[sambonator]

I converted my Forge DV's to be BOV's, in order for me to test some of my theories about hot-air recirculation on engine performance.

Anyway, here's the pic of the completed setup! Its not too noisy, and so far it works like a charm!

[Sniz]

ha...nice! Did you just have those parts laying around??

What did you use to cap off the charge pipe on the front DV?

[5soko]

whoa very cool

[sambonator]

Originally Posted by Sniz

ha...nice! Did you just have those parts laying around??

What did you use to cap off the charge pipe on the front DV?

No... a careful walkthrough of the local Pep Boys yielded the parts I needed . The filters are Spectre Filtered Breathers, at $7 a pop. The hose is a GoodYear Molded Radiator hose #61472. I think its for a Honda Civic CRX 1984-91 according to my research. I cut it into 3 pieces, two of which I used in this install. They let met check out their inventory of radiator hoses and this one fit the breather perfectly, and I liked the shape and length.

The caps I used are from a "HELP Bypass Cap Assortment" package. The biggest 2 weren't big enough to fit over the inlet, so I taped it to the end with emergency radiator hose tape. Its too big to get sucked in, as Outside Diameter of the cap is larger than the inlet. It worked out well!

Now my testing begins

[sambonator]

With this setup, I can clearly hear when the DV's are passing air through it and when its not. With the Yellow springs, you hear it whenever you release the gas, and sometimes during shifts (with my 6AT). The sound is louder the more quickly you lift off the throttle. During light acceleration, its quiet. During WOT, it is also quiet except during shifts. The whooshing sound is really only noticeable during throttle lift.

With the Green springs, I can hear the whooshing MUCH more frequently. Even during part throttle acceleration, I hear it hissing at certain RPM's. I can also get it to vent more by slightly easing off the throttle, still accelerating.

At WOT, there doesn't appear to be any difference between the two springs. However, during partial throttle, I get much better response with the yellow springs.

For now, I will keep the Yellow springs in there, because I enjoy the responsiveness of my car with them .

[fast_lap28]

so you guys are HIGHLY recommending the Forge Dv's over the stock ones? I just read Ocha's review and sounds impressive in particular the throttle responsiveness during different throttle inputs.

For me, running stock right now, will this upgrade be worth it? Improving parts and their functionality is always a plus for me but just want to justify the expense when only in stock trim.

thoughts...

[e90AW335i]

Originally Posted by fast_lap28

For me, running stock right now, will this upgrade be worth it? Improving parts and their functionality is always a plus for me but just want to justify the expense when only in stock trim.

thoughts...

With stock boost I believe you should be ok with the stock diverters.

People have said the stock ones are good up to 12psi....

[BoostedBMW]

Nice... now the BOV haters can hate on DV's also.

I'm interested in seeing what you find as far as IAT's go since I have always thought that there must be some advantage to not recirculating air that has already been compressed, but most people thought that was rediculous. Good to see I'm not the only crazy one.

[HyperM3]

Very interesting setup. Kudos to you for trying something different!

As for the yellow springs, Ive been mulling it over in my head if I should switch out my greens for them. Was it noticeable enough to warrant switching out?

[sambonator]

Originally Posted by HyperM3

Very interesting setup. Kudos to you for trying something different!

As for the yellow springs, Ive been mulling it over in my head if I should switch out my greens for them. Was it noticeable enough to warrant switching out?

I've noticed that the throttle is more responsive, and even more linear with the yellow. Wide-open throttle (WOT), it doesn't seem to make a difference. They both hold it closed.

The biggest difference between stock and the forge DVs, is the change in throttle response, for the better in my opinion. Transient response is much more consistent compared to the stock units. Like Ocha said, it makes you feel more "in control" of the throttle.

I know Walked U cracked his stock DV's, probably from a boost spike. It won't happen with these. Its surprising how light-weight and fragile the stocks ones seem to be.

[HyperM3]

Originally Posted by sambonator

I've noticed that the throttle is more responsive, and even more linear with the yellow. Wide-open throttle (WOT), it doesn't seem to make a difference. They both hold it closed.

Ok, thats what I wanted to know. Im never really at WOT so if the half to 3/4 throttle response is improved with the yellow springs, Ill try those out.

[M3to335]

Looks great.

Im still confused though. Isnt this the same as just running a BOV? The mechanics of this system arent rocket science...its a valve and a spring which is the same as a BOV. Everyone harps on me for having a BOV but honestly, it works fantastic and has already been put through the paces on a drag strip and track.

What did that system run $$?

[BoostedBMW]

^ That can't be a BOV... bov's are rice! Everyone knows that.

The forge diverter valves run around $350.

[sambonator]

Originally Posted by M3to335

Looks great.

Im still confused though. Isnt this the same as just running a BOV? ...

Thanks!

Yes, it is basically a blowoff valve (BOV), the way I set it up. Even with the filters, it still makes a lot of BOV noises. I like being able to hear the venting. Its another piece of information about the function of the engine. Its giving me a good sense of how the boost is being controlled.

I was surprised to find out just how much venting is happening.

[asdflkijd]

How much would it cost to do this??

[BoostedBMW]

Originally Posted by asdflkijd

How much would it cost to do this??

He stated that up a few posts from yours...

http://www.e90post.com/forums/showpo...21&postcount=4

Basically the price of the DV's plus $20 or so in parts.

[hotrod2448]

There is obviously a difference in throttle response form stock to the Forge DV's but, have you noticed any difference between the forged ones recirculating vs. VTA?

Did you run them recirculating to begin with or just right to VTA?

[sambonator]

Spectre Filtered Breathers, $7 each x2
GoodYear Molded Radiator hose #61472. $11.99 (For Honda Civic CRX 1984-91)
HELP Bypass Cap Assortment package $4
Emergency Radiator Hose Repair Tape $3
Hose Clamps 2 pack $2.50 x 2

$40 total.

Some ideas to cut costs: You can use beer bottle caps instead of the rubber bypass caps I used. You may be able to use other tapes, but you'll need to make sure they survive the hot engine environment. You may already have hose clamps that you can use. Main parts are the breathers and the radiator hose, for $26 total.

Originally Posted by hotrod2448

There is obviously a difference in throttle response form stock to the Forge DV's but, have you noticed any difference between the forged ones recirculating vs. VTA?

Did you run them recirculating to begin with or just right to VTA?

Through my testing I've really not noticed any difference turning the DV into a BOV, except sound. I was running them recirculating at first.

My theory is that this isn't going to be a difference you can feel. I believe now that venting the hot gasses will have a marginal effect on reducing engine temps, by allowing the engine to vent hot gasses rather than reingesting it. It may also reduce timing getting pulled when getting back on the gas immediately after shifts, by not allowing it to reingest the hot hair. I think this is why almost every turbocharged racing car uses blow off valves instead of diverter valves.

[hotrod2448]

Originally Posted by sambonator

Through my testing I've really not noticed any difference turning the DV into a BOV, except sound. I was running them recirculating at first.

My theory is that this isn't going to be a difference you can feel. I believe now that venting the hot gasses will have a marginal effect on reducing engine temps, by allowing the engine to vent hot gasses rather than reingesting it. It may also reduce timing getting pulled when getting back on the gas immediately after shifts, by not allowing it to reingest the hot hair. I think this is why almost every turbocharged racing car uses blow off valves instead of diverter valves.

Interesting. I never really thought about difference in intake temps between recirc and VTA but, the logic makes sense. Of course by the time it goes back through the IC it probably doesn't make that much of a difference.

As far as the race car application goes I would be willing it has as much to do with less plumbing and weight by VTA as the intake temps.

[sambonator]

Originally Posted by hotrod2448

Interesting. I never really thought about difference in intake temps between recirc and VTA but, the logic makes sense. Of course by the time it goes back through the IC it probably doesn't make that much of a difference.

As far as the race car application goes I would be willing it has as much to do with less plumbing and weight by VTA as the intake temps.

I've seen that the factory IC will reduce the intake charge temps, but its no where near the temps of ambient air.
http://www.e90post.com/forums/showpo...3&postcount=22

So post-turbo, post-intercooler air is going to be +20 up to +50 or more degrees higher than ambient air.


It could be the weight savings of VTA... but it probably amounts to less than a pound difference. All aftermarket BOV kits for the 335i weigh more than the stock DV setup. Forge DV setup vs. aftermarket BOV... not sure of the weight difference. But yes, VTA/BOV setup is a lot less complex. Anyhow, I'm still leaning toward reduced intake temps as one of the main reason for BOV/VTA on race cars instead of a DV .

[hotrod2448]

Originally Posted by sambonator

I've seen that the factory IC will reduce the intake charge temps, but its no where near the temps of ambient air.
http://www.e90post.com/forums/showpo...3&postcount=22

So post-turbo, post-intercooler air is going to be +20 up to +50 or more degrees higher than ambient air.

Yes but, by the time it mixes with ambient air and goes back through the IC I bet it doesn't raise intake temps by much.

Originally Posted by sambonator

It could be the weight savings of VTA... but it probably amounts to less than a pound difference. All aftermarket BOV kits for the 335i weigh more than the stock DV setup. Forge DV setup vs. aftermarket BOV... not sure of the weight difference. But yes, VTA/BOV setup is a lot less complex. Anyhow, I'm still leaning toward reduced intake temps as one of the main reason for BOV/VTA on race cars instead of a DV .

Yeah, but that's on a car designed to be recirc. On a racecar you most likely don't have your intake air (usually a short direct intake) anywhere near the pressurized air of the turbo system (again usually as short and direct as possible, not like most OEM systems) so it ends up being a good bit more plumbing and weight to get that air back into the intake tract.

I'm sure it's a bit of both.

[pat@forge]

Increased heat is a byproduct of compression, as the air is discharged it will expand and cool. There will be a slight increase in heat but it will only be a fraction of what is seen in the charge pipes.

Also, the volume of the discharged air is so slight it will be consumed in a revolution or two of the motor. So the air will be consumed in about .01 seconds give or take.