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Why I might have been having detonation issues

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Why I might have been having detonation issues

Post by Shelby10' on 4/24/2011, 10:34 pm

Got this from another forum:

Car: 2010 GT500 is having detonation issues.

Jared at Lethal performance's response to the driver hearing detonation.

"Even if you put 91 octane in the car and ran a 93 octane tune the 2010 has a feature called adaptive octane. The 07-09 cars do not have this. It's a feature that actually recognizes the level of octane of fuel in the tank and will make adjustments accordingly. So if you're running a 93 octane tune and somehow get lets say 87 octane fuel the car still shouldn't detonate. The adaptive octane feature will pull timing and make changes to throttle in order to prevent anything from happening. It's actually quite an advanced feature which many don't know about because it's all new with the 2010.

With that said we are obviously concerned about your car and definitely want to help you figure out what's going on. I'd say put the stock tune back on the car and take it out for a cruise. Try to replicate the sound you're hearing. If it's still there than you can rule the tune out. If it's not there then we will work with you and Jon to figure out what's going on.

Please keep us informed and if you have any other questions just give us a call.

Thanks, Jared"

Guy on the forums response to Jared at Lethals comment:

"Like I said before it is most likely because the MAF meter curve is incorrect (MAF transfer functions) What happens when incorrect mass air transfer functions are put into the tune for a specific MAF it causes the engine to opperate in the wrong load tables.

An incorrect maf table will cause load tables to be incorrect and can cause the rich or lean tables to be off.
If it is lean the only thing that would cause that is the maf curve. The a/f table would be the target value and could only obtain that number if the maf curve is correct.

The reason the MAF transfer functions would be incorrect is if the tuner uses "short terms" to develop his meter curve instead of actually having the meter and sensor calibrations done on a flow bench designed to determine the true MAF transfer curve, this is the way FMCO it's transfer functions for it's tunes.

Any other way to develope a meter curve other than on a flow bench is incorrect and will result in an inaccurate meter curve, causing the load tables to be off. This would affect Air Fuel and Timing tables causing them to be applied at the wrong time, thus detonation and/ or a lean or rich condition.

Even with a knock sensor this is still very important because the computer can only make corrections in a limited amount , sometimes that amount is not sufficent to overcome the errors of the tune being in the wrong load tables. ( again....wrong load tables are caused by incorrect MAF transfer functions)

The MAF transfer functions are the most important element in a Mass Air car. Every EEC function get's it's direction from the MAF transfer table. Simply put if the meter curve is not 100% correct these kinds of problems will occur and the problems magnified in extreme conditions such as in WOT on a race track or the street."


Justin Starkey's response to what could be wrong with this guys car:

"Each tune revision from ford has made the knock sensors on the 2010s less and less sensitive, so like any performance car i wouldn't rely on them to save you from really really bad gas.

The 2010s knock strategy is twofold. It has the traditional on the fly knock retard capability that we have seen in ford's for years (and very good since 05 with dual KS and a fast PCM to process the data). Now they have added a knock learning feature, which we first started to see in the 08 bullits. This is more like the GM style of KS where it can retard timing all the time not just on the fly when it detects knock.

Now onto your original problem, if it doesn't clear with good fuel, i'm sure your tuner can fix it. It would be interesting to see datalogs from your car to determine the exact root cause, as several things have been throw around, maf xfer function tuning, spark tuning, or the fact that a few percent of cars are just DIFFERENT. "

Same guy on the forum responding to Jared at Lethal

"Each model year has a specific tune for that year , for example an 07 factory tune is the same for all 07's , where as a 2010 would be different and specific for just the 2010's. The MAF meter curve would be the same for all the cars using that particular meter. They can do this because their meter curve's are determined on a flow bench not on the car using short term fuel trims like we see done by after market "tuners". They do not modify the meter curve from one car to another like many so called "tuners" do which is why we see so many cars having detonation problems as well as idle issues with simple pump gas. "

Justin Starkey VMPs response to the above:

"What you are saying about how ford derives the factory xfer function is 100% correct, but there are many other factors to deal with in aftermarket tuning.

There are so many different factors to calibrate for on an air meter transfer function. You forget to mention that any time air flow over the sensor changes, the reading changes. Something as simple as a different air filter or a different heat shield can effect how air gets sucked into the meter and measured.

The absolute correct way to dial in an air meter transfer function is to measure actual air fuel with an accurate wideband and adjust the transfer function until actual = commanded. And this is what good aftermarket tuners do.

Oh and there is the whole effect of ethanol in the gas which can be anywhere from 0-10% depending on where you fill up. A new variable that tuners have to take into account. "

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Re: Why I might have been having detonation issues

Post by Shelby10' on 4/24/2011, 10:41 pm

So basically My MAF trasfer curve could be incorrect. Not sure if Justin at VMP bench flowed a 2010 with the FRPP resonator delete and AirRaid filter. He would have had to to have the proper trasfer fuction. If not my tables could have been way off and my car may not have had enough adjustment capability built in to stop the detonation.

Tuners should not adjust the curve off of Short term values. I wonder how VMP and Lund come up with their tables?

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Re: Why I might have been having detonation issues

Post by Shelby10' on 4/24/2011, 10:51 pm

Another good response on a separate forum

"The 2010 incorporates the use of knock sensors to help prevent detonation but even with knock sensors in play the engine can still get detonation if the MAF transfer funnctions are incorrect due to the tuner making unwarranted changes to them by tuning with short term fuel trims. Any tuner who does this is flat out wrong and is more than likely the cause of unwanted detonation. This is even more critical in the 07's to 09's which don't have knock sensors to help protect it from detonation.

This is because it can and often does change the load tables the engine is supposed to opperate in durring a specific air flow based on engine torque. This affects both timing maps and fuel maps which means for example that at a given situation the engine may be calling for 25* of timing but because it is in the wrong load table it may actually get 35* of timing and start to detonate.
This is magnified when the engine has been modified and making much higher hp than before and is running all out in a high powerd situation where there is absolutely no room for even the smallest error in the tune. Couple that with agressive spark advance to see a high dyno number and you have a recipe for catostrophic engine failure, which we are seeing more and more these days. Of course we are told it has to be "bad gas" not a bad tune!

Ford establishes it's MAF transfer functions by plotting air flow through the meter and sensor on a flow bench. It is that data that goes into each and every factory tune for that specific model year car using that specific meter. They don't change the MAF transfer functions on each car by using short term fuel trims to change the transfer functions like so many of the so called "good aftermarket tuners" do as stated in the last post by one of those well known tuners..."

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Re: Why I might have been having detonation issues

Post by 07Shelby500 on 4/24/2011, 11:03 pm

Don't get me started on VMP

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Re: Why I might have been having detonation issues

Post by Supersnake on 4/25/2011, 4:56 am

Good read Jarrod 1.0
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Re: Why I might have been having detonation issues

Post by BASixxer on 4/25/2011, 5:34 am

Good read... definitely makes you curious... david, have you gotten anywhere with your issues yet?
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Re: Why I might have been having detonation issues

Post by 07Shelby500 on 4/25/2011, 7:36 am

Had to get the car tuned locally. It runs correctly now. I sent a final email to Justin last night. I'm giving it until end of business Tuesday for him to respond. If I get nothing then I will take further action.

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