Good Sam Club Open Roads Forum: Tow Vehicles: Rated engine power
Open Roads Forum Already a member? Login here.   If not, Register Today!  |  Help

Newest  |  Active  |  Popular  |  RVing FAQ Forum Rules  |  Forum Posting Help and Support  |  Contact  

Search:   Advanced Search

Search only in Tow Vehicles

Open Roads Forum  >  Tow Vehicles

 > Rated engine power

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 4  
Next
4x4ord

Alberta

Senior Member

Joined: 12/23/2010

View Profile



Posted: 11/14/19 07:18am Link  |  Quote  |  Print  |  Notify Moderator

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?


2017 F350 SRW Platinum short box 4x4.
B&W Companion
2008 Citation Platinum XL 34.5

theoldwizard1

SE MI

Senior Member

Joined: 09/07/2010

View Profile


Offline
Posted: 11/14/19 07:28am Link  |  Quote  |  Print  |  Notify Moderator

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).

When you get to medium duty vehicles, I believe the horsepower is measured "at the crankshaft", but again with all accessories (probably not A/C).


The important thing is that it is done CONSISTENTLY across all manufacturers.

ShinerBock

SATX

Senior Member

Joined: 02/22/2015

View Profile



Posted: 11/14/19 07:54am Link  |  Quote  |  Print  |  Notify Moderator

There is a lot more leniency in the SAE J1995 or J1349 test requirements than most think.

Attached is an old J1349 test standards. I have the current J1349 and J1995 standards, but cannot link them. However, not much has changed.

J1349 Test Standard

Pages 10-12 discusses what you are looking for.

J1349 requires most accessories while J1995 doesn't. However, that does not mean the manufacturers do not test with accessories on J1995. Some do when they know exactly what the engine is used for making them no different than J1349. They have to use J1995 because they are not building the complete vehicle.

twodownzero

NM

Senior Member

Joined: 06/07/2014

View Profile


Offline
Posted: 11/14/19 08:08am Link  |  Quote  |  Print  |  Notify Moderator

theoldwizard1 wrote:

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).

When you get to medium duty vehicles, I believe the horsepower is measured "at the crankshaft", but again with all accessories (probably not A/C).


The important thing is that it is done CONSISTENTLY across all manufacturers.


SAE Net Horsepower includes all accessories and emission controls, but is measured at the crankshaft.

https://en.wikipedia.org/wiki/Horsepower#SAE_net_power

ls1mike

Bremerton

Senior Member

Joined: 06/26/2009

View Profile



Good Sam RV Club Member

Offline
Posted: 11/14/19 08:18am Link  |  Quote  |  Print  |  Notify Moderator

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.


Mike
2017 Chevy 3500HD 6.0 Crew Cab Long bed
2012 Passport 3220 BHWE
Me, the Wife, two little ones and two dogs.

Groover

Pulaski, TN

Senior Member

Joined: 10/17/2007

View Profile


Offline
Posted: 11/14/19 09:37am Link  |  Quote  |  Print  |  Notify Moderator

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.

ShinerBock

SATX

Senior Member

Joined: 02/22/2015

View Profile



Posted: 11/14/19 09:49am Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was edited 11/14/19 09:59am by ShinerBock *

ShinerBock

SATX

Senior Member

Joined: 02/22/2015

View Profile



Posted: 11/14/19 09:50am Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was edited 11/14/19 12:31pm by ShinerBock *

ktmrfs

Portland, Oregon

Senior Member

Joined: 06/22/2005

View Profile


Offline
Posted: 11/14/19 10:02am Link  |  Quote  |  Print  |  Notify Moderator

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.

* This post was edited 11/14/19 07:28pm by ktmrfs *


2011 Keystone Outback 295RE
2004 14' bikehauler with full living quarters
2015.5 Denali 4x4 CC/SB Duramax/Allison
2004.5 Silverado 4x4 CC/SB Duramax/Allison passed on to our Son!


ls1mike

Bremerton

Senior Member

Joined: 06/26/2009

View Profile



Good Sam RV Club Member

Offline
Posted: 11/14/19 12:30pm Link  |  Quote  |  Print  |  Notify Moderator

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.

Reply to Topic  |  Subscribe  |  Print Topic  |  Post New Topic  | 
Page of 4  
Next

Open Roads Forum  >  Tow Vehicles

 > Rated engine power
Search:   Advanced Search

Search only in Tow Vehicles


New posts No new posts
Closed, new posts Closed, no new posts
Moved, new posts Moved, no new posts

Adjust text size:

© 2019 CWI, Inc. © 2019 Good Sam Enterprises, LLC. All Rights Reserved. | Terms of Use | PRIVACY POLICY | YOUR PRIVACY RIGHTS