Tuning Nitrous With A Wideband

[ek02]

Maybe some of you guys with Nitrous experience can give me some input. I installed a wideband air/fuel guage on my N/A 274" setup. I have a NOS Super Power shot plate system with a dedicated fuel sytem for the nitrous solenoid with a return line to the tank regulated at a steady 6 PSI. After I rejetted my carb, my A/F ratio at wide open throttle is 12.5-1 and 14.7-1 cruising. When I hit it with a 125 shot of N2O, the A/F goes to 10-1, the lower limit of the gauge. I leaned out the fuel jet .004 and got 10.2-1 for a second, and then back to 10-1. I put the recommended fuel jet back in (.061) and upped the N2O jet .002 to a .057. Same reading. I was looking for 11.5-1 but can't seem to get there. I hate to go too far from the 125 shot jet recommendations. My bottle pressure was 950 PSI and total timing is pulled back to 26 degrees by the MSD box when I hit the spray. I called NOS tech support and the guy said he never heard of tuning a nitrous sytem with a wideband. I can always read the plugs as suggested, but it's a little hard to cut it clean at night and pull the plugs at the end of the track. I can also switch jets between runs and see what the mph does, but using the wide band should be the safest and easiest way to jet this thing. Is 10-1 too rich, and would I see any HP gain at 11.5-1?

 

[bison]

I've seen nitrous engines hurt by being run too rich. They were more than doubling the output of the engine though. You have to read plugs. There's no way around it. 11.5:1 is still too rich. Most bolt on nitrous kits are jetted too rich.

 

[ek02]

My thought is, since the fuel makes the power, increase the size of the nitrous jet instead of leaning out the fuel jet, and then read the plugs after each jet change. From what I have seen on some forums and a couple of jet calculators, I will be almost even on the jet sizes by the time I have it tuned for max power, that is if they are correct. I plan to go a little bit at a time in any case, read the plugs, and watch the knock sensor. I am using VP C16 and 93 mixed 60/40. The O2 sensor is mounted way back before the muffler so it will live a little longer on unleaded. No easy way to get it right.

 

[fuzzyGN]

The other thing to consider is we are only dealing with 6 cylinders and not 8. That will also make a difference in the "recommended" jets. As Bison stated, the systems are WAY rich thus safe for the novice tuner. I am not sure the best way to tune for max power but I would think your plan would get you there. Sounds like your harware is more than adequate (fuel system, etc.) so the average tune/recommendations/trade secrets would be out the window. Most average guys slap a system on a car without much thought of supporting equipment. The nitrous companes know that so they tailor the systems to the average guy.

 

[ek02]

You are correct. HP ratings on most NOS systems are for 8 cylinders. If you divde 125 HP by 8 then multply by 6 you get about 93 HP. I went up one jet size on the N2O. Same 10-1. I went back to the recommended jetting and reduced the fuel pressure to 5 PSI. It flashed to 10.2-1 and then went back to 10-1, so, so the pressure makes a difference, but not that much. I looked at the cold race plugs I used last at the track, and the insulators are white down toward the plug shell like they should be, and a little grey on the nose. I drove home with these plugs, so this does not give me a true reading, but they are not black and don't have signs of detonation. It will be a while before I run it again at the track, but I will experiment with the jetting then. My testing right now is limited to a really long on ramp on an expressway.