Fuel Injection Explained (for dummies like me)

[Arnie]

Subject heading says it all.

I found this text to be very enlightening    You might too

  http://www.bikeboy.org/fuelinjection.html

[ZOA NOM]

excellent! Thanks!

[Pat Conlon]

Thank You Arnie

[Troyskie]

Thanks mate.
Although I think I'm dumber than most.
The explanation was clear, but I didn't understand some of the terms such as 'stoichiermetricly', (which I now understand - thanks interweb).
It has been about 25 years since I had any ability with differential calculus (even then only just competent), so what he meant by 'three dimensional average' is a bit of a mystery to me & even after searching some for it, I still don't really get what he meant by that. It could be a terminology thingy.
It was quite enlightening to discover the input variables, temps, air pressure, timings, etc.
It was also quite interesting to see that a lot of the myths about varying the chip for better economy/performance are blown in this as well, plus wonderfully simply reasons for why.
Of real impact was the comment about aftermarket exhausts for FI bikes. The quest for a nicer note, shinyer can etc. could be a whole lot more expensive than just the purchase of a new pipe. Unless you have one of those control systems re-jetting (well mapping for FI) is going to be really tricky, expensive, and/or time consuming.
A good read mate.

[Pat Conlon]

Hey Troy, with 3D graphs it's easier to see an anomaly vs trying to decipher the numbers in a table.
http://www.tuneboy.com.au/Products/Products_Tuneedit.html

[fj1289]

Very good tutorial. 

But fuel tables in milliseconds is in the minority for aftermarket ECUs.  Most aftermarket ECUs use VE (volumetric efficiency) as the "core" of the calculations.  Then, using information on engine size, max RPM, and fuel injector size along with the VE from the table, the ECU calculated the required PW (pulse width) in milliseconds.  One big advantage with a VE system is you can change injectors without having to create a new tune - the compensation is in the calculations with the new injector size settings.   

All the other corrections (air pressure, temp, etc) are performed in the same manner as described in the article. 

Another difference is the default for most ECUs is to use manifold pressure (MAP)  instead of throttle position to determine engine load.  For most engines MAP is more responsive at low engine loads, while TP (throttle position) is more responsive at higher engine loads.  Many of the tuning algorithms for motorcycles now use a hybrid tuning scheme that blends MAP at low engine loads and TP for high engine loads.

Retuning for something like a change in air filter or exhaust  really isn't too complicated - you just need to be methodical - just like tuning carbs on your own. 

When I get back home - I'll transcribe a much better explanation of the use of VE tables from a couple books on the shelf in the garage.   

[Troyskie]

Hey Troy, with 3D graphs it's easier to see an anomaly vs trying to decipher the numbers in a table.
http://www.tuneboy.com.au/Products/Products_Tuneedit.html

Ah ha!
Thanks mate.