The nitrous O2 safty is near the bottem of the page.
Just wondering what people think about it.

 

sounds good if its on a wideband. narrowband, heck no.

 

why should your car not be at the stoichiometry point under WOT? I knew I learned that stuff in chemistry last year for a reason!

 

What he said.

The guy was thinking about it at least, but 14.7 is not what you want to use as a safety. And for those that read the whole thing, our filter element in that housing is not what is used in a QJet. At least he has good taste. : )

 

Because a 4-stroke gasoline fueled engine doesn't produce maximum torque or horsepower at 14.7:1 stoichiometric A/F ratio. Its generally accepted that you need an A/F ratio in the range of 12.8 - 13.2:1 for peak HP/torque. You need the excess fuel to insure that during the few milliseconds alloted for the combustion process, all the available oxygen is consumed. Dyno testing will prove this to be true.

It gets even more complex when you consider that you are burning two different "compounds" in a nitrous motor - air, with its 14.7:1 stoichiometric ratio, and nitrous with a ~9.7:1 stoichiometric ratio. Generally, you need to run a nitrous motor richer, first because of the stoichiometry, and second because you want to "err" on the rich side, because erring on the lean side will lead to catastrophic detonation.

There is nothing sacred about "stoichiometry" with relationship to power production or even fuel economy. You will generally be able to get better fuel efficiency with A/F ratios in the upper 15:1 range. In this case, you are running with excess air to insure all the available fuel is consumed.

14.7:1 was chosen as the design point because of low emissions considerations. At that A/F ratio, you get the lowest combined levels of unburned HC's, CO and NOx. Go any leaner, and even though HC's and CO drop, NOx formation increases drastically. Go any richer and while NOx formation continues to drop, HC's and CO will increase drastically. The cats are also designed to operate best at this level, since they can "reduce" the NOx to release surplus oxygen, then use that oxygen to oxidize (burn) the unburned HC's and CO.


Hope that answers your question.

 

As noted in a couple of the posts above, the problem is the narrow-band O2 sensor. By the time your nitrous engine gets to 14.7:1, its too late. You would want to shut down closer to something like 12:1, and the sensors aren't too accurate at that level. It is a good idea, and it will prevent a catastophic failure.

Alltronics (sp?) makes just such a device, using dual wide-band sensors, and provides both an audible alarm and an interlock for external circuitry.

http://www.altronicsinc.com/pages/o2alert.html