Yes the air to fuel ratio would definitly be different, but i don't think that would matter. The O2 sensor is not measureing the the mixture before combustion, its measureing the results after combustion.

For a stoichiometric mixture the composition after combustion should be the same regardless of the fuel and its appropriate ratio.

I think that if your running it all the time you'd just need to start from scratch and create a tune for it.

-brent

 

Well, I'm not sure what the AF ratio would be with the mixture, but I do know the stoich AF ratio for nitro is close to 1.8:1- NOWHERE near gasoline's 14.7:1. Also, as somebody pointed out, the nitro would eventually dissolve the o-rings in the fuel system. It even dissolves the o-rings in our oil system over time (because of the amount of nitro that ends up in the oil).

Kevin-
The R/C cars are built for nitro for one, and from what I've been told, the % listed on the fuel for those is not nitro:methanol. It is actually much less if you figure it like that. DISCLAIMER: I do not know that for a fact, someone just told me that.

I imagine the reason the scooter blew up is that the nitro didn't mix with the gasoline and it all of a sudden got 100% nitro in the carb and it turned the motor internals into paperweights.

 

As a simplification, if the PCM is "adding fuel" in Cell 15 in closed loop, its going to continue adding the fuel in PE mode using the BLM's in Cell 15. If the PCM was "subtracting fuel" in Cell 15 in closed loop, it will default to Cell 18 and lock the BLM's at 128 in PE mode.
This has nothing to do with A/F ratio or O2 sensors. This is taken care of by the MAF sensor, or by calculations made based on the MAP and IAT readings in a speed-density system. This isn't "learning"... this is simple data processing - it sees a different air mass flow and it adds the proportional amount of fuel.

Are you saying that you are running this "nitro" additive all the time? I'm not sure that the O2 sensor even responds as indicated in the post by 94formulabz.... The O2 sensor "infers" A/F ratio based on the residual O2 in the exhaust stream. Does a motor running on a fuel other than gasoline produce the same residual O2 levels as gasoline when the A/F ratio is correct to prevent detonation? I don't think so.... but Rich and I have debated this issure with regard to nitrous, without resolution. My point with nitrous is that you are combining 2 different combustion processes... At peak power, you are running the air/gasoline portion at 15% richer than stoichiometric (12.8 vs. 14.7:1), and the nitrous/fuel portion is typically running 35-40% in excess of stoichiometric (7:1 or 6:1 vs. 9.6:1). Does this combined combustion process produce exactly the same partial pressure of O2 in the exhaust gas as a strictly air/gasoline process? Wouldn't it be possible that O2 partial pressure would be even more disturbed by combining two processes... one with a 14.7:1 and the other at 1.7:1.

I honestly do not know whether the O2 sensor will read correctly, unless it knows the fuel stoichiometry... I believe a wideband works on units of stoichiometry (lambda) rather than absolute A/F ratio... but when you tune an alcohol engine do you have to calibrate the wideband for the fuel?

In any case, the issue is not so much the adaptive learning of the PCM/O2 sensor feedback in closed loop.... the real issue would be establishing the proper target A/F ratios for PE mode. That would take care of the need for a possibly much richer A/F ratio at WOT.... not relying on the adaptive learning.

 

Fred: I still asking around to try to find the answer to the question re: conventional O2 sensors and nitROUS. Obviously, the same issues would apply to a nitRO/gas mixture. As you point out, we don't know how to measure teh AF ratio or what it should be. It would take time, money, and probably more than a few motors to figure it out. The info is probably out there. But I don't even know anyone to start asking. I did talk to a guy at Electromotive who basically supported your point that a convention O2 sesnor is not accurate when running nitROUS, that's as close as I have come.

Rich Krause

 

I know this is under a bit different situation, but..... a few years ago i inquired about using nitro in my GN over on the turbo buick boards. I had an alcohol injection system for 100% enthanol mix already on the car and set to inject above 15psi boost. The plan was to switch the pump in the kit to a methanol compatible pump and run pure meth with nitro mixed into it (~5-10% by volume). I can't remember all the details and the old thread has fallen off the server so.... basically some of the bigger name guys [like Jason Cramer, Carl Ijames(engineer i think), etc] said that i would have problems keeping my O2s under control when the system started to inject since nitro is a "heavy" fuel and also would require different timing tables. Under boost it would give huge gains though. If i had an aftermarket computer to tune it for the times when the injection is on or off it probably would've been more feasible. The end result of the discussion was that the mix i intended to use would give gains like that of a healthy nitrous shot but would involve much more trouble to use and set up. So in light of that, i just left the idea alone and stayed with ethanol. If you have a dedicated race car nitro would probably be the hot ticket, but for everything else nitrous would be better. Just my $.02

 

I have often wondered about using nirtomethane in a road car, after research I realised the basics involved.

As someone said earlier about using it as the wet side of a nitrous kit, if you ran two additional fuel cells in your car, one for additional petrol and one for nitro, they could be premixed in the correct ratios by a couple of well chosen fuel pumps and then shot into the intake by a 9th injector by way of a solenoid with a dash mounted switch.

By using this method you have horsepower on tap and one gallon of the nitro would last you a long time. No neat nitro hitting the chambers as the correct amount of additional fuel would be added.

Something to think about, anyone else think this might work out?

 

I was in a rush for work, but thats exactly what i was trying to get at by my statement that it was measureing the results after combustion, it's measureing the partial pressure of the residual o2 compared to the atmosphere.

Thats a good point that i didn't have time to mention, but don't know the answer to either. I have some emmisions residuals data for different fuels, but it doens't list the o2 residuals Its quite possible with the increased burn time there would be considerably more(or less) o2 residuals at an appropriate AF ratio for that fuel blend. However, he was only talking about trying to add about 30 hp, so its not quite as drastic as someting like Fred's nitrous motor.

Considering the fact that he is going to be blending this fuel in his garage, its not like he is going to find any information on a target AF ratio for his particluar blend.

-brent

 

Nitromethaine will not increase octain it will decrease it. Nitro burns much more violently than gas. Thats why top fuel runs them so rich. So the engines can live. Infact the engines are so rich that they are on the verge of hydrolock.

 

The AFR for 90% nitro will be any where between .5:1 up to 2:1 depending but Im not looking to run anywhere near that amount. I think what Brent is saying about the AFR not mattering makes sence, at least in closed loop operation. The o2's arent looking for a specfic target, they are comparing. If the PCM sees that more fuel is required it will add it regardless of its actual ratio.

The after combustion residual should not change except for the addition of nitric acid. In small amounts nitric acid should not harm or effect the o2's. This is only information I have read and have no first hand experience.

Fred, I see what you are saying about having two different combustion proceses but Im not sure the end result would be any different because in effect just the ratios change. More oxygen is helping burn more fuel.

Josh, your friend is somewhat correct in that the ratio isnt nitro:methanol. A combination of lubricants is also included. The nitro content in % is still there based on total volume of the container.

Brent, finding the correct AFR is next to impossible for a certin blend its strictly trial and error or should I say a lot of plug reading. All of the information I have found for running nitro in gas is based on carb induction and is hard to translate it to EFI.

 

Nitromethane does not have an octane rating. So actually it would not change the octane of the mixture. Because it is violent is not why we run them so rich. We have to run them that rich because the cylinders will not fire with less fuel. That is one reason why you see cars 'drop holes'. You are right about the hydrolocking, though.

 

Ahhh, that makes sense. Since nitromethane has a low flash point, it would want to predetonate under compression more than the regular fuel around it.

What about this:

Instead of using it as a dedicated wet side for a nitrous system; just use it by yourself. Have a gallon gas tank in back, a alcohol fuel solenoid and a sprayer hooked up as a 9th injector. Take a 10-25% nitromethane and corresponding number methanol mixture and spray that? It'd take awhile to figure out the math and what jets to use.

 

Nitropropane appears to be the chemical you should add, it mixes with gasoline, nitromethane does not. Hot Rod magazine has done some excellent testing with nitro on a couple of engines, search their website.

They had a 388 test engine that made 25 additional hp on race gas with 10% nitropropane. They used race gas to control the wild detonation. But, as mentioned in other posts there are many problems created by leaving nitro in the fuel system.

As far as tuning goes they suggested one jet size on all four corners per each percent nitro added. With LT1 edit you should easily be able to add fuel, and/or the stock WOT programming is so overly rich small percentages of nitro may require no change. Although Hot Rod's experience shows that a small percentage of nitro isn't worth the effort.

I have no idea how the o2s will contol closed loop operation.

Another excellent source of information is Hot Rod's Anvil engine series, search "anvil" on their site. This engine ran on methanol, which is a little different, but it still provides some excellent insite.

 

we have expereimented with nitro in race engines. only about 5% max and there was No gain to be had.

 

I always hate to leave no alternative, so if it's just 50 hp you are looking for, here's what I did, almost (I made my own).

Get a purge or powershot solenoid and a used nitrous tank. Hook the solenoid to the tank and run poly line to the intake track. Use a micro switch on the pedal and away you go. Insert a .037" orifice for a jet (verify for yourself, I can't remember). The stock programming and knock sensor will do the rest. I can't quite remember but I think I dry sprayed 80 hp without problem.

 

Smokey Unik (sp?) wrote an article on using a 5% or so nitro mix with gasoline in roundy round engines resulting in a little edge over the competition. What didn't he do to get a little edge over the competition?

Perhaps the increase was to small to measure in your application, 93z286speed.

You'd really have to average several before and average several after runs to measure that small a delta.