Go with the MR. The plastic DV can't hold high PSI's this is one of the reasons that the boost spieks then tapers down. The MR valve- being metal- can hold higher boost levels (17+) without any leaking.

 

My JDM MR BOV holds 25psi no problem, aluminum housing is much more durable and the spring is a bit stiffer than stock

 

Yes, not only that but it's JDM!!! BTW If you plan on modifying your car don't go with the FORGE DV.

 

Jdm!!!

 

Mine is on the way. I at first bought the FORGE DV and it worked great until I put the intake on- then it surged like crazy and I didn't want to spend time trying the different spring/shim combos for it... So I said screw it and ordered the MR- since I have heard nothing bad about it.

 

What are the (proven) benefit(s) of having the JDM MR blow off valve over the USDM plastic ones?

 

all stock USDM evo (MR) bov is made for upgrade.

 

the plastic ones dont hold boost and will bleed down to 16/17 psi. the metal one holds it

 

Be carefull because the leak that most of us are facing is due to the OEM BOV clamps. I think that the plastic dilate too much and the oem clamps can't hold or dilate together, when the car cools and the plastic come back to the normal size the clamp is loosened.
Maybe the metal bov has far less dilation... I don't know.
Please see this link about clamps:
http://www.partssystems.com/redir/ht...mps.com/ct.htm

 

I think that 17psi on high rpm is ecu condition....

 

While there is thermal expansion happening, that shouldn't be the source of the leak. When everything is assembled, it is at room temperature. So if the expansion rate of the plastic is greater than that of the clamp, the seal should be getting better as it warms up. I'm too lazy to look up the coefficient of thermal expansion for different metals and plastics right now. Anyone know off the top of their head which one expands faster?

The OEM clamps tend to loosen over time, so you just need to check their tightness every so often. I've noticed my clamps loosen after a few thousand miles. So those clamps in that link seem like a good fix for this issue.

According to the BOV leak test Silver Surfer did a while back, the stock plastic BOV does leak.

 

hmmm interesting... Also keep in mind that you don't want the clamps too tight on the plastic valve- plastic can and will crack if pushed too hard.

Once the MR DV goes on I will put two t-bolt clamps into place. Always nice to have a few of those lying around.

 

My stock BOV holds 21 PSI to redline all day for over a year and no issues. Mine does not leak. If you are experiencing boost leak, it's probably loose clamps, not the valve itself if running stock boost. I had to tighten all my clamps when new and they were all loose from the factory.

I bought the JDM valve and have not installed it as of yet. No need to. It's a back up just in case. Why fix something that's working fine.

 

because it's JDM and not plastic Plus it'll only take a few seconds to install

 

I agree the JDM MR is so much better. And like smp3000 said please do not put a Forge on your car, I had one on my first Evo and tried every combination spring/shim combo, backward and forward orientation and always surged it did it so much it became dangerous in the twisties. It became an expensive paperweight