2nd Generation Specific 1986-1992 Discussion

Underdrive pulleys?

Old 12-28-2006, 02:58 PM
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I have a buddy with a 1990 Ford Thunderbird SuperCoupe. He just put a 5% underdrive pulley on his car. I was wondering if they make one for the TII's and if it is worth buying? Just a thought.
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Old 12-28-2006, 03:06 PM
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Yes YEs Yes....I'm a newb and this is definitely a newb question. I still am trying to figure out what I should and should not do with my 7.
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Old 12-28-2006, 04:03 PM
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They make em. Some are against it because of charging issues with the alternator at idle.



To me, not that big a deal, to some, big deal..



RacingBeat.com

RX7.com

Mazdatrix.com



Many others.
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Old 04-13-2007, 09:45 PM
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i'm just using lighted pullys, i find that the less weight to spin the better charge u get plus it takes some load of the engine to spin, kinda like having lightweight rims.
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Old 04-14-2007, 06:09 AM
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weight souldn't have anything to do with the charge. But the diameter of the pully will a smaller pully won't spin the alternator as fast. The less rotationl mass will help with something.
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Old 04-14-2007, 02:13 PM
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i want just an underdriven waterpump pully, too bad theyre damn expensive on mazdatrix.



jsut cause i spend most of my time at high revs, and i know my waterpumps going to fast and cavitating.

'

plus that wouldnt **** with my alt at all at idle or anything
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Old 04-14-2007, 08:54 PM
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Will these work with N/A 13bBs to?
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Old 04-16-2007, 10:57 AM
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unless you spend a lot of time at high rpm's (like leethslacker said) underdrive pulleys are a waste of time and money. the whole point of an underdriven water pump pulley is to reduce cavitation (air bubbles) underdriven alternator pulleys keep from overcharging (because when you're spinning at 8000 RPM's you're runnin the **** out of your pumps and alt too) so: if you were actually going into the SCCA (or similar) they're necessary. if were doing it to free up horsepower: underdriving your RX-7 for street driving will only reduce the efficiency of you're cooling/ charging system.



here is MUCH better way to spend the $200+ you would have spent on those pulleys: http://corksport.com/store/large/1chrm/2rx...N_A_Header.html

racing beat also offers one for $250
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Old 04-20-2007, 10:00 AM
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i know someone who dynoed +12hp just by doing pullies on an s4 t2. bigger/better alternator might be a good idea too, the charging system isnt so great at idle
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Old 04-20-2007, 07:41 PM
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Originally Posted by hillbilly' post='868361' date='Apr 16 2007, 11:57 AM

unless you spend a lot of time at high rpm's (like leethslacker said) underdrive pulleys are a waste of time and money. the whole point of an underdriven water pump pulley is to reduce cavitation (air bubbles) underdriven alternator pulleys keep from overcharging (because when you're spinning at 8000 RPM's you're runnin the **** out of your pumps and alt too) so: if you were actually going into the SCCA (or similar) they're necessary. if were doing it to free up horsepower: underdriving your RX-7 for street driving will only reduce the efficiency of you're cooling/ charging system.



here is MUCH better way to spend the $200+ you would have spent on those pulleys: http://corksport.com/store/large/1chrm/2rx...N_A_Header.html

racing beat also offers one for $250
Thanks! But the first one doesn't have a hole for an O2 sensor
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