Well, today was the magic day to throw done 400/500. Went to the dyno shop which has a brand new Mustang dyno. Got all hooked up. Started up and we couldnt get a good rpm lead, so after about 15 minutes, I did a pull to check air fuel so I could make some tweaks on my program (JLP program via predator) while he worked on getting his equipment to read rpm. Started my first pull @70mph and it ended at 90mph. Why did it end you might ask, well, I was getting BIG numbers, but it was power, it was air fuel. Big as in 17:1! I about chit myself. We checked his sniffer (tailpipe sniffer, no extra 02 bung and no ez access to an 02 sensor) and the paint was cooked, blistered, discolored, and blown off of it and it smelt horrible. I had datalogged the pull on my predator so I looked at the data. I had my 16 degrees of advance and my 02 sensors read .4volts and .3volts. So I took out all of the timing I could and added all the fuel I could and we ran it again, only this time I tried to pull it to 100. Well, the truck was studdering and would barely pull 100mph on that run. The air fuel was 16.0 to 1 when I let off the gas. Agian the smell was bad. This time I noticed as I was watching the Dyno screen, the air fuel went to 12.1 to 1 and slowly came back up to 14.9 to one where it was idling at. So I knew his 02 was reading the extra fuel after I let off and it must have been working. I datalogged the second run and had the same voltages on my 02 sensors of .4 and .3 volts. The first run I was making 266 horse and 89mph (no rpm as it wasnt working yet) and the second run I made 273 horse at 90mph (still no rpm).

So here is my questions. at an idle, what air fuel ratio should I be looking for? What should my 02 sensors be reading while at an idle?
What does the voltage do on the 02 sensors when it goes lean or rich ie, lower volatge means rich or lean?
Why in the heck is this motor no getting detenation with a 16.0 to 1 air fuel? I have been beating this truck with this program for 3 months and never have heard it detonate. Why are all the rods still in the block at this air fuel ratio?

I need help. I know that the motor should be toast with those numbers, but its not. It didnt miss a beat until I added fuel to the program and when I took fuel back out and ran it again, it didnt stumble at all but made less power (back to 260's horse on run with less fuel). Just to be safe I left all the timing out. Needless to say I drove nice and easy on the way home (100 mile drive).

Most of my pulls show that when I very first step into the gas the air fuel drops from mid 14 to 1's to low 14 to 1's, but then it starts climbing and even when I get off the gas the air fuel is still climinb the wrong direction. When I slowly bring the truck up to test speed my air fuel stay around 14.8 to one until I mash the pedal. I guess I just need to know what my 02 sensors should be reading to verify the his 02 was picking up the correct numbers. If my 02s say Im lean and his 02 says im lean, then I am lean and have a crap load of power to get out of my tune. If my 02s say im rich and his says lean, its not my engine and I need to look for something like an exhaust leak I cant hear or his 02 sensor. btw, he just tuned a mustang yesturday and he used the tail pipe sniffer and it worked flawlessly.

Chris
Edit: Look for pics below

 

Did you see it work flawlessly ?
Some "Tuners" are complete morons.

 

nope, didnt see it personally.

chris

 

Stoichiometric or Theoretical Combustion is the ideal combustion
process during which a fuel is burned completely. A complete
combustion is a process which burns all the carbon (C) to (CO2),
all hydrogen (H) to (H2O) and all sulfur (S) to (SO2). If there are
unburned components in the exhaust gas such as C, H2, CO the
combustion process is uncompleted.

Since the only way and the best way to measure this is to have
a monitor as close to the combustion process as possible, the
extra bung is a great method.

Some of the tuners use a $200.00 sniffer, and some use a
$1,500 sniffer.

I have gotten different a/f just by changing which pipe it's
inserted into.

Isn't the "ideal" a/f 14.1 to 1 ??? Stoichiometrically speaking?
Our computers try to keep that a/f to reduce emissions, and give
proper combustion. When we add gobs of timing, the easiest
way to prevent pre-combustion or detonation is to up the fuel.
That's what every tuner does, as far as I know.

Since at partial throttle you are still tied to the adaptive tables
and the MAF voltage, I think dynos prolly will always show leaner
than you actually are. Your fighting the computer at the start,
and then the tuners fuel tables at the WOT.

For instance, the reason for winter and summer tunes is only
because at WOT in the winter, with denser air, you are gonna
lean right out. If there is NO computer input (as there is in our
ECM) then you absolutely need two tunes. (Minimum)

This is one reason why I think there are a bunch of blown
plugs, motors and rods when it starts to cool down. You ever
notice there aren't so many during the warm summer?

Good luck with the dyno experience.

Cliff

 

Chris,
IMO your air-fuel tail pipe sniffer is reading inaccurate results i have seen this several times at dynos where the air-fuel is way lean on my tune which i knew it was not and i told them to clean there hoses out and put a new filter in the machine and everytime after they did this my air-fuel was back to normal again. No tuner is going to send you a tune that lean,there are many Lightnings most likely using that same tune you have. Go to a different dyno or ask them to clean there unit and change the filter or i would not go back to that dyno shop again. By the way a friend of mine is renting out Stanton this saturday should be a great time try and make it if you can.Later Matt

 

I went today and purchased a new hi/lo pump relay and fuel filter. I was going to buy a fuel pressure gauge (not the autometer type, the auto technician tool box type) but it was $10 less than an autometer. I will probably get an autometer this week and get it installed so I can see whats going on. I ran around today with the predator hooked up and stayed out of the boost. My 0s voltages were pretty low even driving around normal (bouncing .5-.6 volts). I know the 02's in our trucks are not the most accurate, but its something to help me see whats up. I will get the parts installed tomarrow and see whats going on after that. I hope its just a relay and a filter or either one of the two. I dont really want to buy new pumps, but if I have to I will.

I also plan to call some exhaust shops about getting a bung put in or maybe getting the maggy mid pipes and having a bung put into that. I just want that extra bung and its worth a few bucks to have it installed for my peace of mind.

Matt- I have to work this weekend so I wont be able to make. Dont know that I would run even if I did come since I dont know for sure whats going on with my truck. I am going to play it safe for right now.

Chris

 

14.7 is. At idle, your truck should be very close to that number, depending on how the dyno/wideband equipment is calibrated.

 

Here are 2 pics of a run so you guys can see what the sniffer was saying

graph in mph



text layout of same run in mph



Chris