Cutaway photos of 99-00 Head ?
#3
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I would try searching over at M.net
If you can stand reading through all the retarded bullshit posts there is actually lots of info over there
Edit:
Neeeeeevermind
The uncanny man was on the case.
#5
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I was very confused at first by this picture. Then I realized the cat was off center. I'd love to see one right down the middle, going through the center of the valve guides. I thought the ports and the seats looked a bit...off.
#7
With the valves out, and looking only at the runners, what you say makes intuitive sense.
The problem is that flow into and out of the combustion chamber is tremendously influenced by the valves, and the orientation of the runners relative to the valves. All else being equal a straight runner section over the valves, so flow around the valves has a chance of being somewhat symmetrical, is preferable to a straight run at the combustion chamber but cocked with respect the the valve.
Check the angle of the valve seats to the final portion of the runners; the closer to perpendicular the better. When they designed the NA they got it right the first go around.
#10
Compression, better ECU tuning, and most importantly, cam timing.
There's no difference between the 95 head and the 96 head, but with the OBII ECU and perhaps a smidgen extra compression the 96 motor makes five more HP (128 vs 133).
The biggest difference between the variable valve NBs and the non-variable valve NBs is the valve timing where they found another 9 hp or so (133 vs 142).
It's also possible that the NB head does flow better; it just doesn't look like it should. It would sure love to see some flow curves of stock heads measured on the same test stand and at the same valve lift.
There's no difference between the 95 head and the 96 head, but with the OBII ECU and perhaps a smidgen extra compression the 96 motor makes five more HP (128 vs 133).
The biggest difference between the variable valve NBs and the non-variable valve NBs is the valve timing where they found another 9 hp or so (133 vs 142).
It's also possible that the NB head does flow better; it just doesn't look like it should. It would sure love to see some flow curves of stock heads measured on the same test stand and at the same valve lift.
Last edited by Thucydides; 09-13-2010 at 11:11 PM.
#11
Of course this is a four valve head so center of runner isn't center of combustion chamber because the runners run parallel rather than radial (like some single cylinder motorcycles).
#12
Thanks again for posting those photos Doppelganger.
So, when I hear about most guys swapping in a 99-00 head, is it safe to assume that people are choosing the 99-00 because its the improved 1.8 head, minus the variable timing? I can assume that 1990-1998 guys would want the improved head, but cant use the variable timing due to not having a pcm that could control the variable timing devices.
Im also assuming that theres no benefit to someone with a 2001-2005 NB to swap in a 99-00 head, other than to eliminate the variable timing.
So, when I hear about most guys swapping in a 99-00 head, is it safe to assume that people are choosing the 99-00 because its the improved 1.8 head, minus the variable timing? I can assume that 1990-1998 guys would want the improved head, but cant use the variable timing due to not having a pcm that could control the variable timing devices.
Im also assuming that theres no benefit to someone with a 2001-2005 NB to swap in a 99-00 head, other than to eliminate the variable timing.
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