Air Density Adjust

[Dmaxink]

Jake, i gotcha now bud.

Rich, I understand density tables and do not disagree with you...but is my statement incorrect in saying if we are going for a certain % at sea level..that it should not do as well @ 9k? I know at least in dmax world i had no issue running the same table from here to there... I'm completely understand that this may not work in others applications as each truck is different...

I could see the event of a guy running very conservative timing wanting to step it up as alt changes...but generally everyone is going for the most efficient "higher timing" setup...

[DoghouseDiesel]

Kory, you are correct.

The biggest problem with not correcting for altitude is going to be a dirty tune and higher EGT's.

The truck is going to perform regardless. Bottom line, you're making your own atmosphere with a turbo anyway so its no nearly as critical as it is on a NA gas motor. But, for the sake of fuel economy and just plain good tuning, you'd want those tables adjusted.

Without actually living and testing in one of those places, it'd be hard to do. It's a lot easier for a manufacturer that trlests all over the place to collect that data tha ln it is for us to build a hypothetical table.

It's like we talked about with the different size injectors. There are ways to compensate for them and we all do it, but it takes a little dialing in on the receiving end to get it right on.

[comnrailpwr]

Makes sense les, never thought about us creating our own atmosphere being turbocharged.

Jake

[DoghouseDiesel]

You are creating you own atmosphere, but still, less oxygen is less oxgen. We're just much less susceptible to bad air. / fuel ratios than gas motors are.

A diesel may range from 125:1 at idle to 18:1 at peak power where a gas more needs to stay in a very narrow 10.5:1 - 17:1 to run at all and even narrower to run correctly.

A small variation in the AF ratio isn't going to effect a diesel very much, as long as you're not going too heavy on the rich side.

That's what trips gas guys out at the track when my hood is up. 1 - they have no clue what they're looking at and 2 - when they see 2 turbos and the nitrous they think you're gonna burn a hole in a piston and you have to get into the whole long discussion about diesels being polar opposites of gas motors.

[2007 5.9]

How does one determine density?? I live at sea level 14.5-.7...I frequent Tahoe 7500ft...how do I know the density in Tahoe so I can adjust accordingly??

~Les

[DoghouseDiesel]

Density is roughly based on temperature and pressure.

There are a bunch of calculators out there that all you have to do is punch in your altitudes and temps and they give you the densities.

Just google air density calculator and you'll get a 100 of them. You'll also get a few that pop up with the actual formula if you want to hand jam it.

[AH64ID]

I guess I'm still confused about the relationship between the base table and the air density adjust tables. This is from the base table "Start of Main Injection base table. These values will then be further adjusted by the air density adjustment tables.
"

The you to air density table select pages and there is nowhere it talks about using the base table.. So looking at the verbage on base table page it looks like the air density adjust is a mix from base and air density adjust, but you guys are saying they don't mix... Is base table ever used?

[DoghouseDiesel]

Give me a little bit, it'll be easier to show with screen shots than it will to explain....

[DoghouseDiesel]

Okay, this is going to take me a few.

I'm kind of doing this along my EFILive for Dummies style, but I'm building an Air Density chart from -20 to 120 degrees and from sea level to 10000 feet, so give me a few minutes.

[killerbee]

Don't know if this will help, a link to a non-cummins application with calculations. The atmospheric part is no different. There are 3 pages, tabs, to this spreadsheet, fyi.

http://killerbeeperformance.com/down...preadsheet.xls