MAF wish list

Testing and development of Megasquirt 3

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elaw
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Re: MAF wish list

Post by elaw »

jsmcortina wrote:Or perhaps blend between AFR1 and AFR2 target tables depending on TPS.

James
That would meet my needs quite well, although I wouldn't want it to blend over the entire TPS range. I'd say below 50% TPS I'd want it all AFR1, then blend up to 90% TPS where it would be all AFR2. I think that would address Peter's issue of the power coming on unevenly too.

I did think of an alternative: how about have TS pop up an anthropomorphic paper clip with a message stating "It appears you are trying to accelerate. Would you like help?" and then if the user clicks "yes" it switches to AFR2. :lol:
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Peter Florance
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Re: MAF wish list

Post by Peter Florance »

jsmcortina wrote:That depends on engine and intake type for sure. My setup doesn't work like that, I only see >90% load when I'm booting it.
Same here with all but the most extreme SD installations I've done.

So far I haven't found any reason to use a MAF on any performance car I've tuned. But I have interest in learning about them, so I will try one.
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Black99rt
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Re: MAF wish list

Post by Black99rt »

techsalvager wrote:
jsmcortina wrote:
techsalvager wrote:a power enrichenment table.
What's one of those?

James
Power Enrichment

A carburetor or fuel injection system for a reciprocating engine that enriches the fuel-air mixture when the engine is operating at high power settings.

Like it says going above a certain set condition you change from running at stoich to running richer.
TPS% above certain point, and or calculated load above a certain point

so you would have TPS% vs RPM and calculated load vs RPM tables

So the power enrichment table would be RPM vs Lambda and would dictate your fueling once you enter PE mode.
Why would you want the "commanded afr" and the closed loop target for the same load and rpm to be different? That doesn't make any sense, and I think that is where we are not understanding what you want.

Ken
Why do I want to waste gas at mild acceleration if I have no need for it?
No one wants to waste gas unless they need to or its a strictly race setup.
But at the same time, if I mash the throttle and I want to move, it better add in the fuel to accelerate and make the power. This is exactly why

What if my o2 sensor goes bad, I want to err back to my main commanded fuel table which should be separate from the closed loop fuel table

Power enrichment is a relic from OEM narrow band open/close loop systems. When they go into high load and need an AFR other than stoich, they blindly enrich open loop based on the power enrichment table. Incorporate AFR covers this.

As far as cruising "load" is concerned, my v8 truck cruises at 35-50kpa, but my srt-4 is 70-85kpa. Any time my truck would be at 85kpa I would want best power rich, not so much with the little 4cyl. If my srt-4 had megasquirt, I would probably just stay stoich until 90kpa then start enriching up into boost.
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whittlebeast
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Re: MAF wish list

Post by whittlebeast »

I like the idea of having a simple (say 15 data point) slider setup to do the transfer function like this plot but with fewer points. Similar to the warmup table. The units don't really matter as it all falls out in the math with a simple across the board constant.

Image

The thing that makes the most sense to me is have a VE like table that has 100s almost everywhere. If you find that the auto tunes are adding about 10% everywhere, then all you need to do is add 10% to your reqfuel and start over. When testing this sort of thing on the stim, it is really handy to have an instantaneous gauge that is fuel flow. If you slowly change RPM, IAT, TPS, MAP and the fuel flow changes without a change in MAF, something is messed up. It really is fairly simple. We had it working on MS1 years ago. If you make it too complicated, it is too difficult to document and support.

The devil is in the details in tuning one of these things. The ability to tune out the resonant frequencies that always seem to crop up in one of these installs. I am doing a very raspy roadrace car right now that is a Speed Density base tune but has a Ford MAF installed in the intake for data purposes at this point. I should have roadrace data off the car in a few weeks. The MAF is logged on one of the spare ADC channels.

see also http://www.msextra.com/forums/viewtopic ... 25&t=45331

Beast
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