BGRS 4AGE 16V Underdriving Alternator Pulley

Regular price $129.15

Share this part with a friend in need!

  • 6061 T6 - Anodized Green
  • Race version - 50% Underdrive 
  • Sport Version - 25% Underdrive
  • Sport and Race both include oversized alternator belt (required when using a factory-sized crank pulley and water pump pulleys)

We noticed a trend for 4AGE's driven hard or at high speed to have issues with alternators failing.  Add in some oil from leaky cam and main seals while running hard on track and this is a recipe for disaster (don't ask us how we know). Part of this may be to aftermarket alternators not being made to the same quality as OEM, but another aspect is that these alternators are being spun to a very high RPM, especially with the raised redlines that we are seeing with modified 4AGE's  

We have 2 versions, the Street and the Race version, which is pictured here. 

4AGE 16V Race Alternator Pulley 


                                           4AGE 16V Sport Alternator Pulley

The Race version should be used for competition cars only.  It reduces the alternator speed by 50%.  This may result in a lack of charge at Idle, or off idle, but will be suitable for a racecar that will spend time on the circuit at speed.  It's worth noting that we haven't seen much of a voltage drop except for at idle in our own measurements with the Race alternator pulley.

The Sport version is intended for street cars driven with vigor.  You should not see any noticeable charging differences but you will see increased alternator life.

Another positive side effect of spinning the alternator pulley is less parasitic drag at all RPMs.  We have a racer friend (SCCA ITA) that has measured 10HP gains at 9,000 RPM+ from slowing the alternator down.  His engine was built for regular runs to 11,000 RPM and slowing down the alternator was important for his success. We haven't verified this ourselves but it would make sense that there is less drag from friction and electromagnetic drag at speed since the alternator is kept in a more efficient operating range. 

Please note, that a longer alternator belt is included which works with the factory-sized crank pulley and water pump pulley, but please be aware a different sized belt may be needed if your setup differs greatly from this. 

Product Fitment:

1985-1987  Toyotas with 4AGE Engines in RWD format only.