Alpha-N with Baro compensation?

[nemiro]

I have just gotten my 1997 Seadoo GSX 787 2 stroke water craft running with Microsquirt with BG 2.886 code! Yes, I am thrilled. OK, questions. I am running it as Alpha-N, and am having some issues, and questions. Yes, I searched on these, but did not find suitable answers, but if anyone has a link, I'd love to read it.

I am running fuel only, triggered by the Opto-In from the coil. It is open loop, as I think the oil would ruin an O2 sensor rather quickly, but I am debating adding one. I am running Alpha-N, as this 2 stroke does not exactly make any real vacuum. However, I do have a map sensor, functioning as a baro read sensor. I tried setting up the Alpha-N to MAP Table, and must be doing it wrong. Going into the VE table, the engine wants to stay in the 80kPa row, which is what the MAP sensor is reading (I am at nearly 7000' elevation), even though I have it in Pure Alpha-N mode. It will sometimes jump down to the 30kPa line, but only at slow idle. No, I cannot figure out what I am doing wrong.

Three questions. Is it possible to run in an Alpha-N mode, with barometric compensation? I ask, because I run the boat at two lakes. One is at 3400' elevation. That other is at 6018'. With carbs on the engine, I was constantly fiddling to get it to run right when I 'switched' lakes. I would like the Microsquirt to handle this, if possible.

Second, is there a version of the code that would do away with the Alpha-N to MAP Table? Why can't the VE table just be turned over to throttle on the Y-axis and RPM on the X-axis? Instead of MAP and RPM? Maybe it can. The reason I ask is for to be able to set it up to run in or out of the water, which is with and without a load on the engine. I can set it to run perfectly out of the water, but put it in the water, with a load on it, and it is dead lean. Obviously if the engine is running 1500 rpm at closed throttle in the water (with a load), then it will run faster out of the water (without a load), currently about 2400rpm on land. I need more fuel in the water, but get it out, and it will not run, for being so rich.

Third, if I did add an O2 sensor, in an attempt to try to tune this engine, what should stoic be on a 2 stroke engine? That is a number I have never found for a 2-stroke. I have an EGT with a probe in each exhaust port, and that is likely to be the better way to tune this particular engine.

At any rate, this is my first foray into MS/uS with Alpha-N. I do have a SD based MS2 v3 running a 1962 Triumph TR-3, and love the results. Will be really great when I can get the Seadoo running spot on, too! Thanks for any help!

[grippo]

The alphaN eqs do multiply the fueling by baro, but you have to tell the processor you are using a sensor for baro - it is one of the baro options in MT/ TS. In version 2.890 there is also a spark correction for baro meant to be used for alphaN setups.

If you want to simplify your amap table, you can set it up so that you pick any 6 tps and use those for the amap values at all rpms. So when you enter the amap table, amap (rpm, tps) will = tps for all rpms and it will interpolate so you end up with exactly the same tps you used to enter the table, and this value of tps, in addition to rpm, is what will be used to enter the VE and spark tables.

[nemiro]

OK, so you are saying for any given TPS setting, set the kPa the same all the way across?


So, like this:

TPS

100% 100 100 100 100 100 100
80% 80 80 80 80 80 80
40% 60 60 60 60 60 60
20% 40 40 40 40 40 40
10% 20 20 20 20 20 20
0% 10 10 10 10 10 10
500 1500 3000 4500 5000 7000


Like that? Should it be that linear, or should I favor smaller TPS readings, like 5, 10, 15, 20%? Will the code interpolate in between the readings? So, using the table above, would 30% be the 50kPa line? I will look for the baro compensation check box.

[grippo]

No - make the tps values the same as the map values. You did that for tps = 100% and 80%, Do the same for the other tps values. In effect you are getting rid of this table. When you put in a tps in the 6x6 table you will get the same tps back out. Then this value will be used in place of map when entering the 12x12 VE and spark tables - that is what you wanted. It doesn't matter what values you use for tps in the 6x6 tables as long as they cover o and max tps (usu 100%).

[nemiro]

OK, will do that. I do have Baro compensation checked in the General tab. I have the baro sensor hooked up to the MAP sensor signal. Under VE, it goes straight to the row that has the same reading as the Baro, as if I were in SD, and had 80kPa in the manifold. Do I need to hook the sensor up somewhere else? Where is the baro compensation table? Wouldn't I need to scale how much of a factor for various elevations? I know in the OE tuning I do, there are complete tables for this for those SD systems. I really appreciate your help. Thanks!

[grippo]

Independent baro has to be connected to ADC6. Check the megamanual for the correct pin.

[nemiro]

Will check in a moment. Is this the same for Microsquirt?


OK, I see that the SPARE_ADC wire goes to ADC6.


Any tables to set the compensation factors, or is that hard coded?

[grippo]

Yes there is a baro0 and baromax in the code that can be set same as map values if you are using the same sensor. These should be settable in TS or MT.

[nemiro]

OK, I will change it over to the proper spot, and work with it tomorrow. Thanks for all of your help!