Product Review: C&L 76mm
Mass Air System [ back]
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The
cast-aluminum 76mm C&L design is unique in that calibration
changes are affected by changing an aluminum sample tube
inside the unit (The user supplies his own sensor element)
By changing the diameter of the trailing portion of the
sample tube, flow over the sensor element can be altered
for compatibility with different-size injectors.
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Fooling
the system?
Whenever an engine is fitted with larger fuel injectors a
corresponding change must be made in the calibration of the
mass air sensor. Otherwise the sensor will send a voltage
signal to the PCM corresponding to the 19lb injectors (or
whatever you were running), resulting in a rich condition.
Manufacturers
of mass air meters use two methods to modify the calibration,
and it is the difference in these two methods that results
in people taking sides with one manufacturer or another.
The calibration can be changed in two ways, by modifying the
electronics in the sensor itself, or by changing the speed
and amount of air passed over the sensor wires. Companies
like Pro-M (Best Products) modify the sensor, while C&L
uses the latter method. The goal is the same, to make the
computer think there is less air than there really is, thus
reducing the amount of time the injector is opened. Why do
we want that? Because we have upgraded to a larger injector,
and thus it needs a shorter pulse-width than a smaller injector.
Either way the end effect is that the EEC system is "fooled"
because the change made is simply to reduce the signal being
sent to the computer, rather than modifying the actual tables
in the EEC which are created for a 19lb injector (24lb for
a 1993 Cobra processor.) There is actually a third, more correct
way, by modifying the "lookup" tables in the EEC
itself. However this would require a EEC Tuner or similar
software, and is out of the scope of the majority of enthusiasts.

Pre
1989 Mustangs (and other Ford Mass Air cars) used a square
mass air connector. |

Post
1989 used this oval connector. |
So
is there a advantage or disadvantage to how the mass air meter
is calibrated for larger injectors? Well the answer depends
on which camp you are in. In terms of cost, we like the C&L
sample tube method, because if you ever upgrade injectors
size in the future, all you need is a $20 sample tube. With
the other method you must send the entire mass air meter back
to the manufacturer for a recalibration. Some think this is
preferable since you get a "more accurate" calibration...however
the C&L devotees will tell you this offers more chance
of error and problems, since each unit is individually calibrated,
rather than produced the under high-tolerance and consistency
of CNC machining.
We found one other reason why we liked the C&L method.
We noticed both our test cars had different shaped sensor
connectors. The '88 has a rectangular connector, while the
'92 has an oval connector. Because the C&L requires you
to use your existing sensor, the different connectors does
not a problem. However with the other mass air meters on the
market owners of 1988 and possibly 1989 5.0L with the square
connector would be required to upgrade the harness and connector
to the later oval style.
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Testing
and Results
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Stock
Mustang 55mm mass air meter, right, and C&L 76mm left
(shown with 19lb sampling tube.) |
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The
stock rubber "accordian" tube is conducive to
turbulent flow. The aluminum TrueFlow pipe is said to
smooth out flow and provide an increase of about 3-4 horsepower.
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Stock
1992 Mustang
The
first test of the C&L 76mm mass-air system was performed
on our resident '92 LX Mustang, aka "Green Machine II".
At the time of testing the car featured a bone-stock 5.0L engine,
AOD transmission, and stock 3.27:1 gears. Tech editor Jim Langley
made a total of eight passes. Two with the stock 55mm mass-air
meter intact. Then we swapped on a 73mm C&L (with 19lb sample
tube), using the stock rubber duct between the meter and throttle
body. Finally we bolted on the 76mm C&L mass-air with aluminum
duct.
The results were lackluster. The 73mm mass-air had no effect
whatsoever. The 76mm and flow-tube showed a slight (0.5mph)
gain in trap speed when comparing the two best runs of the night,
one with the stock MAS and the other with 76mm system.
Our conclusions is that a stock 5.0L engine is pretty well optimized
with the stock 55 mm mass air meter. While you may see 8-10
horsepower on a chassis dyno, this doesn't translate to anything
overly impressive at the track. The gain from 97.4 mph to 97.9
mph seems to correlate to the published gains on the dyno, but
don't expect to knock down your ET by bolting on a mass air
meter to a stock 5.0L. We also questioned whether the stock
throttle body was a restriction which prevented the larger mass
air meter from achieving all it could, however we opted not
to introduce another variable into this testing. Perhaps more
interesting is Tech Editor Langley's "seat-of-the-pants"
meter claim that the car felt stronger and seemed to pull harder
on the street with the 76mm mass air.
1992
Mustang 5.0L - Stock AOD
Track Results |
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60ft |
1/8et |
1/8mph |
1/4et |
1/4mph |
comments |
Stock
55mm MAS |
2.14 |
9.19 |
77.75 |
14.23 |
97.29 |
ice
intake
|
2.18 |
9.22 |
78.07 |
14.26 |
97.42 |
" |
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73mm
C&L |
2.15 |
9.19 |
78.04 |
14.25 |
96.88 |
" |
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76mm
C&L MAS
system |
2.23 |
9.31 |
77.65 |
14.36 |
97.22 |
no
ice |
2.15 |
9.19 |
77.91 |
14.24 |
97.90 |
no
ice |
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C&L
76mm mass air meter and TrueFlow intake tube installed.
Note the meter is slightly rotated. We found that "clocking"
the meter resulted in a slightly smoother idle with our
non-stock cam. |
Modified
1988 Mustang
The engine in our '88 LX Mustang was recently rebuilt
(see Build
a 5.0L articles). Rather than a stock rebuild, we upgraded
the induction with a set of Edelbrock RPM heads, RPM intake,
and a mild Lunati camshaft (215/222 .522 lift). We also had
a 65mm FMS throttle body installed from the get-go.
We initially set the engine up with the stock 19lb injectors
and 55mm mass air meter. We knew this would not supply sufficient
fuel for the better breathing engine, but we figured it would
make for an interesting test to baseline the car with the
stock injectors/mass air and then upgrade to 24lb injectors
and matching mass air meter. Note that it is really impossible
to run anything other than 19lb injectors with the stock mass
air meter. There are companies that will recalibrate the stock
meter, but it doesn't make sense to do so, especially when
you can get a new and larger meter for around $200.
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Injector
Installation |
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We
removed the upper intake and replaced the stock 19 lb/hr
injectors with FMS 24 LB/hr fuel injectors. Be sure to
de-pressurize the fuel rail using the schrader valve before
removing the injectors, otherwise you'll get fuel spraying
out and on to a potentially hot engine or headers! |
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There
is really no point in installing higher flow fuel injectors
without replacing the stock fuel pressure regulator with
an adjustable unit, such as the BBK piece shown here.
The adjustability (using the allen head screw) allows
fuel pressure to be raised or lowered. |
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Finally
we adjusted fuel pressure at idle to 36 psi with the vacuum
line disconnected from the regulator. Track testing at
lower and higher fuel pressure showed the best results
at 38 psi. |
As
stated earlier in the article, whenever you upgrade injector
sizes you must make a corresponding change in the mass air
sensor calibration. This is either done by modifying the sensor
housing, or modifying how much air passes through the sample
tube, as is the case with the C&L meters. We simply ordered
up the C&L with both 19lb and 24lb samples tubes.
With the 19lb injectors (set at stock 39-40psi fuel pressure)
and stock 55mm mass air meter, the car ran a best of 13.46
@ 103.7 mph. It definitely seemed to be lacking top end
"pull", which we attributed to the engine running
lean with the 19lb injectors.
Unlike
with the '92, we were not able to complete the testing for
the '88 during one track session, since we had to remove the
upper intake to change injectors. So we took the car back
to the shop and returned the following week with the injectors,
fuel pressure regulator and new 76mm mass air in place (see
"Installation" side bar.")
With the C&L 76mm system, and 24 LB injectors at 38psi,
the car immediately felt stronger, especially mid-top end.
We had to play with fuel pressure a little bit at the track,
but finally with 38 psi in the stock fuel rails, we ran a
respectable 13.29 @ 105.
In
the case of a mildly modified 5.0L, it is clear that the stepping
up to the larger injectors and better flowing mass air meter
yields impressive benefits. Obviously the gains here are due
largely to the increased fuel, but there is no denying the
larger mass air meter and tube add measureable power.
1988
Mustang 5.0L Modified - Track Results |
|
60ft |
1/8et |
1/8mph |
1/4et |
1/4mph |
comments |
Stock
55mm MAS |
2.016 |
8.84 |
|
13.67 |
102.2 |
19lb@40psi |
1.925 |
8.67 |
|
13.46 |
103.7 |
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2.19 |
9.02 |
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13.83 |
103.29 |
missed
2nd |
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76mm
C&L MAS
system |
1.99 |
8.75 |
80.91 |
13.53 |
104.6 |
24lb@36psi |
1.89 |
8.59 |
82.77 |
13.37 |
104.8 |
24lb@40 |
1.87 |
8.52 |
81.07 |
13.29 |
105 |
24lb@38 |
1.96 |
8.77 |
81.84 |
13.79 |
100 |
missed
3rd |
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Sources:
207G Green Cove Rd.
Huntsville,
Alabama 35803
(256) 882-6813
www.cnlperformance.com
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