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Posted by VENOMOUS TUNING on Aug 6th 2022


We had the opportunity to remote custom tune a 2007 GT500 this week. It didn't go as planned! 

If you own a GT500 (or any other vehicle) that you want to mod and have tuned, this is an important, detailed story that you need to read.  

Let's examine:

As we peek into the garage at our own 2007, Christine, it's hard to believe she's 16 years old now. But it underscores just one of the reasons why "canned" tunes are potentially dangerous.  When a Mustang rolls off the line at Flat Rock, every component is minty fresh. Hard parts are fastened, mechanical parts lubed and moving as they should and electronic bits all sending and receiving signals as designed.  

And then comes time. And elements. And use. They all take their tolls in different ways, but in the end, components and systems degrade.  

The things that we tell GT500 owners that should pay attention to are: Fueling, Cooling and Tuning.  

Fuel quality is not just consistent anti-knock properties, but the detergents they use to keep the internals clean and consistency. We recommend BP, Sunoco, Chevron, Shell over anything else. Use 93 if you can, 91 if you have to and NEVER use ethanol free gas. That's for your lawn mower and boat, not for your car. 

Cooling is the radiator, of course, but almost more important on these cars is the intercooler system. The system includes the actual intercooler (the"brick" with the cooling fins, located beneath your supercharger), the feed and return hoses, an electric pump, a front mounted heat exchanger and a reservoir or degas bottle and a sensor to provide feedback to the PCM. Common points of failure are fuses/the pump, an air bubble getting into the system and ceasing the flow, the intercooler grid becoming clogged with oily residue from blowby that enters back into the blower (you need a catch can), the internals of the intercooler brick itself and finally the sensor (located between the blower and the fuel rail on the driver's side of the engine.) Examination of a number of "bricks" over the years show a high level of calcification/scaling which again slows the flow of coolant.  This is even worse among the units that run water and additives versus the specified coolant. 

Tuning. Ah, yes. This is our part.  Whether you buy your "canned" tune as a standalone service, use the one that comes on a particular device or one that is provided with a "kit" (blower, cold air, etc), you expect to upload this file onto your car and everything be fine.  Unless it isn't. Most "canned" tunes are provided without specific instructions for you to datalog and how to provide that information to the tuning company.  Understand that this "canned" tune is based on the data of the averages of a LOT of different cars, with different owners, usage, condition, age, mods, fuels.  It has NOTHING to do specifically with your car. It's an estimate. The OEMs can do this and it works, because they have spent millions of dollars and countless man-hours in research and development to make sure that the tune that comes in your car will help it work correctly the first time it fires up and every other time in the future (at least until the warranty is up). 

This is how Venomous Tuning is different. We do not provide you with a plug and play tune. We provide you with a base file that isn't even designed to be driven until we see a start up datalog.  There are no exceptions. Why?  Because the newest of S197 GT500s is now 8 years old! Our guesstimate is that 30 to 50 percent of them have changed hands over the years. One, two, three or more owners. Unknown mods. No handheld tuning device came with the car. Wiring debacles from performance mods, stereo and anti-theft systems. Two-steps. Wrong coil packs. Wrong plugs. Crispy wiring harnesses. We see it all, every single week.  

Which brings us back to this week's example-

The owner did their homework. They did a blower upgrade and had asked us for guidance regarding fueling, electronics, airflow, etc.  Quality components like Injector Dynamics ID1050X, fuel pump booster, JLT 123mm cold air intake we used. Since the car has no means by which to measure air/fuel from the factory, the plan was to do a quick start up datalog so we could confirm fueling, no fuel nor vacuum leaks, etc PRIOR to getting strapped on a dyno. This saves our customers time and  money and it's a part of our normal service. Once we do a quick log and revision, they're good to drive to the dyno (no boost!) and the fun begins.  Unfortunately, this customer's car was not complete in time to do that initial datalog and checkoff.  It went directly to the dyno and was strapped on.  

We did some no-load logging at idle and a slow rev throughout the range.  There was a 15% disparity from one side to the other. That means a fueling issue (injector, o-ring, connection, etc) AND/OR an exhaust leak before the upstream O2 AND/OR and bad/weak upstream O2 sensor. In this case, it was an exhaust leak. The clock was ticking for our client as they made repairs while the car sat on a dyno (NEVER a good idea and exactly why we insist on a checkout BEFORE going to the dyno).  Once repaired, the fueling was dialed in and we were ready for a short wide open throttle pull.

As an aside, to minimize the length of time that the car accelerates at wide open throttle on the dyno, we ask the operator to reduce the "load" on the dyno. Some have load controls to allow them to better simulate real world conditions and factor for vehicle weights, power, etc. This particular dyno was a Mustang and it was loaded more than we would have preferred.  This is also important because the longer the pull, the more heat that can and will build.

The first WOT pull is at a reduced level of timing since we're concentrating on dialing in the air/fuel ratio so that the commanded and actual values agree. The dyno was 1,500 miles away but via a screen share I am watching things happen in real time.  I see the IAT2/downstream temps head to the sky! The downstream temps are post-intercooler. The compressed air from the blower is HOT so it gets pushed down through the intercooler and the water passing through it cools the air charge before it hits the combustion chamber. High downstream temps contribute to detonation/knock. This is why Ford GT500s begin pulling timing when IAT2 is as low as 110F.  Downstream temps will average around 30-35 degrees over ambient while at operating temperature and no boost.  Yes, on a 85 degree day you could be pulling timing in your driveway. This is also the reason why your first stoplight blast feels fine and the next one feels like you lost 50 horsepower. Because you probably did!  As part of our tuning process, we raise that threshold and don't allow the system to pull until it reaches a higher limit. But once it does, we pull the timing VERY aggressively for the safety of the vehicle. 

In this case, the IAT2 on the very first pull from 2,000-5,000 rpm blasted to 165F!!  Our custom tuning pulled the rug out from under it quickly enough that it only had 5 degrees of timing left in just a second or so. It certainly didn't make any power, but it also didn't destroy the engine with excessive knock or by lifting a head (REALLY bad news).

How did this happen?  Think about all the components of that intercooler cooling system described above. The first and simple thing they'll do is change the IAT2 sensor to confirm that the readings were real. We took a physical measurement of the temps inside the degas bottle and they were nowhere near that level, so (hopefully) it's as simple as a worn out sensor.  But if a new sensor shows the same result, it's time to pull the intercooler brick, clean it inside and out and try again. They had an older AFCO dual pass, non-fanned heat exchanger on the car.  Was it partially filled with residue?  Perhaps.  Time to check that as well. 

As the title of this article says, "CANNED TUNES ARE DANGEROUS". 

So is hopping on a dyno without datalogging. 

So is having your car "dyno tuned" by someone other than a specialist with your model of vehicle. 

Let us know if we can help you.