Ok the first thing to point out about this year model is that the computer system was sort of a cross bred. It is identified as eec IV or (OBDI). But it has a lot of the (OBD2) coding especially in the timing department. Where the earlier OBDI (A9L) type processors used basic timing maps driven buy rpm. The 94-95 systems use a load base timing system. This is done with a timing table that has rpm on one axes and load (volumetric efficiency) on the other. The computer looks at how much air is being drawn threw the maf and determines what the volumetric efficiency is at that specific rpm. At say 6000 rpm's an N/A motor reaches 5.0 liters of air or 100% load. So the pcm looks at that load cell in the timing map to determine how much advance is needed. This works great on a Mod motor because they do not rev as quickly as a Windsor. Ford also put some extra timing retarders that weren't included in the GT's pcm. I have seen a lot of good power gains just from doing a custom tune alone. Not to mention how much more responsive the car will react when the tip in re tarders are disabled. We have recently been fortunate enough to tune two of the few 94-95 cobras still on the road with minimal upgrades witch worked out perfect for our tests in this article thank you Tony & John.
 
Ok so the first thing to do is run a base line to find out where we are as far as HP, Torque and air fuel. The only major mod to this vehicle was an h pipe. This test was preformed and netted 224 rwhp and 250fpt. This is within 5hp 6ftq. Of our second test vehicle with the same mods. Next step on this vehicle Tony installed a set of 1 5/8th shorty header's a cat back system and K&N air filter. Back on the Dyno we go. Ok our first priority is to make sure our fuels our correct so we look at the data stream of the primary o2's to make sure they are switching properly this help to tell how much adjustment the pcm is trying to make to correct the fuel mixture. So monitoring the o2 voltage and AFR (air fuel ratio) on a wide band sensor helps us dial in the proper fuel ratio at idle and cruse we are looking for a target of 14.64 AFR. Once we have achieved this we can move on to WOT (wide open throttle) from here o2 voltage will not help us so are next step is to log MAF (mass air voltage). This will allow us to determine where to make the appropriate fuel changes to the WOT curve we determine this by matching AFR buy rpm on the Dyno graph and matching MAF voltage buy rpm in some sort of log (we like the sneecer). The way we use these readings are as follows lets say at 3-5,000rmp's our base fuel table is commanding a 12.5 AFR but we are actually seeing 13.5 on our wide band reading. First to determine how much the change will need to be we take 13.5 and divide it by 12.5 this gives us the difference of 1.08 or 8% ok remember this number we will need it in a few more steps. Next we determine where to make our change. We do this by looking at our Dyno graph and determining where we need to start our change. In this scenario we will start at 3,000 rpm's and work our way up threw the rpm band. Next we look at our MAF vs. RPM log to determine what voltage we are seeing from the MAF at 3,000 rpm's. Ok now we are ready for the next step in the pcm calibration (Binary code) there is a map called the MAF transfer function in layman's terms this map determines how much fuel to be added at a given reference voltage. The transfer function is made up of two columns one side is voltage and the other is pounds of air per minute. OK the more in depth explanation is that the MAF sends a voltage reference to the pcm to tell it how much air is coming in to the engine. This work on a 0-5 volt reference the higher the voltage the more air the pcm thinks is coming in to the engine the more fuel it adds. So we use this MAF transfer function to make the fuel adjustments we need to mach our commanded AFR with our actual.
So on to our next step once we have determined what voltage the MAF out puts at 3,000 rpm's we can then go to the Maf transfer function at that exact voltage reference and make our change to the pond per minute side. In this case we would add 8% to our pounds per minute column from the appropriate voltage all the way up to 5 volts.
 
Then we run the vehicle again and see if our change's made the exact adjustment we expected or are further changes needed.
 
Now that we have adjusted our fuels to a good safe mixture we can start to adjust our timing curve how much timing you say. This really depends on a lot of variables on average for a basically stock motor some where between 25-32 deg total advance it really depends on what the engine like or (the sweet spot).
Tony's 94 Cobra made 248.99rwhp and 302.rwtq not to bad at all for a vehicle with this many miles
 
John's 94 Cobra made 244.13rwhp and 292.42rwtq this is on a stock rebuild with around 5k on it h pipe and welded in flow masters
 
Tony's mods carried more power all the way across the power band.
 
I hope this helps open the window to the tuning world for all of you and if we can ever answer any questions at all please do not hesitate to contact us we strongly believe that if you don't give your knowledge away you lose it.

Thank you
Dan DeSio, Pro-Dyno

Ok where to start... let's take the 93 Cobra N/A for example. One of the first things to make sure of before tuning is that the vehicle is in proper running order (plugs, wires, 02's, fuel filter). It is important for these things to be up to par to properly tune the vehicle. Any mechanical issues with the running of the vehicle will be amplified by the tune.
 
So now that these things are covered we can start tuning. The first thing I always do is set the TPS (Throttle position sensor). I like to see it some where between .97v & .99v in my experience the closer to .99v the more responsive the throttle will be. The next step is to set the initial timing to stock 10deg position. This is done so we can synchronize what the vehicles computer is commanding and is actually happening. When a global adjustment is done to the distributor it changes the entire timing advance curve. This leaves a lot of room for improvement because this only allows the timing to be set to the max advance for a given rpm range. Let's say you set your timing to 14 deg and that is the max that the engine will take before it spark knocks at high rpm's. This might be all it will take up high in the rpm band but down low it may take 7deg advance and mid range might only take 5deg. By recalibrating the factory pcm programming we have the ability to make these fine adjustments to maximize performance in all power ranges.
 
Now on to the fuel the first step is to check the fuel pressure. If you have an adjustable fuel pressure regulator we want to make sure that pressure at idel with vacuum off is set to 39-40psi.This is the stock setting this is also the pressure that is used to determine the fuel injector size at 39.5 psi of fuel pressure a 24# injector flow's 24 pounds an hour. If you raise the fuel pressure the injector's flow more and richen the mixture and lowering the pressure leans the mixture. In the past this was used to add or subtract fuel at wide open throttle to fix a lean or rich condition. This is a bandage and doesn't work very well because it is a global adjustment. If you add pressure to richen your wide open fuel this also richens part throttle and idle. This can cause drivability issues like sluggish throttle response, hunting idle and bucking at cruse from a rich condition. Lean will cause the car to feel over responsive and jerky and the idle to hang.
 
Now before I explain how we adjust fuel in the pcm I need to give you a brief explanation of how the vehicle knows to adjust fuel. The key element is the mass air flow meter (maf) this is the central nerves system of the fuel injection on these cars. This works off flow coming in to the engine. This is calculated by using a heated wire sensor. Basically this works by heating a wire to around 250deg as air passes across the wire it cools. Then the voltage is increased by the pcm to maintain the 250deg. As this voltage is increased the pcm looks at the voltage and compares it to a table called the mass air transfer function. This transfer function is basically a conversion chart. One roe is voltage the other is pounds of air per minute. The voltage range is from 0-5. Volts so the pcm compares the voltage it is seeing from the sensor to the chart to see how many pounds of air are being passed in to the engine. So at X voltage = Y pounds of air are being added if Y pounds are entering the engine adjust fuel by this much.
 
Ok now that you have a basic understanding of how the maf works on to what we do when tuning. First we install a wide band 02 sensor so we can monitor air fuel mixture at idle and cruse we are looking for a mixture of 14.7. Then we monitor maf voltage and rpm's. From here we see how far away from 14.7 we are at each voltage point of the maf and add or subtract from the pond per minute side of the maf transfer function. Until we achieve the desired afr. Ok now the hard part is done on to the WOT tuning. Next step is to put it on the Dyno and dial in our afr's at wide open. For best performance and safety we are looking for a mixture around 12.8. This will lean the engine out enough to produce crisp acceleration wile maintaining enough fuel richness to help cool the cylinders under these stressful conditions. Once we have finished targeting our fuels we can move to dialing in our wide open timing. This is done buy a table of wot rpm vs. timing advance. From the factory these cars are set to see a total advance of around 25deg at 5,000 rpm's. This leaves quite a bit of room for improvement when you consider a GT has around 28deg at 5,000 rpm's and does not have GT40 heads and intake. From here we increase are timing advance across the wot curve until we stop seeing an increase of power. The next step is to work timing in and out to help smooth out any power and torque dips. Once this is accomplished a final cool down is performed and a final run is done to insure the power is repeatable.
 
On average we see these cars put out around 240-250 rwhp bone stock.
With a tune alone we will see around an 18-20 rwhp increase peak and 25-35 down low in the rpm range.
 
With full exhaust, pulleys, cai and custom tuning these vehicles average around 290 - 300 rwhp peak. The full exhaust makes a relatively large power increase because the cats drastically reduce flow.
 
Every car is different these numbers are not necessarily true for every 93 cobra these are based off a few select vehicles we have bean fortunate enough to run testing on. If you have any questions please do not hesitate to contact us.
 
Thank you
Dan DeSio, Pro-Dyno