n2o a/f ratio

[van460]

craig or someone, 466 ford 160inj on gas my tuner who sold me program had me at 11.5 a/f for n2o i pulled 16degrees timing out from 36 total at a350hp shot. made pass car pulled good went to data log and the o2 put in 25% and stayed at 13.5sa/f the whole run, but i pulled the plugs and they looked great the four corners were real fat middle for were perfect. dont want the o2 to correct, i now how to fix that ,but do you suggest to stay so lean or if plugs read goog leave it? or just fix the o2 correction and change the a/f ratio to 13.5, idea two was to put 30% in nitrous fuel table and change the a/f to 12.5. what do you guys suggest for best power?

 

[bruce]

I'd stop right there and figure out why the distribution was so bad.

If you going to run a manifold with that poor of distribution I'd give the J+S Knockguard stuff a good look. It won't cure you mechanical problems, but min the HP loses.

Poor cylinder balance like that costs alot more HP then you would imagine.

 

[Craig Smith]

You are on the edge of demonstrating why O2 sensors are sometimes not the best tool for tuning large amounts of nitrous. With a big shot like that, you wind up with plenty of nitrous in the pipe after the burn cycle. Nitrous as a power adder becomes less efficient as the shot gets bigger, and the unused nitrous goes right out the exhaust. When mixed with the gasses from the combustion process, it tends to cause inaccurate readings from an oxygen sensor.

This is inherent to any oxygen sensor, not just ours. O2 sensors are designed to sample exhaust gasses. When you contaminate the airflow signal to a sensor, whether it is with oil, antifreeze, nitrous, or anything else, the sensor will be inaccurate. It's the "garbage in, garbage out" theory.

That being said, I agree with Bruce that your air distribution problem should be addressed. Plenty to be gained there. If your plugs look good and show no signs of detonation you are probably on the right track. I hate to give advice on something like nitrous over a bulletin board though... you are best to use your own judgement.

 

[bobc455]

Remember that if cylinder 4 is lean, it will detonate, no matter how rich the cylinder next to it is. Been down that road- new engines aren't cheap!

You will have to read the plugs to know what the engine wants. Get the system tuned perfectly without nitrous (you can use the WBO2 for that), then tune the nitrous according to the plugs.

In addition to the J&S Knockguard, if you are running FAST then you might to consider the sequential injection with individual cylinder control.

-Bob Cunningham
bobc@gnttype.org

 

[91cam447]

I have been told to run 9.0 a/f ratio on nitrous. You are asking for inspection windows in the pistons at 11.5. Like Craig stated, when spraying large amounts of nitrous, some of the charge gets pushed thru into the exhaust. That will cause the O2 sensor to give a false read. Always tune a nitrous motor by what the plugs are telling you the engine wants. Also, I have also been told, never use nitrous when in closed loop. Take it for what it is worth. Been told this by someone who has Jeff Prock tuning his combination. He is the best in the buisness when it comes to nitrous. You may want to give Prock a call. Applied Nitrous Technology 813-885-4149