What is this suppost to mean, doesn't make sence, what your saying is the extra fuel does not remain liguid, sence when does it remain liguid in any engine, NA or with power adders, liguid doesn't burn, its the vapors, fuel creates these vapors, thats what accually ignites, not the liguid.

 

lol Q, not G. Liquid (sorry had to).

If you run too rich, it actually can dump enough fuel in that it doesn't evaporate. That's how you get the "ring wash" he mentioned. And I don't know the physics behind lighting gas on fire, but I'd think that if liquid gas didn't burn, it wouldn't react to an open flame. What I mean is, I don't think that the vapors are what is burning nanometers above the liquid fuel. BUT it could very well be the case, and if so that's kind nifty

I'm relieved to know that I didn't have my AFR numbers wrong. And +1 on too lean can cause over heated parts and failure. We just pulled a spark plug form a Caravan that was running so lean that it melted the electrode off the spark plug and the porcelain was white as new.

 

LOL 13.8 is not LEAN!!!!

Yes it is...

Stoic is 14.7 as was mentioned before but what you have to understand is stoic is the point of least emissions not most power.

And Stoich is for cruise with NO Load on the motor...


Your AFR was about 7% richer than stock which is pretty damn good. Won't be pig rich and hurting your fuel mileage but will make more power than stoic. [/QUOTE]

7% richer than stock? Nope,,Stock all LT1's and even the LS1's were in the low 12's, I.E. 12.1, 12.3 ect, thats why all the cars from the factory with white paint jobs had black build up on the rear bumpers...

 

Ok, so i hit the g instead of the q, it was late lol.

You really want the liQuid lol to break down into particle vapors before it reaches the combustion chamber.

I do agree these cars were rich from the factory, i won't say that dropping the A/F ratio too say 13.2 WOT wouldn't help, but 13.8 is not in any means a "danger zone" for a NA engine, hell Chris at Nitrous Outlet shoots for 13.2-13.3 WOT on all his LT1s that he owns off the bottle, he gets the best power in that area.

 

I am the one that tunes the cars at Nitrous Outlet, true his likes that A/F because of combustion efficiency, some like 12.8 some as you say as much as 13.5. I had an LT1 the other day on the dyno and it also liked app 13.3-13.5, richened it up and lost power...

 

This is incorrect, you want fuel to remain a liquid (small droplets) until it is in the combustion chamber and then convert to a gas once the intake valve shuts for best power production. The reasoning is simple the atoms of air and fuel can only fit together so tightly and liquid easy beats vapor by a large margin when it comes to specific volume. If your fuel is vaporized entirely it is taking up space in the port and cylinder that could be used for air, and it will drop your ve. This can be backed up by folks running propane as a vapor for fuel vs the newer systems that inject propane directly into the cylinder as a liquid allowing them to maintain or improve upon the ve of the engine with no other changes.

It is entirely different from a carbed engine in that cause under cruise conditions you want it to do this because the ve is low at this point and the combustion is improved by converting to a vapor because the carb has poor atomization at low velocities. In other words in that case it is better to deal with vaporized fuel than to have it enter as large liquid drops.

13.8 is the danger zone, low 13's are not entirely dangerous and chris is right if you want every last hp you can get. I will take 10fwhp less and have my engine last longer though. Also a flat air fuel ratio is not ideal either, I dont know who started that but there are different targets for peak tq and peak hp.

Seeing as people like to talk about stoich air fuel ratio how about this as food for throught. The stoich ratio is where all air and all fuel are used up in the combustion process, that means that adding fuel will not burn anymore ideally speaking. But there is a huge amount of energy removed from the combustion chamber by the changing of liquid fuel to vapor. As a side effect it also helps to increase pressure in the chamber and combust all available air. As it turns out complete combustion is a little bit trickier than the chemistry would have us believe and there are many other factors involved.

 

[QUOTE=ws6t3rror;11113911]
Also a flat air fuel ratio is not ideal either, I dont know who started that but there are different targets for peak tq and peak hp.

Well this is not entirely true also, I have tried different A/F ratios at different RPM levels, It does seem that a little riche at the bottom does aid in the amount of torque produced, but setting shift point at each gear seems to give greater results, another works the amount of torque at each specific peak reduces or increases so say you might spin your motor to 6800 in first 6500 in second and so on...

 

Well moe while that is true, getting the most out of it on the dyno, and getting it down the track the quickest with all the transient conditions and fun stuff that happens during a run, are not really the same thing.

 

I'm no scientist, but I consider myself learned individual, but I can't quite understand how separated fuel atoms would take up any more space than when grouped together. If you dice up an onion into small bits, it's still the same size but it just looks like there's more of it due to it being cut up and not tightly packed together. If you take the whole onion and try to fit it through a drain pipe it won't work out so well, but with it diced up it'll have a better chance of passing through. So wouldn't passing vaporized fuel through the ports work better than liquid? And also then, why do we aim to buy injectors that atomize fuel better? Might as well just have IV Dropper Injectors by what you're saying


As for the claim of LTx running way rich, I was under the impression we ran a bit too lean from the factory :\

 

You are not picking up what I am putting down.

There are two states of gasoline in a combustion engine intake tract. There are liquid fuel droplets and there are superheated vapors or steam if you like that term. The density of the liquid and the density of the steam are very different, the steam behaves as a gas and takes up a great deal more room. Your analogy does not fit the, onion you chop up never changes states it is still the same its just in smaller pieces but density is the same in each piece as when it was whole. When you go from a liquid to a vapor the density changes, kinda like when you boil water the steam floats up and away as it is less dense than the air. Density is mass per unit volume or lets say lbs/cubic foot. The issue is that your engine can only move a certain volume of anything for a given amount of time, this is a function of your cylinder heads, intake, camshaft, exhaust, current rpm, and displacement. Now the air, you cant do much about the air density there besides keep it cool via something like say a cold air intake. Now the fuel you can do something with you can move it as far down the port as possible and then sqirt it into the cylinder as best you can as a liquid because as a liquid it is much more dense than as a gas and does not get in the way of air moving into the cylinder quite so much.

You have mistaken what I have said as something about fuel injectors needing large droplets. In fact you want the smallest droplets you can get. And as a side droplets from injectors are a function of the design and of the pressure being run to the injector the higher the pressure the smaller the fuel droplet if the injector is designed for it (this is why ls1's run high fuel pressure compared to lt1's). Now the reason you want the small droplets is so they can spread out over the largest surface area available and coat everything as thinly and evenly as possible. This is because every surface of the cylinder, piston, and combustion chamber contains heat from the last power stroke and we want to use that heat to now vaporize our trapped fuel mixture so it will become a nice homogenius mixture and combust well with our air (the energy to do this comes from the steel and aluminum materials and cools them down it too much liquid is in one place the location will cool down and you will end up with liquid fuel during the start of combustion). The compression stroke itself aids greatly in this. We know from thermodynamics if you have a gas (air in this case) and you compress it the gas is going to heat up this will help with making the liquid gasoline into vapor. We also know from heat transfer that the compression stroke is also going to increase the coefficient of convective heat transfer by way of increased turbulence in the mixture and really start to pull heat from the piston and chamber surfaces helping yet again to make the gasoline a vapor. The point of all this is that you want the gasoline to be a very fine droplet until the intake valve slams shut and then you want it to very quickly and completely change states from liquid to superheated vapor to allow for excellent and complete combustion.

Lt1's do run rich from the factory is my experience. This is most generally due to a tolorence in the maf sensor accuracy. Last time I saw the numbers in production oem maf sensors have an allowable error of about 5% in measurement accuracy. As a precaution gm then chose to make sure the mixture was fat/safe enough at 12.8 for the ones that would read lean (not enough g/sec) and the rest would all be at safer wot air fuel ratios. I have not seen evidence to support it but I suspect that this is perhaps the source of the 'factory freak' cars due to thier 'better' air fuel ratios at wot. Keep in mind gm has done this because your car having the most rwhp is not thier primary focus, it is that they have to warranty the clunker for many thousands of miles while lean may be mean, and fat may be slow it is also safe.

I hope all that made sense. I consider myself a learned individual as well. I am about 8 weeks from my BSME.

 

Well I hope I haven't harmed my new engine, I've ran it with no tune for almost a year with an 11.2 A/F ratio.

 

You are correct, the Dyno should only be used a tuning aid, the track says it all....

 

It all made sense, thanks

 

Lean is 15.1
That's what my H/C has been running for two years now and once I put it on the dyno I figured out my problems that I always thought was ignition. Anyway with it that lean it did 324/297. Hence the low TQ numbers.
OP with your TQ being higher like most LT1 cars, I dont think you are that lean. 13.8 is a lil on the high side though

Just thought I would share, hope this helps someone