Pre 2010 ISB6.7 verses EPA 2010 ISB6.7 with DEF

[mjeffrey]

We are looking at two 2011 coaches and one has the older pre 2010 ISB6.7 cummins diesel and another that has the EPA 2010 ISB6.7 version (with DEF).

Which one would you prefer and why?

Thanks

[mjeffrey]

Cummins web-site says 360hp for older and 380hp for 2010 but both have same torque. Also implies 2010 has better performance and some DEF maintenance at intervals.

Any guess as to how much better the performance -- mpg? would be?

Thanks

[dandandan]

I would not get the DEF if you could. Added weight, added complexity, and any increase in efficiency estimated at 2% seems dubious to me. 2% would be off set by DEF costs assuming I never had any costs to repair the DEF system.

I have read about people with bad sensors leaving them to deal with repairs. Covered by warranty for now, but do you think this will decrease with time? Do you think it will always be covered by warranty?

[mjeffrey]

We are still in decision mode and the final price difference between the 2 choices is down to only 10k dollars.

The one without DEF has fewer options that we like, but we can add them later if it was really important in the long run. It is "new" with fully warranty. It cost 10K more.

The one with DEF has the options already and is the 10K less. It is actually a used unit with a little warranty left, so those initial warranty items have presumably been taken care during its use.

So the question is: Will the DEF unit, over say 5-10 years really cost more.

To be fair, maybe the question should be based on the miles we drive a year.

3000 miles?
5000 miles?
8000 miles?
10000 miles?

Were is the break even point for paying more now and having no DEF now, in the future, or trying to sell with DEF in the future? In the future DEF engines might be less desirable?!?

[mjeffrey]

http://www.truthaboutscr.com/media/p...y_2-26-09b.pdf

This info makes me think that the SCR/DEF is the better solution and that to worry about the cost of DEF reaching the 10K dollar difference in the vehicles would take 10s if not 100s of thousands of miles.

This still leaves the difference of selling price, if any, in the future. I suspect that there will be people who would prefer to not have SCR/DEF because there probably will be non DEF solutions that are popular in that future...

[okgc]

What does the RV manufacture show as HP & TQ for that engine? Many 2009/10 ISB 6.7 engines were rated at 340HP 660 tq. This is with or without DEF.

I suspect I would make a lower offer for the used unit. Tough choice you have.

[mjeffrey]

Quote:

Originally Posted by okgc What does the RV manufacture show as HP & TQ for that engine? Many 2009/10 ISB 6.7 engines were rated at 340HP 660 tq. This is with or without DEF. I suspect I would make a lower offer for the used unit. Tough choice you have.

no DEF 360 hp and 1050 ft/lbs torque
w/ DEF 380 hp and 1050 ft/lbs torque

with hp numbers from brochure and matching Cummins web-site
and the torque numbers coming from the Cummins web-site

Link above implies 5-9% better performance in SCR engine and that apparently shows in the hp numbers but not in change of torque.

[Bee950]

Do you like pouring $2.55 a gallon water into the exhaust? If so get the DEF unit

[Cat320]

Quote:

Originally Posted by mjeffrey We are still in decision mode and the final price difference between the 2 choices is down to only 10k dollars. The one without DEF has fewer options that we like, but we can add them later if it was really important in the long run. It is "new" with fully warranty. It cost 10K more. The one with DEF has the options already and is the 10K less. It is actually a used unit with a little warranty left, so those initial warranty items have presumably been taken care during its use.

My dealer told me a coach with DEF could cost as much as $8k to $10k more than one without DEF. Are the two coaches different brands? I'd want to find out why the one without DEF has less options but costs more. Something doesn't compute.

[Spikester]

The newer (2011 (350HP version) ISBXT 6.7L engines has more torque, better fuel mileage, and costs considerably more than the pre 2010 EPA ISBXT engines. But you have DEF to deal with which is an added expense, DEF has a shelve life so you just cannot let it set in you DEF tank for years on end.

With desiels torque is what you looking for, the more torque your engine has the better you will like it probably.

Spike

[mjeffrey]

Quote:

Originally Posted by Bee950 Do you like pouring $2.55 a gallon water into the exhaust? If so get the DEF unit

From the link above...

HOW MANY MILES WILL A TANK OF DEF LAST?
• 2.5 gallons of DEF will yield over 800 miles
of travel.
• You can drive from L.A. to Boston and back
on less than a single 23-gallon tank of DEF
(estimated usage rate is approximately 2%
per gallon of fuel).

Even though the document doesn't have details behind it, it seems that we are talking about pennies per mile. And if offset by a increase in performance/MPG it might be worth it.

The torque numbers seem the same with both engines.

[mjeffrey]

Quote:

Originally Posted by Cat320 My dealer told me a coach with DEF could cost as much as $8k to $10k more than one without DEF. Are the two coaches different brands? I'd want to find out why the one without DEF has less options but costs more. Something doesn't compute.

The used (DEF) unit is at a discount because, well it is used and the person is motivated to sell.

The new (no DEF) is, well new and has a full warranty. Being "new" and no DEF tells me it has been sitting a the dealer for a while, but I don't know how DEF and non DEF units rolled out of the factory and if one unit was one of the first DEF and the other one of the last no DEF, then they might be actually around the same age. Both are 2011 models and that can mean a year apart.

[Perry White]

Ask anyone with a Cummins ISX how they like the new engines. Spend more time getting towed than driving.

[mjeffrey]

Quote:

Originally Posted by Spikester The newer (2011 (350HP version) ISBXT 6.7L engines has more torque, better fuel mileage, and costs considerably more than the pre 2010 EPA ISBXT engines. But you have DEF to deal with which is an added expense, DEF has a shelve life so you just cannot let it set in you DEF tank for years on end. With diesels torque is what you looking for, the more torque your engine has the better you will like it probably. Spike

From the data I can find, the torque seems to be the same. I don't have an input on real mileage improvement, but would love a link to that kind of data.

It would be nice to not have to deal with DEF. Now or when I try to sell in the future unless DEF engines are proven to be superior in the long run. The document I reference above really looks to be saysing that DEF is better in many ways (other than just being greener) and proven over years and millions of travel miles of European use.