nitrous only tuning...

[mgrotel]

what is a safe target a/f when tuning just for nitrous? i am very rich as of now and will be pulling timing, but just curious on a safe a/f to target. will pull about 1deg per 75 shot

thanks

[Accord2nrz]

A safe target to shoot for is around 13 or 12:1. This will give you alittle bit of safety margin in case an unknown variable creeps into your tune. How much are you spraying and how much boost are you pushing? I would trim the a/f before adjusting the timing. A knock light will help you adjust the timing effectively.

[mgrotel]

A safe target to shoot for is around 13 or 12:1. This will give you alittle bit of safety margin in case an unknown variable creeps into your tune. How much are you spraying and how much boost are you pushing? I would trim the a/f before adjusting the timing. A knock light will help you adjust the timing effectively.

ok, no boost, strictly nitrous, on a 100 shot now with just colder plugs and no timing pulled. stepping up to a 150 this weekend, will pull timing and im adding water/meth injection as well. without the meth injection, i was thinking to target 11.8 a/f and with the meth injection, i was thinking to target 12.5-13 a/f. will pull 1 deg of timing per 50 shot or so to start off.

i was under the impression that i would adjust the a/f to my target first, then advance timing slowly till i get knock, once some knock, then pull timing back. is that not the correct way?

thanks

[Turbineguy]

I would not add water/meth if your running nitrous already. The nitrous already cools the intake charge beyond what the water/meth could ever do and you are effectively running a dual fuel setup and a dual power adder setup as well. The main reason for running water/meth is the antidetonant properties of the water. The methanol is added in order to bring the combustable mass back up closer to straight gasoline to account for the fuel displaced by the water. The alcohol also has the ability to absorb a fair bit of heat as well. Water can be absorbed by air up to 100% saturation. Alcohol can also be absorbed by the air up to 100% but Daltons law of partial pressure states that the 100% absorbtion of each is mutually exclusive so a water/methanol mix allows for more heat absorbtion than straight water or straight alcohol.

Nitrous works through the same principal of vaporization. Alot of heat is absorbed when the nitrous goes from a liquid to a gas. Along with this it brings alot of oxygen to the party but is not in and of itself combustable. It's strictly an oxydizer for whatever fuel it's used with. It has 66% nitrogen content and this is done for a reason. The nitrogen acts as an octane booster in the sense that it slows or inhibits the oxydation process to a controllable level. There's a reason why pure oxygen isn't used and thats because it causes uncontrollable acceleration of combustion for the purposes of use in an engine.

The AFRs tossed around so far make me cringe somewhat. Running 13:1 under full load with strictly a knock sensor is asking for burned rings or holes in pistons. If your running nitrous you need to have an EGT gauge to monitor temps. You also need to have a wideband to tune the AFRs since all the extra oxygen in the cylinders will cause a lean spike in a hurry if you have any fueling issues. Ideally you should target what you would normally look for running forced induction if not a little richer. Get a trend on your EGT readings and begin the tuning process. I can't tell you to do timing or fuel first since some engines like a little lean with less timing and some like a little rich with more timing. If you press me for an answer to this one work with fueling first and timing last. Once you start getting it closer to optimal you can fiddle with both until you find the balance between fuel, timing and EGT. I would consider 1600* on the EGT as the ceiling if the probe is mounted immediately after the exhaust port in the head less if it's in the collector.

[mgrotel]

ok, i am melting my number 4 plug fairly regularly, so that tells me i have preignition, since i ruled out a lean condition because my wideband says im crazy rich (9.5-10.5). preignition, as i understand it, comes from fuel igniting before the cycle, likely from too advanced timing or just very hot engine temps, or a combination. my understanding is that water/meth will help with both of those. the intake charge with nitrous is cold, but the burn is very hot.

ive also read that when adding water/meth, you can safely target a much higher a/f ratio and be at the same safety level.

is any of this logic incorrect?

it is not uncommon for nitrous users to add water/meth to avoid detonation and keep things cool.

[Turbineguy]

Your wideband gives a collective reading of all cylinders. You may still have a lean issue in #4. The only way to know would be to take individual cylinder readings but thats obviously cost prohibitive for most of us. Are you running a single nozzle or multiple? It's also possible you may have uneven distribution causing the problem. Take a look at coolant routing through the head/block. Your particular engine may be prone to run that cylinder hotter than the others.

[mgrotel]

single nozzle, and i just did some intake work to it so the air distribution should be better now if that was the cause. ive considered removing that injector and having it bench flow tested, but havent done that yet. i think between the intake work, pulled timing, and meth/water injection, hopefully the problem is resolved. we will see i guess.

[mgrotel]

what about a target a/f ratio for just an n/a tune? i have a spare map that i want to mess with just an n/a tune. thanks

[Accord2nrz]

The AFRs tossed around so far make me cringe somewhat. Running 13:1 under full load with strictly a knock sensor is asking for burned rings or holes in pistons. .

Hey I thought that you want to shoot for anywhere between 12 - 13:1 when picking a target a/f? Have I been misinformed or is this different for every application?

With regards to the target map for the na tune. It's doable but if you're running obd2 its going to be tough fighting that closed loop system if your staying na. If your tuning under open loop its exponentially easier.

[mgrotel]

tuning with a utec

[Turbineguy]

Hey I thought that you want to shoot for anywhere between 12 - 13:1 when picking a target a/f? Have I been misinformed or is this different for every application?

With regards to the target map for the na tune. It's doable but if you're running obd2 its going to be tough fighting that closed loop system if your staying na. If your tuning under open loop its exponentially easier.

It's application dependant. Target AFR is what needs to be worked towards starting from the initial process. I run 11.2 at 22psi but someone else with a different engine type and running a supercharger might look for 12:1 at 9psi. My engine is one of the ones that tends to like rich AFRs under boost. It also makes more power by adding boost rather than timing. The reason I said cringe is due to how finicky nitrous is and working the fueling that lean under load on the giggle gas leaves no room for fueling errors while tuning. If it ends up at 12-13:1 and it's happy and makes good power then thats where it needs to be. I would just start out pretty rich and go up rather than lean and go down.

[Accord2nrz]

That would make sense, honda motors prefer to be slightly lean for optimum power but umm yea I dont see myself shooting for anything lean.