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High duration cams and idle
Posted: Tue Jun 30, 2009 5:43 am
by Piv
Hello, I've just start my all motor B20 VTEC this week end Start up nicely with no smoke and idle like it should be for big cams but I would need some feedback from people who got experience in all motor ITBs and big cams So the setup (shortcut) : B20 VTEC B16B head ported and polished M24x cams (timing done) OBX ITBs ported RMF header ported 12.9:1 CR The video :
http://www.youtube.com/watch?v=KTTNLzSd ... re=channel I can get an proper idle (not jumpy) with -3deg of ignition (dizzy timing done) but dont like the sound of the engine as it looks like it's struggling (running 13.5AFR) On the video its running 14deg and AFR go 13.5->Lean->13.5 with the fuel cut's appearing at 1500rpm Any information about this ? It doesnt bother me but just would like some feedback as I got more experience with turbo built

Posted: Sat Jul 04, 2009 8:54 am
by Piv
Anyone ?
Posted: Sat Jul 04, 2009 1:13 pm
by elevation
Proper volocity is very important with ITBs .givin the reputation of OBX Id bet little to no engineering went into the design of those ITBs. If your at any sort of altitude it would be even worse.Ive been saving for some toda ITBs, they're pretty nice but expensive. the smaller throttle bodys would be good for me @ 6800 feet!
Posted: Sun Jul 05, 2009 8:12 am
by Gaskleppie
I have tuned a car almost exactly like yours. It was a race car so idle was no issue. It idles also not very nice. I disabled the iacv valve and idle ign correction. The guy has to keep it alive the first minute of cold start. After that it idles at 1500rpm fine.
Re: High duration cams and idle
Posted: Mon Jul 13, 2009 5:10 am
by Natural Aspirations
Piv wrote: I can get an proper idle (not jumpy) with -3deg of ignition (dizzy timing done) but dont like the sound of the engine as it looks like it's struggling (running 13.5AFR)
I have always added timing to a big cam engine to help idle. 13.5 afr is good as it will want to be a tad rich at idle. you can also try pulling a deg or 2 back on the exh cam. I was under the impression the m24x idles well. Have you spoken with Rocket at all, he may be more helpful than anyone with this particular cam.