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Discussion Starter #1
I just did a B7 head swap on my D15B8, and I am still running the B8 Intake Manifold until I can get my hands on the D15b7 manifold, now whenever I start the motor, it idles very poorly, and if I try and drive off it bogs really bad for a few seconds and then takes off. Could this be due to the fact that the CX manifold doesn't have a Fast Idle Valve?
 

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How did you get a 16 valve head to work on a 8 valve block (specifically the only 2 valve dish piston)?
 

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Indeed. I did a 16 valve head swap on my D15B8. I had a little of the same problem with idle and bog. I also sometimes have a big dip in the idle when I rev and let it fall all the way back down. Every once in a while it goes all the way down to 500RPM and slowly comes back up to 675-725.

Is that because of the intake mani? I wondered that.
I did the head swap out of necessity rather than singly as an upgrade. The old head was warped when I got the car and I had to replace it because it had actually been shaven past what's acceptable.

I also have AEM intake, JVT 4-2-1 header, and Magnaflow exhaust from there to the back. No cat, one resonator, and the muffler on the end. Every once in a while I throw CEL on hard accel at the top of 2nd gear (about 69mph at 5,650RPM).

Will changing intake mani actually help anything for me?
 

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Calebc, have u ever done just a b7 or z6 manifold swap on a b8 head alone? How was idle and driving lik that?
 

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No, I haven't. I had to swap heads of necessity. Otherwise I really haven't had money to put into the car except small projects like painting headlights/trim/reupholstering/etc...

I've got enough cash to grab a b7 mani right now, I'm just curious as to whether or not it would actually help anything, so I'm waiting on a reply to my questions above still. Sorry.
 

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any manifold with bigger ports then the b8 would help, theres no hope with the b8.

its like breathin with your mouth(ports) almost shut, your not gettin enough air to the lungs (cylinders)
 

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The ports are in the head though and swapping to the b7 head is what allows the motor to really breathe better, right?

I'm just talking about the intake manifold. Oh, ok, maybe I'm slightly dumb--is the b7 intake manifold higher flow? Does it actually have larger intake runners or whatnot?


Please take no offense if we have a misunderstanding. In fact, I mean no offense either way. Thank you.
 

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Discussion Starter #11 (Edited)
Nice to see i'm not alone on the idle/bog issue. I also throw a CEL if I get on it in 3rd gear sometimes (02 sensor) I think I may have a bad ECU as well, but yes the B8 manifold runners are much smaller than the B7's.

*EDIT*calebc, did you also swap the B7 ECU (P06) into your car or are you still running the B8 ECU (P05)?
 
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