Another question for underdrive pulley users
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 1,243
Likes: 6
From: Rowlett Texas
Another question for underdrive pulley users
Did you find a smaller pulley for your alternator so that you'd always have positive output from your alternator?
If you did, where did you find it?
Thanks,
If you did, where did you find it?
Thanks,
Melting Slicks
Joined: Nov 2002
Posts: 2,884
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From: Jamison Pa
St. Jude Donor '11-'25
Melting Slicks
Joined: Aug 1999
Posts: 3,452
Likes: 3
From: Spring, TX
My car runs with 13+ volts on the UD pulley. When it was stock is was 13+ to 14.
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 1,243
Likes: 6
From: Rowlett Texas
Yesterday I was discussing a cam with a major tuner when the UD subject came up. What was said was 'You can get about 6rwhp more if you install a ud when you do the cam. Thus, the original question.
Melting Slicks
Joined: Mar 2005
Posts: 2,364
Likes: 1
From: Rugby North Dakota
I think they say an Underdrive Pulley gains you about 5 HP - I got an Underdrive ALT pulley from Lingenfelter performance, together w/ the correct sized belt for it when I installed my CRANK underdrive pulley.
Drifting
Joined: Dec 2005
Posts: 1,720
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From: East Hampton CT
I don't have a way of checking the amperage output of the alternator before and after the UD, but my output voltage with the UD is approx 13.7-14.2 when cold idling and drops down to about 13.5 once the battery is charged.
Keep in mind that stock idle is around 650-700 rpm....but when you install a cam your idle is usually much higher than that...closer to 850-900rpm. The % difference that you lose by going to the pulley is made up by increasing your idle rpm for the cam. I did try lowering my idle to around 750-800 and I DID notice a charging issue.....so I keep it around 850-900.
Keep in mind that stock idle is around 650-700 rpm....but when you install a cam your idle is usually much higher than that...closer to 850-900rpm. The % difference that you lose by going to the pulley is made up by increasing your idle rpm for the cam. I did try lowering my idle to around 750-800 and I DID notice a charging issue.....so I keep it around 850-900.
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Burning Brakes
Joined: Nov 2003
Posts: 990
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From: North Texas
I don't have a way of checking the amperage output of the alternator before and after the UD, but my output voltage with the UD is approx 13.7-14.2 when cold idling and drops down to about 13.5 once the battery is charged.
Keep in mind that stock idle is around 650-700 rpm....but when you install a cam your idle is usually much higher than that...closer to 850-900rpm. The % difference that you lose by going to the pulley is made up by increasing your idle rpm for the cam. I did try lowering my idle to around 750-800 and I DID notice a charging issue.....so I keep it around 850-900.
Keep in mind that stock idle is around 650-700 rpm....but when you install a cam your idle is usually much higher than that...closer to 850-900rpm. The % difference that you lose by going to the pulley is made up by increasing your idle rpm for the cam. I did try lowering my idle to around 750-800 and I DID notice a charging issue.....so I keep it around 850-900.
MisterC - That's a pretty valid point. The Tuner will have to raise your idle for the larger cam which will increase the "idle" charging point. If the stock idle speed is 650-rpms and you lose 20%, then new idle speed would only need to be 780 to make up for the loss. You may not need the pulley on the alternator. If you do decide to get the two piece kit, we can install the alternator pulley later if you have a charging problem.....
(Had to do that on the Yukon in the summer so I just left it that way).Something to note: that is 5 hp across the entire curve and not just more HP at the high end like the Cam is going to produce. Total area under the curve is really what you care about since you don't race the car that much....Or do YOU?????
Thread Starter
Burning Brakes
Joined: Jan 2004
Posts: 1,243
Likes: 6
From: Rowlett Texas
MisterC - That's a pretty valid point. The Tuner will have to raise your idle for the larger cam which will increase the "idle" charging point. If the stock idle speed is 650-rpms and you lose 20%, then new idle speed would only need to be 780 to make up for the loss. You may not need the pulley on the alternator. If you do decide to get the two piece kit, we can install the alternator pulley later if you have a charging problem..... (Had to do that on the Yukon in the summer so I just left it that way).
Something to note: that is 5 hp across the entire curve and not just more HP at the high end like the Cam is going to produce. Total area under the curve is really what you care about since you don't race the car that much....Or do YOU?????
(Had to do that on the Yukon in the summer so I just left it that way).Something to note: that is 5 hp across the entire curve and not just more HP at the high end like the Cam is going to produce. Total area under the curve is really what you care about since you don't race the car that much....Or do YOU?????