Farmer2

iTrader: (168)

I was at the track tues night and found that I was running 11.6 for the fuel ratio. Is that to lean for the LS1 or is that right in the sweet spot?

I thought it was low but I am new to the LS1 fuel workings

ArcticFormula

My car is stock except for a catback, and my dynosheet shows about a 12:1 air fuel ratio from 4000 to 6000 on the better of my two runs. I think 11.6:1 is fine, its safer to be a bit rich than lean, and 11.6 is not lean, but some forced induction guys or nitrous guys might choose run a bit richer than 11.6, but that is probably for safety concerns.

CMNTMXR57

At WOT you should see high 12's to low 13's for optimum performance. You are waaayyyy to rich. On a scanner that would show up as high 800mV's to low 900mV's (.890mV - .920mV)

That would be more in the range for a forced induction car.

Farmer2

iTrader: (168)

So I am rich not lean. On the intake side I have a Direct Flow lid and I port polished and filled the TB, so if I were to port the MAF ends would I run a bit leaner and maybe put me back where I should be? I heard when the MAF end are ported on a 02 it will run lean is that true also?

sscamaro02

I had my 02 SS tuned on a dyno. F/A ratio was about 11.5. Its now 12.5. Gained 13 rw/hp after tune up.

CMNTMXR57

For A/F ratio, optimum "Stoichiometric" is 14.7:1

What that means is that 14.7 parts of air to 1 part fuel.

If you are running at 11.5:1, that means 11.5 parts of air (less air) to 1 part fuel. Therefore you are running richer.

Farmer2

iTrader: (168)

With all under stood about me being on the rich side now. What would be the best way of leaning it out now? Would porting and polishing the MAF do this for me?

Texas_WS6

iTrader: (9)

I doubt it. How are you reading this A/F ratio? What is your elevation? At WOT the system should be running in open loop mode. That means the computer is operating off of preprogramed maps and not the O2 sensors. It will be looking at the other sensors to decide were it needs to be on the map. If you port the MAF or the TB or do anything to help the air come into the engine, the computer should see this in the MAF reading and go to the map with it to set fuel, timing, and other things. Now if your MAP sensor is out of calibration or malfunctioning, and you are at a high elevation, the computer can be at a low altittude setting which should call for more fuel. There will still be the same flow messurment across the MAF but the air will be less dense causing the end result to be richer then were the computer thinks it is. Again, at WOT the computer never looks at the O2 sensors so it has no idea what the end result realy is. I think this is done do to the fact that at WOT the Factory O2 sensors are to slow to respond to the demand for the load. But i would not be a bit supprised if I am wrong on this subject To close with, it sounds like there is a sensor problem causing you to be that rich. It could be a mechanical problem but I doubt it from what you have said in your post. Or it could just simply a tunning issue if it has had the tunning changed in the past.

Texas_WS6

iTrader: (9)

I just looked back over you sig. Dump the HPPIII. It is junk. I have it too but I do not use the engine program in it. I dynoed my car with the engine program in it and the stock program. I lost Horspower with it, and it detonated like crazy!! So I run my factory program and use the programer only for the gear change. I am looking into the Preditor programer right now. it looks to be a much better unit. You can change your fuel and timing setting were you can not with the HPPIII and it will do diagnostics also. Sounds to be a great unit. Also they told me you can modify your settup and call in the settup and they will make a new file program for you that you can download of the internet into the programer, then you can put it into the PCM. No need to take the PCM out and send it off.

Colonel

14.7:1 is the theoretical best ratio for optimum gas mileage and emissions. It has nothing to do with the ratio for best power at WOT. For best NA power, you'll want a ratio of about 12.7-13.3:1 at WOT.

Porting a MAF WILL make the WOT mixture leaner by reducing the reported load to the PCM. As mentioned before, the PCM does not directly look at the O2 readings at WOT so the mixture will not be corrected through them.

This is important ya'll...DON'T assume that your car is running rich or lean at WOT just based on O2 readings or the exhaust smell. Get it on a wideband O2 sensor to tell.

Farmer2

iTrader: (168)

I want to thank all for the replys. I am more enlightened about this now.

With AutoTap, driving down the road the AF is 14.6 steady but as soon as I go to WOT it goes to 11.6. As you state a wide band sensor would be good. Is there anywhere I can get this so I can do this myself. If so will it give a good reading to adjust as you mentioned with the preditor?

Thanks again

Colonel

Farmer, the O2 sensors on your car were designed to work during closed loop operation only, NOT during WOT. You are not running 11.6:1. You can rig up your own wideband system but it ain't cheap. Unless you're really serious about racing and making changes, you'll be better off just going to a chassis dyno that has one.

Check our PCM diagnostics and tuning section for help on working the Predator.

Ryan K

iTrader: (11)

Farmer, what colonel said is correct. What you are reading is the AFR commanded. Auto-tap can't read the true AFR. You have to have a wide band O2 to do that. However if you are looking at you O2 sensor output in MV, a good range to shoot for is .885-.910mv (when at WOT). That is fairly close to 13:1. Just cruising down the road it should cycle high and low to indicate ~14.7:1.

Ryan K.

1BadAzzWS6

iTrader: (11)

Im looking at my last dyno sheet. On the dyno sheet my air/fuel stays between 12 - 13 untili get to about 4700rpms where it then drops below 12 and down close to 11. So does that mean it's running rich? I have a MAFT but don't have it set to make any changes. Should I set it to lean it out by a few% and if so should I adjust the base or just the wot?

Farmer2

iTrader: (168)

Yes I am reading the AFR command. Thanks for clearing that up. I will check out the Mv volts and see where they are.

I am new to the AutoTap and the LS-1 so I guess learn as I go along. Thanks again for all the help and time. I will let you know how I make out.

Dave

Farmer2

iTrader: (168)

Update.........
I just changed the perameters and moved it to Mv not % and I am reading 885 to 915 on the O2 sensors for the bank 1 and 2 sensors 1 on each.

I guess I am right where I want to be.
I am thinking about dropping the HPP3 and getting the Preditor, due to it has alot more for me to adjust and it also is a scanner.

Thanks again folks