Stock airbox = more black smoke

[Fredrikkk]

Well, since I'm getting my car approved for the Norwegian roads soon I figured I'd throw in my original airbox instead of the open cone filter. I took out the snorkel thingy in the front in hopes of more proper cold air entering than what I got with the cone filter. What I have discovered is that the car smokes more in the low RPMs, and it doesn't smoke at all on boost. ... With the open cone filter it barely smoked. Why?

Secondly, I miss the turbo sound. Will I get the same nice turbo sound and "BOV" sound from the wastegate with an open downpipe? I'm getting it next month

All help is appreciated!

[RabbitJockey]

it smokes more because you're not getting as much air, the cone filter must have flowed much better.  the new exhaust will help with the turbo sound, but i can't say anything for a bov noise

[Fredrikkk]

Yes that makes sense. However, am I right when I say that the car feels a little gruntier in the low RPMs? It seems to pick up much faster than before...

[rodpaslow]

On this - I want to ditch my 1.8 airbox I'm currently using.  What is better in the way of a open cone air filter for a diesel.  I'd like maybe a bit better than stock(if possible) in the way of particle size, but better flow.  Is that asking too much?  Is there a brand everyone perfers?

[R.O.R-2.0]

Yes that makes sense. However, am I right when I say that the car feels a little gruntier in the low RPMs? It seems to pick up much faster than before...

nah, its all in your head..

and theres no BOV on a diesel, so idk where you are getting the BOV sound..

any sound you hear from a diesel is pure turbo scream, not a BOV, but the wastegate opening, and that just makes it get REALLY LOUD..

Rodpaslow:

i use an air filter off a Neuspeed P-flow Kit for a digi 1.8.. it works good. its not too big, or restrictive..

[blackdogvan]

 

All the 1.6 TD's had a BOV or overboost protector from the factory. Giles makes a nice block off plate for the intake mani port http://www.vwdiesel.net/forum/index.php?topic=18289.0.

[bajacalal]

The BOV shouldn't actually open unless your wastegate isn't opening, resulting in too much boost (what is too much is debated around here).

My intercooled TD makes tons of turbo noise, it sounds like a downsized 71 series Detroit Diesel... If you don't have those in Norway, they're huge, old school diesels, supercharged and turbocharged two-strokes, they had them in a lot of old buses... I think you get the idea.

The stock intake is inevitably much more restrictive, so now the air-fuel ratio isn't what it used to be, resulting in more fuel to air and more black smoke, I even notice more black smoke when my air filter is dirty. Black smoke is fuel that hasn't completely burned. It doesn't smoke on boost because of the extra air your turbo adds.

On the bottom part of the stock air box, the air comes in through the right fender, I also removed the angled rubber snorkel, as it's restrictive and I drilled holes around the bottom, front side of the air box so more air can come in. The downside is that hot engine compartment air can come in and the car runs a bit rougher in traffic on a hot summer day but I don't think it's really a problem.

[Fredrikkk]

Hmm... I cut out the bottom front part of the airbox today, but it still smokes like a b... I think I'm gonna put the cone filter back in and shield it.

And about the BOV sound, it's the wastegate closing I guess? When I hit 1 bar and let off really quickly it "wooshes"  Now I don't hear it and there's just a throatier sound from the intake. I miss the whine from my hairdryer..

I get my car approved tomorrow hopefully, so then I can get the exhaust put on. I'm really excited

Thanks for all comments; you guys are truly awesome! 

[R.O.R-2.0]

All the 1.6 TD's had a BOV or overboost protector from the factory. Giles makes a nice block off plate for the intake mani port http://www.vwdiesel.net/forum/index.php?topic=18289.0.

the later TDs had no such devise.. so it must not have been that important.. i think they did away with them in like 1988?

Heres a little quote from Wikipedia:

Definitions
A typical piston-type dump valve, used in auto racing. Unlike a blowoff valve, this one does not vent to the atmosphere. The small hose at the top is a feed from the intake manifold.

A compressor bypass valve (CBV), also known as a pressure relief valve or diverter valve, is a manifold vacuum-actuated valve designed to release pressure in the intake system of a turbocharged vehicle when the throttle is lifted or closed. This air pressure is re-circulated back into the non-pressurized end of the intake (before the turbo) but after the mass airflow sensor.

A blowoff valve, (sometimes "hooter valve", not to be confused with a bypass valve) performs the same task but releases the air into the atmosphere instead of recirculating it. The blowoff action produces a range of distinctive hissing sounds, depending on the exit design. Some blowoff valves are sold with a trumpet-shaped exit that intentionally amplifies the sound. Some turbocharged vehicle owners may purchase a blowoff valve solely for the auditory effect even when the function is not required by normal engine operation. Motor sports governed by the FIA have made it illegal to vent unmuffled blowoff valves to the atmosphere.[citation needed]

Blowoff valves are used to prevent compressor surge, a phenomenon that readily occurs when lifting off the throttle of an unvented, turbocharged engine. When the throttle plate on a turbocharged engine closes, the high pressure air in the intake system is trapped by the throttle and a pressure wave is forced back into the compressor. The compressor wheel slows rapidly and may even stall, and the driver will notice a fluttering air sound. The rapid slowing or stalling stresses the turbo and imparts severe turbo lag if the driver accelerates immediately after the surge event.

and what you are hearing is simply the turbo slowing down once you let off the throttle.. not the wastegate closing, or the BOV (HEY!! your car doesnt even have one!!)

you are smoking more because your cone filter flowed more air.. and it seems like your car has more bottom end, because it actually has LESS top end..

[Fredrikkk]

My car actually does have a factory "BOV." I blocked it off with a piece of wastegate steel line!

But what you say about air flow does very much make sense.. I'm gonna definitely put the cone back on and enjoy the loudness of the turbo, and then after that I'm gonna enjoy the loudness of the turbo out of the exhaust

[Dirtrag2]

and what you are hearing is simply the turbo slowing down once you let off the throttle.. not the wastegate closing, or the BOV

Hey RoR... would not this part of your post suffice to explain your opinion of the sound heard by our fellow diesel enthusiast.  Really? the wiki definition while pertinent is a bit much... no?

you're usually a cool guy with a fair bit of knowledge and advice, hopefully you will get back to the old you soon and I can start enjoying your insight again.

P.S.  sorry Fredrikkk for jacking your thread.

[R.O.R-2.0]

and what you are hearing is simply the turbo slowing down once you let off the throttle.. not the wastegate closing, or the BOV

Hey RoR... would not this part of your post suffice to explain your opinion of the sound heard by our fellow diesel enthusiast.  Really? the wiki definition while pertinent is a bit much... no?

you're usually a cool guy with a fair bit of knowledge and advice, hopefully you will get back to the old you soon and I can start enjoying your insight again.

P.S.  sorry Fredrikkk for jacking your thread.

i feel that people should know the correct terms for their parts..

diesels dont have a blow off valve, or a throttle valve.. so it just doesnt work..

or everyone can walk around calling it what they want, im just trying to keep the human races minds from decaying..

i like how everyone says they can hear their wastegate opening when they let off for a shift, but its actually closing..

and the only reason i posted up the WIKI definition, is because people have had a tough time wrapping their heads around that one since i came here as a newb.

a BOV is vacuum controlled, an overboost valve, is controlled by too much boost..

[catlin_cava]

on my 2001 I have a straight Pipe when i let off on boost i get turbo barks and it sounds like a BOV,

[R.O.R-2.0]

your turbo barks just like mine..

but, to me, it sounds far different from the sound (pssssssshhh) of an actual BOV on a gasser..