why is the RX8 HP All over the place?
10-19-2008, 12:29 AM
#1
Torn Asunder
Thread Starter
Join Date: Aug 2006
Posts: 33
Likes: 0
Received 0 Likes
on
0 Posts
why is the RX8 HP All over the place?
I have heard people say many different HP numbers with their car, its confusing, the official numbers were supposed to be 240 right?
I have heard people say their stock RX8 Dyno'd at 180hp before, and I have head some turbocharged RX8's were only 250, so WTF, whats the true HP of the RX8, and why isnt it what Mazda says it is?
I have heard people say their stock RX8 Dyno'd at 180hp before, and I have head some turbocharged RX8's were only 250, so WTF, whats the true HP of the RX8, and why isnt it what Mazda says it is?
10-19-2008, 12:35 AM
#3
170-185 whp is the typical 6 port manual. With mods, you can hit 200 whp NA.
turbo power is all over because different turbos flow differently and you can run them at various levels of boost.
With 6-7 psi you can expect somewhere from 240 whp ... and at higher levels of boost it's possible to hit 400. Most people sit somewhere around 260-340 whp though.
Remember, crank power != wheel power
turbo power is all over because different turbos flow differently and you can run them at various levels of boost.
With 6-7 psi you can expect somewhere from 240 whp ... and at higher levels of boost it's possible to hit 400. Most people sit somewhere around 260-340 whp though.
Remember, crank power != wheel power
10-19-2008, 12:36 AM
#4
Mazda states that the HP is 237 at the FLYWHEEL. For the 6 port Manual Transmission model. What you hear are reports of DYNO HP numbers. Power at the REAR WHEELS.
Not all dyno's read the same and are calibrated the same. Air temp and humidity can play a big roll in dyno numbers. And also the condition of the gas, spark plugs, air filter, the person running the dyno.
There are to many variables. Also some engines are just built with a little tighter tolerances than some other engines. They are hand built just for your information. And not by the same person.
Not all dyno's read the same and are calibrated the same. Air temp and humidity can play a big roll in dyno numbers. And also the condition of the gas, spark plugs, air filter, the person running the dyno.
There are to many variables. Also some engines are just built with a little tighter tolerances than some other engines. They are hand built just for your information. And not by the same person.
10-19-2008, 12:17 PM
#6
Torn Asunder
Thread Starter
Join Date: Aug 2006
Posts: 33
Likes: 0
Received 0 Likes
on
0 Posts
Mazda states that the HP is 237 at the FLYWHEEL. For the 6 port Manual Transmission model. What you hear are reports of DYNO HP numbers. Power at the REAR WHEELS.
Not all dyno's read the same and are calibrated the same. Air temp and humidity can play a big roll in dyno numbers. And also the condition of the gas, spark plugs, air filter, the person running the dyno.
There are to many variables. Also some engines are just built with a little tighter tolerances than some other engines. They are hand built just for your information. And not by the same person.
Not all dyno's read the same and are calibrated the same. Air temp and humidity can play a big roll in dyno numbers. And also the condition of the gas, spark plugs, air filter, the person running the dyno.
There are to many variables. Also some engines are just built with a little tighter tolerances than some other engines. They are hand built just for your information. And not by the same person.
how much WHP is in the 350z?
10-19-2008, 12:29 PM
#7
Registered
Join Date: Jul 2004
Location: Northern California
Posts: 2,196
Likes: 0
Received 0 Likes
on
0 Posts
Yes everything between the engine and the road eats HP and it's not just a few.....
10-19-2008, 12:29 PM
#8
weeeeeeeeee
iTrader: (12)
Look at all the "stuff" between the flywheel and the wheel... each of those components contribute its own share of resistance / loss... what you see at the wheel is the sum of all ineffeciencies between the flywheel and wheel.
10-20-2008, 12:33 AM
#10
Power!!
Next time you see a transmission out of a car try and turn the output shaft. You probably can't because it take a lot of power to turn it. Yes you lost ~15% hp between the crank and the drive wheels for a rear wheel drive car. This includes the spinning the clutch, the transmission, the drive shaft, the rear differential and the wheels themselves. Nothing is free and it takes power to turn it all.
10-20-2008, 12:57 AM
#11
BHP and WHP are different measuring systems. At BHR we like to use 40 h.p. for driveline losses assuming a factory clutch/flywheel. SpeedSource uses 33. With flywheels in the 9-10 lb. range we use 25 h.p. as a loss figure. Using percentages for driveline losses doesn't apply here.
10-20-2008, 08:43 AM
#13
Are you sure? I thought it was that Mazda originally claimed around 250hp for the 6-speed and offered a buy-back when the actual number was found to come in around 232hp. I'm pretty sure that my car has more than 215hp at the flywheel; it feels more powerful than that.
10-20-2008, 08:57 AM
#14
Registered
iTrader: (2)
Join Date: Oct 2007
Location: Pacific Northwest
Posts: 16,684
Likes: 0
Received 239 Likes
on
109 Posts
http://en.wikipedia.org/wiki/Horsepower
is very good reading. A bit heavy on the technical and math end, but still gives a good grasp on how variable the term "HP" can be.
More specifically:
is very good reading. A bit heavy on the technical and math end, but still gives a good grasp on how variable the term "HP" can be.
More specifically:
Originally Posted by Wikipedia
Brake horsepower
Brake horsepower (abbreviated bhp) is the measure of an engine's horsepower without the loss in power caused by the gearbox, generator, differential, water pump, and other auxiliary components such as alternator, power steering pump, muffled exhaust system, etc. "Brake" refers to how horsepower was originally measured and calculated, by means of a De Prony brake connected to the engine's output shaft. More recently, an engine dynamometer is used instead of a De Prony brake. The output delivered to the driving wheels is less than that obtainable at the engine's crankshaft.
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.[citation needed] 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).
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's supercharged Northstar V8 jumped from 440 horsepower (330 kW) to 469 horsepower (350 kW) under the new tests, while the rating for Toyota's Camry 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).
Effective (true, wheel) hp
Effective horsepower (ehp), True horsepower (thp) or wheel horsepower (whp) is the power converted to useful work. In the case of a road vehicle this is the power actually turned into forward motion as measured on a chassis dynamometer. Thp is generally 10% to 20% less than the engine's bhp rating due to drivetrain losses.
Brake horsepower (abbreviated bhp) is the measure of an engine's horsepower without the loss in power caused by the gearbox, generator, differential, water pump, and other auxiliary components such as alternator, power steering pump, muffled exhaust system, etc. "Brake" refers to how horsepower was originally measured and calculated, by means of a De Prony brake connected to the engine's output shaft. More recently, an engine dynamometer is used instead of a De Prony brake. The output delivered to the driving wheels is less than that obtainable at the engine's crankshaft.
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.[citation needed] 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).
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's supercharged Northstar V8 jumped from 440 horsepower (330 kW) to 469 horsepower (350 kW) under the new tests, while the rating for Toyota's Camry 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).
Effective (true, wheel) hp
Effective horsepower (ehp), True horsepower (thp) or wheel horsepower (whp) is the power converted to useful work. In the case of a road vehicle this is the power actually turned into forward motion as measured on a chassis dynamometer. Thp is generally 10% to 20% less than the engine's bhp rating due to drivetrain losses.
Last edited by RIWWP; 10-20-2008 at 09:00 AM.
10-20-2008, 09:11 AM
#15
Registered User
Join Date: Apr 2008
Location: Knoxville, TN
Posts: 403
Likes: 0
Received 0 Likes
on
0 Posts
hahahahahahahaha.
10-20-2008, 02:20 PM
#16
n00b post whore
Join Date: Mar 2008
Location: San Jose, CA
Posts: 535
Likes: 0
Received 0 Likes
on
0 Posts
Here's the theoretical drive train loss if we go by the numbers:
232hp (engine output) - (drivetrain loss) = 180whp
(drivetrain loss) = 232hp - 180whp
(drivetrain loss) = 52hp or (22% of 232)
That's an absurd amount of drive train loss for a small and low torque sports car.
Here's why 215hp (engine output) makes more sense:
215hp (engine output) - (drivetrain loss) = 180whp
(drivetrain loss) = 215hp - 180whp
(drivetrain loss) = 35hp or (16% of 215)
A 16% drive train loss is much more believable for this car.
10-20-2008, 02:37 PM
#18
I've dynoed my stock rx8 a couple times on the same dyno ( mustang ) and it's always between 18X and 20Xhp. the hotter it is the less hp. Highest numbers are always on the first pull and less hp after every pull even with 15 minute+ breaks.
10-20-2008, 05:45 PM
#20
Registered User
Join Date: Sep 2008
Location: ATL
Posts: 141
Likes: 0
Received 0 Likes
on
0 Posts
there are many conditions that determine the output of an engine. I think its been mentioned before but I'll mention it again. Given two of the same vehicles, being dynoed at two different locations, ambient conditions and condition of the engine are probably the two biggest factors that determine the output.
10-20-2008, 06:35 PM
#22
Registered
iTrader: (1)
Join Date: May 2006
Location: Carolina Beach, NC
Posts: 1,934
Likes: 0
Received 0 Likes
on
0 Posts
I just dyno'd mine on the 11th...79 degrees outside, 42% humidity, with extremely bad plugs and coils...I pulled a 182hp/136tq. Not bad considering I have a K&N Typhoon and HKS 3" exhaust.
Can't wait to see the numbers once the new flywheel and Access Port are installed.
Can't wait to see the numbers once the new flywheel and Access Port are installed.
10-20-2008, 06:49 PM
#23
SHKWAV
What's inbetween? Aside from the engine having to move all of those parts, you have this crazy thing called GRAVITY. With gravity, you get a phenominon called INERTIA... that's the whole concept of "objects in motion tend to stay in motion, objects at rest tend to stay at rest" thing.
Without going into a whole physics discussion, just take my word for it... The engine has an easier time spinning the flywheel than it does spinning transmission which drive the transaxel which turns the tires which has 3k pounds worth of metal (and stuff) sitting on top of it. Let's compare: a flywheel which weighs anywhere between 9 and 25 pounds (depending aftermarket or OEM) OR .. an entire freakin car.
Which do YOU think you could turn faster, a flywheel or a whole freaking car? That my young friend, is the difference between BHP and WHP.
Simple enough?
As for the 2nd question about the 350z, you're on the wrong forum to find anyone who cares enough to worry about what nissan does. Google is your friend.
As a side note, as i recall, the RX8 is rated at 248hp but when you stick the cat on it sucks up about 12hp... don't know if anyone mentioned this before me or not, didnt read the whole thread.
Last edited by Shinka_MJR; 10-20-2008 at 06:52 PM.
10-20-2008, 07:49 PM
#24
your train of thought fell off an unfinished bridge due to gravity.
i cant recall the last time i turned my entire car.
(the concept of things in motion stay in motion has nothing to do with gravity.)
im going to go ahead and call your post a massive fail.
i cant recall the last time i turned my entire car.
(the concept of things in motion stay in motion has nothing to do with gravity.)
im going to go ahead and call your post a massive fail.