Some super basic Questions.

New to tuning? Not sure where to start?
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Some super basic Questions.

Post by Lee » Wed Sep 26, 2007 1:08 am

When a table plots 8 or 10 values I assume that the CPU plots maybe hundreds of points between them?

Accelerator position table. (and others) The extra columns and rows that are repeats, I assume that I can ignore them?

Exhaust back pressure, PSI vs. RPM
What dose the result number do? And there are two charts that look the same, repeats or do they both do some thing?

Desired ICP pressure?
Mass fuel number is presure, voltage or what?

FDCS pulse width ICP vs. volume of fuel desired, Is this milliseconds?

Injection timing high altitude and sea level, does the CPU switch between them at some point or scale between them by barometric pressure?

I guess the real fun starts with the relation ships of Timing, Pulse Width, and ICP Pressure. But where does IPR duty cycle fit in?

Any help is greatly appreciated.


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Re: Some super basic Questions.

Post by Mattr66 » Wed Sep 26, 2007 10:58 am

The computer interpolates between points so if timing goes from 10 in one cell to 20 in the other and your current operating spot is right in the middle of the 2 cells then it will be at 15.

If there are repeats in the tables use the same values in all of them having the same x and y intersection.

Not sure what strategy you are tuning but on some 7.3s (i assume that's what you are tuning) excessive back pressure will reduce fueling so upping these numbers will prevent this.

Icp pressure table's axes are estimated mass fuel and RPM.

FDCS pulse width was meant to balance injector flow across various operating conditions. If you have higher ICP you need less pulsewidth for the same fuel, this table helps balance this out. This is the easiest place to add fuel though. I am unsure on the units in the table though...

Not sure how it determines when to use the altitude timing table (don't have that function in most templates) but I would think it isn't a hard switch at some barometric pressure.

Yes just remember it is about cylinder pressure.... the more during the power stroke the more power you will make. High pressure outside the power stroke or too much pressure and you will start breaking stuff.

The IPR duty cycle is a table that gives the HPOP regulator a "first guess" at what it's operating point will be. There is a PID algorithm that determines how much to close off the pressure regulator for the high pressure oil system to the injectors. If this value isn't close to what it needs to be you will see the check engine light flicker at WOT because the system is having trouble trying to get the oil pressure for the injection up to where it is commanded.

Hope this helps,
Matt R
Matt Robinson
Delta Force Gas and Diesel Tuner

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