EFI tuning

[Jaxkruiser]

Has anyone added any type of fuel tuner on their scoot. I'm just thinking that if and when I upgrade an air filter and exhaust for better air flow that the fuel injectors will need more gas. Can't find a tuner for my GT 300i. I like the EJK but they don't have one specific for the GT 300i.

[hypophthalmus]

Shouldn't the ECU already be adjusting the amount of fuel for the extra air?

[Jaxkruiser]

I'm not totally sure if the ECU can make adjustments, it's like with a carbureted bike a rejet is required with a pipe and intake mod. I see that all other EFI motorcycles require some sort of EFI tuner with these mods, I would assume a scooter needs it too. Bike will run to lean without a tuner.

[hypophthalmus]

Where are you getting that other EFI motorcycles require an EFI tuner?

There could be something I'm missing. But the basic idea behind EFI is that there are sensors to measure the mass of the incoming air. The ECU will adjust how long the fuel injectors stay open based on these measurements.

It will then read the signal coming from the O2 sensor to check how it did in case there's unmeasured air or fuel sneaking in somewhere, and adjust accordingly.

[Jaxkruiser]

@ hypophthalmus. I am surprised that this sounds like something you have never heard of. I take it that you have not changed the exhaust or intake air filter on your scooter. There are dozens of EFI tuners for motorcycles, ATV, wave runner, etc. When a exhaust and air filter are done it adds more air flow through the motor  but the fuel stays the same. This is still by the manufacturer and  programed into the ECU. The ECU will not just add  more fuel. It has a programmed MAP, this can not be done by the ECU and the O2 sensor. This is called a closed loop system. Some of the EFI tuners are: Dynojet power commander, Cobra FI200, Vance and Hines fuel pack, Arlen Ness Big Shot, Dobeck EJK, etc. etc. I think that out should do a Google and YouTube search on motorcycle EFI tuners and then maybe you can understand what I mean talking about.

[hypophthalmus]

This is hurting my brain a bit, but I think I have a basic idea of what's going on.

On these bikes, the ECU controls the air/fuel ratio by sensing the pressure in the intake manifold. It takes that information and determines how much air is passing through the engine using a table of volumetric efficiencies at different conditions, what you and others are calling a map (which is a bit confusing because there's also a MAP sensor which is different).

The problem is when you reduce the intake resistance from the air filter, there's less vacuum in the cylinder and a higher volumetric efficiency (which I guess is the whole point). So the volumetric efficiency table is inaccurate, and you need a new one.

As far as closed/open loop, I've only heard that term used with regard to whether the O2 sensor is being used to adjust the amount of fuel. In closed loop, it should be able to add fuel based on the O2 sensor data, but probably not very gracefully.

Aaaaaaanyways, none of this helps you. But hopefully someone else can.

[Jaxkruiser]

Thanks for your help. So what's your opinion, would I be able to change my exhaust and add a foam pod air filter to my scoot with no other adjustments allowing the ECU and O2 sensor to do the proper adjustments? That would be great!

[CROSSBOLT]

Any EFI system capable of adjusting for elevation, which these Kymcos are, will compensate for changes you propose. Now, if one wants to remap the ECU, one needs a plug-in gizmo to do that. The big deal here is no one makes such a device that will match the connector that exists on each machine.

Karl