When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I'm starting to hear rumbles about how the Z is underrated (or this car or that car) but I wanted to debunk it:
All modern mfrs seem to now publish SAE Certified Power with SAE J2723. When GM switched, the Northstar jumped 30 HP. The Camry lost a bunch.
The FIRST engine ever done this way was my beloved LS7. It jumped from the 500 initially advertised to 505 as we all know.
And from Wikipedia: "SAE tightened its horsepower rules to eliminate the opportunity for engine manufacturers to manipulate factors affecting performance such as how much oil was in the crankcase, engine control system calibration, and whether an engine was tested with premium fuel. In some cases, such can add up to a change in horsepower ratings."
So the number you see, if it's J2723, is the real deal.
As for the old motors like the COPO Camaros being 450hp and the L-88 being over 500, that's silliness too until you started adding (or removing) parts.
Remember the old 454/390 motors dropped to 454/270hp just going to the old SAE number. And they'd likely be 250, albeit with a lot of torque, under today's standard.
In fact, it's more than possible out LT4 produces as much power as two LS-6 Chevelles.
I'm starting to hear rumbles about how the Z is underrated (or this car or that car) but I wanted to debunk it:
All modern mfrs seem to now publish SAE Certified Power with SAE J2723. When GM switched, the Northstar jumped 30 HP. The Camry lost a bunch.
The FIRST engine ever done this way was my beloved LS7. It jumped from the 500 initially advertised to 505 as we all know.
And from Wikipedia: "SAE tightened its horsepower rules to eliminate the opportunity for engine manufacturers to manipulate factors affecting performance such as how much oil was in the crankcase, engine control system calibration, and whether an engine was tested with premium fuel. In some cases, such can add up to a change in horsepower ratings."
So the number you see, if it's J2723, is the real deal.
As for the old motors like the COPO Camaros being 450hp and the L-88 being over 500, that's silliness too until you started adding (or removing) parts.
Remember the old 454/390 motors dropped to 454/270hp just going to the old SAE number. And they'd likely be 250, albeit with a lot of torque, under today's standard.
In fact, it's more than possible out LT4 produces as much power as two LS-6 Chevelles.
It has been discussed at length at various times on this forum and other. My take away (aka opinion) is that the spec keeps manufacturers from over-rating their engines more so than under-rating them. Can you say Dodge Hellcat IIRC when I read the spec I only saw a threshold of what the engine had to make but not a upper limit of what it could make.
Manufacturers can underrate their engines by certifying for a lower HP amount. If you read the actual SAE certificate there is nothing in the language to prevent a manufacturer from underrating. Whether the myths are true is a function of whether a manufacturer wants or doesn't want to underrate. SAE does not set a ceiling HP only a floor. There is a difference.
Variances in dynos adds to the confusion. As does HP versus RWHP. As does "drivetrain loss". Especially when a torque converter is in the mix.
I believe in video. When a tuner makes a claim, I prefer to see a rolling start acceleration test side by side with a stock car. Or actual acceleration/G-force numbers measured by accelerometers and GPS.
What does a dyno run showing 591 RWHP for an A8 actually mean? (Real world example)
Manufacturers can underrate their engines by certifying for a lower HP amount. If you read the actual SAE certificate there is nothing in the language to prevent a manufacturer from underrating. Whether the myths are true is a function of whether a manufacturer wants or doesn't want to underrate. SAE does not set a ceiling HP only a floor. There is a difference.
This is incorrect, SAE J2723 requires production engines to be within ±2% of rated HP...there is no underrating engines allowed under SAE J2723. You've read an SAE certificate somebody posted online, buy the complete SAE J2723 document and you'll know the facts. This has been hashed out before on this forum and I posted proof, please refrain from posting this misinformation.
SAE J2723 requires production engines to be within ±2% of rated HP...
What does the standard require if <somebody> has an engine in manufacture that has the least producing engine one week produce 475 and the most producing engine produce 525? with a nice bell shaped curve centered around 500 HP and 12 HP Standard deviation?
A) 500 HP,
B) 475 HP,
C) not allowed to give any number
It has been discussed at length at various times on this forum and other. My take away (aka opinion) is that the spec keeps manufacturers from over-rating their engines more so than under-rating them. Can you say Dodge Hellcat IIRC when I read the spec I only saw a threshold of what the engine had to make but not a upper limit of what it could make.
See my post above...they are not underrating their engines. Like I said, buy the SAE J2723 document and read the whole thing...don't base your opinion off one page from the document.
What does the standard require if <somebody> has an engine in manufacture that has the least producing engine one week produce 475 and the most producing engine produce 525? with a nice bell shaped curve centered around 500 HP and 12 HP Standard deviation?
A) 500 HP,
B) 475 HP,
C) not allowed to give any number
The standard is very clear: ±2% of rated HP. If "somebody" can't meet that standard, the answer is "C" for certified HP rating. They can still give a number under SAE J1349, they just can't claim it's "certified under SAE J2723".
Rear wheel power is a no BS measure of an engine's prowess. Beyond that, I take most of the marketing claims as just that, statistics to sell a product.
The one question I've always had but never been given an answer is what are the testing conditions? If the conditions are say 100 degrees and its suppose to be a very high DA and is not normal conditions or unfavorable wouldn't that be kind of "underrating" the power? Also most European manufactures don't go by SAE certifications and commonly are found to be underrated.
The one question I've always had but never been given an answer is what are the testing conditions? If the conditions are say 100 degrees and its suppose to be a very high DA and is not normal conditions or unfavorable wouldn't that be kind of "underrating" the power? Also most European manufactures don't go by SAE certifications and commonly are found to be underrated.
This is exactly what a Dodge engineer said they did when rating the HP/TQ of the 392 Hemi engines....They rated them in horrible conditions when doing the SAE cert.
This is exactly what a Dodge engineer said they did when rating the HP/TQ of the 392 Hemi engines....They rated them in horrible conditions when doing the SAE cert.
The standard is very clear: ±2% of rated HP. If "somebody" can't meet that standard, the answer is "C" for certified HP rating. They can still give a number under SAE J1349, they just can't claim it's "certified under SAE J2723".
How do you explain the nice round marketing numbers then? If the new Z06 was 653 HP it would make some sense. But exactly 650?
505 is also a nice marketing number. ZR1 aside, all the engines in Corvette history have tended to be a nice round number.
There are a few facts left out. The SAE ratings are voluntary to start with. GM tests with a witness and sends in the paperwork. How many engines get tested to get that +- 2 percent number? The reality is what used to happen (and what SAE is stopping with the new standard) is overstating of HP. They want to make sure you are getting at least 98 percent of what the manufacturer says you are going to get.
What most manufacturers do is test an engine... say it tests out to 202 HP. They then add up to 2 percent to get their rated number. That 202 likely comes out to 205. What used to happen is they would add a hell of a lot more than that and the 202 would end up at 220 or 225. GM never had a history of doing that though... They have been conservative all along so it really doesn't make a real big difference because SAE doesn't give a rats *** about the tolerance, never test for it, and as long as consumers are getting 98 percent or more of advertised they feel they have done their job.
It's true that temps and humidity will affect HP and TQ readings, that is very much reality.
Is there a standard for that with SAE testing?
If not it is a factor that can be manipulated.
That's exactly my point and everyone that quotes J2723 never gives me those perameters and specs! What if it's simulating worst case scenario like in Denver! That would make most the engines "underrated". Could someone who has bought The document post it so we could read it?
Manufacturers can underrate their engines by certifying for a lower HP amount. If you read the actual SAE certificate there is nothing in the language to prevent a manufacturer from underrating. Whether the myths are true is a function of whether a manufacturer wants or doesn't want to underrate. SAE does not set a ceiling HP only a floor. There is a difference.
Huh? What? I thought it said within 2%. Didn't say a direction, but I'll go re-read it if you're sure.
Anyway, the bigger laugh to me is the "600hp L-88" that was rated at 1200rpm. Or the DZ302 that makes like 2hp per CID, that sort of bench racing nonsense that has now started to become lore.
Want a conundrum? My 2010 Range Rover Autobiography Supercharged (long name) runs a 4.8 0-60 and is 510hp in a 6500lb vehicle. How's that work?
Huh? What? I thought it said within 2%. Didn't say a direction, but I'll go re-read it if you're sure.
Anyway, the bigger laugh to me is the "600hp L-88" that was rated at 1200rpm. Or the DZ302 that makes like 2hp per CID, that sort of bench racing nonsense that has now started to become lore.
Want a conundrum? My 2010 Range Rover Autobiography Supercharged (long name) runs a 4.8 0-60 and is 510hp in a 6500lb vehicle. How's that work?
As far as your Range Rover it is Probably not SAE certified because it is European they have a different standard for measuring in their cars and are often underrated.
When humans are involved "tricks" are always a possibility
I have heard the L88 was made to appear less than the L71 because of readings taken at different RPM's
A well tuned L71 would be one that put about 325 to the ground.
Most often it was down around 300 or less
Back in those days headers and re-jetting made huge differences just like the early four into one exhaust systems did for the 4 stroke 4 cylinder motorcycles back in the 70's
06-14-2015, 01:38 PM
The myth of underrated engines
IIRC when I read the spec I only saw a threshold of what the engine had to make but not a upper limit of what it could make.
