I decided to buy an autometer air fuel guage, my bro had one, and he really wanted to run it off his ECU in his car, but couldn't make it happen, so I took it off his hands. I hooked it up in my GSL-SE today, and I just want everybody's opinion on the reading I'm getting, and if that is where I should be.

At idel, or cruising speed, it fluctuates around, and I'm told that at WOT is what you pay attention to, so....

At WOT, the guage stabilizes and stayes rock solid about 3 bars into the rich on the guage. Now I would've been happier to see it with a less rich reading, but I am happy that it's not running lean, which I really don't want to happen. The car runs great, but I wasn't sure if this is where it should be as far as ratio is concerned, so I wanted to ask. It's not running super rich, just a little, and I'm pretty happy with that, but I was wondering if it would be a benefit to be running just a tad leaner, and how I could tune the car to do so...

 

you could purchase a holley fuel pressure regulator. If there is a way to adjust it without the regulator, i dont know about it.

 

smaller injectors maybe...?

 

Really the only way to lean out the fuel settings is to get an aftermarket piggyback fuel controller, such as the S-AFC. Cost almost $300, but Ive seen gains of up to 10RWHP on N/A FCs... There is a fuel adjustment screw (at least on my FC there is, I think your car has one also) but it is only for idle mixtures, and really should be left alone. Glad to see you got it working

 

Yeah, it seems to be working fine. I stopped down to show you afterwards, but you weren't home. I dunno why my bro had just a hard time. I had it installed in about 15 minutes.

 

What your reading really means, depends on so many factors, it really doesn't mean anything. Autometer A/F gauges depend on the stock O2 sensor to give it a reading. It just compares the voltage read by the sensor against a value set in the gauge, and displays so many LEDs depending on that voltage.

Unfortunately there are many varibles in determining the voltage signal that an O2 sensor will return; sensor age, sensor temperature, system backpressure and variances in the production of the sensor to name a few. Narrowband O2 sensors, like the ones equipped on almost all OEM cars are really ony consistant between 14.2-15.3 AFR or so. Most rotories like to run in the 12.5-13.0 range. So basically, a simple AFR meter like the autometer one, will only tell you when something is seriously too lean.

 

So basically, the fact that rotaries run a little richer than piston engines, could be why the guage is giving a slight rich reading then, because the guage is calibrated for a slightly leaner AFR?

Making sure the car doesn't run lean is really my concern, the only reason the guage is there, is to just make sure that doesn't happen, I'm not to concerned with having a super accurate reading.

 

where exactly, and how far away from the carb are you holding the guage? cuz its hard to get an exact reading because if you notice... moving the guage down bring the fuel pressure up, and vice versa.

 

on our engines you can adjust the idle mixture and thats all that i know of as far as AFM is concerned. to do that it's jsut a little screw thats set ina small balck peice that is attatched to the passenger strut tower. but i don't think that will help you

 

On a NA rotary its pretty hard to get it to ping due to the low engine requirements for octane. Running it a bit lean will likely do no damage beside robbing Hp, and raising EGTs. Without a dyno its a guess as to what mixture is best, and on an -SE it's impossible to tune the mixture without an aftermarket fuel pressure regulator, or a piggyback fuel controller (which I'm not sure there are any that will work with the old analog ecu that the -SE has)

 

I have no carb, it's a GSL-SE...

 

oops

 

That about where the gauge reads on my SE.. so it must be normal

 

The worry of it running lean on the stock SE setup would be rare, usually when EFI components go bad on NA's they will run more rich.

It's good that your concerned though

 

First, the gauge is not really "calibrated", it is just a fancy voltmeter, and displays what the O2 sensor gives it.

The narrowband O2 sensor in production cars cannot be used to tune a mixture for WOT power. It is only used to tune stoichiometric mixtures (14.7:1 for gasoline) which are good for light cruising. The stock ECU uses this signal to optimize gas mileage and emissions. At WOT the stock ECU ignores the O2 sensor and runs from a fuel map in memory.

 

By calibrated, I meant the actual readings on the guage....the red, orange, and green lights. Where they are laid out is not "calibrated" for a rotary.