underdrive pully

peppersac · March 29, 2005

does anyone think this would help?? if so anyknow how much?? also when they say full charge 950 rom what does that mean??

http://www.streetbeatcustoms.com/asp549984.html

rcj_houston · March 29, 2005

does anyone think this would help?? if so anyknow how much?? also when they say full charge 950 rom what does that mean??

http://www.streetbeatcustoms.com/asp549984.html

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I know this is for the crank shaft, but bare with me.

Basically they are saying that the engine accessory pulleys (A/C, Power Steering Pump, Water pump, Smog Pump, etc) will turn 23% less at a given RPM. (RPM = Revolutions per minute of the engine) If they say 950 rpm, they mean that your engine is turning 950 revolutions in one minute (one turn of the crank shaft = 1 revolution).

Keep in mind that with your accessories not turning as much (as they were designed to do) that your alternator will not charge as much. If your alterator is putting out 100 amps at 1000 rpms, then with this pulley installed, your alternator will be turning 23% less and therfore not putting out 100 amps at 1000 rpms any longer. You will have to rev your engine 23% more to achieve the same alternator output.

It also means, that if you live anywhere where it gets hot in the summer, your A/C is turning less and therefore not cooling as much. If you run any decent high power stereo and use your Air Conditioning, dont do this modification. Can you imgine how dim your headlights might be with the A/C on, your stereo thumping and driving at night?

Speaking of it being hot in the summer, think about your water pump turning less and therefore circulating less coolant. In the middle of summer, your engine will most likely run hotter.

Also, if I recall, you might have computer problems depending on the year model of the vehicle you are putting this on. Seems I read a thread somewhere, that with these installed on an 02 Tahoe, the computer was getting false readings for emissions, etc based upon the RPM of the engine not matching something...I honestly cant remember.

This type of modification is more for street-cars or street-trucks (not your average daily driver) that normally won't run an AC unit or a high powered stereo. Especially, if they race alot. They need very minimal amps from the alternator. Sometimes they size the alternator for just enough amps to run the fuel pumps and electric water pump and any other computer recorders.

Anyway, I have babbled far too much. This was just my 2 cents...I am sure you may get a completely different opinion from someone else.

cheers...

99Silver6.0 · March 30, 2005

You can get an alternator overdrive pulley to get rid of the undercharge that comes with the underdrive pulley. RPMOutlet sells both in a kit for $234. It doesnt look like StreetBeat included both in their $221 price tag. These pulleys cant cause a code to be thrown. The pulley doesnt change the RPM signal that the Crank Position sensor picks up.

99Silver6.0 · March 30, 2005

OOps... I messed up...

desrtrat · March 30, 2005

your looking about 8-10 hp. also you will need to replace belts and bolt. that price not bad if belts&bolt come with it .

check out TBYRNE <------------perf. vender

99Silver6.0 · March 30, 2005

your looking about 8-10 hp. also you will need to replace belts and bolt. that price not bad if belts&bolt come with it .
check out TBYRNE <------------perf. vender

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