Can you confirm my understanding of Mapdot please?

Triggsy · Post by **Triggsy** » Mon Feb 13, 2006 3:23 pm

Hi,

My car is fairly well tuned now apart from the acceleration enrichments. My engine is a 2ltr Zetec on ITB's, the idle map is around 45kpa and cruises around 70-80 kpa on average.

I think i need to use Mapdot rather than Tpsdot due to the large ITB's and the large amount of air ingested when stamping on the throttle.

Is the Mapdot threshold the figure below which no enrichments are applied or is it a rate of increase? If i set the threshold to 80 kpa and i accelerate from idle (45kpa) does it apply the enrichment when the kpa hits 80 or does it apply it when it hits 125 (45+80)?

i'm running the latest Megatune 225 with extra code 026h3.

Many thanks
Simon

whittlebeast · Post by **whittlebeast** » Mon Feb 13, 2006 4:38 pm

Any motor with large throttles and an idle value of45 kpa or less should goto MAPDot. Start out with a threshold of around 50 or so. Higher numbers make it more difficult to activate AE, Smaller numbers make AE more sensitive or easier to activate.

AW

Triggsy · Post by **Triggsy** » Tue Feb 14, 2006 9:35 am

Thanks for the reply.

I set it at 50 and it was activating AE even though the kpa never got above 48. I had to set it to 70 to stop the false triggering at idle. Any ideas why this is so?

Thanks
Simon

whittlebeast · Post by **whittlebeast** » Tue Feb 14, 2006 9:48 am

I think I can help.

This MAPdot thing is a calculation that is calcing the change in MAP/time so having a threshold of 60 is realy a way of calcing how fast the MAP is changing. IE is the map line on the datalog going up. With a little experance you will see if that reading is changing too fast the O2 will also report a lean condition. We are using the threshold to predict the lean condition and quick throw some added fuel at the motor for a short period of time. We can get in to the RPM based stuff but that is not normally needed if you have a good MAP signal to work with and the motor is not too high strung.

PS: this stuff was all developed as we were working on an 8500 RPM Honda B16a that was getting 15000 RPM/sec on down shifts and a 7500 rpm 2 stroke jetski that climbs 35000 RPM / sec on a throttle stab.

AW

Triggsy · Post by **Triggsy** » Tue Feb 14, 2006 11:47 am

Ah, that explains that then.

I just need to play around with the bins now then.

Thanks again
Simon

Bernard Fife · Post by **Bernard Fife** » Tue Feb 14, 2006 1:15 pm

Just to add to this thread, "dot" is Issac Newton's original notation for the rate of change of something (aka. a 'derivative'), which arises often in calculus. He wrote this by putting a dot above the variable, and in computer programming we can approximate this notation by appending 'dot' to the variable name. Gottfried Leibniz independently invented calculus, and used a "d/dx" notation. The more common Leibniz notation has the advantage of being explicit about what the variable is changing with respect to (i.e., d/dx is with respect to the X spatial axis, d/dt is with respect to time, etc.). In the Newtonian 'dot' notation, we have to assume from context what the change is in respect to. However, the d/dx notation is more cumbersome to incorporate into a coherent variable namng scheme. (Lots more on this here: http://www.angelfire.com/md/byme/mathsample.html)

So for MegaSquirt, MAPdot means the change of MAP with respect to time. That is, how fast the manifold absolute pressure is changing. Pressures going up have a positive number (aka. "slope"), pressures going down have a negative number. For example, if your idle kPa is 30 and you open the throttle fully in one second (naturally aspirated), the MAPdot is roughly (100-30)/1 = 70 kPa/sec

TPSdot means the change of TPS with respect to time. That is, how fast the throttle opening is changing. Throttle openings have a positive number (aka. "slope"), throttle closings have a negative number. For example, if your idle TPS is 0% and your slam the throttle open in one second, the MAPdot is roughly (100%-0%)/1 = 100 %/sec

Lance.

whittlebeast · Post by **whittlebeast** » Tue Feb 14, 2006 1:34 pm

What he said hehe

As a side note ms2 works in pct/sec All the older stuff works in kpa/sec when in MAPdot or v/sec when using TPSdot.

Extra is an all MAPdot or TPSdot, pick one
MS2 has a slider for a some of this and some of that

Have fun tuning

AW

Triggsy · Post by **Triggsy** » Tue Feb 14, 2006 1:35 pm

Lance, that's a good explanation.

I'm now going to lie down and absorb it all.

Thanks
Simon