lightsource

I'm getting a backfire from my engine.

The only time it happens is when I go over 2K RPM, and let it coast down past 1500RPM, and it's only when I'm moving. So whenever I go passed 2K rpm as SOON as it gets to 1500RPM I get the backfire, it's not loud (full stock exhaust) but it's a problem that I would like to get diagnosed/fixed.

lightsource

bump, any suggestions?

nzmoman

its the same thing linked to your BOV. you have excess fuel but your BOV has released some of the air that is supposed to be in the mixture.

That fuel passes into the hot exhaust and ignites making the noise. it not really a backfire though. a back fire is ignition in the intake, what is happening to you is normal, its the same thing that causes flames to shoot from built turbo cars.

lightsource

thank you,

since this was posted I recirculated my BOV and I no longer have this problem.

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SoSideways

Sounds like you're running either a GReddy Type-S, Type-RS, or Type-R BOV with your BOV vacuum hose tee'd off to the wastegate.

Give yourself a dedicated vacuum hose to the BOV and you wouldn't need to recirc the BOV to get it to stop backfiring.

lightsource

it's the stock BOV, however the vacuum hose IS tee'd off.

I'll make sure to do that. Thanks!

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jonathan12uiz

Interesting! I've had the same issue with the backfire issue on decel around 1500rpms. I've only had the issue since I installed my new Greddy Type-S BOV. With my HKS SSQV I've never really had the backfiring on decel issue. I think I'm going to have to get an SAFC so I don't have to recirculate. I love the type-s sound. LOL! BTW my bov is not tee'd off, it has it's own line coming from the bottom of the throttle body. So I don't really know if it's just the Tee'ing thing that is causing your issue like the last person said. All I know if that I don't want VAC applied to my wastegate, so I tapped into my hotpipe and installed a nipple that runs a vac line from the hotpipe straight to my wastegate. when I had my bov tee'd with my wastegate, I was getting weird boost issues. no problems now. runs like a champ.

SoSideways

Um...

The nipple on the bottom of the throttle body is not a source for vacuum. The hole where that nipple draws air from starts right underneath the throttle butterfly, making it a "positive pressure only" nipple.

You need to use the nipple on the top right of the intake manifold, right after the throttle body.

The one on the left is good for the FPR, and people usually tee that line off to the boost gauge.

The one on the bottom of the throttle body you could use for the WG.

If you run your vacuum lines like this, and you mess with the GReddy Type-S's spring pressure (and make sure you take the little spring out, I heard that makes it work better), you shouldn't have the backfire at 1500rpm upon decel in gear.

jonathan12uiz

LOL! i'm sorry I was thinking of which one I capped off. Yeah my bov is connected to the top right. fpr is on top left. and i capped off the bottom one. Sorry about the mix up. I just posted on another post about my vacuum setup... but i didn't F it up on my other post. LOL! sorry but ^ is correct. top right is bov.

but are you saying i should take the adustment spring out to stop the backfiring?

SoSideways

No.

Some people have said that if you remove the smaller spring inside the Type-S's diaphragm chamber then it would open better, while being able to adjust it so it doesn't open under idle or open at 1500rpm.

Do a search on here about it. It's been discussed a few times.

jonathan12uiz

ok thanks for the info. i didn't know that about the type s