Post by
DjPantsSpecR »
https://forums.nicoclub.com/djpantsspecr-u24575.html
Tue Dec 05, 2006 11:17 am
yeah, i got really really confused to and i had some things backwards.
so, if you really are at 1.5 atdc, which is probably true for altima 248s (i dont necessarily believe what everyone says about s13 248s...) then a +5 degree advance would put you at 3.5 degrees btdc.
it seems like a bit much advance, especially when with 248's youre looking for top end power. i believe it works for s13 248's because our math on its position has been off and it is already too far retarded (it opens up a long ways after tdc) if you try and retard the 248 further i havent been able to make any decent powerbands. that alone leads me to believe that is is already too retarded, and needs some advancing.
thats where you come in: almost every dyno ive seen of 248 intakes has a dip in power around 4k. a little advance should helped get rid of this dip. there is all kinds of things ive discovered about these cams that i'd like to discuss, but im actually in class right now so i cant. but if you do this, you can let me know if you lose a bunch of top end and gain low end. so lemme know ASAP.
i would definately recommend drilling many holes like the JWT gears. it'll make your life more convienient later. hwat i do is drill one gear for advance (+2.5, +5, +7.5) and then do the same for a retard gear. And then i have two retard gears (cuz i wont be advancing both sides i can imagine....)
but another interesting thing to note about these gears is they are actually in increments of 2.1 degress. so 2.1 degrees, 4.2 degrees, 6.3, and 8.4 compared to 2.5, 5, 7.5, and 10. pretty big difference in actual advance i'd say.... so huge steps in advance or retard arent as huge as they might seem...
so for your case, i want you to help me with some research. on your 248, try everything. retarding should work to make top end power, while advancing should fill in the low end. try +5, +2.5, -2.5, -5. tellme what you like, then start messing with that 232. for that low duration and and early exhaust closing event i would try 2.5 degrees of retard , -5, and maybe -7.5
so for right now, and for a while now, i was *** backwards, and i dont believe that a 248 rotated 4 teeth really opens at 1.7 BTDC. so i ****ed up, and for altima 248's try retarding to make top end, advancing to make low end.
but thats why i need you to TRY it, and tell me if you find the same things