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post #1 of 24 (permalink) Old 12-13-2003, 10:40 AM Thread Starter
 
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what is an imrc?

title says it all. what is an imrc? i have heard people talk about it and alos talked about cleaning them and stuff. i guess i always felt stupid so never asked.
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post #2 of 24 (permalink) Old 12-13-2003, 11:31 AM
 
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Intake Manifold Runner Control - butterfly valves that choose which runners are used on a splitport setup.
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post #3 of 24 (permalink) Old 12-13-2003, 11:56 AM
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A lot of people get the IMRC confused with the ICRM which controls the electric fan. Not sure what the "I" stands for, though?

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post #4 of 24 (permalink) Old 12-13-2003, 01:32 PM
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Ford service manuals suffers from TDMA-------Too Damn Many Acronyms------Dan
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post #5 of 24 (permalink) Old 12-13-2003, 02:04 PM
 
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Originally posted by Old_coot
Ford service manuals suffers from TDMA-------Too Damn Many Acronyms------Dan


so true
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post #6 of 24 (permalink) Old 12-13-2003, 04:53 PM
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Your car has 2 intake valves per cylinder, 2 intake ports per cylinder.

A long runner intake anifold will help make good torque but choke up at high rpms. A short runner manifold breathes up high, but little torque down low.

Each cylinder has 2 intake manifold runners, one to feed each intake port. One runner is a long runner, the other is a short runner. The IMRCs are little valves (look like throttle bodies) that close the short intake runners at low rpms and force the engine to breathe through the long runners, giving you good torque and bottem end power. Above a set rpm, those open up and the engine can breathe through both runners.

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post #7 of 24 (permalink) Old 12-13-2003, 05:04 PM
 
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So when they are closed, how does the other valve get air? From the long runner?
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post #8 of 24 (permalink) Old 12-13-2003, 05:05 PM
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Quote:
Originally posted by Pooperscooper
So when they are closed, how does the other valve get air? From the long runner?
When they're closed, the long runner valve is the only one that can breathe. Both valves open because of the cam, but only the long runner valve gets air.

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post #9 of 24 (permalink) Old 12-13-2003, 05:36 PM
 
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Would you make more power if both valves got air at lower RPMs? The way I understand it, at lower RPMs the engine is a 2-valve until the IMRCs open and the other valve get air, making it a 4-valve. Why would anyone want this?
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post #10 of 24 (permalink) Old 12-13-2003, 06:28 PM
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Quote:
Originally posted by Pooperscooper
Would you make more power if both valves got air at lower RPMs? The way I understand it, at lower RPMs the engine is a 2-valve until the IMRCs open and the other valve get air, making it a 4-valve. Why would anyone want this?
Intake charge velocity. The longer runner gets a higher velocity in the intake which will get more air into the chamber. If you open both valves to getting air, you lose velocity. They eliminated IMRCs in 99 and went with tumble port which has only one port feeding both valves.

And as for the power at low rpms, I've already stated why they shut out one valve.

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post #11 of 24 (permalink) Old 12-13-2003, 06:57 PM
 
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Runners are meant to do one thing: boost incoming air charge. What happens is the shockwave of the intake valve closing travels back up the intake and ends up bouncing off of the metal up in the manifold. This, if harnessed properly, can actually give you a "boost" effect (similar to an itty bitty turbo). The runners are calibrated to a certain length, so that the shockwave will be coming down, right when the intake valve of another cylinder opens. (Actually this is sort of simplified, the runner is a factor of the runner length needed to produce the boost effect at a certain RPM, since a runner tuned for say, 1800 RPM would need to ideally be 10ft or so long, but if you make it a 2-based factor (x/2, x/4, x/8, etc) of that length, it still works because the shockwave will bounce around.) By introducing variable runner lengths, you can produce that effect at two RPM values, that's what this part does.
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post #12 of 24 (permalink) Old 12-13-2003, 07:54 PM
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I covered the layman's terms, the technical terms have been brought to you courtesy of the good Captain.

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post #13 of 24 (permalink) Old 12-13-2003, 08:25 PM
 
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I understand what intake runners are for. Thats not the question. The question is wouldn't having only one valve open at low rpm kill power? What if a medium lenght runner was put in with both valves being fed 100% of the time? I think power would increase wouldn't it?
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post #14 of 24 (permalink) Old 12-13-2003, 08:29 PM
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Quote:
Originally posted by Pooperscooper
I understand what intake runners are for. Thats not the question. The question is wouldn't having only one valve open at low rpm kill power? What if a medium lenght runner was put in with both valves being fed 100% of the time? I think power would increase wouldn't it?
Hence, Tumble Port.

And as for only breathing through one port killing power, it doesn't really. The engine can't flow enough air for one valve to be a restriction at the rpms when the IMRCs are open.

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post #15 of 24 (permalink) Old 12-13-2003, 09:22 PM
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Also, IRCM is the Integrated Relay Control Module. It's got the relays for the fuel pump, electric cooling fan, and so on.
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post #16 of 24 (permalink) Old 12-13-2003, 09:30 PM
 
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Quote:
Originally posted by AverageJoe


Hence, Tumble Port.

And as for only breathing through one port killing power, it doesn't really. The engine can't flow enough air for one valve to be a restriction at the rpms when the IMRCs are open.
Ok, I guess that answer works. How does the tumble port design work? Is that where they got the extra 15 horses from?
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post #17 of 24 (permalink) Old 12-13-2003, 09:43 PM
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Quote:
Originally posted by Pooperscooper
I understand what intake runners are for. Thats not the question. The question is wouldn't having only one valve open at low rpm kill power? What if a medium lenght runner was put in with both valves being fed 100% of the time? I think power would increase wouldn't it?

do you have the Motorsport catalog? IMRC delete plate..the EEC needs to be tuned on cobras to assist driveability at lower RPMs, but the motor picks up more top end. Pauls HP makes a custom manifold with cut runners, he wont divuldge the length on the runners but all are different lengths.

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post #18 of 24 (permalink) Old 12-13-2003, 09:50 PM
 
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What kind of power gains can a Cobra get with those mods?
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post #19 of 24 (permalink) Old 12-13-2003, 10:12 PM
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AJ and the captain are correct, however I want to add that the intake runner lengths aren't nessessarily tuned, you will benifit from dual intake runners even if they are not (as long as they of different lengths, and the butterflies are tuned to open at the correct rpm).

The benifit of SPI is a dual torque curve. It's along the lines of having a supercharger and a turbo. My SHO's engine makes 80% of it's peak torque at idle, as does the new 4.6L 3v heads.

Now, the reason for 2 exhaust valves is simple geometery. Two circles can take up more area than one in the space allowed. Not only is there not a benifit, there is a loss from having two exhaust valves (compared to the same area of one valve).

BMW is coming out with a new intake...a Continuosly Variable Intake Runner Length Manifold (CVIRLM). Basically, it will allow the motor to have a perfectly flat torque "curve". The car would be a great daily driver, and also VERY fast.




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post #20 of 24 (permalink) Old 12-14-2003, 05:13 AM
 
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Quote:
Originally posted by GreenBird
BMW is coming out with a new intake...a Continuosly Variable Intake Runner Length Manifold (CVIRLM). Basically, it will allow the motor to have a perfectly flat torque "curve". The car would be a great daily driver, and also VERY fast.
can you get some links to some info about that, im interesting in how it works.. well. i wanna know more indepth. -greg
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post #21 of 24 (permalink) Old 12-14-2003, 06:13 AM
 
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Originally posted by glowing escape


can you get some links to some info about that, im interesting in how it works.. well. i wanna know more indepth. -greg
It's probably a piston of some sort in the runner mandrels. As RPM's change, you need different runner lengths to provide the proper shockwave timing. A piston could be used to change the length pretty easily, and if it had a collapsible or telescoping connecting rod, then it could fit in a tight space even.
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post #22 of 24 (permalink) Old 12-14-2003, 06:07 PM
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Quote:
Originally posted by glowing escape


can you get some links to some info about that, im interesting in how it works.. well. i wanna know more indepth. -greg
Here is a link to a PDF format description of the continuously variable runners on the new BMW V8.

Continuously Variable Intake Runners

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post #23 of 24 (permalink) Old 12-15-2003, 12:25 AM
 
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Wow! That design of the BMW runners is really something! Like Greg said, I'd really like to see more detailed info, but the concept is really easy to understand from the pics. And full reaction in 1 second! I wonder if Ford will ever come up with something like that, or if patent laws will prevent it?

And that plastic. Ford should have used that for their crummy intake manifolds, (they probably saved all of 12 cents per engine by using cheaper stuff...).
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post #24 of 24 (permalink) Old 12-28-2003, 12:35 AM
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defenately learned something here...never knew some of that stuff about the DOHC engines....

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