I'm planning on putting on a pro-flo intake system with a K&N filter and possibly a new exhaust on my wolverine.
I will obviously have to re-jet my carb, which got me thinking of the advantages of EFI.
On motorcycles & atv's with EFI, do you have to re-map the fuel injection system? Change an e-prom or something, or does it automatically adjust for the change of intake and exhaust?

 

Well, it all depends

If it is a MAP based system (more than likely), it uses a manifold absolute pressure sensor to calculate engine load, there is no actual measurement of incoming air, so.... Having a calibration tuned to your exact application is always a good thing, but they can rely on feedback from the O2 sensor to try and "learn" to a certain extent.

MAF based systems use an air flow meter to actually sample incoming air to calculate the amount of fuel to inject. This allows the ECM to compensate to a certain extent for intake and exhaust changes, but MAF sensors are restrictive, expensive, have limited resolution, and can be tempremental. MAF systems can also use O2 (closed loop) feedback & have learning capabilities.

Some systems use a combination of MAF and MAP, more complications. All systems have trouble dealing with the low vacuum of a big cam, there's ways around that though.....

Newer technology brings us what is known as a wide band O2 sensor, although this has not been implemented in many fuel injection systems yet, it will be the way of the future. Current O2 sensors are merely a switch that shows if the engine is rich or lean compared to roughly stoich (theoretical perfect mixture). Many people believe that standard everyday O2 sensors can be used as "wide band" sensor (like those AFR meters sold at performance mail order companies, such as Summit Racing), but the truth is that they are very inaccurate anywhere except at stoich. Current ECMs use the rapid switching of the O2 between rich and lean to try and keep everything in check.

The wide band sensor can discern in an accurate fashion various Air/Fuel ratios, and feed that data back into the ECM making for much better mixture control.

A common misconception is that the EFI can compensate for big changes, in reality it all depends on how the system is designed and programmed. Some systems are very primitive, some very complex, some have strict operating limits & little adjustability for emissions purposes. Any fuel injection system can benefit from a custom tuned calibration for a particular application, eg. exhaust, intake, engine mods....

Modern systems use a Flash prom, for programming instead of a removable EPROM. Flash proms are soldered on the board and are programmed via software in a laptop or similar device. Some systems allow changes on the fly, this is very nice for experimenting....

What it boils down to, is fuel injection can typically compensate to a degree, for small changes - things like engine wear, altitude changes, temperature changes, etc.... Some systems can do mild cams, exhaust changes, and intake changes as well, but these will also benefit from a custom calibration, as I said before.

 

Uhhhh.... o.k., thanks for the answer, I think.

All kidding aside, I appreciate you taking the time to answer my question, and I actually did understand. (most of it)

 

Gabe,

Great post. You sure cleared up a lot of questions and misconceptions I've had about EFI.

Thanks,

Dennis

 

If you have any particular questions, let me know, I will answer best I can. Fuel injection is one of my hobbies.

I have a Vette with an Electromotive aftermarket system and a Truck with a GM Tuned Port system. I have been playing with the truck quite a bit here lately, burning my own chips, etc..... Fun stuff..

Both vehicles can be seen on my webpage