Dynatech headers,cats,xpipe, breathless cai, 160 stat and a tune.. (stock axle back) here's the results. numbers are conservative due to the Mustang Dyno..

It's definately a different car..

 

 

 

Did the dyno shop people say anything about why the air fuel ratio was so rich stock and why it is still so rich? Maybe the indicated reading is different from actual?

Joe

 

No, they didn't say anything about it. But correct me if I'm wrong, when engine is cold won't it run rich? I'm thinking that if he ran stock run before car had warmed up then that might explain it, because I left the car with them the night before. And as far as the final run it could have been a similar situation.. my car runs so cool now it's almost not right.. i'm cruising in 96 degree heat at a coolant temp of 174-176 and oil temp of 200 - 205.. plus 10 degrees in stop and go.. so I doubt that he ever got the car really warmed up.. ????

I do plan on asking him because I'm curious as well.. my fuel consumption has taken a pretty good hit..

I'll let you know when I find out..

 

They should have (and probably did) warm the car up thoroughly on the dyno before making a wide open throttle pass both before and after the modifications. Your part throttle gas mileage should not have changed with the headers and cold air.

The reason I asked is that the stock air fuel ratio won't usually be as rich as they indicate on the dyno graph and the final tune air fuel ratio both look about 1 point richer than normally what I would expect to see. The dyno shop guys may know that there is a reason their graphed values show up this way, there may be a good explanation, and there may not be anything wrong with what they did at all, other than the display of the data needs a correction before interpretation.

 

ALL testing and tuning is done at normal operating temperature, and no, you won't see drastically richer air to fuel ratios in a 40-60* range cooler.

All sampling is at 100 samples per second, with a 5% smoothing. The vehicle weight and aerodynamic load is programmed, and the AFR sample is taken from RIGHT AT THE ENGINE, not the tailpipe. Tne air to fuel ratio will be the exact same on the street or the track.

The c6 has a wildly screwed up wide open throttle AFR curve, and it varies by 1.5 to 2 points throughout the range. BTW, it is in the low 11's from the factory, and that is not with catalytic overheat protection functioning.

As far as 12.0:1 being rich, no it is not, and as is usual in some cases, .2 richer AFR results in 3-4 degrees of knock retard. The fact of the matter is, I, in 18 years of tuning EFI, have not seen any vehicle making more power (once the combination of fuel, first, and timing second, is done) at 13:1, versus 12:1. Combine this with the other fact that catalytic converter overheating is an issue that needs to be accounted for as well.

The assumption that a vehicle will run the same degree of richness or lean-ness at all ranges, based on what they see at wide open throttle is also matter of ignorance, and all EFI vehicles will run a completely different set of AFR ranges, in 5 key areas of operation(keep in mind that I program for .1 AFR variances, repeated 10 times, at all temp levels, which multiplies those points by 16, on over 300 points on the basic curve, which you will not see anyone else do), not including modifiers, so do not assume something as ridiculous as thinking this car runs at 12:1 at part throttle, steady state conditions.

How many vehicles will you see with as flat and AFR curve throughout the entire wot run as the one you see in the previous graph? Not many. Many alleged tuners will tell you you need to run 13:1, as well as tell you tuning is a one hour job, and make excuses for less than perfect work, because they are lacking skill sets, and just don't put forth the effort to do a complete job of anything on your car, especially tuning.

Misinformation runs rampant here, as well as everywhere else, so this type of reaction to someone's good results, is not surprising to me, but hopefully, this brings you a slightly better understanding of some of the concepts of proper tuning, and that following blanket numbers and statements will not get you where you need to be. All vehicles are unique, and I started the custom tuning concept 18 years ago, based on this fact.

 

Hex--I certainly didn't mean to step on your toes, and tried to write my question so as not to provoke the response you provided. The stock "before" curve does not show the "wildly screwed up wide open throttle AFR curve, and it varies by 1.5 to 2 points throughout the range" you pointed out versus rpm as typical for a C6 and that is precisely why I asked the question.

The final results look great to me, and I'm glad you are happy with it, I'll be getting back to work now and I'll just forget about that stock curve that wasn't what I have seen before, that's all.


Joe

 

No, you didn't, but you have been programmed to think a certain way about how things ought to be on a car, and your knowledge is as accurate as what you've been told. The graph does not show the stock afr curve, as I don't need to see it, and it saves setup time for the baseline. The only thing I care about is the end result, and so you know, you've not see me "unload", I was only telling you the specifics of what you asked, and I get to the point real quick. Some get offended by it, but I'm not here to make friends, but rather to do a job, and educate, if one is of a mind to listen and pay attention.

As far as what you "seen" on a stock C6 AFR curve, there are variables in the way shops sample their data and run their tests. Most I have seen are incorrect, however, there are probably some out there that do it properly, but I would not go so far as to say that's the majority.

 

 

Very interesting stuff. I hope our local tuner has that kind of knowledge and posture in defending his abilities. Way to go Hex, I don't think anyone is challenging your work: it's like you said, too much misinformation on this forum. The end result is that you had a happy customer, who I'm sure will recommend you to anyone who asks. Keep up the good work and feel free to give good information: we really do appreciate the knowledge.

 

That is what I wanted to know--the stock AFR curve I questioned doesn't go with the dyno data and should be ignored. That is all I wanted to know. The "after" graph does go with the dyno run and is exactly the way you wanted it to be 11.7-12.0. Fine. Your customer is happy, and should be, and my questions were answered.

I use three wide bands, HPTuner, SCT Advantage, own one C6 myself as well as a turbo/nitrous Mustang and have tuned 3 other C6s locally, plus about 30 Mustangs. I have "seen" plenty, datalogged and analyzed many dyno and drag strip runs and have not been "programmed" in the slightest. I have a little personal experience tuning these cars myself and that is why I asked the question I asked.