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DWAlthaus · 11-03-2016, 10:29 AM

My CAT C7 is in a 2004 35' National RV Tropical MH. The engine was rated at 350HP when sold and cost about $5000 extra compared to a 330HP which was standard in the model MH when new. Recently I added a data bus decoder to look at the various codes that the engine computer makes available. The data is put on the bus by the engine control system so it makes no difference which data bus decoder is used. The data on the bus is controlled by the CAT computer not the decoder. When I select the parameter for Horsepower I find that the absolute maximum that I can get out of the engine is 253HP which is not anywhere close to the 350HP that it is rated for. Does anyone know what the HP parameter on the data bus is actually measuring? I talked to a C7 "expert" at a truck repair facility and he said that HP is meaningless and that I should only pay attention to torque. I know that torque is the measurement that that puts power into turning the tranny so won't get into the standard argument over HP and torque. But would like to know why the HP parameter on the data bus is so much different from what the engine is rated for.

Dave Althaus
Fallbrook, CA

FIRE UP · 11-03-2016, 12:25 PM

Quote:

Originally Posted by DWAlthaus

My CAT C7 is in a 2004 35' National RV Tropical MH. The engine was rated at 350HP when sold and cost about $5000 extra compared to a 330HP which was standard in the model MH when new. Recently I added a data bus decoder to look at the various codes that the engine computer makes available. The data is put on the bus by the engine control system so it makes no difference which data bus decoder is used. The data on the bus is controlled by the CAT computer not the decoder. When I select the parameter for Horsepower I find that the absolute maximum that I can get out of the engine is 253HP which is not anywhere close to the 350HP that it is rated for. Does anyone know what the HP parameter on the data bus is actually measuring? I talked to a C7 "expert" at a truck repair facility and he said that HP is meaningless and that I should only pay attention to torque. I know that torque is the measurement that that puts power into turning the tranny so won't get into the standard argument over HP and torque. But would like to know why the HP parameter on the data bus is so much different from what the engine is rated for.

Dave Althaus
Fallbrook, CA

Wow,
$5,000 extra for 20 horse power??? Well, our coach is also an '04 but, it's an Itasca Horizon 36GD with the 330HP CAT. I don't have a clue as to how many coaches, (Itascas or Winnebagos) of the same assembly line did or didn't have any 350 CATs in them. But, I've seen a zillion with the 330 CAT in them. I've seen many, many '05 and later Journeys and Meridians with the 350 in them.
But, anyway, I just had my valves adjusted for the first time at about 60K at a place in Sparks NV. And the tech that was doing the work, had years of CAT experience in all phases. Motor homes, Mine work, over the road, boats, and more and when I asked him about the 350 version over my 330 and whether or not it would be worth the flash of the computer to get that extra 20HP, his reply, "Nope, not worth it at all, not for $650 anyway".

You see, It's CATs engine and they still have the rights to the programming of the ECM etc. So, in order for the company that was working on my motor home to use the programming, $500 goes to CAT and, the $150 goes to the company in labor charges. So, $650 for 20HP, wasn't and, never will happen for us, let alone "$5,000" for 20HP.

Now, to answer your question. If you are genuinely concerned about the true HP of your CAT, the very first thing I'd do is take it to a certified CAT tech/company that has a dyno. Then I'd run that dyno test on it to see just what YOUR engine is putting out in all the parameters.

Then, you can goof around with your specs and add-ons to see what they're reading in comparison to a real, bonified dyno set of test results. At least that's my way of thinking.
Scott

DWAlthaus · 11-04-2016, 04:43 PM

The HP data on the data bus appears to come from a calculation that is done in the engine computer. That figure is totally different from what a person would see on a dyno. Dyno data of course is the actual power that hits the road but there is no way to measure that as you are going down the road. Figures of up to 20% loss can be experienced due to the tranny and differential. That wasn't my question. I'm looking for information regarding how CAT calculates HP in the engine computer and how that does or does not correspond to the HP rating that engines are sold with.

Cat · 11-04-2016, 07:44 PM

The horsepower calculation is done by the Full Load fuel setting and Full Torque fuel setting.
These FLS and FTS are a calulated number and that if the engine has the correct hardware = turbochager, fuel injectors. Then the ecm will deliver power to the injectors longer or shorter times to inject the fuel into the engine.
The power settings are comfirmed at the factory on engine dynos. And minor FLS FTS settings can be made then.
When a rerate in the field occurs- the tech installs new software/flash files and puts the fuel setting FLS FTS in to the parameters. This changes the horsepower of the engine. They are also suppose to type the new horsepower into the Ecm. If they dont the engine would still have the increased horsepower but it just wouldnt show up on the display. They are suppose to be safe guards to make sure the horsepower is typed in but it doesnt always happen.

The cost to rerate an engine can vary greatly. Some engines have a smaller turbcharger and smaller injectors for lower horsepower ranges. Say 175 to 220 horsepower. It is a software change to rerate from 175 to 220. But if you want to go from the 175 to 220 range to the 250 to 350 ranges then injectors and turbochargers and possible pistons would have to be changed.
What is your engine serial number?