Actually, reading up on stuff, the AFR in a nitrous motor is somewhat dynamic. For a 50 shot you can pretty much just plug it in, as long as you are still running stock compression and cams. If you car is tuned NA, then youll be ok on the juice.
get a fuel management system like vafc or hondata. i have a feeling youll want that anyways to retard your timing since i dont think youll be using that low of a shot for too much longer
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Those a/f ratios are way lean!! From my mechanic who builds 9 sec ls1 cars he said the optimum a/f ratio N/A should be about 12.7:1 and with Nitrous about 11.6:1
93 Honda Prelude SR-V/ VTEC 5-Speed Milano Red 92,000 miles
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Every nitrous kit I used, wet or dry, set up as per instructions by manufacturer, fell within those guidelines. I never had a bit of detonation with 50, 60, 75, 100 or even the 150 DP.
Here is an article by Barry Grant (runs Nitrous works)
"One of the most important aspects of keeping an engine healthy when using nitrous oxide is to ensure it operates at the proper air/fuel ratio. Running too lean can cause detonation, resulting in damaged engine parts. Running too rich can also harm performance and destroy engine parts, too. At NitrousWorks we flow-test our systems to calibrate them. Once calibrated, they'll inject the proper amount of fuel with the nitrous system to maintain the correct air/fuel ratio. We also ensure the amount of nitrous that the system is engineered to dispense does not exceed that which the intake system can flow. This prevents fuel ‘puddling’ or distribution problems.
A further advantage of a ‘Wet’ system is that it lends itself to fine-tuning. By adjusting the fuel pressure and fuel orifice, either up or down from the baseline, the system's performance can be further improved. In addition, on a direct-port nitrous system each cylinder can be fine tuned to optimize performance and overcome rich or lean cylinders that the engine may have naturally aspirated.
A ‘Dry’ nitrous system relies on the vehicle's computer system sensing that the engine is, say, running too lean and adding additional fuel. Most stock computer systems were not designed for this purpose, and may have difficulty in
The internal-combustion engine is basically a large air pump and its ability to pump air is one of the factors, which determine how much power it can produce. Air contains oxygen and by drawing more oxygen into the combustion chamber, more power will be produced. In order to achieve efficient combustion, the air needs to be mixed with fuel in the correct ratio. The stoichiometric (chemically correct) ratio is for basic gasoline is 14.7 parts air to 1 part of fuel.
Greater quantities of oxygen can be drawn into the combustion chamber by simply introducing nitrous oxide. By weight, Nitrous contains 36% oxygen while air has only 23%. A charge of nitrous oxide is capable of burning much more fuel than the equivalent amount of air.
Because nitrous is more oxygen-rich than air, the recommended air fuel ratio becomes 9.5 parts of nitrous to 1 part of fuel (9.5:1). That means when oxygen-rich nitrous is introduced additional fuel must also be supplied in order to maintain the optimum ratioWithout the additional fuel the mixture would become dangerously lean - circumstances that will almost always lead to severe and expensive damage. "
Here an article from Marlin Davis, from "Hot Rod". This one explains the dynamic AFR due to displacement differences.
"Air/Fuel Ratio
With bottle pressure under control, the rest of the tune-up can be established. "Tuning for nitrous is no different than tuning any other power adder," says Nitrous Express. "When the air/fuel ratio is correct, the results are great; when the ratio is incorrect, the results are not so great." As to what constitutes correct A/F ratio, most recommend running slightly rich (generally, between 11.5-12.5:1), but agreement on this point is by no means universal, and some sources recommend going even richer under some circumstances. Musi believes in tailoring A/F ratios to the power level: "At 250 hp and under, you can run the same as the engine's air/fuel ratio. But at 450-500 hp I run 11.5:1 as a safety factor. Nitrous injection is not sequential like EFI, so when the valves are closed, the nitrous stacks up in the ports, runners, and plenum. The mixture may no longer be totally homogeneous."
Prock advocates adjusting the exact air/fuel ratio according to engine displacement. A 400hp kit delivers about the same 400hp boost on a 400ci engine as it does on a 600ci engine, but because the larger engine has much more total cylinder volume, the mass fraction of nitrous inducted into that engine as a proportion of that volume is less, so it is more easily absorbed. According to Prock, the big engine may be happy with an 11.5:1 A/F ratio, but you may have to go as rich as 10:1 on the smaller motor.
Speedtech notes that finding the exact A/F ratio to run can be somewhat tricky because nitrous carries its own oxygen. The ratio in effect becomes a variable of how much nitrous you put into the engine. Although exact recommendations vary among racers, Speedtech has found the following equation to work well as a starting point: Target A/F Ratio = [(engine hp / total hp) x 13] + [(nitrous hp / total hp) x 7] Actual A/F ratio tuning is accomplished with either a fairly costly high-end, wideband oxygen sensor, or (more commonly) by reading the spark plugs. Usually a light tan porcelain color on the plug is an indicator of the right timing. You need to read all eight plugs. If tuning with a wideband O2, ZEX cautions that the higher the ratio of nitrous power to engine power, the less accurate the O2 sensor will be. That's why most hard-core guys look at the plugs and exhaust-gas temperatures. Plugs don't lie."
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