Tuning with wideband for NOS

CivicVTi · Post by **CivicVTi** » Sat Mar 06, 2004 6:01 pm

I've heard that when using NOS, widebands are not accurate and show a different A/F ratio than actual. What should my target A/F ratio be with NOS?

RMS · Post by **RMS** » Sat Mar 06, 2004 7:50 pm

who said that, and what was their reasoning?

CivicVTi · Post by **CivicVTi** » Tue Mar 09, 2004 1:04 am

Can't remember who said it or where I've read it. It's been a long time. What is important to know is whether this is true or not.
The reasoning is that the amount of oxygen increases in a given amount of air with NOS and thus the stoich A/F ratio decreases. So you have to run much richer to compensate. Around 11.5:1 or even less for a large shot.

RMS · Post by **RMS** » Tue Mar 09, 2004 10:14 am

the amount of fuel must be increased, but the way the air/fuel ratio works is the same (you are adding an oxidizer, not an oxygen-bearing fuel like nitrometh). tuning at 11-11.5 is a good target nonetheless. n2o makes max torque as soon as you engage it...that makes for high cylinder pressure at fairly low rpm, and with a much higher possibility of detonation. rich, timing retard, and good fuel are the answer.

jbbauer · Post by **jbbauer** » Sat Apr 24, 2004 11:38 pm

RMS wrote:who said that, and what was their reasoning?

I've attached below a quote from a pinned www.clubsi.com nitrous junkies forumn as to your question above... BTW have either of you tuned for Nitrous with hondata's "Nitrous" tab. I'm thinking of going nitrous and wondered if you are using Hondata to arm nitrous and adjust fuel enrichment based on nitrous being armed

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From Payntech's post I was reading a post from a month ago about this that was turning into a pissing contest. So, I decided to start a new post. Tuning with an O2 sensor with nitrous is not as straight forward as tuning an NA car or a boosted car. This is mainly due to the fact that the percentage of oxygen per volume is higher with nitrous when compared to air. If you were to run the engine on straight nitrous your A/F would be very rich relative to an engine with the same volume of straight air. You must always remember that most A/F meters are calibrated for air and gasoline. A stochiometric mixture of 14.7 is only for gasoline with air at STP (Standard Temperature (60 deg F) and Pressure (29.92)). For instance, an engine in Denver can run a much leaner A/F ratio at both cruise (peak fuel economy and WOT due to the amount of oxygen in the air per volume. Stochiometric A/F ratios for other fuel/air combinations are different. Some A/F meters like the ECM lambda pro that we use for tuning have different settings for different fuels. We can configure the meter to read in Gas, Alcohol, Propane, or Diesel. Getting back to the subject at hand. When using nitrous you must always look at the ratio of motor power to nitrous power. For example, a 150 hp and a 300 hp engine will not require the same A/F with the same nitrous shot. Let say we are using a 75 hp shot on both, the 150 bhp engine would have a 2:1 ratio and the 300 bhp engine would have a 4:1 ratio. Using some basic assumptions for the example... the 150 bhp engine would r
un around 11:1 one nitrous and would want probably want 2 deg or more timing taken out of the engine. The 300 bhp engine would want to run around 11.8:1 and probably not need little if any retard. A good real word example is my hatchback with a B16A that makes around 195 bhp (160 whp) NA and around 270 bhp (220 whp) with a 75 shot of nitrous. We played with it on the dyno and it was happy around 11.0-11.2 A/F (Gasoline) with 2 degrees of timing pulled. I have also had 300 bhp V8 cars that like about the same tune with a 150 shot. The only other thing that I would like to add that is also mentioned in the FAQ section is that all kits are not the same and different manufactures rate their kits different ways. You must also always know what your bottle pressure is when tuning. I hope this helps with this issue. And as for the pissing contest most engines will make best power between 12:1 and 13.5:1 depending the combustion efficiency of the engine. ITR1416 is right in that an engine is not 100% efficient and needs to saturate the combustion with excess fuel in order to get the maximum burn. jon3k is right in that if you could produce an engine that could create a 100% burn at WOT, it would want a 14.7:1 A/F. Although jon3k is wrong in thinking that just because the engine is not showing signs of detonation under a leaner mixture that it is making better power. Honda will run very lean with out detonation, although they usually make best power around 13:1 A/F.

RMS · Post by **RMS** » Mon Apr 26, 2004 5:18 pm

we recently dynoed a daily driver 2 liter: pistons and rods but no sleeves. 353whp/300torque all juice

. tuned on c16 to low 11:1AF. while max hp wasn't our target reliability was. he has used hundreds of pounds of juice without a failure.

air/fuel ratio is air fuel ratio, wether you are at sealevel or in space. it is a chemical reaction. what you can get away with in your engine is dependant on atmospheric conditions, but the wide band doesn't know the difference (it is true that for different fuels the wide band must be adjusted, but n2o is an oxidizer not a fuel)

hondata's n2o tab doesn't allow enough enrichment for a large shot...i think this is a glitch that can be fixed, though. hondata will support 2-stage control soon, too!

CivicVTi · Post by **CivicVTi** » Tue Apr 27, 2004 5:30 am

Define 'large shot' please!

RMS · Post by **RMS** » Tue Apr 27, 2004 9:33 am

we tuned a 42 n2o jet last week using 55#/hr injectors. it required the fuel value to be maxed: 999. Derek fixed that in the next release though (as i found our this moring

) so this isn't an issue anymore.

CivicVTi · Post by **CivicVTi** » Wed Apr 28, 2004 1:51 am

You mean 0.042" jet? Isn't this supposed to give an 80hp shot?

RMS · Post by **RMS** » Wed Apr 28, 2004 12:57 pm

a 42 n2o jet usually gives about 60whp+/-10. we have dynoed LOTS of juiced cars, and i've kept track of hp increases at the wheels.

but yes, 60whp is about 75hp at the crank...very close to the 80hp claimed. remember, too, the hp gain is different at every rpm so it depends on wether you are interested in the peak gain or the max gain.