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journeyman · 01-28-2021, 07:23 AM

I have looked a LOT and cannot find real engine curves for my ISL. There are a lot of "marketing pics" (crude HP and torque graphs that look like they are strictly for "sales puposes"), but i have yet to see a serious graph with:

1. engine torque over the full range
2. horse power (calculated directly from torque and RPM)
3. Brake Specific Fuel Consumption.

These should not be hard to find unless they are somehow secret... But how could they be?

Does anyone have a source with good performance data on these Cummins ISL engines?
Mine is a 2002 CAPS motor

Thanks in advance

journeyman · 01-28-2021, 07:34 AM

This is what I would LIKE to see from Cummins for he ISL:

Busskipper · 01-28-2021, 07:39 AM

Following

Fiesta48 · 01-28-2021, 07:04 PM

Me too. Never found any. I'm doing some intake improvements. But 35k lbs just isn't like my Corvette. Ha think?

journeyman · 01-28-2021, 10:53 PM

Quote:

Originally Posted by journeyman

This is what I would LIKE to see from Cummins for he ISL:

Image did not post. Try #2:

Hopefully this will show!

This is for a very different engine, but has all the elements of a true performance chart

Ivylog · 01-30-2021, 06:50 AM

A ISL is capable of more torque than what a 3000 transmission can handle so below is its torque curve and HP curve when used in a MH with the Alison 3000 tranny. The sweet spot would be 1650 rpms but most are geared for 1800+ rpms at 65.

journeyman · 01-30-2021, 10:41 PM

I am especially interested in the BSFC curve.
It seems reasonable to expect an engine mfg. to publish this, but maybe I am expecting too much.

journeyman · 01-30-2021, 10:47 PM

Quote:

Originally Posted by Ivylog

A ISL is capable of more torque than what a 3000 transmission can handle so below is its torque curve and HP curve when used in a MH with the Alison 3000 tranny. The sweet spot would be 1650 rpms but most are geared for 1800+ rpms at 65.

Ivylog, where is this chart from? I have seen a lot of them, but not this one.

MrAlexander · 02-01-2021, 05:33 PM

This data is only published internally or to one of Cummins OEM partners who have a real need to know.

Also, the Cummins doesn't exactly match the 3000 MH torque limitations across the whole curve but for 2021 is very close in the 450 HP rating up to at least the governed speed.

journeyman · 02-01-2021, 10:55 PM

Quote:

Originally Posted by MrAlexander

This data is only published internally or to one of Cummins OEM partners who have a real need to know.

Almost sounds like a clandestine government operation!

Ivylog · 02-02-2021, 05:43 AM

Quote:

Originally Posted by journeyman

Ivylog, where is this chart from? I have seen a lot of them, but not this one.

10 years ago I posted the curves for my ISL 400-1200 ftlbs on another forum... flat from 1200 to 1500 rpms. Did a Google Image search for ISL torque curves and picked the one above knowing the newer 450 was up to 1250 torque when mated to a 3000 Alison.

MrAlexander · 02-02-2021, 07:46 AM

Quote:

Originally Posted by journeyman

Almost sounds like a clandestine government operation!

Not really, but I never see this data published for on-highway engines and only for engines in stationary and occasionally off-highway equipment to help a user decide where to operate their engine. For an on highway vehicle, you can pretty well bet using the highest gear allowing operation above peak torque speed will provide the best fuel economy and most are already automatic in the rv market anyway.

Ivylog · 02-04-2021, 08:26 AM

Happened upon these curves for a ISM 500 HP. If you extend the ISL 450 red curve it looks like it’s capable of 1400 torque, maybe why it’s such a popular DP engine.

While I was happy with a ISL for 14 years, no way would I go back to it after having 1650 torque, even in a rig that weighs substantially more.

MrAlexander · 02-04-2021, 07:27 PM

Paccar has a pretty good set of curves plotted for the L9. Example of the 2021 here:https://paccarpowertrain.com/wp-content/uploads/2018/12/PX9SpecSheet2021.pdf