Your experience w/ nitrous.

[dan0617]

I would like a good tech explanation. Please look at those links and help me understand how to calculate what afr to see on my gauge if the formulas in the links are wrong. There are some pretty experienced guys and vendors on there.

If i understand correctly, I understand that the more of your power that comes from nitrous the lower the AFR on the wideband gauge needs to be. I understand calculating it from how much of the power comes from nitrous compared to how much comes from motor is a fairly accurate way I figure it without getting into weights. I know my plugs look good if I use this formula, and it seems on smaller shots you can just target 11.5 and be ok.

If this is way off base then let me know please

As a side note, if I ran an engine on 100% nitrous and no air at all, what fuel ratio would I want to see on a gauge that was calibrated in fresh air?

[SRT10KLLR]

Originally Posted by dan0617

I would like a good tech explanation. Please look at those links and help me understand how to calculate what afr to see on my gauge if the formulas in the links are wrong. There are some pretty experienced guys and vendors on there.

If i understand correctly, I understand that the more of your power that comes from nitrous the lower the AFR on the wideband gauge needs to be. I understand calculating it from how much of the power comes from nitrous compared to how much comes from motor is a fairly accurate way I figure it without getting into weights. I know my plugs look good if I use this formula, and it seems on smaller shots you can just target 11.5 and be ok.

If this is way off base then let me know please

As a side note, if I ran an engine on 100% nitrous and no air at all, what fuel ratio would I want to see on a gauge that was calibrated in fresh air?

With no air only 100% nitrogen your car would not run period. Oxygen is needed for combustion.

The nitrogen in N2O is not being used for combustion only the oxygen that is being broken free from the N20 molecule gets used for combustion along with fuel. The nitrogen comes out your tailpipe.

Nitrous, superchargers or turbos all just add more air into the cylinder. Your motor is an air pump.

[dan0617]

Originally Posted by SRT10KLLR

With no air only 100% nitrogen your car would not run period. Oxygen is needed for combustion.

The nitrogen in N2O is not being used for combustion only the oxygen that is being broken free from the N20 molecule gets used for combustion along with fuel. The nitrogen comes out your tailpipe.

Nitrous, superchargers or turbos all just add more air into the cylinder. Your motor is an air pump.

What you are saying about nitrogen I agree with. Just like everything else in freah air goes out the tailpipe, everything else in nitrous goes out the tailpipe. I totally agree. I'm not talking about the nitrogen at all. I didn't say 100% nitrogen. I asked 100% nitrous.

Nitrous oxide doesn't add more air, as you said above. It adds more oxygen. It adds more oxygen per pound than air adds.

In my understanding, an n/a motor makes best power at say 12.7 pounds of air to 1 pound of fuel. Hence 12.7:1 AFR. If that same engine was fed all nitrous oxide and no air at all, it would make best power at around 6 pounds of nitrous oxide to 1 pound of fuel, 6.0:1. Per pound, nitrous oxide has more oxygen than fresh air.

Now, the engine is running on fresh air AND nitrous oxide. That is why I use the equation in the links posted above to figure out what AFR to see on the gauge. The amount of air going in needs to be at 12.7:1 and the amount of nitrous going in needs to be at 6:1 and its all blended together and burnt before the 02 sensor and everything but the oxygen goes out the tailpipe as you stated. So i figure out by an equation what to see on the AFR gauge. I use the hp from motor and hp from nitrous equations as I don't have the equipment to weigh the nitrous and the air being burnt over a period of time and figure it that way.

Now that I'm spraying a boosted car I use 11.7 for motor Ratio and 6.0 for nitrous ratio.

And now because my gauge is calibrated for the E10 that I run, I use 11.2 for motor ratio and 5.5 for nitrous oxide ratio.

That said, my plugs look great at 11.2:1 when on E10 fuel and boost alone, and they look great at 10.3 on boost and a 125 shot.

When I had my vette I was running 9.7:1 when spraying and plugs looked perfect. On that setup alot more of the power came from nitrous oxide in comparison to air than on my camaro. On that car I once doubted all this and started to target 11.5:1. Even with timing back 2 degrees per 50 shot and super cold plugs, I melted the plugs and lean detonated bad. I fixed it and went back to 9.7:1 and all was good again.

Right or wrong, i do know my spark plugs always look great on every nitrous car I've seen done this way so I know the motor is happy.

[SRT10KLLR]

Not sure about the formula but what seems logical to me is the following:


Air contains about 20% oxygen and nitrous oxide looks to be about 33% given that it has two parts nitrogen one part oxygen so one third or 33% . But to me that is mostly irrelevant because how much oxygen is in the cylinder is what would matter regardless of how it got there. Important part is to have enough fuel to burn all the oxygen or at least most of it.


Again I don't know the math but say the valve opens for one second and 10lbs of air enter the motor that would be 8lbs of nitrogen and roughly 2lbs of oxygen. If you want an A/F of 12.7 you would need .157lbs of fuel. Now if you introduced 1lb of nitrous oxygen then you would be introducing .66lb of nitrogen and .33lb of oxygen. Now you have 2.33lbs of oxygen in the motor so if you still wanted to stay at 12.7 A/F you would need .183lbs of fuel. If instead of nitrous oxide you boosted the motor to get 11.65lbs of air you would get 2.33lbs of oxygen so you would still need .183lbs of fuel.

Bottom line, I just know I want the A/F where I want it regardless of how oxygen came to be in the motor. The nitrogen in nitrous oxide is just a buffer in my book.

[dan0617]

Your thought and logic is correct but you are thinking oxygen to fuel ratio. But your gauge is showing air to fuel ratio. It is calibrated in fresh air not in pure oxygen.

This is hard to explain, but, I think what you are saying is correct and would give the motor the fuel it needs in your examples but because the AFR gauge is calibrated in fresh air, feeding the engine oxygen from any other source than fresh air will change the gauge accuracy. The equation I use makes up for that.

If just reading plugs to see if engine is getting enough fuel the equation and calculation are not needed. If you could calibrate gauge in the exact mix of nitrous oxide and air being used, the equation and calculation would not be needed.

[SRT10KLLR]

I thought you or I might be misunderstanding the difference between Nitrous:Fuel ratio vs Air:Fuel ratio but your last statement isn't about that at all.

I thought the O2 sensor picked up the oxygen content without discerning the nitrogen or other elements in air. I'll have to do some reading on Oxygen sensors and how they work.

[Denis]

The idea of using nitrous has crossed my mind lately. But as someone who isn't well versed in aaaaaaaand like a lot of you guys have already said, all people ever hear is the negatives.

So I was thinking about jumping on the Zex kit that RDP is running a special on. Is there anything else I would need?

http://www.camaro5.com/forums/showthread.php?t=305828

I don't plan on running more than a 75 shot. Maybe 100 if I get crazy. But it's mainly just to have a little more fun with from time to time.

Now as far as the tune goes. If I'm understanding correctly you need to pull timing. Now wouldn't this negativly effect the car on a day to day basis? I mean your power off nitrous would be less due to the timing being pulled?

I'm pretty new to the idea of nitrous so I'm trying to understand. I've done a little reading but there is A LOT of info.

[dan0617]

Originally Posted by Denis

The idea of using nitrous has crossed my mind lately. But as someone who isn't well versed in aaaaaaaand like a lot of you guys have already said, all people ever hear is the negatives.

So I was thinking about jumping on the Zex kit that RDP is running a special on. Is there anything else I would need?

http://www.camaro5.com/forums/showthread.php?t=305828

I don't plan on running more than a 75 shot. Maybe 100 if I get crazy. But it's mainly just to have a little more fun with from time to time.

Now as far as the tune goes. If I'm understanding correctly you need to pull timing. Now wouldn't this negativly effect the car on a day to day basis? I mean your power off nitrous would be less due to the timing being pulled?

I'm pretty new to the idea of nitrous so I'm trying to understand. I've done a little reading but there is A LOT of info.

For a shot of 125 or less you can go by the Zex recommended jets and be good on AFR and not worry about the conversation we are having on this thread. I put in an LNC 2000 Lingenfelter box for timing retard and I love it. It is plug and play and I have it set to only retard timing when I hit the nitrous switch. Have someone like Jannetty do a tune for you when on motor but tune the trans (if its an auto) for the extra power. You will love it. Check on fueling, stock pump might be ok, but consider a ZL1 pump and ADM FPCM.

[Denis]

Great thanks for that info!

I'll look into that lingenfelter box

[dan0617]

Originally Posted by SRT10KLLR

I thought you or I might be misunderstanding the difference between Nitrous:Fuel ratio vs Air:Fuel ratio but your last statement isn't about that at all.

I thought the O2 sensor picked up the oxygen content without discerning the nitrogen or other elements in air. I'll have to do some reading on Oxygen sensors and how they work.

Yeah, I knew we weren't on the same wavelength for a post or 2. I have spent probably 1000 hours researching and tuning nitrous (and rebuilding after screwing up LOL) but that doesn't mean I'm exactly right here. This is what works for me and my setups.

If I understand correctly the AFR gauge uses the 02 content from the fresh air calibration versus the 02 left over after combustion and determines an AIR to fuel ratio as what it was as it entered the engine. Once you change the oxygen delivery method to something that has more or less 02 content per weight than air does, the gauge becomes inaccurate. I really believe this is why there are alot of lean backfires and detonation going on when people look at their gauge and think they are fine.

I apologize for not starting with the above paragraph. I am not the best with getting my thoughts out of my head and into words. Looking back I knew what I said but I didn't explain it well enough for anyone else to know!

Don't get me wrong, I think most street setups and small shots are fine and likely even spot on with out of the box jetting and 11.5 to 1 afr's, but when the shot gets big or you start running nitrous along with boost the fact that the AFR gauge is now inaccurate gets overlooked. IMO you have to use the equation like I do or a more thorough weight equation and figure out what the AFR gauge should say, run it a pass, and read the plugs for the final answer.

[dan0617]

Originally Posted by Denis

Great thanks for that info!

I'll look into that lingenfelter box

Nice looking car!

[Denis]

Originally Posted by dan0617

Nice looking car!

Thanks!

So just so I'm clear. With that lingenfelter box I wound need to retune the Carmelite that small of a shot? That box should take care of the timing retard? How spot on should that kit get my AF ratios? I don't wanna run lean.

[SRT10KLLR]

Originally Posted by Denis

Thanks!

So just so I'm clear. With that lingenfelter box I wound need to retune the Carmelite that small of a shot? That box should take care of the timing retard? How spot on should that kit get my AF ratios? I don't wanna run lean.

You don't need a retune with the Lingenfelter box it's just a suggestion for you current NA setup. The box will pull the necessary timing when activated. As far as fuel goes most of the times the recommended jets are on the rich side for safety.

[Denis]

Awesome. Thanks both of you for the info. Definitely helped answer some questions and put my mind at ease