Would someone please clear the whole "CrankHP/WHP/AWHP" thing up for me?

[S4DIT]

Ok, so I've been following all these threads for two months now and I can't seem to get my mind around these figures:

Crank HP
WHP
All wheel HP

I know that there is some drive train loss when transferring the "crank" HP to the wheels, but why does everyone seem to post different figures?? Isn't the "WHP" the only thing that matters? Why don't all the "crank" people just subtract the 15% loss (or whatever it is) and give us the WHP up front?

But here is my real question: Obviously we all are driving the B8 S4 which is all wheel drive - how does all wheel drive play into this? If someone says they got 400 AWHP does that mean I should multiply 400 by 1.25 to get the "total" or "real" HP?

And, what is the difference between "Peak gains" and "max gains"??

My apologies in advance if these questions have been answered in previous posts - I'm sure they have...

[Voltrons_Head]

Here ya go!

[YZracer]

HAHAHAHAHAHAHA. Ok sorry now to....

Crank HP = Power the motor is making at the crank, or the flywheel

AWHP and WHP are the same thing. AWHP just stresses the fact that it is an AWD car. Both refer to the power being made at the wheels that DRIVE or PROPEL the car.

The difference is drivetrain loss from the Crank HP to the Wheel HP.

Front wheel drive generally has about 10-12% loss from crank to wheel
Rear wheel drive generally has about 15% loss from crank to wheel
All Wheel drive generally has 22-25% loss from crank to wheel

Lastly, Peak and Max are the same thing. lol

[81bear]

Here ya go!

lol...but I prefer your usual video clips.

OP...MFG's advertise crank as it is the larger number and that sells cars...tuners and retailers use whp because thats what we have access to...drivetrain loss increases with all wheel drive cars but the exact % of loss for both two wheel and all wheel cars are unknown.

[wwhan]

Also, the drive train loss is slightly nonlinear & not a constant, including dependence on temperature.

We can make estimates on drivetrain loss, but it will only be an estimate & various people will have different estimates.

Conversion from crank HP to wheel HP is error prone & often leads to endless arguments.

[S4DIT]

Funny :) Yeah, I know how to Google, it's just more fun asking B8 S4 guys directly. I'm not interested in what Subaru or Nissan guys have to say.... :)

My main question had to do with "AWHP" - I thought I had read somewhere that you need to multiply something by 1.25 to get the correct figure. What am I thinking of?

[Un1k]

Here ya go!

I love your responses LOL

I'll give it a go, but all my knowledge is from lurking around this forum and I might've understood some of it wrong.

Max gain = any point in the powerband where you gain the most power (torque or hp)
Peak gain = the gain at the point where your hp or torque is at its highest

ppl have diff figures because dyno 'corrects' your figures. And diff dynos read power differently. Some are generous, some are not.
When you get on a dyno, or if someone posts a dyno of CHP, it means that they got the AWHP and did some multiplying to get CHP.
So what actually happens is (i think..) they get the WHP and then correct it to CHP which becomes less accurate.
Drive train loss is not a 'set' figure, it differs by car and whether it is AWD or RWD etc. (AWD has greater Drive train loss) and this is why I said it is less accurate

if someone says they have 400 wheel horsepower, then you don't multiply anything b/c like you said, WHP is what we need. CHP is near useless.

The ad you see, and the official website listings of HP is usually CHP.

So, in short, try to ignore CHP. What's even more accurate than WHP would be WHP per ton, or whatever it is called.

**-edit
forgot to say that dyno reads WHP not CHP

[Un1k]

I'm not interested in what Subaru or Nissan guys have to say.... :)

That's rude

[S4DIT]

That's rude

Sorry, wasn't trying to be rude - what I meant is that a lot of what "other cars" do is irrelevant when talking about S4's. Thanks for your response - it's helpful!

[rktskicar]

WHP = CHP/(1-DTL)

where,
CHP is crank HP
WHP is wheel HP
DTL is drivetrain loss (e.g. 20% DTL = 0.2)

Bruce

[Voltrons_Head]

Funny :) Yeah, I know how to Google, it's just more fun asking B8 S4 guys directly.

I almost didn't do it cause you're new and maybe wouldn't know I was joking around.

[S4DIT]

I almost didn't do it cause you're new and maybe wouldn't know I was joking around.

I've been here long enough to notice you're a funny guy. :) LOL

[Un1k]

Sorry, wasn't trying to be rude - what I meant is that a lot of what "other cars" do is irrelevant when talking about S4's. Thanks for your response - it's helpful!

lol, sorry I was kidding haha I tried to help you the best I could and then followed up with that short comment, that was the joke :) a poor one, I know

[skiracerblah]

Don't forget to toss in the dyno factor into WHP as each dyno manufactuer will read differently from each other. I.E. Mustang Dyno will read significantly lower compared to a Dynojet Dyno...

Even if you have the same dyno from the same manufacturer, they will be slightly off from each other....

[Vogz]

Sorry, wasn't trying to be rude - what I meant is that a lot of what "other cars" do is irrelevant when talking about S4's. Thanks for your response - it's helpful!

What "other cars" do is not irrelevant. The relationship between CHP and WHP is the same regardless of the make and model of the vehicle.

[Vogz]

Lastly, Peak and Max are the same thing. lol

No, they aren't. Un1k hit the nail on the head.

[NWS4Guy]

Isn't the "WHP" the only thing that matters?

Pretty much sums it up. Crank is for show, WHP (or in our case since we have AWD, AWHP) is for go.

It's what you put to the pavement that ultimately matters, ask the resident comic (Voltron) about heavy wheels affecting his times at the drag strip. Didn't matter a bit how much his motor was putting at the crank.

[t0mt0m]

sorry to the that guy but is this true?

"US HP ratings are based on 91Octane
German HP ratings are based on 93<Octane"

found it lurking on m3 forums trying to figure out there base dyno #s
339.54hp/257.90tq

[NWS4Guy]

sorry to the that guy but is this true?

"US HP ratings are based on 91Octane
German HP ratings are based on 93<Octane"

found it lurking on m3 forums trying to figure out there base dyno #s
339.54hp/257.90tq

Not sure, but Europe uses RON not our Octane calculation method [AKI, which is shown on every pump - (R+M)/2]. So our 91(octane) is 95 RON in EU, and our 93(octane) is 98 RON in EU. As to what standards they use for dyno, in reality, it shouldn't make an enormous difference, a few extra HP and TQ, call it 1%-2%.

[Voltrons_Head]

heavy wheels affecting his times at the drag strip

Not sure what you mean.








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MS Paint ftmfw!

[Leor604]

WHP = CHP/(1-DTL)

where,
CHP is crank HP
WHP is wheel HP
DTL is drivetrain loss (e.g. 20% DTL = 0.2)

Bruce

UUUUUUmmmmmm, isn't that backwards??

I think you meant CHP = WHP/(1-DTL) or WHP = CHP*(1-DTL).

Don't want to add more fuel to the confusion fire.

[Leor604]

The relationship between CHP and WHP is the same regardless of the make and model of the vehicle.

Really?? That would mean every car, regardless of make, model, transmission, FWD, RWD, AWD has exactly the same drivetrain loss. I kinda doubt it.

True, WHP will always be less than CHP, but I am pretty sure the percentage of the difference will differ from one model to another. If it was the same for every vehicle, I am sure that somewhere between the Benz Patent Motor-wagen (1886) and the Veyron, someone would have figured out the percentage and then we wouldn't all be guessing about the difference between CHP and WHP

[Chestlock]

Not sure what you mean.








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MS Paint ftmfw!

Priceless! HAHAHAHAHAHAHAHAHAHAHAH

[rktskicar]

UUUUUUmmmmmm, isn't that backwards??

I think you meant CHP = WHP/(1-DTL) or WHP = CHP*(1-DTL).

Don't want to add more fuel to the confusion fire.

No. DTL is a loss, appears in the denominator, not the numerator.

Bruce
an engineer if you can't tell.

[Vogz]

Really?? That would mean every car, regardless of make, model, transmission, FWD, RWD, AWD has exactly the same drivetrain loss. I kinda doubt it.

True, WHP will always be less than CHP, but I am pretty sure the percentage of the difference will differ from one model to another. If it was the same for every vehicle, I am sure that somewhere between the Benz Patent Motor-wagen (1886) and the Veyron, someone would have figured out the percentage and then we wouldn't all be guessing about the difference between CHP and WHP

No it wouldn't because I didn't say "every car has the same drivetrain loss". Thanks for putting words into my mouth though.

The fact of the matter is the only time you can really figure drivetrain loss is on a bone stock vehicle, and even then it doesn't always make sense. As with the car in question, there are B8 S4s that have put down 333awhp and therefore they must have ZERO percent drivetrain loss, no? There's no magic number for drivetrain loss for any vehicle model and the relationship IS always the same. CHP is more than FWHP/RWHP/AWHP because of drivetrain loss. End of story.

I look at CHP as virtually irrelevant in a modded car since the end user doesn't have the capability to measure it.

[helix139]

power numbers are somewhat useful. When taken from different dynos, you really can't compare with a high level precision (i.e. you can probably say 600WHP on dyno A is more than 300WHP on dyno B, but comparing 2 stock S4's on different dynos or trying to find out how much HP you have gained after a mod on different dynos will be inconclusive), and anytime WHP is converted to CHP, it should be taken with a grain of salt. Really, the only time you can directly compare power is using the same dyno on the same day in the same conditions. Anything else is not going to provide a truly acceptable comparison. There is just too much variability among dynos and dyno operators

[Sprode]

No. DTL is a loss, appears in the denominator, not the numerator.

Bruce
an engineer if you can't tell.

Sorry buddy. I'll give you a break cause you posted at 220 in the morning, but your post was not correct. Your formula asserts that WHP would be MORE than CHP, because you are dividing by a number less than 1.

WHP = CHP/(1-DTL)

where,
CHP is crank HP
WHP is wheel HP
DTL is drivetrain loss (e.g. 20% DTL = 0.2)

Bruce

is wrong.


This:

UUUUUUmmmmmm, isn't that backwards??

I think you meant CHP = WHP/(1-DTL) or WHP = CHP*(1-DTL).

Don't want to add more fuel to the confusion fire.

Is right

-John

A good engineer.

[zcd2.7t]

[Keith@APR]

I've been here long enough to notice you're a funny guy. :) LOL

[Voltrons_Head]

I'll see you one TNG and raise you a DS9.

[Keith@APR]

I think everyone understands the overall picture pretty well.

No dyno reads the same as another dyno, even if from the same manufacturer, unless they are operated in the same conditions with the same dyno calibration settings.

Everyone that owns a dyno seems to change up the calibration, correction factors, ramp time, run up time, etc. as they see fit. And that's fine, that's why the dyno's have those features. However, it makes it very easy to manipulate the results as well and it also makes them inconsistent for comparison.

A good example is a time when I had a client purchase some mods from us. He and I expected he would achieve about 50whp increase from the mods. He had a baseline performed and all looked as expected, installed the parts and went back a week later.

He only made 15whp. Now, obviously there is an immediate burden on me to explain why and to help correct. Is the car sick? Are the parts installed correctly? Can you send some datalogs? All of the usual stuff to diagnose the problem. Weeks go by and I can't find anything. I call up the engineering team, get them involved, the client is frustrated, we reconfirm our testing here, blah, blah.

So, we just are about to the point to where I am going to refund this guy and get back a bunch of used parts I can do very little with. Someone suggests I call the shop that did the dyno and just ask some general questions about the dyno set up. Lo and behold, I find out they recently recalibrated the dyno with new settings from the manufacturer. Thankfully, he saved the previous settings, returned to those settings, got the customer back in and voila, a 65whp gain.

Now, APR seemingly does it differently than anyone else in our space at this time.

We know how the OEM's do it. They measure Engine Power on a ton of Engine Dyno's. They measure Wheel Power on several Chassis Dyno's. They measure Crank Power on several Chassis Dyno's that calculate Wheel Power back to Crank Power.

Then they analyze and normalize the data and certify an engine with an internal power rating that can be recreated in a wide range of conditions with an acceptable amount of variance or tolerance, i.e. +/-.

From there, the marketing guys get involved, determine where the engine/vehicle needs to be positioned in the market against the competition, ask the engineering teams to arrive at the marketing power and as we've seen, sometimes the marketing power isn't consistent with the internal power rating. Thankfully, the OEM's will never over rate but marketing power is sometimes underrated.

APR uses our Chassis Dyno to collect hub/wheel power, compare that data to the OEM Crank Power and apply the necessary calculations to bring the wheel power back to OEM crank power.

For measuring and displaying gains from modifications, we use our chassis dyno to collect the new hub/wheel power and apply the same calculations we used during the OEM power data collection to bring it back to Crank Power.

We collect several runs, we analyze and normalize the data to include throwing away the highest and lowest outliers, and arrive at both a hub/wheel power and calculated crank power that is an average of what we saw and typically results in something everyone can expect to recreate as far as delta, no matter the dyno, the dyno calibration, the dyno operator, etc. We verify the gains or the delta of both our hub/wheel power and our calculated crank power across several different kinds of dyno's in as many different ambient conditions possible through Beta Testing in the field prior to release.

[primetime]

. Thankfully, the OEM's will never over rate but marketing power is sometimes underrated.

The 1999 Mustang Cobra was grossly overrated by Ford.... to the point that they issued a "fix" to get the cars to the claimed HP # of 320HP..... It consisted of a different intake, exhaust and some other little things if I remember correctly....

[S4DIT]

Excellent info, thanks Keith. I think it's safe to say that APR can certainly be trusted in regard to their testing & expertise. That's why I'm getting the APR tune on Monday rather than the Stasis. Who needs assurance of OEM warranty when you're in APR's hands? :)

[Keith@APR]

The 1999 Mustang Cobra was grossly overrated by Ford.... to the point that they issued a "fix" to get the cars to the claimed HP # of 320HP..... It consisted of a different intake, exhaust and some other little things if I remember correctly....

Yeah, well.....lol!

Hopefully no one will do it again I should have said!

[Keith@APR]

Excellent info, thanks Keith. I think it's safe to say that APR can certainly be trusted in regard to their testing & expertise. That's why I'm getting the APR tune on Monday rather than the Stasis. Who needs assurance of OEM warranty when you're in APR's hands? :)

Thank you for the kind words.

I need to start an ad campaign with this:

Who needs assurance of OEM warranty when you're in APR's hands? :)

[sworksone]

Sorry buddy. I'll give you a break cause you posted at 220 in the morning, but your post was not correct. Your formula asserts that WHP would be MORE than CHP, because you are dividing by a number less than 1.

This: Is right

-John

A good engineer.

Seconded by another (good) one.

[rktskicar]

Sorry buddy. I'll give you a break cause you posted at 220 in the morning, but your post was not correct. Your formula asserts that WHP would be MORE than CHP, because you are dividing by a number less than 1.


is wrong.


This:


Is right

-John

A good engineer.

Sorry, you are correct. CHP and WHP need to be swapped.

Bruce

[Vogz]

The 1999 Mustang Cobra was grossly overrated by Ford.... to the point that they issued a "fix" to get the cars to the claimed HP # of 320HP..... It consisted of a different intake, exhaust and some other little things if I remember correctly....

They didn't overrate it on purpose though. There was a gross oversight in the final design process of the exhaust that caused a huge restriction that was not there during initial development.

Another car that didn't make advertised hp was the Mazda RX-8.

I'm pretty sure Audi underrated the B8 S4 on purpose :)

[primetime]

They didn't overrate it on purpose though. There was a gross oversight in the final design process of the exhaust that caused a huge restriction that was not there during initial development.

I wasn't in design/marketing meetings at Ford so I can only speculate but I struggle to see how they would rate a car that wasn't even done yet..... Also, the exhaust was not the only change when you got the "fix"..... Whatever though... my point was the car didn't make the marketed horsepower that buyers were told it would make and it forced Ford to take action to correct..... Was just letting Keith know there are/were examples of cars being overrated, and the RX8 came to my mind as well :)

[wwhan]

This was from GM;

http://www.autotropolis.com/krome-on...ttle-but-.html

""2011 Chevrolet Camaro Wins HP Battle, But ...
Yes, the 2011 Chevrolet Camaro V-6 has won the horsepower battle against its arch-nemeis, posting a mark of 312 hp compared to the '11 Ford Mustang V-6's 305. ....


Here's the money quote, straight from the General:
“The 304 horsepower in the 2010 Camaro was actually a conservative rating on our end,” said Tom Sutter, GM V-6 chief engineer. “But we knew already that this award-winning engine produced at least the amount of power we stated, but now we’ve gone the extra step in certifying the engine for this application and have verified an additional 8 horsepower.”
Really, Tom? You guys couldn't find the time/resources to make any actual, physical tweaks to the powertrain itself? You just had the old mill recertified?""