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Discussion Starter · #1 ·

It is funny to think that twenty years ago, when Ford Mustangs were introduced with computer controlled engine systems, many people felt it signified the end of hot rodding. "EFI and EEC controlled engines will be too complicated for the lay person to modify", the nay sayers lamented. Obviously time has proven them wrong, and late-model Mustangs have become some of the most modified vehicles on the planet. While there is no denying that today's vehicles do indeed have more complex engine systems, the aftermarket companies have stepped up and created modern tools to make tuning and modifying a cinch.

One such class of modern tools is the handheld tuner. If electronic tuning devices were subject to evolution then the handheld tuner is to the performance "chip" as humans are to chimps. When the 5.0L Mustang came out with it's EEC-IV processor companies responded to the need for modifying the factory parameters by creating piggy-back chips which plugged into the service port on the EEC-IV processor. The chip held modified parameters to affect air-fuel ratio, idle speed, and other engine functions. While chips helped many owners of wild engine combinations solve their tuning issues, they were limited in their flexibility. For one, the chip had to be burned by someone with the appropriate know-how and burning software. Secondly, because chips held custom "one off" tunes, you typically had to get on a dyno so the chip tuner could make changes while seeing the effects. A custom burned chip would likely end up costing you $600 or more once you add up the dyno time, chip tuners time and chip cost. To add insult to injury if you made a subsequent modification to the engine, such as change a manifold or throttle body, you'd have to get the chip reburned.

Bring on OBD II
That was the Mesozoic era. In 1994 the Feds mandated all vehicles sold in the US beginning in 1996 were required to have OBD-II, or On Board Diagnostics System second generation. OBD-II is a standard for emissions systems monitoring. Since virtually all of a vehicles engine and
driveline systems can potentially impact emissions the OBD-II system is a quite complex electronic integration between the vehicles PCM (powertrain control module), sensors, and dash display. The OBD-II system can detect and display a trouble code for engine components and systems failing or about to fail. OBD-II also mandates a standard 16 pin diagnostic port, or DLC (diagnostic link connector) where technicians can plug in a scan tool to monitor virtually every sensor on the vehicle. Besides diagnostics the other benefit to the OBD-II standard is that many PCM's (such as Ford's EEC-V) can be reprogrammed, or "flashed", through the OBD-II port. Flashing or programming requires a device which contains flashing software/firmware and either stored programs, or a human interface to allow parameter modification.

Enter the Diablo Predator.
While certainly not the only handheld tuner on the market, the Predator might however be the most versatile. The unit appears as a typical scan or code-reader tool. In fact while it does indeed scan diagnostic trouble codes the real brawn is in it's ability to put a performance tune into your Mustangs brain. Note that while this article features testing of the Predator on a Mustang, the unit is also available for a wide range of Ford performance cars and trucks, including the Mercury Marauder, SVT Focus, F-series trucks and Powerstroke diesels. The units comes prepackaged with a Diablo engineered tune for that specific make and model vehicle. The unit's DLC connector is attached to the vehicles OBD-II port (typically located 16" from the steering wheel under the dash or near the center console). Once connected the unit powers up and the on screen display provides instructions for loading up the performance tune, backing up the stock tune, and making additional modifications.

The Predator provides several options. The first is to load up the tune provided by Diablosport. Like many tuning companies they have done their homework on a stock Mustang, or whatever vehicle the unit was purchased for, and come up with a canned program that will result in some increase in performance over stock. This generally boils down to air-fuel ratio and timing changes, and the amount gained usually depends on how much slack the factory left in the stock tune.

When the unit is connected to a vehicle for the first time it "marries" itself to that vehicles VIN number and creates a backup of the factory settings. Then the owner is free to load up the supplied tune, modify the stock settings and effectively create their own tune, or to modify the supplied tune. The Predator enables tuning wide-open throttle air-fuel ratios to a certain percentage leaner or richer than stock, in two rpm ranges; 2000 to 4000 rpm and 4000 to 7000 rpm. Timing can also be advanced or retarded for those two wide-open throttle ranges. A host of other very useful parameters are modifiable. RPM and speed limits can be adjusted. For automatic transmissions the torque firmness and modulation can be set adjusted for all gears. There are also several emissions related settings, such as turning off the EGR or downstream O2 sensors, for vehicles using off-road components. A nice feature is if you have modified your differential gear ratio, or installed different height tires, you can use the Predator to program the correct speedometer differential. With capabilities such as this the $400 unit begins to pay for itself when you consider the savings from having to spend on external speed calibrator devices, or O2 sensor MIL eliminators.

Installing and Testing
On our test vehicle, a 2001 Mustang GT, we loaded up the supplied Diablo performance tune, version v.7r50c. Diablo's website maintains a list of updated tunes, so it is wise to check it often for new and improved files. Using a serial cable the Predator can also be connected to a PC for downloading new tunes into the unit, or uploading the backup tune and on your laptop or desktop. The Predator also has a live data view and logging utility which is useful to see actual engine sensor data. The log can be transferred to a PC for viewing with free software available from Diablosports website.

Once the Predator writes the tune to your vehicles PCM, a process which takes several minutes, the unit can be disconnected. The tune is now permanently in your engines computer and can only be removed by the same Predator unit which installed it. The Predator unit cannot be used on another vehicle until it has restored the factory tune to the vehicle from which it was backed up. Once the new tune is written to the vehicle you can opt to make additional changes, or fine tuning.

Dyno Testing
We headed to our dyno affiliate Custom Dyno Tuning in Hayward, California to spend the day with owner Arlee Taylor testing out the effects of the Predator tuner. Arlee's shop does considerable late-model tuning, Fords and otherwise, but is actually an SCT dealer. SCT (Superchips Tune) is Diablosports competitor, so naturally Arlee had some interest in seeing how well the Predator performs. We made nearly a dozen pulls ranging from the factory 2001 GT tune to the Predator's performance tune, as well as our own variations of both tunes using the units ability to adjut air-fuel ratio and timing. Our test pony has a fairly stock 4.6L 2V motor, with the only modifications being an off-road X-pipe, Plasma Booster ignition, and aftermarket upper plenum.

We had installed the Predator tune to the vehicle several days prior to
our dyno session in order to compensate for any "learning" the PCM might do as a result of the new parameters. The idea that the computer needs to spend some amount of time adjusting to new modifications is a shaky concept used sparingly by many late-model owners and tuners. While we certainly have witnessed a late-model Mustang perform better several days after bolting on a modification, we have however never seen this tested this in a controlled environment. The plausible explanation is that some modifications, particularly those effecting the air flow into the motor, result in immediate short-term fuel trim changes as the PCM tries to compensate for the different air-fuel ratio feedback from the O2 sensors. Over time these short-term fuel trim changes are incorporated into the engines long-term fuel trim strategy, hence resulting in some variance in overall performance. Again, this sort of "learning" probably does occur but we haven't spent any considerable time analyzing to what extent.

Our first pulls on the dyno were therefore
with the Predator performance tune as delivered in the unit. We then reinstalled the factory tune and made additional pulls. This was followed by reinstalling the Predator tune and manually adjusting the air-fuel ratios to various stages of lean in order to approach 13.0:1 at wide-open throttle. Finally our last pull was with the PCM flashed back to the as-delivered Predator tune. This would give us a chance to compare the effects of the Predator tune when the car has had several days to "learn" it, versus immediately loading the tune and making a dyno pull.

The Results
With the PCM tuned as Ford delivered it, our normally aspirated 4.6L 2V made 231 horsepower and 262 ft-lbs of torque. For those who are already comparing our numbers to their '99-'04 GT keep in mind that load-bearing dynos such as the Mustang Dyno operate differently than inertia-only dynos such as the Dynojet 248. Look for an FM original article soon on the differences between various chassis dynos. For now it is important to realize Mustang Dyno numbers tend to be slightly less than Dynojet figures, as they reflect true load conditions on the vehicle, such as air resistance at speed. The key in any dyno testing is comparing apples to apples and looking at the differences using the same measuring equipment.
With the PCM flashed with the as-delivered Predator tune the numbers improved to a peak of 234 horsepower and 268 ft-lbs. While initially this seems to be hardly a significant gain, take a closer look at the charts. Horsepower with the stock tune (black) peaks out at 5150 rpm and then drops off. Horsepower with the Predator is 232 at 5150 and it continues to rise up to 234 at 5600 rpm and pulls to 5900 without dipping below 233 HP. In fact, horsepower with the Predator is up 3-5 points all across the rpm range. Torque increased 4-6 ft-lbs from 3300-4500 rpm.

Looking at the data from our wideband O2 sensor we still felt engine was rich. With the factory tune our '01 GT would approach 12.0:1 A/F at wide open throttle. With the canned Predator tune the ratios are leaned up slightly to 12.5:1. We used the Predator's parameter edit mode to further lean out the the A/F ratio in small increments. The Predator enables adjustments of the A/F ratio up to 15% leaner and 40% richer than stock. Surprisingly the engine didn't respond at all to a leaner A/F ratio. We went in steps from 12.5:1 to 12.8 to 13.0 and the power actually dropped 1-2 HP across the board. It appeared that the Predator tune was as good as it was going to get, and that was only a handful of horsepower and torque above stock.
Is there more?
Not fully convinced that a 4.6L 2V delivered from the factory with pig rich A/F ratios has only 5 horsepower to be found from tuning, we emailed the guys at Diablo with our numbers. They indicated that these gains are about what they see on normally aspirated GT's, but suggested going back to the dyno and maxing out the spark advance. The Predator allows for up to 10% more advance over stock and 40% retard from the stock set point. We followed their advice and sure enough that is is where the hidden power was. We picked up an additional 7 horsepower and torque over the canned Predator tune. Overall were achieved average gains of 10 horsepower and 12 ft-lbs. over the factory tune. What is more impressive are the gains at every rpm point in the power band. With the Predator tune the motor pulls 400-500 rpm beyond the factory peak horsepower point. With the added timing advance on top of the canned Predator tune we gained as much as 16 ft-lbs of torque below 4000 rpm. Of course with the added timing you must run the high pump octane. We have encountered no pinging so far with 91 octane in the tank. That might change during the summer months however.

When it comes down to it, all performance mods must be rated on a horsepower to dollar scale. The Predator at around $400 for 12 horsepower is a pretty good deal as is. In fact while not represented in this article we've seen double those gains on supercharged GT's as well as the 4V Cobra's. Add in all the other cool cost saving features, such as a built in speedometer adjustment, downstream O2 sensor control, code scanner and data-logger and you have easily covered the costs for buying those products individually.

Horsepower Gains
Stock Tune versus Predator Tune with Max Timing Advance
Stock Tune HP
Pred & Advance +/-
3100 143 148 +5
3300 154.8 163 +8.2
3500 166.26 177.4 +11.1
3700 178.5 190.4 +11.9
3900 190.4 203.2 +12.6
4100 203.5 214.8 +11.3
4300 213.6 224.6 +11
4500 221.1 232.1 +11
4700 226.5 237.1 +10.6
4900 230.1 239.2 +9.1
5100 231.1 240.2 +9.1
5300 230.5 240.7 +10.2
5500 226.5 240.8 +14.3
5700 225 240.5 +15.5
5900 224.4 230 +5.6

Torque Gains
Stock Tune versus Predator Tune
with Max Timing Advance
Stock Tune HP
Pred & Advance +/-
3100 242 250.4 +8.4
3300 244.6 258.9 +14.3
3500 249.3 265.8 +16.5
3700 253.1 270.1 +17
3900 256.7 273.2 +16.5
4100 260.8 274.7 +13.9
4300 261 273.8 +12.8
4500 258.1 270.5 +12.4
4700 253.1 264.8 +11.1
4900 246.5 256.3 +9.8
5100 237.7 247.3 +9.6
5300 226.6 238.3 +11.7
5500 216.8 230 +13.2
5700 208 222.5 +14.5
5900 203.2 210.5 +7.2

150 Posts
so...........somebody clarify for me..........

are they saying it is safe to put the timing up all the way on the predator? I've got one, but i'm just about completely stupid with it. i've been running 93 octane since i got it with no pinging, but i didn't want to push my luck. i'm not the best with money so having to buy a new engine anytime soon would just really really suck

88 Posts
DarqueGT said:
so...........somebody clarify for me..........

are they saying it is safe to put the timing up all the way on the predator? I've got one, but i'm just about completely stupid with it. i've been running 93 octane since i got it with no pinging, but i didn't want to push my luck. i'm not the best with money so having to buy a new engine anytime soon would just really really suck
Timing on the DSP is measured in % and not degrees. So if your stock timing is 10* (in most cases a stock GT is set from the factory @ 10*) and you set your DSP timing to 10%. That's just 11* base timing no biggie! But that also means 10% added to the entire timing curve. So to be safe get your stang on a dyno and find out what your timing is b4 messing with it on the DSP because not all stangs are alike. Your timing changes throughout the entire rpm curve. It doesn't stay @ 10*. Plus you may want to lower your tstat to 180* instead of the stocker to help keep thing a little cooler. Plus if u do set the timing on the DSP to 10% keep running 93+ oct.
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