SR20DET leaky BOV question

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nisileighty
Posts: 30
Joined: Tue Jan 05, 2016 8:17 pm
Car: 1989 240sx KA-E
1989 240sx KA-ET
1990 240sx RB20
1991 240sx KA-DE
1993 240sx KA-DE
1993 240sx SR20 19psi
1990 300zx TT
1992 300zx TT
2003 350z VQ-DE
2008 350z VQ-HR
Location: Seattle, Wa
Contact:

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Hi,
Recently I was checking my redtop swapped s13 and I found that my blow off valve has been leaking from the diaphragm. My motor was having a slight misfire at idle and i never thought much of it being that I'm a few degrees advanced in timing so I thought that was the cause until I covered my BOV with my hand and the miss dramatically reduced. Pissed at my eBay intercooler kit, I went covered the outlet with a condom and surely enough, it filled up with air in a matter of seconds.

Near the top of my rev band, the turbo (S15 spec R) starts to trail boost off. It'll hold 19 psi until about 6k and then fall to 15 until redline. I had a dyno pull done only reaching 280 peak RWHP, which is odd for an SR on 19 psi because I was expecting about 320-330 at the wheels.

So my question is, with the leaky blow off valve and the loss of about 4 psi, how much power would I be losing and could this be THE cause of the misfire at idle?

Any input helps, Thanks!


User avatar
Hijacker
Posts: 15759
Joined: Wed Aug 13, 2003 4:57 am
Car: '92 240sx Convertible
'94 F-150
Location: Fredericksburg, VA

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You have a massive boost leak, while I can't give you any accurate glimpse into how much lost power it equates to, it's most certainly quite a bit. You should also be running pretty rich, too, since you're losing air post metering (assuming you're still running a MAF). That could also be messing with your car's ability to fire properly.

Corky Bell likened a pound of boost to be about 9 hp, if you're looking for a rough estimate.

nisileighty
Posts: 30
Joined: Tue Jan 05, 2016 8:17 pm
Car: 1989 240sx KA-E
1989 240sx KA-ET
1990 240sx RB20
1991 240sx KA-DE
1993 240sx KA-DE
1993 240sx SR20 19psi
1990 300zx TT
1992 300zx TT
2003 350z VQ-DE
2008 350z VQ-HR
Location: Seattle, Wa
Contact:

Post

Hijacker wrote:You have a massive boost leak, while I can't give you any accurate glimpse into how much lost power it equates to, it's most certainly quite a bit. You should also be running pretty rich, too, since you're losing air post metering (assuming you're still running a MAF). That could also be messing with your car's ability to fire properly.

Corky Bell likened a pound of boost to be about 9 hp, if you're looking for a rough estimate.
Hijacker, thanks for the response. I am running a MAF sensor and my car does seem to run pretty rich at both idle and under load.

I went ahead and ordered a new hotpipe without a BOV so I'm gonna be running a lot of flutter. There seems to be a lot of discussion on this, but is there any harmful side effects to this? Other than increased spool time between shifts, I can't think of any downsides to this. I've never seen a turbo ware prematurely due to turbo flutter so I'm not thinking it'll be a big deal, also being that I have another RS3871 ready to go.


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