ummm, if you were spraying at wot and just cut the spark, wouldn't you expect a pretty loud bang when it hit the cats? or maybe melt them?
I agree. I think BTLFED mistyped. I think we're all saying that it looks like spark is still there and only the injectors are turned off.
So can someone give me a short blurb on the fuel/afr issue, because I don't have a clue. I'm just speculating that the mix is very different (like a lot) when you shut off the injectors but continue to spray a wet shot. Jeff said he was seeing a spike to maybe 12.8:1 during this time. Is 12.8:1 without nitrous the same as 12.8:1 with nitrous? I mean, I'm thinking that the sensor reads mainly O2? If it's air and gas then most of the air that is not O2 is not flammable right? If the sensor is not reading the nitrous, which is flammable, is it the same reading? Even if the the sensor is reading some or all of the nitrous a 12.8:1 mix of air and gasoline will not burn the same as a 12.8:1 mix of air, gasoline, and nitrous? So the question here is: Is knock/detonation a concern when the charge has a greater proportion of nitrous and smaller proportion of gas? Your ignition timing would be the same as before the injectors cut off. I understand that this may not be a HUGE difference but I'm wondering if it could be significant if you're pushing the limits.
Dave(Quick) yes I mistyped but you guys got it figured out. Here is what I can answer about your fuel/N20 mixture. My A/f is 11.7 on my N20 tune when I dont spray, if I spray my AF stays at 11.7. So that means that I am spraying just enough fuel for the amount of extra oxygen(N20) Im pumping into the motor. Now if you remove fuel from the injectors cutting off but engine still spinning from 6200 down to 4200, your going to be lean no matter what you do because the engine(Air Pump) is still bringing the air in. I wont be home to drive the Jeep for 3 weeks but I still have a light 1/2 way wired to show when my kit(Solenoids open) is on. I will complete the dummy light install and verify for sure that the kit sprays the entire duration of the shift. It might only be spraying as the shift comes to a completion and not as the rpms are still falling.(Please tell me that made sense) :laugh: Jeff- I dont suppose you have ever taken a trans apart have you ? Do we have a valvebody where we can put a stiffer spring or something to make the shift happen faster. Im guessing its impossible to cut duration down with the computer, even though this is usually the wrong way of making a shift happen faster. Go info guys, keep the wheels turning:headspin:
Well yes, that all made sense. (...but if your light is only 1/2 wired it's probably only going to be on 1/2 as much as it should :wacko::grin I'm still not clear though. I do understand why it would go leaner when the injectors cut off. No problem there. Not sure how to describe this... You're spraying into the manifold. At the cylinder (fixed volume) it sucks in whatever is in the manifold and some fuel is added by the injector. The wideband detects O2. You said you read 11.7:1 with or without the spray. I'm trying to figure that out and the implication of that. The spray must be displacing air (some of which is Oxygen). The fact that you're spraying fuel (adding to that of the injectors) with the nitrous and the fact that your a/f (O2 measurement) doesn't change implies that the nitrous is adding oxygen that is measured by the sensor. So if you sprayed a dry shot there would be more oxygen molecules in the mix than regular air would contain. Is this correct? That might sort of explain why your a/f reading is the same with or without spray.That may or may not have anything to do with anything but I was wondering how the nitrous effects the sensor reading. So you might tune an engine without spray to run 12.8 Why do you tune for 11.7 if you're going to spray? You're adding a whole lot of fuel (and maybe pulling timing) when you spray for some reason. On the non-spray engine going from 12.8 to 13.8 (under WOT load) is not good. Maybe not critical, but not good? If you go from 11.7 to 12.7 while spraying just how "not good" is it? Is it about the same "not good" as above? or would it be worse because of the way that nitrous burns.
There are three points. First, nitrous oxide is comprised of 2 parts nitrogen and one part oxygen (36% oxygen by weight). When the nitrous oxide is heated to approximately 572F (on compression stroke), it breaks down and releases its load of extra oxygen, However, it is not this oxygen alone which creates additional power, but the ability of this oxygen to burn more fuel. By burning more fuel, higher cylinder pressures are created and this is where most of the additional power is realized. Secondly, as pressurized nitrous oxide is injected into the intake manifold, it changes from a liquid to a gas (boils). This boiling affect reduces the temperature of the nitrous to minus 127 Degrees F. This "cooling affect" in turn significantly reduces intake charge temperatures by approximately 60-75 Degrees F. This also helps create additional power. A general rule of thumb: For every 10 Degrees F. reduction in intake charge temperature, a 1% increase in power will be realized. Example: A 350 HP engine with an intake temperature drop of 70 Degrees F, would gain approximately 25 HP on the cooling affect alone. The third point, the nitrogen that was also released during the compression stroke performs an important role. Nitrogen acts to "buff or damper" the increased cylinder pressures leading to a controlled combustion process and better slower heat release
Ahhhhh, that was great! So you're adding fuel because you can burn more fuel with the added oxygen. Cooler air charge is a bonus -- is this is why you use nitrous instead of spraying oxygen? or is it that liquid oxygen is not pratical. So why do you want a richer a/f when spraying? The sensor is in the exhaust after combustion so why wouldn't you want about the same percentage of fuel burned?
Dave, Im using a wet shot(both Fuel and N20) I was just letting you know that my Nitrous tune runs a 11.7 A/F ratio without me adding any fuel via the fogger. When I spray the wetshot the a/f ratio stays at 11.7, in other words Im adding just enough fuel via the wet shot to compensate for the amount of nitrous Im spraying. If my a/f was let say 12.7 I would be adding less fuel than needed for the amount of N20 I add. On the other side, if my af ratio dropped to 10.7 I would be adding more fuel than is needed for the volume of nitrous I was adding. Did that make sense ? The reason the light is only 1/2 hooked is because 1/2 way thru the install I decided it was needed:shifty: On the bright side, I did the hardest 1/2, wiring it inside and thru the firewall:smart: The reason you want to run more fuel is to keep cylinder pressures down. Just as running NA, the leaner you are the higher your chances are of detonation. Detonation at higher power levels or under Nitrous/Forced induction leads to blocken pistons or thrown rods. Lean a/f ratios leads to melt down, its all a very fine line and you know when you cross it. Lean is mean but safe lets you race another day
....I too would like a small mechanical tranny mod to make it shift a little harder, and maybe clamp a little more. I think BuilderBill tried a shift kit, and said benefits were negligible? On the nitrous notes........... I recently simply started blipping the manual "button" in between shifts, and it honestly seems to work better for me. I don't think with this much hp & tq, not to mention the huge load of these juice boxes... ...that spraying through the shifts is good for them. My theory is also why the nitrous truck are faster right now than the turbo, supercharged.... heavily motored truck is..... They are under constant load.....and the computer, TCM, tranny nanny whatever is getting a constant high torque reading.... but with the juice, and especially letting off and on, when the computer "looks" at everything right before the shifts, and we are letting off....it does it's business as usual, thereby letting us TRICK the truck into running faster???? make sense???
