Reconfig MSII code?

[WizardBlack]

I am just wondering if anyone has gotten rid of the old fueling formula currently used by Megasquirt:

 

PW(fuel) = Req.Fuel x MAP/(100kpa) x VE/(100%) + E

 

and simply switched to a fuel map where you tune the pulsewidth directly like most standalones. I know it can't be any harder on the processor (actually quite a bit less calculation) and it is certainly easier for anyone who has tuned many standalones. You could still use the handy power and engine size calculator to fill in starting numbers and simply reconfig them to plug pulsewidth in directly. I mean, you can take someone's VE table and get their 'required fuel' number and actually calculate it in a spreadsheet such as excel (or even better, the free and compatible alternative).

Any thoughts? I'd be down for it.

[X64v]

PW(fuel) = Req.Fuel x MAP/(100kpa) x VE/(100%) + E

 

 

I believe that's incorrect. In my experience messing with it, it does not take MAP/(100kpa) into account. That's why for the same afr at two different kpa values (say 100 and 110 kpa) one must multiply the 100kpa value by 110/100 to enter into the 110kpa box.

 

So, for VE to equal PW, make Req.Fuel. 100ms. Then, where VE is the number you put in the fuel map, you get:

 

PW(ms) = 100(ms) x (VE/100) x k (k for a correctional constant, using air temp, warm up enrich, etc)

 

which equals

 

PW(ms) = VE(ms) x k

 

so then you just enter your desired pulse widths into the fuel map. My question is whether you can enter decimal values into the fuel map, and how MS I (or MS II) will interpret that.

[WizardBlack]

I believe that's incorrect. In my experience messing with it, it does not take MAP/(100kpa) into account. That's why for the same afr at two different kpa values (say 100 and 110 kpa) one must multiply the 100kpa value by 110/100 to enter into the 110kpa box.

 

So, for VE to equal PW, make Req.Fuel. 100ms. Then, where VE is the number you put in the fuel map, you get:

 

PW(ms) = 100(ms) x (VE/100) x k (k for a correctional constant, using air temp, warm up enrich, etc)

 

which equals

 

PW(ms) = VE(ms) x k

 

so then you just enter your desired pulse widths into the fuel map. My question is whether you can enter decimal values into the fuel map, and how MS I (or MS II) will interpret that.

 

Here is a direct copy and paste from Megamanual under Tuning; almost halfway down on that page:

 

PW = REQ_FUEL * VE(kpa,rpm) * MAP * E + accel + Injector_open_time

 

You know, I thought the same thing about using 100 ms for Required Fuel as long as the ECU can handle the extra digit in the size of the number until I saw that MAP is indeed used as a variable; or so it says. It certainly wouldn't be much of a 'volumetric efficiency' if it didn't take pressure into account already.

[X64v]

Well I retract my previous statement, I looked over some datalogs and ran the numbers, and that is 100% correct. Now I've got hours of calculation ahead of me to figure out why my engine even ran the way I had it tuned.

[WizardBlack]

Well I retract my previous statement, I looked over some datalogs and ran the numbers, and that is 100% correct. Now I've got hours of calculation ahead of me to figure out why my engine even ran the way I had it tuned.

LOL. Well I never really was much of a fan for the 'linearized' theory or using PV=nRT. I have tuned dozens and dozens of turbo cars with standalones with direct access to pulsewidth. They never make a very good linear ramp IMHO. A good place to start? Yes, but they need more work. Likewise, most of the maps you see on here don't sport very close to 100% VE all across the map. They SHOULD, though, if that theory were true. Like I said, the very high vacuum areas are always much lower which goes to show it doesn't work like that. The nature of turbo cars affects part of it, plus powerband, head porting, cams, etc. etc. Basically any part of the powerplant that isn't 'plain vanilla' design. I don't think any of us (nor the Datsun engineers) are going for that...