Bolt-ons. Advertised HP compared to real world numbers on the dyno here!
Super Ford, May 1996
Dynojetting the popular 5.0 Mustang performance mods to
see how much power they really make
text by Donald Farr
"How much power does it make?" must be one of the all-time most asked questions when the talk turns to 5.0
Mustangs and the plethora of high-performance parts that help them make more power. Over the past 10 years,
the performance aftermarket has exploded with 5.0 Mustang goodies, from simple bolt-ons like underdrive
pulleys to several varieties of aluminum heads. We know the parts work, at least most of them, because we feel
the results in the seat of our pants and we see the improved numbers on the drag strip scoreboard.
To find out just how much improvement 5.0 owners can expect from certain components, or a combination of
components, we strapped a stock '89 5.0 LX Mustang onto a Dynojet chassis dynamometer, took a baseline
reading, then begin bolting on many of the popular high-performance parts and noting their horsepower and
torque improvements. During our buildup, some parts were surprisingly effective, others performed as expected
and a few fell short of our expectations. In all, we learned nearly all of the 5.0 high-performance parts work, some
better than others, and it's the combination of parts that really wake things up under the hood.
As a quick, easy and reliable method of measuring power at the driven wheels, Dynojets have been installed at
shops around the country at a dizzying rate in the last year. Dynojet owners include K&N Engineering,
Hypertech and Kenne Bell, Mustang-specific shops like Kenny Brown and Steeda Autosports have Dynojets on
order, and several Winston Cup teams, including those of Rusty Wallace and Ricky Rudd, recently used
Dynojet's portable unit to test their Thunderbirds prior to the Daytona 500.
While Super Ford will continue to test on engine dynos and drag strips, the Dynojet has joined our
parts-evaluating toolbox. Unlike engine dynos, the Dynojet simulates road or track conditions, with the engine in
the car and running through its drivetrain and full exhaust. And unlike drag strips, the Dynojet is not affected, or
at least not as affected, by driving, weather, or track conditions.
To obtain its data, the Dynojet mounts a vehicle's drive tires on a pair of 48-inch-diameter drums. By calculating
how fast the drums accelerate, the Dynojet delivers precise measurements to a personal computer programmed
with Dynojet's software, which calculates horsepower and torque among other data. The design of the drums
prevents tire slippage or deformation, which results in precise, repeatable information, although like any testing
tool, it must be used carefully to assure repeatable information. Think of the Dynojet as an improved and vastly
more intelligent version of the old two-roller chassis dyno, with a 1200 hp capability.
For our test, Dynojet delivered it portable unit, along with Eastern U.S. Director of Operations Marc Hayes, to
Steeda Autosports in Pompano Beach, Florida. For the four days of testing in late January, Steeda's Dario
Orlando was kind enough to devote two of his technicians, Steve Chichisola and Chad Boy, to the project. Since
Steeda Autosports is primarily a late-model Mustang business complete with installation shop, Steve and Chad
are intimately familiar with the 5.0 Mustang. They constantly amazed us with their speed, removing and installing
short-tube headers in 15 minutes and swapping heads in just over three hours.
We started with a 1989 5.0 LX Mustang, "an old Steeda workhorse," Steve said. With 126,000 miles, the
five-speed LX hatchback was typical of many 5.0 Mustangs on the road today and a good place to start. The
Steeda crew made sure everything was stock, including the exhaust system and air intake silencer inside the right
With a manual transmission, Marc says you can expect a 10-percent power loss, typically 20-25 horsepower for a
5.0 Mustang, on the Dynojet due to frictional losses through the drivetrain. (With an automatic, Marc says you
can expect to lose 40 or more horsepower). The Dynojet is capable of determining the frictional loss, with our test
Mustang showing only an 18 horsepower drop. The frictional horsepower loss remains constant as long as the
drivetrain is not changed, so it is not accrued as modifications increase horsepower. In other words, to get a
flywheel, or "advertised," rating for our modifications, just add 18 horsepower to the rear-wheel numbers.
Every run on the Dynojet was identical -- make the modification, warm up the engine and drivetrain on the dyno,
then accelerate the engine, in fouth gear, from 1500 to 5500 rpm at wide-open throttle. In most cases, three runs
were made for each change: one to get the engine up to operating temperature, a second for the real number and
a third for backup purposes. For consistency, Steve operated the car for every run, while Marc orchestrated the
For our baseline number, Steve made three runs on the Dynojet, reaching a peak rear-wheel horsepower of 201.7
at 4300 rpm. Adding in the 18 horsepower for drivetrain loss, the number comes to 219.7 at the flywheel, very
close to the factory 225 horsepower rating and impressive for an engine with 126,000 miles.
PHASE 1 -- BOLT-ONS
Remove intake silencer. Ford used a plastic air intake silencer, mounted inside the right front fender, to reduce
the noise caused by air rushing into the induction system. The design of the box restricts airflow, so removing it
has become one of the first modifications performed by 5.0 owners. Removing the silencer from our Mustang
supported this modification, showing a peak horsepower of 206.2 at a higher 4700 rpm for a 4.5 horsepower gain.
Not bad for free.
K&N filter. Continuing to free up induction, we yanked the stock air filter and replaced it with a K&N
Filtercharger, a reusable high-performance filter. We expected another large gain, but the K&N netted just over a
horsepower for a peak of 207.3. The only explanation was that the K&N may not work as good with a stock
engine, and that it may prove more beneficial as we make further modifications.
Underdrive pulleys. With many reports of quarter-mile improvements, we had to try underdrive pulleys on our
dyno Mustang. March Performance supplied their lightweight aluminum three-pulley "street" set, part number
2010, powder coated in a brilliant red to match our test 5.0, to reduce the horsepower-robbing drag from the front
engine accessories, including the water pump and alternator.
Steve bolted on the pulleys in less than 10 minutes, and the test run showed a peak horsepower number of 217.4,
an impressive increase of 10.1 horsepower, even more impressive was the fact that the underdrives helped across
the rpm band -- 5.2 horsepower at 2500 rpm, 9.4 at 3000 and 12.5 at 5000. The pulleys also improved torque all the
way across, with a peak improvement of 13.6 lb ft.
One side effect of the pulleys during the remainder of our test was the additional heat in the engine. Since the
underdrive pulleys slow down the water pump, the engine ran about one notch hotter on the temperature gauge
after a series of dyno runs.
SplitFire spark plugs. These plugs, with their unique "split" electrode, have benefitted tremendously from their
marketing and advertising campaign. We wanted to see if our test would back up their claims. After swapping a
set of brand-new SplitFires, part number SF2E, im place of the 5.0's somewhat used Motorcraft ASF32C plugs, we
saw a peak horsepower number of 218.9, a 1.5 horsepower increase that could be attributed to fresher plugs and
not necessarily to the design of the SplitFires.
At this point, we tried two Pro-M mass air meters, a 75mm and a 77mm. Neither showed an improvement with our
minor modifications, so we replaced th4e stock meter and decided to try the Pro-Ms again after amking exhaust
Crane 1.7 rocker arms. Originally designed and manufactured by Crane Cams for the 5.0 Cobra engines, these
bolt-on, roller-tipped rocker arms increase the ratio from the stock 1.6 to 1.7 for more valve lift with the stock
camshaft, not to mention a tad less friction with the roller tips. After bolting on a set of these rockers, we saw a
peak horsepower of 223.2, a significant 4.3 horsepower increase over our previous number. The gain also agrees
with engine dyno work we've done.
PHASE 2 -- EXHAUST
Exhaust modifications rate second in terms of popularity among 5.0 owners after the simple bolt-ons. Regardless
of their performance improvement, mufflers provide a powerful sound, and there's always something sexy about
headers. Going with the popular items -- short-tube headers and Flowmaster mufflers -- seemed like the logical
route for our test.
Before proceeding with our exhaust modifications, we wanted to try a set of off-raod pipes with the stock
headers and mufflers. Off-road pipes, which bolt in place of the factory catalytic converters, are not street legal,
but many 5.0 Mustang owners bolt them on for the drag strip or road course. So after our Phase 1 bolt-ons and
before discarding the stock headers and mufflers for Phase 2, we slipped in a set of off-road pipes from
Pacesetter. We immediately noticed a more high-performance growl from the stock mufflers. On the Dynojet, the
off-road pipes picked up 5.5 horsepower.
To keep our subsequent modifications street legal, the stock cats were replaced before proceeding.
Flowmaster mufflers. Realizing that mufflers are one of the most popular bolt-ons among 5.0 Mustang owners,
we ditched the factory mufflers and tailpipes in favor of Flowmaster's American Thunder kit with two-chamber
mufflers and 2 1/2-inch tailpipes. The free-flowing mufflers, which also gave our Mustang that power rumble
we're so familiar with, netted 227.9 horsepower, and increase of 4.7 horsepower.
Motorsport short-tube headers. We had expected more from the Flowmaster mufflers, so we felt that perhaps the
stock headers wre restricting exhaust up front. Figuring that the larger short-tube headers may open up the
restriction, the Steeda crew bolted on a set of Motorsport's unequal-length, short-tube headers, part number
M-9430-SSC. Surprisingly, we got nothing; in fact, with the 227.6 peak horsepower number, we actually lost a
fraction of a horsepower.
Pro-M 75mm mass air meter. With the exhaust opened up, we felt the time was right to open the induction with
a larger mass air meter. Pro-M's 75mm meter did the trick, raising peak horsepower to 230.8 for a total increase of
Hooker equal-length short-tube headers. After seeing such a small increase from the Motorsport short-tubes,
we really weren't expecting much more from the equal-lengths. We were right. The Dynojet showed a 1.1
horsepower improvement, for a total peak power of 231.9. the Steeda technicians, who swapped the
unequal-length short-tubes in about 15 minutes but labored for more than an hour installing the bulkier equal
lengths, wondered if the extra effort was worth it.
Needless to say, we were somewhat dismayed by the "only" 8.7 horsepower, 5.8 lb ft torque increase from the
performance exhaust -- which included the 75mm mass air meter in our test. Had we changed the sequence of
modification, adding the exhaust after induction and heads, it's possible we would have seen a larger increase.
As part of a complete performance system, however, exhaust modifications are a must. Our exhaust experience is
another way of illustrating how important the combination is, and how tests can be skewed to show gains or
75mm air meter
PHASE 3 -- INDUCTION
GT-40 intake. Tour any car show or drag strip and you'll see Motorsport GT-40 intake everywhere. In addition
to looking great, the GT-40 induction system, which includes upper and lower sections, provides larger diameter
intake runners in conjunction with a larger 65mm throttle body, which should easily compute to better airflow
and more power.
Without making any other changes, the Steeda crew bolted on a GT-40 intake with the adjustable fuel pressure
set at the stock 32 lb. On the first dyno run, Steve said he could feel the additional horsepower in the car, but the
numbers came up shorter than anticipated, a peak of 238.6 for a gain of 6.7 horsepower over our best Phase 2
number. Raising the fuel pressure to 35 and 38 lbs hurt horsepower, so we went back to the stock 32 lb setting.
Computer module. For his own information, Dario Orlando brought out a computer module that Steeda has been
developing. When the module gave us a remarkable increase, up 10.2 horsepower for a 248.8 peak, we decided to
leave it in as part of our test. In fact, subsequent testing of the module in Phase 3 and 4 showed that it worked
better as other modifications were added. Stteda now offers the module under part number STB89.
We also tried a variety of mass air meter and chip combinations. Switching to the Pro-M 77mm meter lost a
couple of horsepower, but adding the Steeda chip with the 77mm meter brought it back up 6.3 horsepower. In the
end, we were not able to better the 75mm mass air and Steeda module combination.
PHASE 4 -- HEADS
GT-40 aluminum heads. With more air coming in and more exhaust going out, we finally got to the plugged up
funnel in the middle, the stock heads. By replacing them with a pair of Ford Motorsport's GT-40 aluminum heads,
with their better flowing intake and exhaust ports, we expected to open up a large horsepower increase.
Swapping heads is no small feat, but Steve and Chad bolted on the preassembled GT-40 heads in just over three
hours, fitting them with the 1.7 Cobra rocker arms and SplitFire plugs (SF10Ds for the GT-40 heads). Without
changing anything else from Phase 3's 248.8 horsepower peak, the Mustang made 272.4 horsepower, a 23.6
horsepower increase for our best improvement yet. The heads also provided a 17.3 lb ft increase in torque,
putting us over the 300 lb ft mark for the first time with a 308.9 reading. It's been said many times before, but it's
worth saying again; the biggest stumbling block to small-block Ford performance is he exhaust port in the stock
cylinder head. Port it or, preferably, replace it for a solid performance foundation.
We also tried a combination of mass air meters, modules and increased fuel pressure, but nothing performed
better than out 75mm MAF/Steeda module/stock fuel pressure combo. We also tried the Pro-M mass air again,
thinking the increased airflow potential would allow it to work. It didn't, losing horsepower across the rpm band.
Perhaps the 77mm piece should be reserved for blowers.
24 lb. injectors. Steeda's experience with injectors has shown 24 pounders work well with the GT-40 aluminum
heads. Dario explained this is primarily because the larger nozzle spreads out the fuel charge for better
atomization. On our test Mustang, the 24 lb injectors pumped up the horsepower to 275.6, a 3.2 horsepower
increase. With so many miles on the original injectors, this increase could have come from the new injectors
cleaner, more even spray pattern, but we really don't know for sure.
24 lb. injectors
PHASE 5 -- FINAL TWEAKS
With 275.6 rear-wheel horsepower in street-legal trim (adding in the 18 horsepower frictional loss gave us 293.6
"advertised" horsepower), we wanted to try some final tweaks to see if we could eke out more horsepower,
hoping to attain that magic 300 mark atthe flywheel.
Off-road pipes. Surprisingly, replacing the factory cats with the Pacesetter off-road pipes netted an increase on
only 2.8 horsepower over our previous best. We expected better results from opening up the exhaust even more,
but I guess we learned exhaust modifications, while making our Mustangs sound great, don't always provide
huge horsepower increases. This would likely change if nitrous or a blower was added.
At this point, we wanted to check the benefit of the K&N Filtercharger atthis level of modifications, so we
replaced the K&N with the stock filter. This resulted in a loss of 4.1 horsepower, demonstrating that the K&N,
which didn't add much when the engine was basically stock, really does it's job with other modifications.
Cool down. When Dario suggested letting the Mustang cool down, which included icing the intake, Marc
commented, "We've been doing this for four days; let's don't get stupid all of a sudden." Marc ate his words
when the Mustang responded with a 6.7 horsepower, 12 lb ft torque increase, which supports the actions of all
those 5.0 owners who drag coolers filled with ice to the strip. With a total peak rear-wheel horsepower of 285.1,
adding in the 14 horsepower frictional drivetrain loss brought us to 303.1 flywheel horsepower.
Cool, ice intake
What did we learn from our 5.0 Dynojet test? For starters, we discovered "huge" horsepower increases are not
part of most individual bolt-ons. Heads generated the biggest gain, which suggests they should be one of the
first modifications made, and the underdrive pulleys and Steeda's new computer module made good impressions
as well. The main point: Putting everything together as a complete system really tallies up the horsepower. We
added over 83 horsepower with just bolt-on parts.
Best of all, we learned you can buy a used 5.0 Mustang for around $5000, then duplicate our modifications for
around $3200 (according to quick calculations based on advertised prices, not including installation). So for
under $8500 and a little grease under the fingernails, anyone can build a 300-horsepower 5.0 Mustang that'll
outrun brand-new $25,000 Camaros.
BLACK ON BLACK 95 GT VERT FULLY CONVERTED TO A 95 COBRA AND MODIFIED WITH ALOT OF GOODIES AND A BB SINGLE T67 TURBO KIT. 526.14RWHP 496.00RWTQ @6PSI. RAN OUT OF FUEL @5500RPM
PROJECT CAR AKA MONEY-PIT LOL!...
TUNED BY GEORGE @ AKRON HP.