I'm looking for some help with a little project.

My motorbike has 2 narrow band sensors in the exhaust (one for each bank of the V4 engine). As standard, obviously it goes into closed loop fuel control under some conditions, and the throttle response is not very nice. I'd like to fool the ECU into thinking that it is running a bit leaner than it actually is such that the closed loop control point is slightly richer than Lambda = 1.

To do this, I was thinking of using a wideband lambda sensor with a controller that has a programmable simulated narrow band output and modifying the output accordingly. Sound reasonable? Or is there a better way?

AFAIK, the Techedge units all have programmable outputs, do any others?

As there are 2 sensors, it will be quite costly to do as I will need 2 WB sensors and 2 controllers - unless I use something like the Techedge 3H1 which has 2 inputs and 2 programmable outputs (the WB output could be programmed the same as a simulated NB).

Anyone have any better ideas?

 

Isn't this a mapping issue? Can you even get that done? I have no idea on bikes...

 

Do you actually know that your engine will benefit from being a little richer?

 

it is and it isn't. closed loop will always cycle around lambda = 1 with a standard narrow band sensor.

some bikes can be remapped within the ecu, but not hondas AFAIK.

most people do it by using a Power Commander which is an add on unit that takes the injector timing and modifies it to go richer or leaner. that won't help in my case as if you try to richen it up at certain rpm the closed loop will just bring it back down again you can of course remove the lambda sensors and run open loop all the time.

only because other people have removed the lambda sensors and used a Power Commander to richen it up and in general it's likely to be better by being a little richer isn't it?

 

You can't really generalise, some engines will prefer to be a little richer and some a little leaner, plus a whole host of other variables too.
If it's been seen that your engine benefits from a slightly richer mixture then your idea should work yes mate, although this only effects the closed loop area's of the map, idle and cruise (At least that's what they do on a car).

 

I think the higher the lambda voltage the leaner the ECU thinks it is (That's how a WBO2 works) so maybe be you could get something to just intercept the lambda signal's and up the voltage a little? If it was the other way around you could just use resistors to lower it.

 

i was thinking of a little circuit that could just put a variable offset onto the NB sensor output but didn't want to mess about with making something, putting it in a box etc, etc if something off the shelf already existed

 

Unplug the sensors....no more closed loop. And it's totally free.

 

but doesn't help if the open loop mapping is also not great...

 

It doesn't, but you could then just raise the fuel pressure a little and you'd be richer everywhere without the lambda's pulling it back out.

 

also a bodge. some places it doesn't need to be richer.

 

So which area's do you want it richer in? With your initial idea it will only be idle and cruise as I mentioned earlier.
Sounds like maybe standalone or a piggy back system might be the way if you only want it in certain area's.

 

Closed loop can often be a bodge. It will always be fighting you simply because it is relying on a slow sensor to make changes to tuning.

A simple resistor might fool it, and would be the cheapest option. Certainly best to try that first before spending any money.

If you stuck a resistor in the signal line, it would offer the ecu a lower voltage so the ecu would think the bike is lean and should add a little more fuel. Although dont forget, most engines are usually only in closed loop at part throttle and low loads/rpm's anyway.

 

i'm not convinced that a resistor can do anything useful with a narrow band sensor output. all a resistor will ever do is drop a bit of voltage across it and with a NB sensor, the output is not proportional to lambda. the ecu would just see slightly less voltage both when lean and rich.

an ecu (generally, particularly old types like i am using) in closed loop adjusts the fuel to see a big difference between the 2 voltage and cycles around that point using a simple step/cycle control method - they can't have a tuned loop like a PID controller to settle somewhere as the feedback signal is not proportional to the controller output (injector duty cycle)

it's at the light throttle openings and cruising where it's worst, which is how i know that it's during closed loop conditions.

obviously ideally i would do a full datalogging exercise with a couple of wideband sensors first to know what's fully going on, but there is enough evidence for me to know that my initial idea should be an improvement, although costly. a piggyback system of some kind might be an answer, but it would have to be one that modifies the lambda sensor outputs or i lose them and go open loop all the time which is not really something that i want to get into as it will require a lot of mapping effort. as would a stand alone ecu - unthinkable on a v4 engine with vtec revving to 12000 rpm really with the effort that i would want to put in.

some potentially interesting products here: http://www.perfectpower.com/ but they require more research

 

My ZX12R used to have serious lean stumble at low rpm very slight throttle openings, remapped and job jobbed !