Blk00EJ8

i believe ive read before that when a jrsc is installed with aem underdrive pulleys, the alternator pulley must be swapped back to stock. is there any truth to this, and if so, then why? the only thing i can think of is that it increases the angle of the belt against the blower pulley (slightly) and the alternator pulley (slightly), therefore decreasing contact surface area (slightly again). if the upper idler pulley can be tightened down for tension, would the slight change actually matter?

and amidst my frustration to get my crank pulley off (with still no success in 3 days), i was wondering why the crank pulley needs to be replaced anyway. the size of the "sub-pulley" on the crank pulley for the alternator would determine the boost. along the same line of thought, if it happened to be smaller than the jrsc pulley (i actually havent measured it yet), than nothing would be affected accept the blower speed, aka the boost, correct? thats why ive heard of people using larger crv crank pulleys to increase boost beyond the boost upgrade pulley with a claimed 8 psi (to ~11 psi i think). any thoughts? im thinking of installing the kit with my stock crank pulley and then taking it to get removed once my car is driveable.

heres a pic for visual reference. please disregard the lovely colors.

The-LS

I'm not quite sure what you are asking and how the layout is on the SOHC JRSC kits. But what ultimately drives the SC is the crank pulley. So usually underdrive pullies will spin accessories slower and the SC being added on like a accessory, will also spin slower. Yielding lower boost levels across the rpm band. So overall, a larger crank pulley will always increase boost, and a smaller crank pulley will always decrease boost.

Blk00EJ8

Mainly I'm asking if its necessary to change the alternator pulley back to stock. If what I said was somewhat confusing, I'll try again.


Looking at the pic, you see the alternator pulley in the diagram on the right by the purple dot and blue line. Now imagine it was larger. The belt's path would then be moved to the righthand side of the diagram to compensate, and by doing so, it would make slightly less contact with the blower pulley. I'm asking if this change will make a difference or not. Less contact usually = more chance of slipping so thats why i ask.

My second paragraph was just a realization, if you will, that I've spent the past 3 days busting my ***** trying to get the crank pulley off to get everything up and running while i could have just left it and gotten everything back up and running anyway with the stock pulley for the time being.

/long run-on-sentences

greenmonster

the reason why you have to swap out to stock alt pulley is because the setup may not charge the battery adequately. changing the size of the alt pulley wont affect boost. you may not experience a problem when driving during daylight. but at nighttime when you have your headlamps on the current draw is more, then you MAY experience a problem.

greekspeed

changing the size of the alternator pully will affect boost..... so to raise boost would be the ONLY reason to put the bigger stock pully back on... the car will run with either. (i would put the bigger stock pullys back on anyways to get a decent about of boost )

the bigger the crank pully and/or alternator pully the more boost.
the smaller the blower pully the more boost.


my kit had a special alternator pully with two belt groovs because there was one belt going to the alternator-to-blower and another going from alternator-to-crank pully. didnt know d-series kits had one big belt going from the the blower to the crank.

Blk00EJ8

ok, first in reply to greenmonster:

the larger alternator pulley does make the alt spin a little slower, but before the super i was running the same oversized pulley. i need a better method of grounding to help but so far i can put up with the lights on the center console a little dimmer. however, after finishing that part today i realize why the stock alt pulley is called for - the belt for the standard boost doesnt fit. i wound up using the belt for the boost upgrade kit since the upper idler pulley cant adjust enough. i just wonder what belt im gonna havta get ahold of if i decide to do the boost upgrade since i already have all the parts.


and secondly in reply to greekspeed:

the size of the alt pulley wont affect boost, it just affects the speed at which the alternator is driven. the crank pulley and the blower pulley are still the same sizes so the path in which the belt moves (around smaller or larger alt pulley) doesnt matter since the whole belt moves at the same speed.

youre right when you said the larger the crank pulley, the more boost. but i believe its the same with the blower, larger = most boost. if you take a pulley and mark a place in the middle of it, and one along the edge, and spin it, youll see that the outter mark moves faster because it has to travel a farther distance than the inner mark in the same amount of time. unless i just brainfarted, i think thats right.

edit: after rereading your post, thats why you said the alt pulley size depends on boost. in your case, yea, youre right since the alt pulley drives the blower. for mine, theres no room for an expanded alt pulley so the kit adds two idler pulleys as in the pics to prevent slippage on all the pulleys. the alt pulley is just along for the ride

The-LS

briefly looking at your belt config pics, (I'm a little off because I have GSR which is setup slightly differently. So just by looking at the diagram you cannot have a underdrive crank pulley or you will lose boost. So thats why they say you need a stock crank.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by EKcivicEX &raquo;</TD></TR><TR><TD CLASS="quote"> but i believe its the same with the blower, larger = most boost. if you take a pulley and mark a place in the middle of it, and one along the edge, and spin it, youll see that the outter mark moves faster because it has to travel a farther distance than the inner mark in the same amount of time. unless i just brainfarted, i think thats right. </TD></TR></TABLE>

Also a larger pulley on the SC will decrease boost NOT add, if you want more boost make the blower pulley smaller (this may cause belt slippage tho). On the B18Cx setups, we have a belt from the crank to the alt, then a belt from the alt to the SC.

Blk00EJ8

its not an underdrive crank pulley, the pulleys im talking about are only on the alternator and the power steering. i left both of these alone, but there was an issue with the pulley on the alternator due to it being on the same belt as the blower and crank. i just used a larger belt to accomodate. if i step up the boost, ill wind up switching the alt pulley back anyway. guess i kinda fudged it for the time being.

and maybe i did brainfart.

calvinPGMFI

i can sell custom made pulleys that a jcrs will make 18 psi

The-LS

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by calvinPGMFI &raquo;</TD></TR><TR><TD CLASS="quote">i can sell custom made pulleys that a jcrs will make 18 psi</TD></TR></TABLE>

JRSC for Hondas are pretty much maxed out at 11psi. You are just making heat after that.

Blk00EJ8

ive read that based on the setup and tuning the blower can still put out power up to around 15 psi. the increase is still linear to this point, at which it just levels off with anything higher and is counteracted by heat. but to just slap a new pulley on there and hope for the best is a bad idea. plus my stock d16 would be hurtin with that much anyway.