Portable air/fuel ratio tester

[Jerry G.]

I'm getting near the point where I need to set my FI unit up on the race car. The unit has been modified so I won't be able to use the factory procedure. The plan is to use a portable A/F ratio measurement device to set the power and economy stop settings. Does anyone have experience with a good reliable handheld device. I don't want a dash mount system. I run race gas which has lead so I will have limited life on the o2 sensor , I think I just have to live with that. I'll remove the sensor following setup. The sensor will be in the header collector. Any ideas or experience would be appreciated. Jerry

[Clem Z.]

Re: Portable air/fuel ratio tester

I'm getting near the point where I need to set my FI unit up on the race car. The unit has been modified so I won't be able to use the factory procedure. The plan is to use a portable A/F ratio measurement device to set the power and economy stop settings. Does anyone have experience with a good reliable handheld device. I don't want a dash mount system. I run race gas which has lead so I will have limited life on the o2 sensor , I think I just have to live with that. I'll remove the sensor following setup. The sensor will be in the header collector. Any ideas or experience would be appreciated. Jerry

take the car to a shop with a chassis dyno and a A/F measuring system. i have a portable EGT measuring device i used to check WOT temps but you need to drill a 3/16" hole in the header tubes. my device holds and displays the highest temp reached so no one has to read it while on the track

[Jerry G.]

Re: Portable air/fuel ratio tester

I'm just getting old and lazy. I was trying to avoid going and getting the trailer, loading it up, transporting , offloading , setting up on chassis dyno and reverse entire procedure. I was hoping there would be a spiffy handheld unit I could use in my shop.

[Jim L.]

Re: Portable air/fuel ratio tester

Innovate Motorsports makes air/fuel gauges that use wide band O2 sensors and they are moderately priced. I use one when I calibrate FI units and it gives reliable results.

You will find that you have to have the engine under a road load to get an accurate air/fuel indication.

In the shop with no load, the AFR will be artificially rich because the throttle won't be open far enough to turn off the idle and off idle signal boost.

Under road load, in contrast, the throttle blade will be open far enough to render the signal boost negligible and AFR readings will be accurate.

Here is a sample recording from a recent calibration. You are looking at the air/fuel ratio during steady cruise, several seconds of wide open throttle, followed by a return to steady cruise:



O2 sensor life will be shortened by the use of leaded racing gas, but it's just the price of admission. The Innovate gauge uses a Bosch O2 sensor that retails for about $60 and is readily available at NAPA stores.

Jim