I've made a digital air/fuel ratio gauge and I'm thinking about adding a tuning function so you can scale the O2 signal up or down, forcing the engine lean or rich. My big question is will running a little more lean than normal mess up my engine at all? I've heard a leaner mix burns hotter, so can I just keep an eye on engine temps if I do this? Are there long term side effects, like decreased engine life?

 

2 things. unless you can control the air/fuel mixture through out the rpm range independantly I wouldn't do it. what's lean on one point in the rpm could be very lean or even very rich at another point in the rpm range.

second no it wont mess up the engine if you run a little lean than normal.

 

:werd:

Lean does burn hotter, which means more power...but also closer to detonation. This won't be reflected in engine temps, but the exhaust gas temp will go up. However, you'll need an exhaust probe, and an EGT gauge. At any rate, I hope you are using a better gauge than the Autometer one that reads the O2 signal. If you want accurate results, go get yourself a wideband O2 and a digital A/F meter.

 

Exactly.

I run a touch on the lean side but you definitley have to be careful about at what RPMs and how lean...bad things happen when you get too happy with ith:

 

Well the device will work like this. The 0V to 1V signal goes into my unit, get's scaled up or down (say like 80% to 120%) then gets sent to the ECU. The scaling factor would be adjustable, or completely bypassed with a switch to run like normal.

How does mixture change through the rpm band? Can you not run as lean at higher rpms? The idea is to save fuel, so ideally it would be capable of running a little lean at around 3500rpm for highway driving.

So if it runs hotter and closer to detonation, I may have to use a higher grade fuel? I'm already running premium as is required with my engine. Will that be a problem?

What would happen if I got too happy with it? How would I know when enough is enough? I guess it was start misfiring? What other bad things are there?

Thanks a bunch for all the help.

 

Why don't you just get something like Hondata that you can tune.

 

Because Hondata would probably cost me $800 when I can build something for next to nothing. I'm in my 4th year of EE, so this is the kind of stuff I'm interested in.

 

Are you willing to risk a motor over it? Do you know how much voltage change there is for different a/f ratios? Do you know the change in voltage/current sent to the injectors telling them to open/close?

 

Well that's why I'm asking all these questions. Yes, I know how much voltage change there is for different a/f ratios. I don't know the signals controlling the fuel injectors, but that's another project.

 

You might look into the circuitry of a VAFC or SAFC unit. They can adjust the injector trim by percentage. Also, I believe the new Hondata systems and the AEM EMS have an autotune feature, where you enter a desired A/F ratio and it will tune itself around that...something else to look into.