# Blow off valve



## DerekCaven (Feb 24, 2011)

Will I be able to run a Blow off valve on my Mk4 8v 2.0L build, or will it have to be a splitter/diverter. 

Probably a stupid question sorry:screwy:


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## kushdubber (Jun 8, 2010)

DV:laugh:


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## DerekCaven (Feb 24, 2011)

Ive seen a few Mk4 2.0L builds with BOV's though. Which confuses me


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## cabzilla (Jan 3, 2000)

DerekCaven said:


> Ive seen a few Mk4 2.0L builds with BOV's though. Which confuses me




cars that either are on standalone or do not run right.


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## kevinescobar15 (Apr 27, 2010)

DerekCaven said:


> Will I be able to run a Blow off valve on my Mk4 8v 2.0L build, or will it have to be a splitter/diverter.
> 
> Probably a stupid question sorry:screwy:


depends on your tune and if you are using a maf or a map. thats all. you can get a dv/bov.


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## Capt.Dreadz (Jun 4, 2003)

Alotta people say you can't run one with an MAF yet there are an awful lotta people running them (incl. me)


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## DerekCaven (Feb 24, 2011)

Capt.Dreadz said:


> Alotta people say you can't run one with an MAF yet there are an awful lotta people running them (incl. me)


No issues? I hear either problems with leaning/too rich right after shifts... I may try it.


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## Capt.Dreadz (Jun 4, 2003)

I haven't noticed any. Then again i'm also using a Pro-MAF


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## DerekCaven (Feb 24, 2011)

Whats pro maf haha


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## Capt.Dreadz (Jun 4, 2003)

CLICK


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## Capt.Dreadz (Jun 4, 2003)

Another CLICK. This is what i run.


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## DerekCaven (Feb 24, 2011)

Im not sure how that changes wether or not you need to run a SV or BOV though..


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## Capt.Dreadz (Jun 4, 2003)

I have no problems with running a BOV on my setup. I know a few people that's running the same setup and they to have no problems running one either. My assumption was based on this fact.


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## -RalleyTuned- (Nov 17, 2008)

Totally depends on your setup and if your ecu will run with a BOV. Usually MAF systems do not like bov since the air that was metered going in is being vented out of the system, and this can cause an over rich running condition at some spots. If the ecu will not go into limp mode, then you would be fine running a bov.

I switched to a forge splitter after having a tial replica bov. I immediatly noticed a little less lag in between shifts, which is very nice. The splitter makes the noise of the blow off while retaining the performance of a diverter :beer:


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## DerekCaven (Feb 24, 2011)

I already own a RFL BOV..Ill be running a C2 tune, 440 injectors , GT25 turbo, front mount, stock maf, 2.5 exhaust on a 2004 Golf 2.0. Anyone know if I can run a BOV with that setup, as I already own one.


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## -RalleyTuned- (Nov 17, 2008)

Contact C2 and run whatever they recommend :beer:


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## Capt.Dreadz (Jun 4, 2003)

Most BOV on the market can be converted to a recirc. That being said, if you're looking for the sound, a GReddy/Tial/TX recirculated will still give you the sound & the recirc that C2 recommends.

You're RT. Also another reason is that the recirc helps keep the turbo spooled between gears.


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## DerekCaven (Feb 24, 2011)

If I just remove the horn from the BOV and machine a fitting that I can hook a rubber hose onto , is that gunna do the trick...and because my car wasnt turbo before..where am I recirc-ing too...the intake side of the turbo? or the intake manifold?


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## Capt.Dreadz (Jun 4, 2003)

What BoV do you have?


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## DerekCaven (Feb 24, 2011)

RFL type H...the horn unscrews

http://www.speedforsale.com/nissangtrparts/images/TurboXS Type-H-RFL BOV.jpg


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## -RalleyTuned- (Nov 17, 2008)

If you route the air back into the intake, it is essentially a diverter...you kinda answered your own question...


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## DerekCaven (Feb 24, 2011)

I was asking where you divert the air to... *IF* I have to


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## -RalleyTuned- (Nov 17, 2008)

into the intake for the turbo :beer:


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## flat rate lackey (Jan 27, 2011)

wouldnt you vent it pre maf so that the ecm can read the incoming air and compensate for it? or does it matter at all?


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## Capt.Dreadz (Jun 4, 2003)

flat rate lackey said:


> you vent it pre maf so that the ecm can read the incoming air and compensate for it


 :thumbup:


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## -RalleyTuned- (Nov 17, 2008)

flat rate lackey said:


> wouldnt you vent it pre maf so that the ecm can read the incoming air and compensate for it? or does it matter at all?


Negative, because it already metered the air coming into the turbo, circulating it pre-maf would measure the same air 2x


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## flat rate lackey (Jan 27, 2011)

i see, so dumping in front of the turbo inlet wouldn't cause a rich condition between shifts


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## -RalleyTuned- (Nov 17, 2008)

It does, however that slight rich condition won't cause any ill effects with how the car runs/drives, and i doubt very much you would see any fuel economy loss...

The biggest thing is if the dumping of that air trips the ecu in to limp mode. Some ecu's do not trip, others do, it really just depends on your setup.


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## flat rate lackey (Jan 27, 2011)

I am going to be using c2 stg 1 software, so it probably would. So it would send the ecm into limp mode because a large sum of air goes away? just making sure I understand. When I turbocharged my prelude it had a map, I'm new to the MAF thing lol. Recirc is good for keeping compressor speeds up as well right? kind of like the setup in a td04h-16c?


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## -RalleyTuned- (Nov 17, 2008)

I have heard of a lot of oem systems not going into limp mode using a blow off, I havn't used oem software or wiring on a car that I have modified in years so I can't say for certain

I switched from a bov to a diverter/splitter type (which works as a diverter, but makes the noise of a blow off) and i most def noticed a difference in lag between shifts, so yes for sure it helps compressor speed


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## flat rate lackey (Jan 27, 2011)

Sort of off topic, but whats your opinion on just using water/methanol with decreasing inlets temps, example: run straight from the turbo to the throttle body with a pressure switch and water /meth?


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## Capt.Dreadz (Jun 4, 2003)

You'll be filling that thing up everyday...


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## -RalleyTuned- (Nov 17, 2008)

flat rate lackey said:


> Sort of off topic, but whats your opinion on just using water/methanol with decreasing inlets temps, example: run straight from the turbo to the throttle body with a pressure switch and water /meth?


Water/meth, imo, is a band aid fix for a poor setup. You are either trying to compensate for poor cooling of the air or a crap tune. Do it right and you will never need water/meth. If you do not wish to spend the time/money on a good setup, then you can def use it to help keep the motor together. I however, clearly, don't recommend it personally :laugh:


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## flat rate lackey (Jan 27, 2011)

yeah, I figured a well thought out air to air would be a good option for a dailey driven vehicle, I did some reading somewhere on some rally cars that used setups like that with success.


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## rweird (Apr 10, 2004)

rally cars arent daily driven...


i ran a bov when my mk3 was running (aba, t3to4e 50trim, c2 42lb obd2) ran great. i was running 3" turbo back with no cat though...shot flames, it was fun. if youre running a cat i would use a dv or youre going to melt your cat.


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## Capt.Dreadz (Jun 4, 2003)

rweird said:


> if youre running a cat i would use a dv or youre going to melt your cat.


 HUH~!? :what:


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## DerekCaven (Feb 24, 2011)

NO cat for me...shouldnt really have any effect on your choice of BOV or DV...if you used a BOV and it "shot flames" and "melted your cat" doesnt sound like it was running properly haha


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## rweird (Apr 10, 2004)

Capt.Dreadz said:


> HUH~!? :what:


on a maf tune the metered air that is released when you close the throttle plate(between shifts) will cause the car to run very rich (flames from tailpipe) for a second possibly doing damage to your cat.

sorry for not being more specific :thumbup:


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## DerekCaven (Feb 24, 2011)

Still doesnt sound to me like its running properly


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