Hey folks

I'm starting to research bigger turbo's and I see there are more and more people running them these days. I couldn't find any specifics on this but am curious. Those that have the bigger turbo's installed are you all using diverter/recirc valves or straight up atmpospheric blow offs? I'm concerned mostly with the N18 but interested in what people are doing with their N14's as well. Is Forge the only thing going or are others making something useful?

 

Most larger turbos require 2 DVs or a stand alone one. From what I understand, a k03/k04 hybrid does not and will hold up to 25 psi

 

I run an E45R K04 from JMTurboCoopers.
His turbos come with upgraded diverted valves. So it was just a direct turbo swap for me. And plug in the new diverter.

 

Yes the E45R comes with the latest upgraded DV. If you install the Alta stiffy spring it will hold 40 pounds of boost according to Alta. Put one in mine and no issues with the DV at all.

 

Thanks Gents that's good to know. That wasn't mentioned when I discussed the issue with the JM TURBO folks. If I can get away without buying an aftermarket DV/BOV that would be nice. The option is always there if the stock valve fails.

 

The nice thing about the Forge DV is it doesn't dump as much boost as all the others, so when you go to up-shift your boost is almost right where is was before your shift. That's the best way I can describe how it feels, not sure if you can run one on a larger turbo though. Best performance updade for the money period!

 

That's kinda my thinking but now knowing the JM turbos come with an upgraded DV I'll probably stick with that to save a few bucks until if/when that DV fails or fails to hold boost as planned. At that point I'll go with the Forge. Unless I'm wrong, and I could easily be, Forge is the only aftermarket option as far as I know.

There's been a lot of argument for and against using BOV's in these cars vs. DV's. I don't really see an advantage of one over the other unless some of you guys have any knowledge on this?

 

You need to use a recirc valve on the N18 instead of a BOV because the MAF deviation table is tighter. When you dump the air that has already been metered via the MAF to atmosphere the ECU can't account for it. Same goes for venting PCV to atmosphere. Both will trigger the error code.

 

Ahh ok I see. So is it more about throwing a cel than any real detriment to performance?

 

No BOV I wouldn't recommend any, only recirculating (diverter) valves. Forge manufacturers both, the Forge DV comes with three different springs in case your dealing with higher than stock boost levels.

Like I said earlier I'm unsure about whether using the Forge DV is appropriate for these big turbos.

 

When choosing between a recirc and bov yes they both provide the same function. When you let off the throttle under boost, the pressure between the turbo and intake is very high at the same time that the wastegate is opening to reduce boost. The pressure differential between the intake pressure and ambient causes a pressure wave to act as an airbrake on the impeller blades slowing their rotation suddenly. This is compressor surge and puts a great deal of stress on the compressor exducer blades and turbine shaft and will destroy a turbo.

The difference between the upgraded DV and Forge DV is the speed with which they operate. The standard DV has a large electrical solenoid that directly actuates the DV. The Forge unit uses a much smaller and therefor faster solenoid that controls pneumatic pressure / vacuum to actuate the DV. Because the Forge unit opens faster, less aerodynamic braking occurs. In addition since it closes more quickly less boost is lost while the turbo spools up. The Forge unit also will not suffer from a torn diaphragm or cracked retaining ring as sometimes happens with the stock DV. The only downside to the Forge unit is the pneumatic piston becomes dirty over time and requires cleaning to function properly.

 

Wonderful analysis. Thank you!

 

the 710D-series DV solenoid we use on our products is tested to hold in excess of 30psi. It's the same unit we use in our hybrid turbochargers for VW/Audi 2.0L engines. On those cars we're seeing 400bhp using that diverter valve. It holds just fine.