What is the function of the butterflies in the 4.6 intake manifold??

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Sep 28, 2002
Okay ..I just picked up a 4.6 intake allegedly from a 2004 Towncar just because it was cheap. The thing has the plenum sitting in what would normally be the lifter valley (it is an OHC setup). The individual intake runners look like an octypus off of this plenum. If you invert the intake you see 16+ ports. 8 have the injectors on them (square) and 8 oval ports that have butterfly plates in them. There are also 3 rectangular recesses in between each pair of oval/square ports that have what appears to be counter weights for the shaft that runs down each side of the intake. These shafts are acuated by a vacuum pod. This is in addition to the butterfly on the throttle body. This isn't anything beyond curiosity. I envision some type of neo-extra (as in pre or external)-combustion chamber "stratified charge" type thing.  -
Gary, I think what you have there is a "variable port" intake manifold. The design appears to be very similar to the Audi manifolds. The butterflys are supposed to open at a certain RPM which lengthens the intake port, thus creating more intake velocity.
Those will open at high RPM to get more air in the cylinders. With those butterflies closed, the low-speed operation of the engine still sees relatively high intake velocity in order to help atomize the fuel and increase swirl in the combustion chamber.
This is called "Split Port Induction" although I've only heard that term used in relation to the 2.0L SOHC engine used in the Ford Escort. Other Ford engines using this setup that I know of include the 2.5L/3.0L DOHC V6 engines. From Ford's glossary: Split-port Induction (SPI) Most split-port induction systems have a dual-runner engine intake design promoting high-volume/high-velocity airflow to increase engine performance. The dual-runner design features long, small-diameter runners tuned for low engine rpm torque and short, large-diameter runners tuned for high rpm horsepower Runner usage is controlled by the electronic engine controls and integral throttle- body valves The Focus and Escort 2.0L I-4 engine uses a cylinder head with two runners per cylinder. These runners carry the air charge to the intake side of the combustion chamber. At lower engine speeds, the air charge is directed through a narrow pathway that results in a higher air velocity, quickening engine response. As engine speed increases above 3000 rpm, the second path works to further enhance engine power and operating efficiency
Hi, Porsche's DOHC 32v V8s had "this" type of arrangement in the mid 1980's (prior to cam actuators) and the change in torque is quite noticeable when the "step in" is actuated. The complex magnesium chamber is linked to the EFI and vacuum systems and is engine revs sensitive in these engines Regards Doug
Originally posted by Doug Hillary: Porsche's DOHC 32v V8s
The 2.5/3.0L DOHC V6 Duratec Ford engines were developed by Porsche, according to what I heard.
mazda protege been using split port induction sence the 80's. heck my 96 kia sephia has it too. its nothing special or unique to porsche and ford. by the way, the ford ecsort gt 1.8 also has this feature.
Okay ...now some bulbs are blinking here. This is somewhat like the ZR1 (??) Vette engine that had 4 valves per cylinder ..running two different cam grinds for each set of intakes. Under normal driving you would effectively be running off of the "econo" grind intake. Under other conditions the plenumn would open up the set of runners to the other intake valves and the injection would dump in more fuel to take advantage of the higher air flow.
That's right. On the 2.5L Duratec the fuel injection only dumps in extra fuel as a result of the increased airflow measured via the mass-air-flow sensor. Many people on the Contour forum were under the mistaken impression that their engine consumed more fuel when the secondaries opened up. Well, yea, sure, if you keep accelerating, but if you hold a steady speed it won't matter whether the secondaries are open or not, it'll use the same amount of fuel either way. Put another way, if the secondaries open at 80MPH in 5th gear, the only fuel savings from driving 79MPH instead of 81MPH will be those from reduced aerodynamic drag.
Here's a pic of my custom painted Ford Taurus SHO intake.  - One of the most beutiful pieces of automotive art ever made(IMHO). Here you can clearly see that each cylinder has a long and short runner attached to it. The silver pieces are the butterflies that open the short runners at 3950RPM. The result is massively increased airflow at high RPM and a very broad torque curve with 2 peaks. You can really hear and feel when the butterfly valves open. The SHO was one of the first american cars to have this type of intake, but nowadays, it's commonplace. But none have matched the eye appeal of the SHO V6.
How many separate pieces is that Taurus SHO intake made of? I saw one up close and it looked as though it was made of several pieces--must be real fun to replace the rubber seals joining all of the pieces if they start deteriorating?
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