Rated engine power

[4x4ord]

How do manufacturers, presently, determine how to rate their engine's crankshaft horsepower? Is the cooling fan engaged and drawing air? Alternator charging? Power steering pump and A/C installed and working?

[ls1mike]

ScottG wrote:

ls1mike wrote:

ScottG wrote:

Cummins12V98 wrote:

ScottG wrote:

Cummins12V98 wrote:
" Every DYNO event I have been to the Stock Cummins nets about 85% of advertised HP. Sometimes a bit more.

That's in part because the intercooler is out of the picture. They make a big difference!

WHY is it out of the picture?

Not much different than on the road with a big fan blowing at the front.

I've only been to a few dyno events but none ever used a fan - do they sometimes? It would take a big one. Banks uses an elaborate setup of 40 HP worth of electric fans a bunch of ducting for dyno runs. Anything short of that isn't going to move enough air to make a difference IMHO.

You are in Bothell? I have used 3 different Dynos in this area. I have always seen a fan used. I have been to about 25 dyno days. I can't imagine not using one. Come to Auburn and watch my Caprice get Dynoed after I install the cam and headers. Those fans make a difference.

:C

I met my wife in Bothell, she grew up on Whidbey Island.

[ScottG]

ls1mike wrote:

ScottG wrote:

Cummins12V98 wrote:

ScottG wrote:

Cummins12V98 wrote:
" Every DYNO event I have been to the Stock Cummins nets about 85% of advertised HP. Sometimes a bit more.

That's in part because the intercooler is out of the picture. They make a big difference!

WHY is it out of the picture?

Not much different than on the road with a big fan blowing at the front.

I've only been to a few dyno events but none ever used a fan - do they sometimes? It would take a big one. Banks uses an elaborate setup of 40 HP worth of electric fans a bunch of ducting for dyno runs. Anything short of that isn't going to move enough air to make a difference IMHO.

You are in Bothell? I have used 3 different Dynos in this area. I have always seen a fan used. I have been to about 25 dyno days. I can't imagine not using one. Come to Auburn and watch my Caprice get Dynoed after I install the cam and headers. Those fans make a difference.

:C

[ls1mike]

ScottG wrote:

Cummins12V98 wrote:

ScottG wrote:

Cummins12V98 wrote:
" Every DYNO event I have been to the Stock Cummins nets about 85% of advertised HP. Sometimes a bit more.

That's in part because the intercooler is out of the picture. They make a big difference!

WHY is it out of the picture?

Not much different than on the road with a big fan blowing at the front.

I've only been to a few dyno events but none ever used a fan - do they sometimes? It would take a big one. Banks uses an elaborate setup of 40 HP worth of electric fans a bunch of ducting for dyno runs. Anything short of that isn't going to move enough air to make a difference IMHO.

You are in Bothell? I have used 3 different Dynos in this area. I have always seen a fan used. I have been to about 25 dyno days. I can't imagine not using one. Come to Auburn and watch my Caprice get Dynoed after I install the cam and headers. Those fans make a difference.

[ScottG]

Cummins12V98 wrote:

ScottG wrote:

Cummins12V98 wrote:
" Every DYNO event I have been to the Stock Cummins nets about 85% of advertised HP. Sometimes a bit more.

That's in part because the intercooler is out of the picture. They make a big difference!

WHY is it out of the picture?

Not much different than on the road with a big fan blowing at the front.

I've only been to a few dyno events but none ever used a fan - do they sometimes? It would take a big one. Banks uses an elaborate setup of 40 HP worth of electric fans a bunch of ducting for dyno runs. Anything short of that isn't going to move enough air to make a difference IMHO.

[ppine]

It is logical that manufacturers would measure hp at the flywheel with everything off. That would be the way to get the highest reading.

[Groover]

I wonder how much the manufacturer can play with the numbers. I am more familiar with outboard boat motor ratings and know that they have to be within 10% of the rated power, more or less, doesn't matter which way. Today most brands are selling performance more than power and with computer controls the typical outboard makes about 109% of rated power at the prop shaft. It is common to use the same engine to make several different power outputs, frequently with nothing different but the computer programming. I have heard that one engine that is advertised as 225hp at the rated RPM (5500) actually makes about 270hp at 4000RPM. This is within the rules since that is not the rated RPM. This brand like to advertise how strong their acceleration is. It is amazing how people can find ways around the rules.

[Cummins12V98]

ScottG wrote:

Cummins12V98 wrote:
" Every DYNO event I have been to the Stock Cummins nets about 85% of advertised HP. Sometimes a bit more.

That's in part because the intercooler is out of the picture. They make a big difference!

WHY is it out of the picture?

Not much different than on the road with a big fan blowing at the front.

[ScottG]

Cummins12V98 wrote:
" Every DYNO event I have been to the Stock Cummins nets about 85% of advertised HP. Sometimes a bit more.

That's in part because the intercooler is out of the picture. They make a big difference!

[Cummins12V98]

"In the US, all light duty vehicles are rated using the same testing procedures defined by the Society of Automotive Engineers. It is horsepower at the rear wheels with all accessories installed (A/C is likely turned off)."


No way this can be true. Every DYNO event I have been to the Stock Cummins nets about 85% of advertised HP. Sometimes a bit more.

[ls1mike]

ShinerBock wrote:

ls1mike wrote:
All manufactures rate horsepower at the crankshaft when it advertised. It is full accessories and emissions.

Not exactly. Especially for those who use J1995.

J1349 is used by the manufacturer who makes the completed vehicle while J1995 is used by the manufacturer who does not. For example, Cummins uses J1995 because they only sell engines and do not make a completed vehicle.

You are right, I should have been more specific. I was thinking GM, Ford and Mopar. When they advertise cars it is at the crank. I would assume it is the same for the Diesels, but I never really thought about it.

[ktmrfs]

as mentioned today engine power is determined with the alternator, water pump, fan etc. all connected and operating along with the factory air intake, air filter, exhaust system installed etc. Often referred to as SAE Net HP. This was instituted sometime in the 1970's for U.S. sold cars and Light trucks.

AFAIK there isn't any load added to the alternator to represent what power might be needed for other electric loads in the car, nor do I think the AC is on, but the AC belt and pulley are connected.

Before that there was SAE Gross HP which was used by U.S. mfg which was determined without driving water pump, alternator, an open air intake system, and no muffler installed, and in some cases running non factory header pipes. At the Same time many european vehicles coming to the U.S. were advertizing DIN HP which was much closer to the SAE net rating.

[ShinerBock]

ls1mike wrote:
All manufactures rate horsepower at the crankshaft when it advertised. It is full accessories and emissions.

Not exactly. Especially for those who use J1995.

J1349 is used by the manufacturer who makes the completed vehicle while J1995 is used by the manufacturer who does not. For example, Cummins uses J1995 because they only sell engines and do not make a completed vehicle therefor they do not know what accessories or air filtration system will be attached to it.

[ShinerBock]

Groover wrote:
On a related subject I would still like to know what the difference is between "certified horsepower" on the medium duty and apparently not certified horsepower in pickups. Also, why do diesels consistently dyno much closer to rated horsepower than gas engines? There should be only one way to rate horsepower and that is at the rear wheels with all standard items on. On diesels that should probably include numbers just before and just after particulate filter cleaning.

"Certified power" just means that they had a third party SAE licenced person witness them do the J1349 or J1995 test.

As far as power at the wheels, this is not possible for all applications. For instance, Cummins certifies the power of their engine and sends it to Peterbilt to sit in a warehouse until that specific engine and power level is needed for a truck that is ordered. Peterbilt then puts the engine into the truck that can have one of thousands of different cab, trans, PTO, and drive line configurations. If they put a fifth wheel on it, then it is a complete tractor and they would have to dyno every one that comes off the floor with a different configuration. If they don't put a fifth wheel or box on it, then it is not a completed vehicles and it gets sent to a final builder who would up-fit the truck with various different things that would also effect power output. In some cases, the final builder is the customer.

[Groover]

On a related subject I would still like to know what the difference is between "certified horsepower" on the medium duty and apparently not certified horsepower in pickups. Also, why do diesels consistently dyno much closer to rated horsepower than gas engines? There should be only one way to rate horsepower and that is at the rear wheels with all standard items on. On diesels that should probably include numbers just before and just after particulate filter cleaning.

[ls1mike]

All manufactures rate horsepower at the crankshaft when it advertised. It is full accessories and emissions.

Cars in the 50, 60, 70's were rated with no accessories. That is why if you were to test them today you see they are lower than was advertised and slower then what they should be for rated power.

On average when you do a dyno pull in a manual you expect a 10 to 15 percent loss through the drive train. In auto 15 to 20 percent loss. This is average and it varies case by case.

I will use my WS6 for an example. It was rated at 320 to crank by GM. It dynoed at 328 bone stock. Underrated by GM. You hear about that one on a lot of cars. It also depends on what kind of Dyno and conditions that day.

The rated HP from the manufacture is done in controlled conditions and has to be repeatable.