Warning! Nitrous Air Fuel Ratio
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Teching In
Joined: Jun 2003
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From: Odessa, Texas
Warning! Nitrous Air Fuel Ratio I put a 150 horse shot on my car a few weeks ago. I took it up to my local dyno shop and pulled it on the dyno. When I dyno my car I have the air fuel ratio sniffer on the car at the same time. With the "recomended" jets it pulled 427 rear wheel horse power "554 corrected". The pull was great and I was very excited. Problem was the dyno showed I was running at 14:1 air fuel ratio/ I had to go up several jet sizes to get it to 11.5 (104 ambiant temp) and 12.4 (74 Ambiant temp). Now I am not 100% positive the sniffer is correct but to save the engine I fattened the mixture up anyways. Bad thing is I lost 21 rear wheel horspower at my elevation (3200 feet). Good news is I have gone through 5 or 6 10 lbs bottles and have had no problems. So the point I am trying to stress is if you run Nitrous, don't take the manufactors word on the fuel jets. Run the Nitrous jet they sujest, then sniff the car on a good dyno pull and richen or lean the fuel jets as needed. Remember also, if you have a drastic ambient temp change you need to sniff it again and record your ranges. Also if you make a drastic alttitude change you should do the same. Also, DO NOT RUN THE FACTORY PLATNUM PLUGS OR ANY PLATNUIM PLUG FOR THAT MATTER. I got my buns chewed out for an hour for running them in the car with the Nitrous. Other wise you are taking an unnecessary risk and will probly learn to hait nitrous. 
Re: Warning! Nitrous Air Fuel Ratio Real soon I will be dynoing my car with a 150 wet shot and wanted to know what jets you used and what kit? For my NX wet kit my jets are 62 for nitrous and 33 for fuel. Now you said you had to change the fuel jets, what did you change it to? Also what did you dyno on motor I would like to know what a 150 shot is actually putting to the wheels.
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Teching In
Joined: Jun 2003
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From: Odessa, Texas
Re: Warning! Nitrous Air Fuel Ratio I wound up with a 38 fuel pill. Iy gave me 11.5:1 air fuel at 104' ambient temp and 12.5:1 air fuel at 74' ambient temp. I stayed with the 62 nos pill. At my altitude (3200") and the hot day I pulled 289 actual rwhp (completely stock car) 319 SAErwhp. With the juice it pulled 427 actual rwhp with the 33 Fuel pill but at an air fuel ratio of 14:1 which is too lean acording to NX. With the 38 Fuel Pill I pulled consistant 405 to 408 actual rwhp. That was 104' and 74' ambient temp differences. So the SAE rwhp was 455 with 1000 lbs bottle pressure, 62 nos pill, 38 fuel pill, NO PLATINUM PLUGS, gapped at .035" as NX recomended, and everything else on the car being completly stock. I tryed it with a K&N air filter and Whisper lid the same night. The Dyno shop was trying to sell them to me soI made them prove to me they work. With both I saw a 2.5 rwhp incress. I did not like the fit and the price of 250 dollars total so I do not even run that junk. I can find better gains with 200 dollars you know. Now back to the air fuel ratio, like I said, I am not 100% positive their sniffer is correct but I would rather loose 20 horses then loose a complete engine. I am looking for something to check their sniffer with then I will put the car back on it.
Re: Warning! Nitrous Air Fuel Ratio Thats pretty good to know, Thanks
So you ended up with alittle more then 100rwhp with the 150. Also from it being a hot day. Thats pretty good for a stock car, what a sleeper. Yeah lids help out but not that much for $200. I would rather spend a little more and get a cam if I were still stock.
I wonder what fuel jet I will need, since I have a 340 intank fuel pump I wonder if I will be ok with the 33 or maybe even 36?
So you ended up with alittle more then 100rwhp with the 150. Also from it being a hot day. Thats pretty good for a stock car, what a sleeper. Yeah lids help out but not that much for $200. I would rather spend a little more and get a cam if I were still stock.
I wonder what fuel jet I will need, since I have a 340 intank fuel pump I wonder if I will be ok with the 33 or maybe even 36?
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Teching In
Joined: Jun 2003
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From: Odessa, Texas
Re: Warning! Nitrous Air Fuel Ratio Well, I really do not know the answer to that one, but if it is running the stock fuel pressure you might need to go up on it a bit. But it seems if the fuel pressure is increesed, then more fuel would make it through the same sized pills. But keep in mind what I said in the other post about my car. My stock pump will not keep up in 3rd gear running down the track. The system turns on and off several times at that point due to the fuel pressure safety switch. I am at this time looking for a good pump to fix that problem. Altutude, ambient temp, humidity, bottle psi, other engine mods, and probley every thing else in the world can and most likely will efect the air fuel ratio. My hope with this post is to get new bottle guys to check their a/f and not just go off what the paper says or your unique situation could give you good reason to build it faster sooner. (Building it faster sooner is my way of saying destroyed engine, its a positive way to look at the negative things)
Give the guys at NX a call, they are very good at what they do.
Give the guys at NX a call, they are very good at what they do. Air fuel ratio is the thing to look at when getting a wet NOS shot on the tuning side and you are the living proof!
Your lid will be giving more hp when your engine is gonna need more air with a cam/heads/exhaust. Its a must with mods but with stock engine, it doesnt show a big hp gain.
Your lid will be giving more hp when your engine is gonna need more air with a cam/heads/exhaust. Its a must with mods but with stock engine, it doesnt show a big hp gain.
When we did mine we started the jetting small (50 on each stage, tested individually) to see how the jetting trended and ensure the system worked as it should, we upped the shot and followed the trend. Less risk than jumping right into a 150.
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You run it richer/fatter to have a safer AF to run a power adder. You are looking to avoid detonation.
Also, you want to make sure your fuel system is up to snuff, whether it's injector size (for dry), and what power level your fuel pump can support.
In my case, my Camaro dynos (unlocked T400) like 420RWHP NA, and 550RWHP with a 150 shot. I don't have enough fuel system probably to spray both kits safely, unless I add a boost-a-pump voltage blaster.
Also, you want to make sure your fuel system is up to snuff, whether it's injector size (for dry), and what power level your fuel pump can support.
In my case, my Camaro dynos (unlocked T400) like 420RWHP NA, and 550RWHP with a 150 shot. I don't have enough fuel system probably to spray both kits safely, unless I add a boost-a-pump voltage blaster.
Teching In
Joined: Dec 2007
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From: Bradenton, FL
That makes complete sense. Less timing, more fuel, and higher octane decrease the chances of detonation. So would 14.7:1 be "Unsafe" on a nitrous assisted engine? What about an N/A engine?
Agh old thread.
14:1 would be unsafe for nitrous, there would be no room for possible detonation.
Assuming a Dynojet, for NA folks might target 12.x:1 assuming that on the street the car would be more in the 13.x:1 range. So carrying this out a bit, if a tuner suggests 11.x:1 on the dyno for nitrous, and it's not a load-based dyno, it's their assumption that the car will run leaner, like 12.x:1 on the track and on the street under full load.
14:1 would be unsafe for nitrous, there would be no room for possible detonation.
Assuming a Dynojet, for NA folks might target 12.x:1 assuming that on the street the car would be more in the 13.x:1 range. So carrying this out a bit, if a tuner suggests 11.x:1 on the dyno for nitrous, and it's not a load-based dyno, it's their assumption that the car will run leaner, like 12.x:1 on the track and on the street under full load.
Joined: May 2002
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From: windsor, ont. canada - Home of the fastest LT1 6spd.
read your plugs!!!! don't trust a gauge, until you read your plugs. then and only then will you know how accurate the gauge is. that is my .02 i spray twice that, so i am a little critical about these things, but...once you read ALL of your plugs on a particular tuneup, and get it right, you know whatever your a/f readings are actually reflecting. i hope that makes sense.
i spray twice that, so i am a little critical about these things, but...once you read ALL of your plugs on a particular tuneup, and get it right, you know whatever your a/f readings are actually reflecting. i hope that makes sense. 
I had the same problem when I dyno'd with my NX system (with Daves plate) I had to move all the way up to 41 jets to get 11.5-11.8 with 1180 PSI, (and I have a racetronics fuel pump!) but I later found a "slightly" crimped fuel line from the fuel supply to the solinoid
By the way, I picked up 151hp (412-563) with the 150 jets and full bottle at 1180psi
So with that being said, how rich does it get before you wash the cylinders and blow apart a piston from fuel underneath a ring, and why have I been told in the past that - lean is mean. Is it strictly a safety standpoint to run 12.5-13.0 on the strip/street even though more power is supposedly to be had going closer to stoich and possibly beyond?
Even though this thread came from the depths of hell I figured since the question had been brought up I'd post here instead of making another thread.
Even though this thread came from the depths of hell I figured since the question had been brought up I'd post here instead of making another thread.
So with that being said, how rich does it get before you wash the cylinders and blow apart a piston from fuel underneath a ring, and why have I been told in the past that - lean is mean. Is it strictly a safety standpoint to run 12.5-13.0 on the strip/street even though more power is supposedly to be had going closer to stoich and possibly beyond?
Even though this thread came from the depths of hell I figured since the question had been brought up I'd post here instead of making another thread.
Even though this thread came from the depths of hell I figured since the question had been brought up I'd post here instead of making another thread.
As for the lean is mean that doesn't just entail going as lean as possible. With anything there is a point of dimishing returns. In the case of a motor the return could be a bunch of dead pistons if you go to lean. I would never run a pump gas N/A motor leaner than 12.5. For the few extra HP the risk just isn't worth it, especially with the changes in pump gas from day to day, pump to pump.
I would stay within the time tested ranges, but if you decide to go leaner keep in mind the outcome could be expensive.
I also brought it up because I just tossed a WB on the vehicle this weekend and saw how far out of whack my factory tune really is. And at 15-16 AFR at WOT I did just splurge and pick up a copy of HPTuners.