MAP sensor sampling

[prj]

OK.

Settled on doing the enrichment on LOAD delta alone.
Seems to work well enough.

Once I stopped trying to average the signal per stroke and took a single precise reading, it got lots more responsive too.
So removed all my TPS code, and only kept modified stock load delta code.

It is perfectly tunable now to get correct mixture even on sharp gradients.
For all intents and purposes this project is done and will find it's way to an ECU near you.

[quattro84]

Good man.

Does Motronic solarly need rpm & fuel qty to determine load?
Your "simple precise reading" is the 10 bit sampling you mentioned earlier?

[Ross]

Not suitable for low-power engines? I assume that is anything below 500hp

Sounds really interesting, but is this 'recommended' for higher power cars or a non-MAF alternative to suit wire munching cars? Personally still leaning toward your RS4 MAF upgrade when the car is back on the road, but obviously curious as to what your recommendation would be for a 400-450hp car.

[prj]

Good man.

Does Motronic solarly need rpm & fuel qty to determine load?
Your "simple precise reading" is the 10 bit sampling you mentioned earlier?

Fuel qty? Hey, it's not a diesel

Load by default is MAF voltage*MAFLIN/RPM.
Now load is MAP*VE(MAP,RPM)*IAT.

And yes, I sample at 10 bit once for every cylinder, just before the load gets calculated for that cylinder (this is during the start of the intake stroke of the previous cylinder). And this seems to work great for me and give better response than averaging more samples.

Not suitable for low-power engines? I assume that is anything below 500hp

Sounds really interesting, but is this 'recommended' for higher power cars or a non-MAF alternative to suit wire munching cars? Personally still leaning toward your RS4 MAF upgrade when the car is back on the road, but obviously curious as to what your recommendation would be for a 400-450hp car.

HP has little to do with it actually.
You can read an explanation here, for the upsides and downsides of each method:
http://prj-tuning.com/?p=363

The upsides and downsides of running speed-density are:
+ No need for a MAF, so plumbing is simpler.
+ Atmospheric dump valves and an atmospherically vented N75 can be used further simplifying plumbing.
+ No problems with the MAF maxing out, as MAP sensors are readily available even for 6 bar boost.
+ Little effect of air leaks on cylinder charge calculation.
- The MAP signal is somewhat slower than the MAF signal.
- The air charge calculation relies on an engine efficiency map in the ECU, thus if engine efficiency (flow) changes, it means that the air charge calculation will be wrong and a remap will be required. For example changing the intake or exhaust manifold, camshafts, porting the head and so on.
- Difficult to dial in the VE table properly on the road, as every possible pressure and RPM has to be visited, because linearization is RPM and MAP based.

Compared to mass-flow:
+ Directly measures airflow, so changes to engine efficiency do not affect charge air calculation.
+ Somewhat faster signal than a MAP sensor.
+ Very easy to map on the road, as a pull goes through the entire range and linearization is flow based.
- All air flow must be re-circulated, no air can leak after it has gone through the MAF, as otherwise the charge calculation will be off, more difficult to plumb
- If the MAF maxes out, charge air calculation does too. Meaning that after it does the ECU essentially runs Alpha/N, which is inaccurate.

[Sir Buff]

For all intents and purposes this project is done and will find it's way to an ECU near you.

Congratulations

[quattro84]

Fuel qty? Hey, it's not a diesel

Load by default is MAF voltage*MAFLIN/RPM.
Now load is MAP*VE(MAP,RPM)*IAT.

LOL, it was good enough like that in that era emission wise.


Basically MAF readings are more accurate if corrected/calibrated for numerous inputs.
Bad side is that they will loose (a bit of) accuracy due to oil/dust/surge over time, making it compared to Speed-density less robust.
MAP on itself is not accurate enough to run closed-loop to reach current emission lesiglation, needs at least VE correction (and VE corrected by O2) and more inputs such as NOx sensor to correct combustion process.

Both are just fine since our MOT emission levels will not be the restriction now, it's more the aspect of fuel quantity control the ECU uses (or what PRJ uses ) to get best response / mpg / whatever you are after.

More practical: Big hp cars max out standard MAFs so Speed-density is the easier solution. Big MAFs are expensive, big accurate MAFs are even more expensive.

For aftermarket ECU´s it is easier to find or calibrate MAP sensor signal output compared to MAF. (which isn´t lineair, needs scaling, and how to check sensor output versus an actual air flow?)

[prj]

LOL, it was good enough like that in that era emission wise.


Basically MAF readings are more accurate if corrected/calibrated for numerous inputs.
Bad side is that they will loose (a bit of) accuracy due to oil/dust/surge over time, making it compared to Speed-density less robust.
MAP on itself is not accurate enough to run closed-loop to reach current emission lesiglation, needs at least VE correction (and VE corrected by O2) and more inputs such as NOx sensor to correct combustion process.

Both are just fine since our MOT emission levels will not be the restriction now, it's more the aspect of fuel quantity control the ECU uses (or what PRJ uses ) to get best response / mpg / whatever you are after.

More practical: Big hp cars max out standard MAFs so Speed-density is the easier solution. Big MAFs are expensive, big accurate MAFs are even more expensive.

For aftermarket ECU´s it is easier to find or calibrate MAP sensor signal output compared to MAF. (which isn´t lineair, needs scaling, and how to check sensor output versus an actual air flow?)

Calibrating MAF is a piece of cake if you have known injector calibration.
Just make target equal requested. Same way as you calibrate VE in an aftermarket application