sbulik

Why does Ford insist on making the 4.6 unnecessarily complex, in this case the sticks Charge-Motion Runner Control (CMRC) on the Three-Valve 4.6?

Basically Ford sticks the CMRC contraption that looks like partial throttle plate in each intake runner path, which blocks ultimate airflow and power. Mustang 5.0 magazine tested one of a CMRC-delete kit: “at no point did the factory CMRC setup provide any power or torque advantage”. Peak-to-peak gains with the CMRC deleted were 9.7 HP and 10.2 lb-ft.

However the CMRC shouldn’t be eliminated unless the computer is re-tuned; has anyone done this? Drivability? Dyno?

Andys06GT

there was a question about this earlier, and no, the CMRC didnt actually make a difference. it's essentialy because at WOT, the CMRC is also completely open, meaning its at 0% function. which is the same as deleting it. up untill that point, its tuned to work WITH the engine. not claiming to be a mechanic, but the last thread on this mentioned AFR. so it serves a purpose untill WOT, at which point it doesnt matter. would recommend leaving it alone.

2k05gt

I read on another forum where someone did exstensive testing with the CMP's and found no gains or losses by removing them, they did report that the Idle problem with the aftermarket 62mm Throttle body did not exist with the plates removed. so there must be some interaction between the TB and the CMP's at idle.

Most Supercharger Kits removed the CMP's

757GT

I have the delete plates. I made 270rwhp and 299twtq tuned for intake and my axle back before them, after them and the tune for them I made 287rwhp and 299rwtq. I got a good hp gain but no tq. My next trip to the track was 2 tenths better with a trap 2mph higher. I think they are worth it. With the tune, the drivability is no different. I recommend them.

Sleeper05

they are all the way open after about 2500rpm at WOT, but serve the purpose of gas mileage and emmisions control before that at WOT, or at anytime at partial throttle. regardless, i plan to replace mine because i feel that after extensive mods to the airflow through the engine, and with plans of ported heads and cams, they will be nothing but a hinderance

W1ldcat

How do you go about removing them. Is it something average person with good tools do?

CrazyAl

You can't just "remove" them. You have to have one of the aftermarket removal "plates". Basically, it's a replacement for the OEM housing, except there's no plates in it and it's totally smooth. I know that Steeda carries these, perhaps other companies as well.

I haven't done the install so I can't say for sure, but it appears that you could do it with standard tools and some time. The intake manifold comes off, remove the factory parts, replace with the aftermarket version, update your tune. It seems pretty simple.


I think Sleeper05 has the right idea: They're only worth replacing after other mods are already done. On a stock or lightly modified engine, I doubt that you'll see any HP.

W1ldcat

I just lookes at the Steeda and for the money I have a lot to do first..

chevykiller

The experts have done extesive research into these and here is the short version...

They are just fine with n/a cars. Most of the twin screws delete them anyway and the only people who need to worry about them are the centrifugal blower guys and they are the ones who need to buy the steedas. The problem is under high boost, they tend to bend and block the cylinders when they are supposed to be wide open. They have no problems on n/a engines.

sbulik

I disagree that removing the CM plates isn’t worth it on “normally aspirated” cars.

When 5.0 Magazine did the dyno testing it was with a mildly modified GT with JBA headers and exhaust, along with underdrive pulleys- that it. With the stock CMRC in place peak power was 291.7hp and 311.6 lb-ft, with the CMRC eliminated 301.4hp and 321 lb-ft. So peak-to-peak gains were 9.7 hp and 10.2 lb-ft, which are pretty impressive PLUS you eliminate some complexity (the KISS rule).

I do agree that at WOT the CMRC tumble valve is completely open but the valve actuator rod still in the middle of the intake path. Remember at no point in the dyno test did the stock CMRC provide any power or torque advantage even below 1000 rpm, so basically worthless. (GM doesn’t use CMRC in the 400 hp Corvette engine and it passes emissions and gets 28mpg).