I have a question to anybody that can help me out. I'm thinking about getting the Dejon charge pipes with a bov flange welded onto it but the question is where do I hook up the vacuum lines from the aftermarket bov? Some people on the cobalt forums say I will need a block off plate and some say I won't. Do any of you know how to run it to make it work? Thakns in advance

 

i too was thinkin about the Dejon kit. But i haven't heard anything about the vacuum and block plates. I have a feeling this will be enlightening for many, so if you have info please post!

 

If you put a BOV on though, wouldnt that mess up the NLS? Seems like you will be losing boost on the NLS?

 

I do not think it is a good idea to put a BOV on the LNF because of the placement.

Releasing unmetered air does bad things, unless the ECU is able to compensate for the BOV. The ECU will have trouble understanding why the air is passing by the MAF, and why it isn't making it into the engine. If it like the cobalt ss....which it is your going to get a CEL.

GM LNF Motors use a MAF system to measure the air before the turbo pulls it in, so when it releases boost the ECU can not handle it. A blow off valve works fine on most MAP based systems.

Hahn Racecraft is developing a Recirculating BOV and/or a BOV that is mounted Before the MAF sensor. According to everyone the Recirculating BOV would be better, and help keep the turbo spooled more.....in the LNF cobalt, but not in other applications. ~~Off Memory~~ Hahn could probably explain more.

Also the way the LNF turbo is designed it seems that a recirculating BOV helps to eliminate/prevent compressor surge, but that is only a theory....and is not proven, yet.

 

Yeah I've been talking to bill and I will be getting my bov from hahn. Thanks for the response. The Dejon pipes look tempting for the price but I will have hahn do everything

 

I have not found any major vendor besides HRC taking this position. Dejon, BTFR, and others have been bypassing to atmosphere for some time and the buyers don't seem to be reporting issues. Having said that, I agree with your assessment from a technical perspective IF the discharge was happening after the MAF. The above mentioned products release BEFORE the MAF.

To the OP's questions, you're going to need a boost source to signal your BOV. Grab it from any of the stock lines and you're all set. You'll also want to disable the stock diaphragm valve. There are 2 methods-- replace it with a block-off plate (Hahn sells one of these... it's a flat piece of metal that bolts where the stock unit was), or neutralize the stock valve by providing a boost source to both sides of the unit. In stock form, it has a boost source on one side and a vacuum source on the other. Putting boost on both sides confuses it into thinking everything is balanced and so no need to open.

 

Thakns xxl. Yeah I was getting mixed reviews on this. But I think I will stick with the hahn bov after I get my pipes and all. Afterall they will be installing everything so I know it will be done right

 

That is because they are moving the location of the Blow off valve to before the MAF sensor in the charge pipe. As you stated.