Air fuel question

[Juiced 66]

Maybe some of you guys can answer this for me.. My Paxton car has a Lund tune with the timing locked at 16°. I had it remote tuned back in October and it was like 30° outside, and when we were finished my air fuel was perfect around 11.5-12.0 when at wide open throttle.
Well today I took the car for a drive and noticed that a/f was at. 9.6 when at WOT.. I know with the warmer temperatures the car can't get as much air into the cylinders, but shouldn't the mass air meter compensate for this and lean the car out a little bit? Or do I need to have it retuned for warmer weather?

 

[2005Redfire6]

Maybe some of you guys can answer this for me.. My Paxton car has a Lund tune with the timing locked at 16°. I had it remote tuned back in October and it was like 30° outside, and when we were finished my air fuel was perfect around 11.5-12.0 when at wide open throttle.
Well today I took the car for a drive and noticed that a/f was at. 9.6 when at WOT.. I know with the warmer temperatures the car can't get as much air into the cylinders, but shouldn't the mass air meter compensate for this and lean the car out a little bit? Or do I need to have it retuned for warmer weather?

WOT should be open loop meaning the fuel tables, etc are set in the tune so it will not adjust. My car also runs on the rich side when it is warmer outside due to being tuned in the cold.

 

[Juiced 66]

That makes sense then. I guess I could have it retuned, or maybe just back off on the boost a pump some and see if that will help lean it out a little. I have the Aeroforce gauge, so I can monitor it. It reads dead on with my laptop when I data log it.

 

[s8v4o]

If it's a 5.0 it does not go into open loop at WOT.

Does the power feel "normal" like when the AFR was correct?

 

[Juiced 66]

No, it feels a little down on power. I noticed it, and thought it was weird.. Not sure why it would be so fat if it doesn't go into open loop. I've got some 100 octane in it, but I wouldn't think that would cause it. I mean I know it burns slower, but it shouldn't be making the car run rich like that should it?

 

[2005Redfire6]

If it's a 5.0 it does not go into open loop at WOT.

Does the power feel "normal" like when the AFR was correct?

I've learned something new, can the tuner still not set it to be open loop at WOT?

 

[BruceH]

No, it feels a little down on power. I noticed it, and thought it was weird.. Not sure why it would be so fat if it doesn't go into open loop. I've got some 100 octane in it, but I wouldn't think that would cause it. I mean I know it burns slower, but it shouldn't be making the car run rich like that should it?

Do you know the stoich of the fuel? By any chance is it leaded?

 

[Juiced 66]

No, it's 100 unleaded. I get it at the pump at the track when I go.

 

[Unreal]

Gas could easily do that.

 

[Juiced 66]

I hope that's what it is.. I topped it off with 93 on the way in to work tonight, I'll run this tank out and see if it goes back to normal.

 

[Swarzkopf]

On 3V cars, the MAF does determine fueling at WOT. It's the O2 sensors that are ignored in open loop.

I wonder if the WB is going bad? At 9.6, the car should be billowing black smoke out of the tailpipes - that's VERY rich.

 

[s8v4o]

Gas could easily do that.

How?

 

[Unreal]

Stoich ratio for different gasses. Just running sunoco 110 leans a car out a few points. If the car is setup for 14.1 AFR stoich for e10, then running a non-ethanol race gas that may be 14.5-14.9 stoich depending on its properties can change the wideband readings and the car may compensate.

Just like if he ran E85 is would be lean because it needs more gas, going from e10 to pure gas (in this case a UL100 gas) would make it richer.

 

[86GT351]

That makes sense then. I guess I could have it retuned, or maybe just back off on the boost a pump some and see if that will help lean it out a little. I have the Aeroforce gauge, so I can monitor it. It reads dead on with my laptop when I data log it.

Before you make any adjustments to the Boost a Pump, I would contact your tuner at Lund and see what they suggest!

 

[Juiced 66]

^^ I agree, better safe than sorry.

 

[ebrow21]

Maybe some of you guys can answer this for me.. My Paxton car has a Lund tune with the timing locked at 16°. I had it remote tuned back in October and it was like 30° outside, and when we were finished my air fuel was perfect around 11.5-12.0 when at wide open throttle.
Well today I took the car for a drive and noticed that a/f was at. 9.6 when at WOT.. I know with the warmer temperatures the car can't get as much air into the cylinders, but shouldn't the mass air meter compensate for this and lean the car out a little bit? Or do I need to have it retuned for warmer weather?

A few things.

How are you measuring the a/f ratio? The factory sensor and a datalog? An aftermarket wideband? If aftermarket, does it match the factory sensors?

Where is your maf? Before or after the blower? I would imagine after, based on your information.

Does the a/f seem correct partial throttle? Does the car stumble at WOT or partial throttle? Have you checked your plugs recently?

It sounds like you have a loose clamp somewhere, that only shows up under full load. Metered air is not getting to the engine. I imagine your short term fuel trims are in the negative on a datalog. Are you using tbolt clamps? I would start there before contacting the tuner.

Your tune has temperature compensations for fuel and spark, it should automatically account for ambient/weather.

Stoich ratio for different gasses. Just running sunoco 110 leans a car out a few points. If the car is setup for 14.1 AFR stoich for e10, then running a non-ethanol race gas that may be 14.5-14.9 stoich depending on its properties can change the wideband readings and the car may compensate.

Just like if he ran E85 is would be lean because it needs more gas, going from e10 to pure gas (in this case a UL100 gas) would make it richer.

1.) Its not going to richen by 2 points from pump to 100, or any race gasoline for that matter. Roughly, figure 10% fuel difference per a/f point. No normal race gasoline (not e85) has a 20% different stoich than pump gas. Period.

Quick internet search:

Race Gas Stoich Ratings

Sunoco MO2X UL – 14.5
Sunoco 260 GTX – 14.4
Sunoco 260 GT – 13.9
Sunoco 260 GT Plus – 13.7
Sunoco Standard – 14.8
Sunoco Supreme – 14.9
Sunoco MO2X – 14.5
Sunoco HCR Plus – 14.8
Sunoco Maximal – 15.0
Sunoco MaxNOS – 14.9

Turbo Blue Unleaded (100 octane) -13.9
Turbo Blue Unleaded Plus (104 octane) - 13.7
Turbo Blue 110 - 14.7
Turbo Blue Advantage - 14.9
Turbo Blue Extreme - 15.0

VP Street Blaze 100 - 14.16
VP C10 -14.53
VP C16 - 14.77
VP 110 - 15.09
VP MS109 - 13.41

2.) The tune on a coyote should compensate for differences in fuel (within reason). For instance, I've run a 13.7x:1 oxygenated fuel on a 14.07:1 tune for a LONG time, with no issues, and my car makes over 700hp. The short term fuel trim picks it up. It adds about 3%.


Lots of misinformation, its going to have the op running in circles. But its a chit chat subforum, so that makes it ok I guess, right?

Edit: Forgot about the wideband follow up.

 

[Juiced 66]

The car runs perfect, and doesn't miss at all at part or full throttle. I'm data logging it off of the factory wide bands. A/F is spot on when cruising, and I did a full pull to 7500 this morning, and it was in the 9.80 range from tip in at 3500 until about 5000 where it climbed back to 11.20's

 

[Juiced 66]

I guess that's why I was wondering if it maybe could be the fuel I put in it, because it's never that rich under the curve, and it's closer to 12.0 from 5k till redline.

 

[ebrow21]

So you're converting the a/f number manually, or have the conversion equation input into the software? Whats the lambda reading, and what are the stft's showing.

What brand of fuel? Yes, .8 of a point is a much more reasonable adjustment to different fuels. I assume you all have e10 there, so the lund tune would be for 14.07:1.

Have you tried to re-load the tune and reset the kam? If the old tune had +4% in the ltft's and the stoich of the 100 octane is a couple tenths different, it could account for what you are seeing as well.

Edit: Do you all get summer and winter blends for fuel?

 

[Unreal]

I completely agree. I was just saying that fuel could be part of it, but I wouldn't expect fuel to change it from 12.0 to 9.8. Someone asked how fuel could change the AFR so I answered that. In this case something else is going on.