I'm going to wait to reply in detail till I talk with someone familiar with Nitro engines at work. Until then I will leave it alone. I don't agree at all, but I need to get my information straight.

 

99 White Light:

Mass/Volume flow of gasoline is easy to measure. Simply look at injector pulse timing. (as you say in your post). actual effecientcy is not.


Second:
O2 is a better reading for tuning an engine that strict mass readings because you often want extra fuel in the cylinder for things like cooling etc. The real world doesn't follow the rules of chemistry Often it impossible to actually burn all the fuel (or air). Measuring what is actually going on is better than "knowing" what should be going on.

Coldie

PS: I just want to say it's nice to have an imformative post and I hope I'm not offending anyone.

 

They only use alcohol in the squirt cans for fireing the engines. They do their burnout on the lean side of the pump and go to full rich as they are staging. One of the reasons for so much lead is a 426 style head has such a huge combustion chamber. When everyone used to run 392 type engines they did not run nearly as much lead. I guess I am showing how old I am. Skip

 

I could be wrong but I was under the impersion that thye used the alcohol for the burn out to that is what I was told by a guy I know that runs FM/TA.Stan

 

There was this one time, at band camp................

 

I agree you can look at the pulse width's, but then you need to know the composition and density of the fuel to get the A/F ratio, along with the injector calibrarion. But yes, that is a good method if you don't have a fuel mass flow meter.

The real world follows exactly the rules of chemistry. There are tables (STANJAN) and programs (ChemKen) that allow you to look at combustion. I know what you mean when you make the statement and that is that you don't always go to complete combustion. This is very true. In fact you never go to completion which is why things like HC and CO emissions happen. Those tables allow you to track over 100 species to calculate the products of combustion.

I also agree that you want extra fuel but it is a little more fundumental than not being able to burn all of the fuel. The mixture burns faster a little richer than stoich, and you also get cooling from the fuel the more you put in. That helps in not only getting a higher mass is the cylinder, but it also increases the knock tolerance. That is why ford richens the A/F to about 10.5:1 during WOT (and also to keep the cats cool). But the tuning can still be done with mass flows. Just because you use mass flows doesn't mean you can't go richer than stoich. The O2 sensors are just low cost and easy to use (portable and 12 volt) alternatives for a full emissions bench. I guarentee you that the OEM's all have a full emissions bench's running when tuning engines. Aftermarket tuners don't have the the means or the need for such equipment.

 

Keep in mind that your A/F is a combined total. The actual A/F ratio varies from cylinder to cylinder. The most dangerous thing about a power adder is you can have one cylinder running extremely lean. However, because you gain the totals after the cross over pipes, your measurement is far from accurate. Cylinder #8 may require a blueprinted 44# injector and may throw off your combined A/F by nearly .3 to .5 points, where as cylinders 1-7 can be right on the money. Octane doesnt affect a/f significantly. But as Sal has pointed out, the minute you start increasing timing to take ADVANTAGE of the increased octane, your A/F will begin to lean out. That is basic tuning 101. You need to keep throwing fuel down to tame those #'s.

Its always good to monitor cylinder temps on the dyno to see where you are leaning out at.

Ive seen how these trucks like to run lean and make additonal power. But one has to draw the line between greed and that extra tenth of a second. Its your wallet in the end of course.

 

Well d@mn, you did run into somebody over there. I got out of my Chemistry classes as fast as I could. I'll stick to computers, and let wizards like y'all blow ***** up butt tubes. But really, its good to know that there are people out there other than OEM that understand this *****.

Maybe you wizards could email each other, figure it all out, and come back with a post worthy of Cliff.

Happy tuning

 

This is something I just do NOT agree with. I have never seen this happen. The only thing that could cause those readings on the UEGO to change would be if the ECU had some sort of compensations so that timing affected open loop fueling. When open loop the ECU measures airflow and computes fuel flow needed for desired A/F ratio. This is independant of timing. The chemistry is identical for two different timings. Something funny may be going on in the cylinder that I can't explain that is causing your UEGO to SEE a change, but it is most definately not a change in the actual A/F. It is just a change in what your sensor is telling you.

These trucks are no different than any other engine ever made. When you you say like to run "lean" to make power, that is false. They are in fact running rich to make the most power. From the factory they run VERY rich for the added cooling for knock tolerance and to keep that cats alive. They make more power when you lean them out a little becaue of how rich they were originally running. But trust me, they are still running rich.

The engine dyno (actual engine stand brake dyno, no inertial chassis dyno) data I saw showed A/F numbers down in the 10:1 range, especially at higher speeds. Rule of thumb for maximum power is around 13:1. For a supercharged engine with an inefficient blower (like the eaton), running a little richer will help out power because of the cooling so maybe 12.5 to 12:1 is better. The tuners will know that one. Stoich is around 14.5:1, so rich is better.