RomRaider

Consider these tables, from my 05 LGT's ROM:



What if I...

• Replace my MAF sensor with a variable resistor.
• Turn on the ignition, but don't start the car.
• Adjust the pot until SSM says the car is pulling 100 g/s
• Replace pot with fixed resistor of same value.
• Re-do the RPM axis of the "Load Comp (MP)" table to range from 500-7000
• Re-do the MRP axis to cover -10 to +20
• Fill the columns of the "MAF Comp (intake temp)" table with values that reflect the change in air density as temperature varies above and below 68. (Only the rows above and below 100 g/s would actually matter.)
• Fill the cells of the "Load Comp (MP)" table as if it was a VE table - not entering actual VE percentages, but values that would appropriately scale the 100 g/s lie that the ECU is getting from what used to be the MAF sensor.
• Start the engine...

Kaboom? Or vroom?

I'm not sure I have the courage to try this, but it's not out of the question either.

How would idle work?

The same way as in pure SD mode..

To NSFW:

There is no need in the resistor. Just put your favorite 100 g/s into all cells of the MAF calibration table.

in theory it would work. however you may run into issues with the max/min permissible values in those tables... ie, they are not xpected to have a huge degree of authority.

never know until you try it though!

Oh, yes... much simpler that way.

And that gives me another idea.... With a bit of creativity (and Excel), one could run a MAF / SD hybrid that way. Keep the MAF scale stock below 100 g/s (chosen mostly because it's a nice round number) and then flat above that point. Then change the "VE" table (Load Compensation) so it uses zeroes in the sub-100-g/s region, and pseudo-VE values everywhere else. And change the MAF Compensation table to use normal values below 100 g/s, and use Boyle's Law above 100 g/s.

Something tells me that the transition between MAF and SD would be very difficult to get smooth, but in theory it seems possible. Might be better to put the transition around 50 g/s, or even 25, so the engine won't be working so hard at that time. At 25 g/s, you could fine-tune the transition at moderate speeds and spend a lot of time dialing it in.

Yeah, that's my biggest worry. Especially the manifold pressure columns.

...and the ECU's closed-loop logic could be used to help smooth out the transition.

That isn't going to work because load does not always include that compensation. It depends on a number of conditions and comparisons between the corrected load and uncorrected load and previous load values.

I should say that pure SD setup is not the best from the driveability point of view.

It should be blended. I am currently running AlphaN mode (driving NA Audi), AlphaN\SD blending maybe preferrable. For NA setup I simply dislike the MAF for its short lifetime.

ahhh, foiled by the code!

Bummer. Thanks for stopping me from trying it, though.

btw, that's what I asked on Freon's Speed Density FAQ
topic2947-75.html
I'd like to play with these tables for tuning above 300g/s with maf in stock position, but I've had no chance to play with this as some big turbo setup needed

Ah, you beat me to it.

How were you planning to use these tables?

Any why not just try them for 200+ or something that's in range of your current turbo?

Merchgod's comment about a "number of conditions" factoring into whether these tables are used has me thinking that this probably isn't reliable enough to bet my motor on it.

The plan was to scale engine load compensation table for high boost and high rpm, so when MAF ends at it's limit, it will be possible to provide accurate timing and fueling by manipulating compensation. But I'm not sure it will work exactly like I want it. And yes, this can be tested with lower g/s's