AFR questions

[art leong]

I am running 2 wide band O2 sensors on the 4 cylinder drag race car naturally aspirated, no nitrous, just racing fuel. One an Innovate LC1 is located about 15 inches from the #4 exhaust port (I use analog Volt 2 for this one). The other an AFX unit is located in the common collector ( aft of all 4 exhaust tubes merge ). About 6 inches from the end of the collector. It uses analog Volt 4.

The AFX unit is usless at an idle due to it's proximity to clear air (using a big duration, long overlap cam shaft).

My problem is when I leave the starting line. The sensor in the collector shows a very rich condition as low as 9.5 afr. The other sensor (Innovate) stays at 14.0 or so for a second or 2. I have recalibrated them and changed the sensors (they take different sensors). With no changes.

I've been told that the AFX sensor is much faster to change than the Innovate sensor.

Once in high gear both sensors are close (13.2 and 13.5 on a good run)

One big question I have for you tuners is should the motor go way rich when leaving the starting line? It stays rich for about 2 seconds. I'm using an automatic trans with a torque converter, and I think the sprag in the converter is broken. Causing no torque multiplication. Once I get some wheel speed the motor takes off and runs fine. Attempts to lean it out at the launch rpm 3000. seem to slow it up.

Should a motor go rich when launching? I think about diesels that blow black smoke when starting to accelerate.

[Dave Kriedeman]

Hi Art,

are you using any type of launch limiting etc.

When you say it goes rich at the start are you referring to when you are loaded at the 3000 rpm launch speed, or when you actually launch and start to move.

Regards

Dave.

[art leong]

It goes rich when I release the launch control button and start to move. When I'm on the launch control it shows lean. Because it cuts a random cylinder out creating unburned oxygen.

On my good runs it would go rich for a very small section of time, now it stays rich for over 2 seconds. In my carbureator days, accelerator pumps made the mixture rich till it got moving. Now I launch at 100% throttle position. So the acceleration enrichment doesn't come in to play.

I'm looking at the probability of a problem in the torque converter. Stopping it from multipling torque. And putting an excessive load on the engine. Till I get some wheel speed, then it takes off and runs great.

My 60 foot elapsed times are 4 tenths of a second slower than the best times. And the car doesn't start to really accellerate till about 100 feet.

I'm pretty much done for the rest of the season. I'm going to get O2 bungs welded to the other 3 header tubes. So I can move the sensor around to see if all are close.