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Author Topic:   O2 Sensor
340duster
Dirt Full Roller

Total posts: 70
posted June 18, 2002 01:28 PM
Anyone tried an O2 sensor for jetting??? I am installing one for this weekend's race to check air fuel ratio to see how it works. Any tips or suggestions?

ddoti1
Dirt Roller

Total posts: 23
posted June 18, 2002 06:31 PM
Thats interesting give details, I d like to hear the results !

ZIGGY
Dirt Roller

Total posts: 25
posted June 18, 2002 09:37 PM
Just don't forget the reading you see is an average.

c21
Dirt Freak

Total posts: 346
posted June 19, 2002 12:17 PM
o2 sensors are very sensitive to (will eventually be damaged by) chemicals contained in many silicone sealers and the Lead found in most racing gas. Additionally unless you are using a Wide-band sensor you will not get accurate readings for mixtures richer than 12.5:1. The sensors found on fuel injected cars(and sold with cheap displays in Jegs, etc) with outputs of 0 to 1 volt DC are designed to be accurate between 17:1 and 13:1 in order to tune for best gas milage/lowest emissions. While this type might be useful for letting you know if you have a big problem, it probably won't be much of a tuning aid due to it's lack of granularity or accuracy in the zone you are interested in.

o2 sensors used on dynos are all the wide-band type (very accurate from 25:1 to 10:1 ratios)and usually cost $1000 to $3000 or more (the high cost is due mainly to the support circuitry required to maintain the correct heater voltage). There is a Do-it-Yourself wide-band kit available for under $400 (less if you supply your own $150 5-wire wide band sensor)at http://www.techedge.com.au/vehicle/wbo2/default.htm

c21

340duster
Dirt Full Roller

Total posts: 70
posted June 19, 2002 01:20 PM
Thanks for the reply C21. I bought the gauge for my street driver, but thought I would try it in the race car first. We have to burn pump gas so the sensor should survive. I have a copy of the mV vs A/F graph of the inexpensive sensors so I can see how it may be difficult to get a precise reading. On the subject, what is optimal A/F ratio under full throttle/full load conditions? Also, ever experiment with an exhaust temp gauge (pyrometer)? I notice the jet boat racers use them as well I had a set on my snowmobile. Seems to work good in these applications. The stock car may not have enough time at full throttle to get good numbers. Any comments?

dgb
Dirt Roller

Total posts: 7
posted June 19, 2002 02:04 PM
I've been looking into doing the same thing. Does anyone know whether or not methanol will damage these sensors? I've read that leaded fuels and the wrong silicon are bad for them, but haven't been able to find out anything about methanol.

c21
Dirt Freak

Total posts: 346
posted June 19, 2002 05:06 PM
I would ask Steve Hendren what a good A/F ratio is. On my race car I always go off of plugs and exhaust gas temps .... speaking of egt's, They can be very informative on a Stock Car, but first you need to find out what temps are normal for your car (when the plugs are good) then watch your egt's for change which would normally indicate a need to change your jetting to suit conditions. I use a DIGATRON digital egt display with datalogging in the race car ...... and love it. Please check them out at http://digatron.cc/ (they are great people with great products!)


I use a Wide-band o2 currently (but have used a narrow band display in the past) on my supercharged street car. My set-up is fuel injected running up to 11 psi on pump gas and I look for A/F ratios around 11.5:1 and 12:1. On a non-fuel injected set-up without programable engine management (ie, a street stock)I would think you would need to run richer still (11:1 TO 10.5:1 ?) for an added margin of safety.

You can use an o2 sensor for gas,propane or alcohol, however, I think with alcohol you are looking for A/F ratios like 6:1 or 7:1.

Here is a link to a place that sells the narrow band display I used to use ... http://www.twminduction.com/Halmeter/Halmeter-FR.html
I think they have more info on using the o2 sensor for alcohol.

c21

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