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Old 08-28-2012, 10:29 AM   #1
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Default New tech article: Tuning MegaSquirt acceleration enrichment

MegaSquirt Acceleration Enrichment Tuning

Having trouble dialing out flat spots when you hit the gas? Stumped by the Acceleration Wizard? This article can help. If you have any questions it doesn't answer, post them here and I'll see if I can get them added!
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Old 08-28-2012, 10:30 AM   #2
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Now write the same for the accel-pump in MS3 for all the noobs. and then EAE
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Old 08-28-2012, 12:08 PM   #3
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Nice. Thanks Matt.
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Old 08-28-2012, 01:07 PM   #4
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Can't wait to reap the benefits of the changes that will result from this. Nice job.
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Old 10-10-2012, 09:52 AM   #5
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i guess there's no way to make MS1 do accel enrichments based on % PW rather than absolute? or to tell it to reduce the AE when going from 0% throttle.

i find that from a decel just transitioning into a bit of throttle, TPSdot is quite high so it dumps more fuel in than i need just because the load is lower, and i need to tune AE at higher loads.

also i find that cold accel enrich, it seems slow to respond and i get a big initial lean spike. my TPSdot threshold is at the minimum and the first blue dot on the graph is at a lower TPSdot than the threshold... changing the cold mulptiplier or adder just makes it more rich when it kicks in. AE is fine when warmed up tho.
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Old 10-11-2012, 10:49 AM   #6
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Quote:
Originally Posted by skinny View Post
i guess there's no way to make MS1 do accel enrichments based on % PW rather than absolute? or to tell it to reduce the AE when going from 0% throttle.
Technically yes, but the answer would be to modify the firmware.
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Old 10-11-2012, 12:06 PM   #7
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I think MAP based enrichment is needed, on top of TPS based enrichment, to take care of turbo spoolup, after the throttle is floored. On a fast spooling turbo in 1st gear, floored at a low RPM, MAP could rise at >250 kPa/sec. Depending on the filtering in the MAP signal, the reading could lag the actual MAP by 15% or more. This is where you need dMAP/dt based enrichment.
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Old 10-11-2012, 02:01 PM   #8
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Quote:
Originally Posted by Matt Cramer View Post
Technically yes, but the answer would be to modify the firmware.
OK thanks Matt - way beyond my capabilities.

Guess it doesn't do a huge amount of harm dropping a little rich now and then, i'm just fussy about my tuning!!
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Old 08-19-2013, 06:53 PM   #9
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Im having trouble with my accel settings, looking back at my logs from day 1 (owned mspnp 3 years) nomatter what you do bit7 never activates and bit8 is on the moment you start the car, has a mind of its own (regardless of mapdot), hit the gas and it goes away, setting kpa/s threshold really high makes no difference.

Is it possible that the mspnp I purchased came wired for a vtps ? Or am I missing something? (Purchased brand new from diyautotune) first gen Pnp 9093 no afm
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Old 08-20-2013, 05:10 PM   #10
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Bit 7 and 8 are different on MS1s; they only mean that for MS2 and later.
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Old 08-20-2013, 07:16 PM   #11
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Good timing on the bump of this thread. I have a question.



In this website it says: (when disusing how to use VEA)

Quote:
Drive car through as many throttle positions and RPM ranges ans possible. There is no need to disable Gego correction, Accel enrich or over run drive under the same configuration as you would any other time you are driving the car.
source: MegaLogViewer - VE Analysis


And your article states:

Quote:
Before you start tuning the acceleration enrichment, make sure your VE tables are dialed in.

So if I am still dialing in my VE tables using megalog view and VE analyze should I turn off all AE then tune the AE after, or leave it on as the first article suggests? Thanks
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Old 08-24-2013, 04:27 AM   #12
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VEAL filters AE events. If the AE activation threshold is reasonable then it should not matter if AE is on or off for autotuning.
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Old 08-24-2013, 01:07 PM   #13
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Quote:
Originally Posted by southernmx5 View Post
VEAL filters AE events. If the AE activation threshold is reasonable then it should not matter if AE is on or off for autotuning.
Is AE filtered if running the analyze feature in MegaLogViewer also?

I have always had a bump in VE values in the low rpm/high kpa region (<2600rpm and 70-100kpa). The VE values are about 10-15 higher in this bump. Note that this isn't a single spike, but a region of maybe 3x6 cells. This is a 1.8L VVT engine with MS3 ECU (NA, no turbo yet). Thought it had something to do with needing more AE, but adding fuel in the AE settings doesn't seem to change that region much at all.
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Old 05-24-2014, 04:09 AM   #14
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Bumping with a quick question.

The datalog always shows the AFR go lean for a very short spike then immediately dip into rich and taper back to normal.

How do I make the lean spike smaller? Incleasing the PW seems to just make the rich patch richer.

This is with a TPS on MS2, cheers,

Dann
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Old 05-24-2014, 10:24 AM   #15
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lower the threshold.
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Old 05-24-2014, 04:43 PM   #16
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Quote:
Originally Posted by Braineack View Post
lower the threshold.
I have been working on the same issue with my tune. As Braineack said, decrease the Accel TPS threshold % setting (and/or Accel MAP threshold %, if you are using MAP based enrichment.)

I was in the using values around 100 for the threshold and had problems with lean spikes. I now have the threshold set to 25. I also changed the enrichment curve to start of the a lower %, but ramp up quickly with higher TPSdot % values. Lowering the threshold has helped much more than just dumping in more fuel at higher TPSdot values.

Good luck!
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