shutzero

so i had the bbk underdrive pulley and was getting low charges at idle. it would hand around 1/4 when idling and shoot up when i would accelerate. so i thought it was due to the alternator not being turned enough. so i went and bought the asp pulley kit which included the alternator and crank pulley. still the same problems. however, i notice the car only idles low after i drive it for about 2 minutes. when it starts up and idles, it idles fine. any ideas guys?

RamAir95TA

iTrader: (2)

How low is your RPM? After your car is warmed up, factory idle is set at 550rpm.

shutzero

I wanna say around 800...but like I said the charges are still low....I even had the alternator tested and it passes

koolaid_kid

iTrader: (21)

Depends on the transmission. Autos are closer to 800 rpm.

RamAir95TA

iTrader: (2)

Stock idle speed is 550rpm in drive, 650rpm in neutral for an automatic.

Manual transmission cars shoot for 800rpm.

shutzero

bump for ideas

blackz6sp

iTrader: (11)

Cold start=high idle After it warms up it drops a couple hundo rpms.

koolaid_kid

iTrader: (21)

You have a valid point, my error. I checked my stock tune, and its settings are as follows:
Cold (1200 rpm at insanely low temps, 1000 up to 89 degrees, F, both in neutral).
Warm 650 rpm in neutral, 550 in gear (approx. 200 F).

shutzero

ok but still doesnt help my low charge problems haha

blackz6sp

iTrader: (11)

I picked up a smaller alt. pulley for nothin at a local auto elec. shop. That worked for me.

shutzero

Well I bought the asp kit with a pulley...the pulley was actually bigger...weird

blackz6sp

iTrader: (11)

Yeah the bigger alt pulley is actually gonna slow it down. Not gonna help your low voltage problem.

shutzero

What pulley should I get and what size belt?

shutzero

So I've learned that the asp pulley kit was completely useless to me haha I had the bbk pulley and got low charges so I bought the asp pullies thinking it would fix the charges not knowing the alt pulley was BIGGER haha oh well time to pick up a smaller pulley at my race shop or order the march pulley from summit and measure what size belt ill need *sigh*

koolaid_kid

iTrader: (21)

So, before you spend any more money, stand back and think for a moment.
First, you now have 2 crank pulleys and 2 alternator pulleys, right?
Second, the important factor here is not the absolute diameter of each pulley, but the relative size in relation to each other. Let me give some examples:
a) C1 pulley is 6 in diameter, A1 pulley is 2 in diameter. This is a ratio of 3:1.
b) C2 pulley is 4 in diameter, A2 pulley is 1 in diameter. This is a ratio of 4:1.
c) C2 pulley matched with A1 pulley is a ratio of 2:1.
d) C1 pulley matched with A2 pulley is a ratio of 6:1.

Hopefully, you can see where I am going. You should be able to mix and match and get a better ratio to spin your alternator faster. For example, measure the 2 crank pulleys you have. Select the larger of the 2. This will yield the highest inches of belt travel per engine revolution. Measure the 2 alternator pulleys and select the smaller one (sounds like the original one will do). This will give you the highest ratio of alternator rotation per crankshaft rotation (like example d). Using that combination, you will have the fastest turning alternator at that point. Cost, possible one drive belt (if it works out).
Hope this makes sense.

shutzero

Im pretty sure the bbk and asp crank pullies are the same size