Should I sell my 00 Mustang GT for a Mark VIII?! W/ Pics!

"I race for the fun of it, as long as both racers are laughing"

My thoughts exactly! Fun to drive everyday!
 
J said:
So, no matter what they are 100% open, no matter what throttle position after 3200 rpms, or are they "variable" based on load and throttle?
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They are simply open or closed - they are not variable.

The Gen1 IMRCs are simply controlled via a vacuum actuator. They are normally closed with engine vacuum applied to the actuator via a vacuum solenoid. The vacuum solenoid valve is controlled by the PCM which then closes off vacuum supply and vents the vacuum actuator causing the IMRC to open. You can simulate this by unplugging the vacuum solenoid.
 
Ok, that makes sense. On/off vacuum solenoid. So...NO MATTER WHAT at 3200 they are open 100%?
 
J said:
Ok, that makes sense. On/off vacuum solenoid. So...NO MATTER WHAT at 3200 they are open 100%?
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Basically, once the solenoid switches the IMRC plates open. They are 'normally open' by the spring in the vacuum actuator when no vacuum is applied. This is assuming the IMRCs operate freely and are not gummed up with EGR/PCV sludge.
 
Lol, you still didn't confirm Driller :) AS SOON as the rpms hit 3200, they are open, or does engine load matter?

Like I said before....it would make more sense to have them open only at a heavier load because if they always open at 3200, you're wasting a huge amount of gas(theoretically), I'm sure the ECU compinsates a bit for this......

Here is what I found on the net....

WIKI...With the short runner secondaries not opening until 3250 rpm, it made these early modular Cobras more responsive at low speeds

It featured an aluminum block, Intake Manifold Runner Control (IMRC) system and cylinder heads with split intake ports

Some tell tale signs are 16 second 1/4 mile times or the absence of hearing the secondaries open at part throttle at 3,400 rpm's

Ford 2.0L, 2.5L V6, 3.8L, and 4.2L engines all use what is called an Intake Manifold Runner Control, IMRC for short, better description below.

Ford 3.0L V6, 4.6L V8 and 5.4L engines use a Intake Manifold Tuning Valve, again description below.

This is how Mitchell On Demand describes them:

IMRC:

IMRC system consists of a remote mounted electric actuator with an attaching cable or linkage to operate the housing butterfly valve plate levers for each housing on each bank. PCM uses a positive change in Throttle Position sensor along with the increase in engine RPM from Crankshaft Position sensor to open butterfly valve plates.

IMRC housing is an aluminum casting with 2 intake air passages for each cylinder. One passage is always open and the other is opened and closed with a butterfly valve plate(s). IMRC housing uses a return spring to hold butterfly valve plate(s) in closed position. Electric actuator houses an internal switch or switches, dependant on application, to provide feedback to PCM indicating butterfly valve plate(s) position.

When engine speed is below 3000 RPM, electric actuator will not be energized, allowing IMRC butterfly valve plate(s) to remain in closed position. When engine speed is about 3000 RPM, electric actuator is energized, causing butterfly valve plate(s) to the open position. Some applications will activate IMRC butterfly valve plate(s) when engine speed is about 1500 RPM.

Here is how my ALLDATA explains it...

Intake Manifold Runner Control (IMRC)
The intake air system improves engine performance by using the Intake Manifold Runner Control (IMRC) assemblies as follows:


The intake manifold has two runners per cylinder, feeding each of the intake ports in the cylinder heads.
The IMRC assemblies are located between the intake manifold and cylinder heads, providing two air passages for each cylinder.
One air passage is always open and the other passage switches from closed to open by means of a valve plate.
Below 3000 rpm , this valve plate is closed to improve low speed and cold engine performance.
Above 3000 rpm , this valve plate opens to improve high speed engine performance.
The valve plates are opened and closed by the IMRC vacuum actuator, which is controlled by the IMRC solenoid and the Powertrain Control Module (PCM) .

Below 3000 rpm :


the solenoid is de-energized.
the vacuum actuator holding the valve plate closed is vented.
the spring-loaded vacuum actuator pushes the valve plate open.
 
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The gen 1 IMRC's are vacuum operated and the gen 2 has the same setup as the 98 Cobra, there is a remote electric actuator. The gen 1 setup is slightly better in my opinion because it defaults to open if the IMRC's malfunction instead of closed like the gen 2/cobra. But Ford must have had a reason to switch the Cobra design from the early Mark VIII design. And with both designs, the IMRC's open at 3250rpm no matter what the load is.
 
46callaway said:
But Ford must have had a reason to switch the Cobra design from the early Mark VIII design. QUOTE]

Probably because its "cleaner" to use electric vs. vacuum and easier for the PCM to control. Less solenoids and crap with the electric motors. They also changed to a plastic in 98 for the following reasons(as per Sean Hyland)
"The plastic version is more desirable due to the larger port passages and the insulating qualities of plastic that transfer less heat to the intake from the cylinder head."

46callaway said:
And with both designs, the IMRC's open at 3250rpm no matter what the load is.
Click to expand...

This is what I've been trying to get answered, haha. Is this "offical"? Do you have any info on that?
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The plastic IMRC's with the larger ports come stock on every Gen 2 Mark VIII as well as the 98 Cobra in case you didn't know.
 
It's a good book, I used to have it but I gave it to Craig for helping me work on my car. I need to get another copy, it's a little outdated but a good read anyways.
 
J said:
46callaway said:
This is what I've been trying to get answered, haha. Is this "offical"? Do you have any info on that?
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Yes, it's official. If you look at an IMRC controller, its an actuall DC motor, and not a stepper motor.

Id' upload a picture so you can see what the IMRC controller box looks like on the inside, but it seems I'm not allowed to do that just yet.
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SammyK said:
J said:
Yes, it's official. If you look at an IMRC controller, its an actuall DC motor, and not a stepper motor.

Id' upload a picture so you can see what the IMRC controller box looks like on the inside, but it seems I'm not allowed to do that just yet.
Click to expand...

Ok, that makes sense. Bout damn time, lol if you re-read the thread, everyone was beating around the bush, lol.

So....I guess at 3250rpms at about 82-83mph, my gas mileage is going to blow, even though the message center isn't going to show it.

Sammy...start a PhotoBucket.com account and use the IMG links to post pictures here.
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I have a directory on the Company webserver, but for some reason the
 
It'd sure make more sense to have it a step motor, full open/closed just doesn't seem economical. It would seem that if it was a step style, you'd get better performance AND mpg.
 
Lol..........back to the topic at hand. Keeping the stang or upgrading to a Mark 8?
 
46callaway said:
03/04 Cobra motor and Shelby GT500 motor come to mind...
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This was more in relation to actual parts.....and while the Cobra/Shelby motors are GREAT, the cars they put them in can "see avatar". You can only put so many different engines in the same "exact" car before the entire car just gets played out.

03/04 Cobra with 390bhp out of the bag(sweet) independent rear suspension that wheel hops so bad your fillings fall out(not so sweet).
 
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