I'm trying to get a handle on how the EFI is set up on these sleds. I'm VERY familiar with EFI on automobiles, so I'm not looking for the basics. What I'm trying to figure out is how the EFI can determine air density. So far all I've been able to find is an air temp sensor. There's no MAP-type sensor, nor a mass airflow sensor to figure out air mass or density. It also doesn't seem that there's an oxygen sensor for the control module to determine whether it's buring close to stoich.

I understand how an open-loop EFI system can operate, but I was also under the belief that for an open loop system to compensate for altitude, it would need to know the air mass or air density. I can't figure out how Cat is doing this.

I also wanted to know how cat is timing the firing of the injectors. I'm assuming that the ignition timing and injector firing is controlled by the computer in much the same way that it would be on a car. Is this assumption correct?

Is there any info out there that I can read to learn about Cat's EFI? I'm really very curious how they do some of the things and how it compares to what I know about automotive fuel injection.

The A/C efi is a speed density type system. It uses air temp, engine temp, throttle position, rpm and atmospheric pressure as inputs. The pressure sensor is built into the computer black box. The sensor vent tube is the plastic tube you see stuffed down between the air box and the oil tank.

2002 + efis are build to shut down if you mess with them. They also track certain conditions for the factory to check such as “last time ethanol shunt was used” etc. (can’t remember all conditions but I think there were five).

I am sure someone will eventually figure out how to reprogram these things but for now they appear to be fairly secure. Some have claimed to alter the inputs to “fool” the computer such as engine temp and air temp but you could be playing with fire if you go too far as these altered inputs could shut the thing down.

BobCat

Thanks for the info. That's the type of stuff I was looking for.