A/F ratio concern/question

[IronHorse]

Just had the car dynoed for the first time... This was on a 02' Trans am...

The only mods done to the car besides the performance tune (Predator U7198) is a lid and catback exhaust. The temperture was 90 degrees F & 47% humidity at time of dyno...(Yea, I know not the ideal conditions to get the best dyno numbers) The car put down 330HP to the wheels and 340 Ilbs TQ on the Dynojet dyno...

My concern was the A/F ratio was runing a bit lean as the Tech pointed out to me. The A/F was 15.0 in the begining of the wide open throttle (WOT) and hovered around 14.5 to 14.2 up to 4800 RPMs and only begin to dip into the 13.9 at about 5000 to 6000 RPM... He said that was way too lean with it at WOT... He said I need to be as close as possible to 13.1 A/F at WOT but that the 14.5 to 14.7 A/F was fine for a crusing speed, just too lean a number for WOT.

Now what I was wondering is how can I adjust this tuner to reach that 13.1 A/F at WOT? Mind you I don't know diddle about these tuner things or how to go about trying to fix this? So, your help is greatly appreciated?

Other than this I've been pleased with the tuner but if I can't cure this lean condition then I'm just going to re-upload my stock program back into the PCM and sell this thing. I don't need pistons melting on my show car it has already won more awards than I have shelf space...

[06MonteSS]

when you go into the Modify Tune menu, there should be a parameter for Power Enrichment or WOT Fuel.

Yours probably has WOT Fuel. This is what you need to adjust to richen up your WOT fueling.

When you go into the Modify Tune menu, select this parameter, and then go positive to make it richer and add more fuel. This will bring your AFR down. I would start by setting it to +4% and see where that brings your AFR number down to.

[IronHorse]

when you go into the Modify Tune menu, there should be a parameter for Power Enrichment or WOT Fuel.

Yours probably has WOT Fuel. This is what you need to adjust to richen up your WOT fueling.

When you go into the Modify Tune menu, select this parameter, and then go positive to make it richer and add more fuel. This will bring your AFR down. I would start by setting it to +4% and see where that brings your AFR number down to.

Bumping the enrichment up by 4% should net me what point number? I've been told I need to richen it up 1.5 to get it where I need it? I don't know if the tuner will go that much? The manual says and I quote " When adjusting the power enrichment we allow up to 5% increase or decrease of fuel trims at WOT this translates to approximately a 1.5 point air/fuel adjustment range plus or minus. So, is that saying I can only reach a .75 increase with this tuner set at it's maxium enrichment setting?

[johan]

I am not sure why your a/f is that lean. During cruise the a/f should be around 14.7 always, if it isn't check your 02's and for any leaks in your exhaust/intake system.
I honestly do not think the predators adjustment range has enough to bring you down to ideal a/f which is 12.8:1 on the LS1's, but then again i have a feeling that something else is going on with your vehicle, do you have the stock maf on it?
Either that or the guys a/f meter was not calibrated properly as you would made squat for power at that a/f.

[IronHorse]

I am not sure why your a/f is that lean. During cruise the a/f should be around 14.7 always, if it isn't check your 02's and for any leaks in your exhaust/intake system.
I honestly do not think the predators adjustment range has enough to bring you down to ideal a/f which is 12.8:1 on the LS1's, but then again i have a feeling that something else is going on with your vehicle, do you have the stock maf on it?
Either that or the guys a/f meter was not calibrated properly as you would made squat for power at that a/f.

Yes, the MAF is the factory one... I'll look into your suggestions but I doubt the 02's are the problem the car has less than 20,000 miles on it. I've never had a code thrown for the 02's... Furthermore nearly everyone was registering a lean mix with their A/F that dynoed except for one car. The one exception to that was the vehicle that registed correctly has been tuned on that particular dyno...

[mikel]

I am not sure why your a/f is that lean. During cruise the a/f should be around 14.7 always, if it isn't check your 02's and for any leaks in your exhaust/intake system.
I honestly do not think the predators adjustment range has enough to bring you down to ideal a/f which is 12.8:1 on the LS1's, but then again i have a feeling that something else is going on with your vehicle, do you have the stock maf on it?
Either that or the guys a/f meter was not calibrated properly as you would made squat for power at that a/f.

Yes, the MAF is the factory one... I'll look into your suggestions but I doubt the 02's are the problem the car has less than 20,000 miles on it. I've never had a code thrown for the 02's... Furthermore nearly everyone was registering a lean mix with their A/F that dynoed except for one car. The one exception to that was the vehicle that registed correctly has been tuned on that particular dyno...

This sounds to me like a bad wideband!
Stock cars run tremendously rich....if he had untuned cars on the dyno that were showing lean conditions on the wideband, I would have to suspect something is up....especially if the only car that had a decent A/F was one that was tuned to that particular wideband.

Thanks
Mike

[IronHorse]

This sounds to me like a bad wideband!
Stock cars run tremendously rich....if he had untuned cars on the dyno that were showing lean conditions on the wideband, I would have to suspect something is up....especially if the only car that had a decent A/F was one that was tuned to that particular wideband.

Thanks
Mike

Well, that is a good question and some others who have seen the results found it a bit unusal for that many cars to be running lean? I can give you a link to the results but I don't know if that's cool on this site? Maybe if you looked at them yourself and compared them you might be able to either confirm or deny your suspicions?

I reviewed the data on what some of the non-tuned cars were making. A 06' Corvette LS2 completely stock was doing 13.8 to 13.9 for most of of the RPM range and began to slightly fall at 4,000 RPM with a dip starting at 4600 rpm from a 13.6 to a flat 13.0 at 5,000 RPM. It dipped into a 12.9 at about 5400 RPM but came back to a flat 13.0 by the time it was turning 5600 RPM. That Vette was totally stock! The Dyno showed it putting 342HP to the ground & 342TQ...

Not sure if this is a good comparasion on not. A totally stock Pontiac G6 with the 3800 engine... It showed a 13.7 A/F at its start begining at 3500 RPM and it climbed steadily at an even rate to 13.9 as it reached 5500 RPM and remained at that mixture up to redline at 6400RPM. The little G6 managed to put out 184HP & 181TQ...

Your help is greatly appreciated

[01Z]

Other than this I've been pleased with the tuner but if I can't cure this lean condition then I'm just going to re-upload my stock program back into the PCM and sell this thing. I don't need pistons melting on my show car it has already won more awards than I have shelf space...

I wouldn't be so quick to think the tuner has caused the lean condition. My LS1 with air lid and catback dyno'd very similar to yours and the a/f registered nearly identical. I didn't have the predator at that time; it was the factory tune.

They stuck the probe down the tip of one side of your exhaust right? I'm figuring you have cats as well. I'm not trusting my numbers of 14.5 down to 14.0 at red line. My LTFTs do not show that kind of lean condition and I am not registering any knock retard. I'm wondering if testing the way they did on my exhaust didn't somehow mix in a little outside air or like Mike remarked, the wideband might not have been calibrated.

I have bought an Innovate wideband to use in the place of one of my narrow band sensors so I hope to get to the bottom of this. I'm half wondering if we didn't use the same speed shop.

[01Z]

when you go into the Modify Tune menu, there should be a parameter for Power Enrichment or WOT Fuel.

Yours probably has WOT Fuel.

JFYI, the U7198 shows Power Enrichment.

[IronHorse]

Other than this I've been pleased with the tuner but if I can't cure this lean condition then I'm just going to re-upload my stock program back into the PCM and sell this thing. I don't need pistons melting on my show car it has already won more awards than I have shelf space...

I wouldn't be so quick to think the tuner has caused the lean condition. My LS1 with air lid and catback dyno'd very similar to yours and the a/f registered nearly identical. I didn't have the predator at that time; it was the factory tune.

They stuck the probe down the tip of one side of your exhaust right? I'm figuring you have cats as well. I'm not trusting my numbers of 14.5 down to 14.0 at red line. My LTFTs do not show that kind of lean condition and I am not registering any knock retard. I'm wondering if testing the way they did on my exhaust didn't somehow mix in a little outside air or like Mike remarked, the wideband might not have been calibrated.

I have bought an Innovate wideband to use in the place of one of my narrow band sensors so I hope to get to the bottom of this. I'm half wondering if we didn't use the same speed shop.

Yes, I have cats... And yes that's just how they used their wideband.

I did get one knock retard reading right there at redline on one of the two pulls... When your at that RPM level it could mean anything, poor gas, they accidental hit the rev limiter before letting off the gas and thus showing a miss or knock in the graph, etc...

I'm not thinking the tuner lead to the lean condition it may not have helped the situation either... I don't really know why I'm reading lean but a few people I've talked to have said the same thing as "mikel" and wondered if it the Wideband was reading as it should... The LS2 Vette all stock was hovering just under 14.0 at a 13.9 or 13.8 for the most part... If it's true that the factory settings are on the rich side then that should be wrong? However, I find it hard to believe that a factory setting would run on the rich side? The main reason being: runing rich sure isn't going to help the car get a governmental EPA passing grade, I'd think as lean as possible is the only way to get an EPA approval rating?


The Ironic thing is the Dyno we used is the actual offical dyno used by a competator of Diablosport... I'm not talking a Dyno just like one of their competators might use, I mean the real thing!!!! (Sorry, Diablo no offense it just worked out that dyno day for the club was at that location)

Just leaves me confused why I'm reading so high. Nevertheless a friend of mine who has the identcal set up as me except he has a tuner from the competator had an almost identical graph as me. His A/f was at worst only a .1 or .2 under mine at any given point along the A/F graphs. His hovered around a 13.8 to 14.0 were as mine hovered 14.2 to 14.0

[dynometer]

i would say before you got too worried-
#1- is your MAF clean and free of all oil/ debris from your K&N filter/ etc? Pull it off and look at the elements and make sure they are clean
#2- Was the filter on there wideband starting to get dirty? We go through at least one a day when we are doing solid dyno days- This is generally the leading cause of AFR mis calcs that I have seen
#3 Check your 02 volts on your upstream sensors @ WOT- they should be constant between .87 to .89 to achieve approx 13:1. If these are in place, check on the status of the filter on the wideband, then politly ask for your money back. If everyone's AFR was high that day, I can GUARANTEE you that the filter on the wideband was plugged or they have a tear in one of the hoses going into the vacuum pump (the black box)
andy

[01Z]

This all is good insight. I don't think many people know what happens behind the dyno scene. It's a valuable thread and the fact that IronHorse has other people's a/f to set along side his own puts more clues out there.

As for government emissions, I don't know how the whole thing works but the stoichiometric figure is hard coded into all of our PCMs and it seems that power enrichment is almost considered an emergency region. I wonder if that falls under the rules . I know that the E-check here never tests open throttle, ever. What is allowed at open throttle would be interesting. I know my 95 with the LT1 is notoriously rich from the factory.

[IronHorse]

This all is good insight. I don't think many people know what happens behind the dyno scene. It's a valuable thread and the fact that IronHorse has other people's a/f to set along side his own puts more clues out there.

As for government emissions, I don't know how the whole thing works but the stoichiometric figure is hard coded into all of our PCMs and it seems that power enrichment is almost considered an emergency region. I wonder if that falls under the rules . I know that the E-check here never tests open throttle, ever. What is allowed at open throttle would be interesting. I know my 95 with the LT1 is notoriously rich from the factory.

Yes, I thought it would be helpful to others too. I hope to have more info soon, so stay tuned.

[Westx07zo6]

Correct me if i am wrong but your dyno shop should take the o2 reading Before the cats as exhaust gases become leaner (1-1.5) from traveling through the converters. I played that o2 game with two differiant dyno shops which one read Lean and the other Rich, i sloved that my welding in a o2 bung on the engine side of the cats.

[06MonteSS]

yes, the wideband should be put in before the cats... if they just put the sniffer in the tailpipe, take it somewhere else... or tell them to do it the right way and weld in a new bung for the wideband sensor... before the cats...