I just bought an Evo 8 and I'm on the fence about what to do with the current setup.

The only mod it has is a blow off valve the previous owner installed. I have the stock diverter valve and I'm wondering a couple of things.

I haven't had issues with idling and the BOV installed so I'm wondering if it's likely the car was tuned. I don't believe it was but I've read that there can sometimes be idling issues without a tune.

I think I ultimately want to reinstall the stock diverter valve to prevent the car from running rich, but I'm also wondering if it's worth upgrading the stock GSR diverter valve to an aftermarket or Evo 9 diverter valve. I'm going to keep things stock but if I'll get better performance out of something other than the what it came with, I'd be willing to upgrade a little there.

Lastly, if the car was tuned for a BOV and I swap that back to a diverter valve, what issues may arise and should I get a tune to accommodate the swap back?

Thanks!

 

Is the BOV VTA (vent to atmosphere)? What is the brand? I doubt if the only mod is BOV the owner tuned it. Maybe they just wanted the cool "WHOOSH" sound

My guess is that 95% of Evo VIII owners on here have changed from the stock plastic VIII DV and gone with the Evo IX DV or an aftermarket reputable brand. If you search on the VIII DV you will find all sorts of info about how leaky it can be.

 

If you don't run Synapse DV then f!#k you. </rickybobbyvoice>

 

A couple things I can tell you right now.

Think of the BOV as a valve that opens to bleed off pressure when it sees vacuum (lifting off the pedal)

1. Changing out the BOV/DV doesn't affect the tune. *There are some special considerations to this. I am mostly talking about stock lightly modified setups*
2. A BOV/DV can cause the evo to run rich if its leaking and needs a rebuild.
3. There are two types of stock BOV :
a. Evo 8 black plastic BOV
b. Evo 9 all metal BOV <--- This is the better one and holds more boost.
4. Plenty of aftermarket options that work better than the Evo 9 BOV but unless you are going over 21 psi they aren't needed.

 

What's in there now is VTA and I'd like to recirculate the air. I'm not sure of brand but I can check tonight.

If I plan on running stock is there any reason to run something other than an OEM Evo 9 DV? Has anyone seen advantages of running another brand?

I'd image this is based on the brand but can some aftermarket BOVs be converted from VTA to recirculating?

 

Mostly good info BUT the evo 9 BOV will hold way over 21psi.
my plastic evo 8 bov held 23psi fine, switched over to evo 9 and ran 26 psi no problem, currently also running an IX BOV running 26PSI without a single problem.

 

So it looks like the vacuum nipple on the stock one I have is broken which means I'll have to buy a replacement.

Does anyone have any suggestions for a low maintenance DV that should drop in with minimal adjustment? I'm mainly looking for maximum drivability on winding roads.

I've read a lot about the synapse but it sounds like a lot of tinkering.

 

Synapse DV is simple. Use the out of the box setting, use port b only. No tinkering needed. I have it set up on 3 cars this way, it works great.

 

Ok so last question.

Where does everyone tend to buy parts? It seems like everywhere I look these are on back order.

 

I have a Synapse BOV brandy new with the EVO Specific side port to connect to OEM/Stock Flanged UICPs. It can be set up to VTA or recirc. Top port will recirc to the Intake Tube

I was actually just going to return it cause I'm not going to use it after all but could probably sell it along.

It's sitting in the back seat of my car at the moment but I should have the car back this week from my tuners.

 

Yup Evo 9 BOV no questions asked, I dont know why anyone looks elsewhere for anything under 500HP

 

Just to follow up, I ended up getting both a Synapse and Evo 9 DV/BOV; I'll probably go with the Evo 9 to start out with but I'm curious about trying out the Synapse one day. The tech is pretty interesting and they look a bit smaller than the Evo 9's.

Thanks for all of the help everyone!

 

A factory bov operates much more slowly and will always dump more boost between shifts. I've seen the Synapse shine over a stock bov in drag racing use and in other uses such as autocross.

 

I mean it will but its not the best option. I was trying to give beginner advice rather than telling someone to do. In addition, I forgot that Evo 9 BOVs are now outdated and because of use and age they can get leaky. People should be trying to buy used/new Evo X BOVs.

Anyway piston style BOVs are superior to stock BOVs. As another poster mentioned its better to use a piston style BOV for motorsports use.