" high performance engine, yet it produced only 376 horsepower (280 kW).[9]
SAE net horsepower
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 hp 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. The change to net hp effectively deflated power ratings to assuage the auto insurance industry and environmental and safety lobbies.
Because SAE gross ratings were applied liberally, there is no precise conversion from gross to net. Comparison of gross and net ratings for unchanged engines shows a variance of anywhere from 40 to 150 horsepower. The Chrysler 426 Hemi, for example, in 1971 carried a 425 hp gross rating and a net rating of 350 hp, while the same company's 225 Slant 6 carried a rating of 145 bhp but 110 net hp. SAE certified horsepower
In 2005, the SAE introduced a new test protocol for engine horsepower and torque.[10] The new protocol eliminates some of the flexibility in power measurement, and requires an independent observer present when engines are measured. The test is voluntary, but engines completing it can be advertised as "SAE-certified".
Many manufacturers began switching to the new rating immediately, with multi-directional results; the rated output of Cadillac'ssuperchargedNorthstar V8 jumped from 440 horsepower (330 kW) to 469 horsepower (350 kW) under the new tests, while the rating for Toyota'sCamry 3.0 L 1MZ-FE V6 fell from 210 horsepower (160 kW) to 190 horsepower (140 kW). The first engine certified under the new program was the 7.0 L LS7 used in the 2006 Chevrolet Corvette Z06. Certified power rose slightly from 500 horsepower (370 kW) to 505 horsepower (377 kW).
We we discussing the differences between GROSS HP and NET HP on another thread. Here is some musing on this from Wiki:
No pre-1972 engine in its unaltered, production line stock form, as installed in the vehicle, has ever yielded documented, qualified third party validated power figures that equal or exceed its original gross rating.Claims that such engines were "under-rated" are therefore dubious; for example, the 1969 427 ZL1 Chevrolet, rated at 430 bhp (320.7 kW), is frequently cited as an "under-rated" high performance engine, yet it produced only 376 horsepower (280 kW).[9]
I don't know who writes this stuff for Wiki but I would certainly take it with a grain of salt, no make that a BOULDER of salt.
Some of you have probably heard of Dan Jensen, who co-founded the Pure Stock Muscle Car Drag Races held in Michigan each September. Dan has been rebuilding muscle car engines (particularly Pontiacs) for as long as I can remember to both stock and NHRA certified specs. He is also the recognized tech expert for POCI and GTOAA for 70-72 Pontiac A bodies and is quoted as an authority in numerous muscle car publications. There is no substitute for real world dyno results vs. some analysis based on magazine reports that can be all over the map. Last night I corresponded with him and asked about the certified dyno output of various engines (1970 RAIV, 71/72 455HO and 73/74 SD) he had rebuilt to stock specs. Here are excerpts from his response:
We dynod the engine in my 70 Judge before the car went back together and it made about 393 hp and about 440 torque. The compression was never checked, but I bet it was a little less that 10.0. I did the RAIV for Joe Ciones 69 TA (it was just in a recent issue of one of the Pontiac mags with a 69 Judge) and with the stock compression of 10.75, it made 438 hp and even more torque. The engines that we maxed out the compression closer to NHRA specs have come in around 455 hp and 470 torque. If a 70 was truly maxed out with nothing left on the table, I think it would be in the 480 hp and 485 torque range.
The generally accepted % of reduction to the rear wheels are what you stated, 15% for sticks, 20% for automatics. The best 455 HO Ive dynod so far has made 438 hp and 547 tq. That is with NHRA maxed out compression, which is around 10.0. The best SD has been 421 hp and 534 tq. Its compression was NHRA maxed too at 9.5. The reason the SD is down on power is because it has too much cam for its compression.The stock HO in my T-37 (068 cam and maybe 8.4 compression) made 368 hp and 500 tq.
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Hillar
1970 LS4 (eventually an LS5) Laurentian 2dr hdtp -and a bunch of other muscle cars...
These numbers are what I expected not the numbers from the article. I can't believe a 427 did not crack 400 hp. Thanks for posting true dyno figures Astro Jet.
The L-88 and ZL-1 427's required a "minimum" of 103 Research Octane, and were never intended to operate through factory cast iron manifolds and exhaust systems.
Chevy knew that they were being bought to race, and the exhaust system would be replaced by tuned headers almost as soon as they rolled off the delivery trailers.
The generally accepted standard for both engines is between 550 and 570dyno hp depending on the state of tune.
This is a really great debate with lots of good information being exchanged. Let's put aside the handful of special drag engines that were made and concentrate on the masses for a minute,
No one has yet been able to explain to me this simple fact. How is it that the original musle car, the grand daddy of Goats the 1964 GTO with 325 HP can only equal the acceleration times of my example 180 HP 1986 Monte Carlo SS ?
When someone can explain that then they can explain how a lowly 4,200 pound 300HP Deville keeps pace with them both.
This is a really great debate with lots of good information being exchanged. Let's put aside the handful of special drag engines that were made and concentrate on the masses for a minute,
No one has yet been able to explain to me this simple fact. How is it that the original musle car, the grand daddy of Goats the 1964 GTO with 325 HP can only equal the acceleration times of my example 180 HP 1986 Monte Carlo SS ?
When someone can explain that then they can explain how a lowly 4,200 pound 300HP Deville keeps pace with them both.
These numbers are what I expected not the numbers from the article. I can't believe a 427 did not crack 400 hp. Thanks for posting true dyno figures Astro Jet.
Al
same here, a recent stock rebuild of a L72 427 (factory rated at 425hp) dynoed at 461hp. an early Z28 302 rated at 290hp...right.
These numbers are what I expected not the numbers from the article. I can't believe a 427 did not crack 400 hp. Thanks for posting true dyno figures Astro Jet.
Al
same here, a recent stock rebuild of a L72 427 (factory rated at 425hp) dynoed at 461hp. an early Z28 302 rated at 290hp...right.
I guess those Z28's had good tires, a good driver and an excellent track when they hit 150 MPH at Watkins Glen and what not. or maybe that was 290 Net HP, really 415 Gross HP !
A lot of the original numbers quoted back in the 50's & 60's were not accurate that's for sure, but when the horsepower wars were on ,it has been said "horsepower developed in the brochure" was a common practice by the Big 3. It's still going on today. I doubt all the claims made by manufacturers are true on the latest factory performance cars but now they are a lot easier to prove or disprove due to all the dyno's available to the public.
Forgot about this one, but the LS4 vs. LS5 discussion reminded me I had yet to respond.
I think the answer to your questions are right in the articles Ray. The GTO is severely handicapped by having a peg leg 3.23. With only one 7.50 x 14 bias ply to get the power to the ground, it's 60 foots must have been terrible. They even said in the article that their acceleration runs resulted in smoke shows each time. Plus from what they say in the articles the GTO had at least 400 more pounds to lug around, plus it had two testers on board as opposed to one (I'm assuming) in the Monte Carlo. Give the GTO the Monte's 3.73 posi rear end plus modern rubber and I'm sure it would have run at least half a second faster.
Another generally accepted axiom in drag racing circles is that for each mph a car traps faster in the quarter, you need to generate an additional 10 hp. So as it is, the GTO had to be generating at least 60 net hp more than the Monte but if you put the same tires and rear end as the Monte had on the GTO, I'm sure it's ET and trap speed would have improved considerably, and thus would have demonstrated at least a 100 net hp difference.
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Hillar
1970 LS4 (eventually an LS5) Laurentian 2dr hdtp -and a bunch of other muscle cars...
I accept your arguments Hillar, as you know we hashed them out on a hour drive on the QEW BUT you can't turn back the clock and tires in 64 were as they were, everything was metal in the car too so in effect advances in technology are a big reason. A larger car weighing less with 84 less CID and at least 100 less HP, with superior tires leveled the playing field.
I agree though, give the 64 GTO a posi 3.73 and decent tires, equal weight then do it again.... but then we'd be in the present.
The big difference to me Ray is how a modern car gets to the end of the 1/4 mile vs. the '60's muscle cars. I used to drag race a 70 Cobra Torino 429 SCJ Ram Air back in 75,76. Just once in awhile, strictly due to funds. Most of the time it was Fri nite street action.That car was scary fast. It was a factory Drag Pak car, drum brakes,3200 stall,can't remember the axle ratio. But anyway it let you know a whole lot of hell was breaking loose when you put your foot into it. When it shifted into 2nd gear under full throttle it would go completely sideways until you let off a bit. A few years later I got a 454 Corvette that was almost as fast but nowhere near as dramatic, but would still snap around on you when ever it was pushed hard enough. Both cars kept you busy sawing the wheel to keep them under control. Brakes on the Cobra were non existent at high speed, handling was...way out there, somewhere. Corvette was light years ahead of it, but you needed all of your skills, luck, and a prayer to keep it out of the ditch. It eventually ended up there anyway in '80 In '87 my buddy let me try out his brand new GTA with the 5.7 rated @ 220hp. What a difference between those cars. This went about it's business in a new more civilized way but still kicked ass. Now, my similar '89 GTA feels like a neandrathal wagon with stone wheels compared to my former 2000 STS. It's OK until I take out the '06 Charger Daytona. Which brings me back to the Cobra. Same performance level, well almost, in the Daytona but no where near as visceral as the the mighty 429 or 454. The modern Hemi lets out a nice growl, leaves a bit small patch of rubber then tracks nice and true while it clicks off shifts thru the 5 speed auto without touching the shifter. at the end the brakes haul you down, the ESP keeps the car from skidding into the ditch, etc. Fun, but not scary and definitely not hairy. The Cobra was under rated @ 370hp (someone can check this for me please?) The 454 was a '74 rated @ 365 (I think) The Daytona is @ 360. I think that is overrated compared to my earlier cars, but it's the TORQUE numbers that tell the truth, and scare the crap outta you,eh Ray?
.......but it's the TORQUE numbers that tell the truth, and scare the crap outta you,eh Ray?
E-x-a-c-t-l-y.
For example, the 302 Z-28 has been mentioned, and I love that engine. But, if the driver didn't keep the engine high up in the rpm zone, it was a dead weight. Not enough torque. Off the line, you'd better be launching close to redline, or not much was happening. Once the car got rolling, and if the driver kept the revs "in the zone" it was a sweet car to drive, and beautiful to listen to through the chambered exhaust.
However, when I push the loud pedal on my ZZ502 (at any rpm), I have an instant 550 ft.lbs. of torque, even waaaaay down at 2,750 rpm, climbing to 567 at 3,750.....and it sure doesn't take much time to get to 3,750 rpm.
Launching with the 502 is a bit different than launching with a 302.
a few years ago on "Dream Car Garage" they were talking to their engine builder. He was talking about torque vs horsepower. Basically he was talking about the horsepower equation takes torque and also an rpm element to it. I remember him saying something about how an engine might be making x hp at a particular rpm, then stated "but make no mistake, the engine is still only making x ft lbs of torque".
Everyone focuses on hp as it sounds sexy, but torque is what gets you going.
The best torque is that which doesn't drop off dramatically at higher rpms. Gobs of low-end torque, that goes away quickly as the revs climb, won't win against horsepower at high rpms (other factors being equal). You want sustained torque levels as the revs climb.
And, did you know that it's impossible to measure horsepower from a running engine. What is actually measured on a dyno is torque. The computer then calculates the actual horsepower by converting the twisting force of torque into the work units of horsepower.
427/425hp Torque = 460 @ 4,000 (more torque and sooner)
Oh, and for reference, the L-78 was..... 396/425hp Torque = 415 @ 4,000
By the way, did you know the the L-72 was assigned a 450hp rating during the early run of 1966 Corvettes.....then the insurance companies took notice.....and suddenly it was 425hp.
Astro Jet wrote:I don't know who writes this stuff for Wiki but I would certainly take it with a grain of salt, no make that a BOULDER of salt.
I recently came across a debate between some guy who represented Wikipedia and another guy who represented traditional printed encyclopedia, very interesting (sorry I cannot remember where I came across the debate, internet or print?) and the key point was:
- Wikipedia says they are not held back by lengthy lead times due to stringent measures to ensure authenticity by experts, and are not limited by how much can reasonably fit on a printed page, but since ANYONE can submit stuff and fill up the internet with as much as they want (unverified by ANYONE except if someone else on the internet wants to challenge it) and the result is a gazilliion factoids and rumours about Madonna versus nothing at all about the Muncie M-22, well , that's what the masses of today want, and if popular culture overwhelms useful knowledge, so be it!
FMTT!
Dave
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1956 Pontiac Pathfinder 2dr sedan, 496 - dyno'd 545 hp, stick shift, 4.11 posi - Hot Rod
That's what is written in the first post. I think Wiki can at best be described as a collection of broad based colloquial knowledge.
That sentence above suggests that Wiki is not held out as facts, rather musings. Musings generally mean thoughts, especially when aimless and unsystematic. They often prompt discussion and further musings. I guess with 24 posts on this it worked ! I think that a lot of facts are contain in that however and the primary argument that Gross Horsepower is not a true reflection of an engine's output as installed in an automobile is accurate.
In general Wiki has high standards for contributing and an extensive verification process. My son contributes but I doubt anyone on here even knows how. In addition what motivation is there to publishing material which is not accurate? If Wiki is intent on becoming a credible and reliable source of information that would just go against eveyting it is trying to achieve.
1956 Pontiac Pathfinder 2dr sedan, 496 - dyno'd 545 hp, stick shift, 4.11 posi - Hot Rod