How does the MS2 and Tuner Studio work?

[708803]

How does the MS2 and Tuner Studio work?
I believe MS2 is typically closed loop.
I believe the Trigger wheel sensor and the Map sensor are the only required sensors.
I believe initially both the VE and A/F tables are best guesses.
I believe that TS uses just the VE table and the Map sensor and Trigger wheel sensor to operate MS2.
I believe that the TPS, O2, AIT, and coolant temp are all sensors used when data logging.
I believe that Auto tune corrects the VE table by looking at the O2 sensor and referencing the A/F table.
I believe that if “autotune” is not used that the A/F table could be empty and the O2 sensor could be removed.
Are my assumptions correct or am I way off base and things are way more complicated????
I have read many theories of operation and am still viewing all the above as assumptions not facts. Also the tune on my engine has pretty much proved the above to be correct.
Thanks for any assistance and I hope I have put this in the correct category.

[Bernard Fife]

70883,

This is a frequently asked question. See this: http://www.megamanual.com/MSFAQ.htm#work You must have an air temperature sensor in addition to the tach trigger and MAP (or MAF) sensor. A coolant temperature sensor and throttle position sensor are very, very helpful too. You might want to see this: http://www.megamanual.com/v22manual/mintro.htm#applic

BTW, TS doesn't control the fuel algorithm (i.e. it does not "operate MS2"), it just lets you change the user parameters (including the VE table) and collects the output channels for display or logging. It does have some ability to change the VE table based on the EGO feedback (I believe this is called VEAL), but it doesn't do anything you couldn't do on your on by looking at the output channels (or that couldn't be done by MS-II itself using automatic mixture control, see: http://www.megamanual.com/ms2/amc.htm)

Lance.

[DonTZ125]

Tuner Studio is the tuning and configuration software loaded on your computer. It is with this software that you make adjustments to the various settings stored on the MS2 and used by the firmware loaded on the MS2 to control the various injectors, spark coils, etc that operate your engine. TS doesn't actually OPERATE the MS, but rather sets up the configuration that the internal processor uses when running the firmware.

The MS can operate in open loop (purely off stored tables with RPM vs Load settings) or closed loop (operating off stored tables with RPM vs Load settings with adjustments due to EGO sensor data).

Yes, the initial VE and AFR tables are best guesses, and some aspects may be wildly wrong. That's why you need to tune your engine in a careful and orderly fashion.

The MS2 *can* operate with just the crank sensor; you would need to include a resistor as a 'dummy' sensor in place of the MAP and IAT sensors. You'll find however that the more sensors are used and the more data the processor has to work with, the greater the sensitivity and accuracy of the response and the smoother and stronger the performance will be.

All of the sensors can be datalogged, but - as mentioned above - the unit works best when TPS, MAP, O2, IAT, and CLT are all used to actually operate the MS.

You can use Autotune or the TS VE Analysis Live along with a WBO2 sensor. Attempting to tune with a NBO2 sensor is a fool's errand. I have no experience with Autotune, but VEAL is a *powerful* tool. Once the tune is established and you are satisfied, VEAL / Autotune can be turned off and the O2 sensor removed.

[708803]

May be I need a step by step answer.
First the car operates fine. Always starts idles when warm and has reasonably smooth operation for a (2) cylinder air cooled 1970 N600 Honda car.

For example; I am idling at 1100 rpm and I change a value in the VE table. I can never find what I would call the smoothest setting. There is no sweet point. It is like it runs with that value and it also runs with all these other values. Of course there is extremes where the engine dies.
Why is this happening?
Do I need to move to the A/F table and make a change and than back to the VE table?

When I tune a VW with a carb at the shop it can be banging around and than be adjusted until it is smooth as glass. I would think changing values in the VE table would be very similar to turning a screw.

[Bernard Fife]

I am idling at 1100 rpm and I change a value in the VE table. I can never find what I would call the smoothest setting

708803,m

You shouldn't be working towards the "smoothest setting', you should be working to achieve the lowest MAP value (highest vacuum) at idle. See: http://www.megamanual.com/ms2/tune.htm#howto

Lance.

[708803]

I am idling at 1100 rpm and I change a value in the VE table. I can never find what I would call the smoothest setting

708803,m

You shouldn't be working towards the "smoothest setting', you should be working to achieve the lowest MAP value (highest vacuum) at idle. See: http://www.megamanual.com/ms2/tune.htm#howto

Lance.

This write up makes sense to me. Thanks.

In the formula below is the AFRactual value gotten from the sensor or a/f table?

VE = (actual air mass)/(theoretical air mass)*AFRstoich/AFRactual

[Bernard Fife]

708803,

Unlike the pulse width formula, the formula for VE isn't in MegaSquirt at all. Instead MegaSquirt uses a VE that you enter. So that direct answer to your question is that the AFRactual is not based on any factors in MeagSquirt at all. That formula in the manual shows you what you should be considering when you put those VE numbers is the table. So since that is the case, you should be considering the target AFR you want to achieve (at a particular rpm and load).

Whether the AFR table is used in the PW formula depends on a user settings, see 'AFR Table Fuel Calc Usage' here: http://www.megamanual.com/mt29.htm#so.

The AFR value derived from EGO measurements is only used as a part of the EGO correction algorithm. It in turn can be used to alter the VE table over time as part of the automatic mixture control function: http://www.megamanual.com/ms2/amc.htm.

Lance.