I like my Grimmspeed AOS. It was simple to install, works like a champ, puts the separated oil back where it should be with no operator involvement.

After checking, I've never had any cold weather issues. I did check it a few times when I first installed it (3-4 years ago). The last two winters have been very warm.

Plus, it's color coordinated ;-) There's also a Grimmspeed knock-off AOS available - identical to the real deal, but a few dollars cheaper. Look around on eBay or maybe Amazon for either. BTW, to remove the central plug (as for adding oil), your tire lug wrench will work.

 

We have a Prova AOS + MFactory oil catch can installed in both our Foresters.

Here's a link to the write up in my Member Journal: Kartboy oil cap & Prova AOS (Air Oil Separator) installed!. :wink:

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

 

get the iag, im running the crawford atm

 

My vote is for the IAG/Perrin, with IAG winning out. The valve covers and crankcase vent with a decent amount of pressure and air velocity, and these two companies design their AOS to slow down the airflow (by physics of larger volume), allowing for the most oil condensation. They also separate the left and right valve cover vents to further slow the airflow.

If​ feel the IAG wins out because it is larger, holding to the theory above.



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Good To hear all the feedback. I really had my eye on the grimm speed unit so it's good to hear that it's working out on the same platform I have.

 

Other big thing (for me), IAG and Perrin are both heated by coolant.

 

Currently using a custom hybrid of Grimmspeed unit + a catch can as a dual layer of protection. Catch can gets about 8-10 OZ of mixed water and oil foam in it between each 2500-3000 mile oil change, as it rightfully should. As oil temps occasionally exceed the boiling point of water, it boils it off (in the form of steam, vapor and oil vapors) and ends up condensing in the catch can at the end of the AOS line.

 

I've got a Crawford one. A required add-on from the place that built my engine... if it were up to me I would have gone IAG, but I've had no problems with it.

 

I have the grimmspeed one, seems to be working well. I also replaced some of the stock piping with the rubber hose.

 

IAG! I have it. After tons of research, this is the only one that retains a pcv valve, which is NEEDED to prevent boost from going places it shouldn't at the wrong times! In my opinion, all of the other ones, while doing their job of removing blowby, will damage your engine over time because of this.


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IAG! I have it. After tons of research, this is the only one that retains a pcv valve, which is NEEDED to prevent boost from going places it shouldn't at the wrong times! In my opinion, all of the other ones, while doing their job of removing blowby, will damage your engine over time because of this.

Ehhhh? The Grimmspeed AOS retains the PCV valve. Or, at least, mine did, and I followed the official installation instructions.

Here's a discussion of the Grimmspeed unit from NASIOC - also mentions that the PCV is retained. In fact, they are touting the Grimmspeed unit as if it were the only one which retains the PCV valve. Go figure.

I'm not suggesting the Grimmspeed unit is best for you. But, don't 'not buy it' for the wrong reason.

 

Good stuff here. I am leaning toward the Grimm speed unit but like the idea Mikedrives1 mentioned above about a catch can hybrid with Grimm speed.

 

thanks for the props!

There seems to be some misconceptions about the grimmspeed unit ill share my knowledge/opinion on.

Is the grimmspeed unit alone, good for track racing? Easy Answer is no, go with an IAG or perrin unit. That unit (GS) is more ideal for a daily driver that you want some added protection with. The large argument years ago i saw was that oil could slosh back up the neck and into inlet line. So, to determine if this was happening, i put an inline catch can in place of that line to see what kind of oil would slip by.

After a few track events and autocrosses over the past 3 years, im happy to report that the lines were clear after pushing the car hard. However, with this inline catch can, it does catch a fair amount of boiled off vapors (water vapor and oil vapor) in it from daily driving, esp since there is a wide swing in temps from where i reside. This happens to almost all cars driven on planet earth. Atmospheric humidity is there. Its nearly inevitable that you will get some form of water contamination in your oil, but lucky for you, its so relatively low that you change your oil (per your normal oil change rotation) before it could ever become a problem. The cars MOST at risk for contaminated oil would ones who see only short drives and never long ones, where your oil temps reach the boiling point of water every so often and helps to literally flash it off in the form of steam. It then collects in cooler areas, commonly seen as that yellow "sludge" that everyones so darn afraid of. Whether you want to or not, crack your motor open, chances are youll find some in cooler areas. A good AOS just helps cut down on this, but crack that same engine open, chances are you will still find yellow build up in places, just less than one that had no AOS. This has been an ongoing thing since the gasoline combustion engine was first invented.


Case and point, one person has a bad experience with the unit and word spreads like wildfire that its a flawed design. So someone found a little goo under the cap (breather) and now they think its worthless.

A little bit of the goo isnt going to blow your motor. You change your oil too often for it to ever truly become an issue. Never once have i seen a story where someones rings or engine blew up and goo was to blame.

 

I use a Moroso AOS can set. Unlike the Grimmspeed, it does eventually have to be emptied, but I liked the fact that it has two separate chambers for case ventilation. not sure that this is really necessary, but it seemed like a good idea to me.