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Elite DSMtalker
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Discussion Starter · #1 ·
ok this might sound like a dumb question but on a 1g why does the stock BOV exit back into the intake, and what whould happen if you disconected it :)
 

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this is a big debate, but IMHO on my 2g, I felt no difference with the BOV venting to the atmosphere. Also, since you are venting already metered air so you will run richer. I would leave it connected to the intake.

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'99 GST
http://www.geocities.com/mospeed9844
Akimoto Air Fitler
GReddy BOV
GReddy Intercooler Piping
GReddy Cat-Back
GReddy Profec B
Front and Rear Strut Bars
 

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The vented air is already past the MAF sensor and totally dumping to atmosphere will cause the car to run real rich at times. Converting to a MAP style air metering system (such as the VPC) will allow you to vent the compressor bypass to atmosphere. I have noticed that venting a 2G is not nearly as bad as a 1G.
 

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Elite DSMtalker
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Discussion Starter · #4 ·
Ok so what happens when you put an aftermarket on, they vent into the air? also can the stock BOV hold 15 psi
 

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yes the stock unit will hold it. Stock 1G BOV has been used on 10 sec cars so I think it work fine for most.

What BOV it is doesn't matter they all do the same job. The point it that if it passes the MAS ( in rule of thumb) it MUST be burnt by the motor. It thinks the air is in the system and has added the fuel for it. if it does get vented out of the system the car doesn't know this and adds the fuel for the air that isn't there. this causes it to go rich. the ECU sees this and starts to lean out the Fuel Inj Block learn ( a bit more then you wanted to know but this is what happens ) when the block is lowered it causes the car to not have enough range in the inj adjustment and causes all sorts of problems.

What most people lack is the idea that a car is like a chain and one thing may effect MANY other systems so you never know. personally I ahve NEVER seen a vented BOV that was on a car with a MAS run well. Yes fast but never as fast as it SHOULD have been.

Shoud'a,Could'a, would'a, but it didn't!!!

For VERY high boost ( in CFM's not PSI ) the BOV needs to be cruched but if your at that point just asking if it will hold then your not going to have a prob with this. trust me you will hear much more talk about crushing the BOV in time. a very common Mod.



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Bill Marino
NYC DSM
[email protected]
 

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another reason it is good to have it going back into the intake track is that it helps keep the turbo spooled when you let off the gas, this really helps when you are running bigger turbo's such as a 20g or bigger. with my s20g i really noticed a difference when i vented it to the atmosphere compared to when it was hooked to the intake track...i only did this for about 20 minutes bacause of
this :D . also the air comming out of your bov has already been cooled by the ic, so why would anybody not want cool air going into the turbo??? kinda like a cold air intake but only when you shift, still helps though.

bill

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95 tsi-awd
91 tsi-fwd
95 civic turbo
82 gti
 

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What are the steps in crushing a BOV? There is a faq on DSM.org, but it seems very vague to me.

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John Lewis
1991 Eclipse GS Turbo
 

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by 4npower:
also the air comming out of your bov has already been cooled by the ic, so why would anybody not want cool air going into the turbo<HR></BLOCKQUOTE>

actually, unless your intercooler is more than 100% efficient, it cannot cool the air past the ambient temp. Really good intercoolers usually only come within about 15 to 20 degrees of ambient temp. A really good air/water intercooler can be more than 100% efficient, but only for as long as it takes to cycle the water supply.

From a performance standpoint there is no good reason to vent the BOV to the atmosphere. The car runs rich and the turbo will take longer to spool every time you shift. But someone already said that.
 

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Not to nit-pick here, but you can never get 100%, not to mention more than that, efficient cooling. True, when you're using an air to water intercooler, you are getting below ambient temperatures. However, when you're talking about efficiencies, you are comparing temperature difference between the air being cooled and the cooling medium which in this case is water. So the air is cooled below ambient but still above the water temperature.
 

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>
Not to nit-pick here, but you can never get 100%, not to mention more than that, efficient cooling. <HR></BLOCKQUOTE>

You are definetly nit-picking.
The efficiency of an intercooler is rated as its ability to cool charge air in referance to its original temp. If the intercooler can cool the air back to its original temp, then it has performed its job 100%.

I understand that in physics no energy exchange can be 100% efficient. But that has no relevance to the point.
 

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Actually if you remve the BOV return line that goes back into the intake it will help lean your car out a little when under acceleration. That hole is sucking in un-metered air and the computer has no clue it's there.
 

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Now, who's definition of intercooler efficiency is this? Yours? All I can say is that technical definition of efficiency of a heat exchanger is ALWAYS in reference to the temperature of the cooling medium. If you are performing a calculation on the intercooler, what matters is the temperature at the inlet, the temperature of the cooling medium, and the temperature at the outlet. For this application, there's no way you could or would take the temperature upstream of the turbo into consideration.
 

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If you're saying to leave the "hole" in the intake tube open, it's not a good idea as
1.) The air going through the hole is unfiltered.
2.) You have no way of adjusting the amount of air ingested through the hole. It might get your a/f ratio too high and then you'll be rebuilding the engine.
 

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<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by Jehu:
If you're saying to leave the "hole" in the intake tube open, it's not a good idea as
1.) The air going through the hole is unfiltered.
2.) You have no way of adjusting the amount of air ingested through the hole. It might get your a/f ratio too high and then you'll be rebuilding the engine.
<HR></BLOCKQUOTE>


I've never really worried about that whole ingeting something. It's in a relatively safe spot so I won't have to worry about ingesting any bugs or anything. As for getting your A/F ratios too much out of wack it won't happen that hole simply isn't big enough. I picked 2/10's before I had fuel control doing this. I had an AFC and still did it anyway.
 

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LOL, I've actually heard of someone fitting a small K&N to the BOV return. I just wouldn't advise it because there's no way of judging how much air is coming in. It might also lead to idle issues, similar to what happens in the 1Gs when too much air is bypassed through the unmetered section. Otherwise people would be cutting holes in the intake tube instead of getting an AFC. BUT if you really have to do it, at least put an air filter over the hole. Bugs might not get in but dirt sure will.
 

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All of you guys missed the bigger point. At part throttle (vacuum) the bov is an open hole past the mas. A big one at that. Acts exactly like a huge vac leak and the car runs like crap at part throttle (and idle for that matter). thats the biggest reason you have poor driveability with a vented bov.
 

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I agree with Jehu. Removing the BOV return tube is bad as is, but leaving that hole open? If you have AFC, why do you have the hole open? The car will run lot quicker if you close up the hole by connecting the BOV return tube, but of course this advice only applies if going fast is your priority.

Jeff
 

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Hmmm, I have an HKS SSBOV on my '98 Eclipse GSX. I had gotten a universal one so I didn't get one of those caps to block off the BOV return tube since it vents to the atmosphere. I was told and found out that a 35mm film canister fits perfectly in the BOV return tube...just remember to clamp it down.

BTW, I believe that HKS just came out with a kit to have it vent back into the intake.

~Tranman
'98 Eclipse "GS"X
 
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