3.4 Whipple, 3.25" pulley vs. 3.75" pulley


PeteK

PeteK

GT Owner
Mark II Lifetime
Apr 18, 2014
2,283
Kalama, Free part of WA State
Hey guys, I checked the archives, but didn't find a ready answer, so let me toss it to the experts who have these on their cars. I have a 3.4 Whipple that I'm finally getting around to putting on my car (bought from Gulf GT before when he left the community). I'll be using Torrie's tunes. He asked me what size pulley I have, and...I have two. The 3.25" is currently on the supercharger. I will be running pump 93 octane gas. I'm kind of inclined to be conservative and use the 3.75. Any advice based on experience on which pulley to use?
 
N

nota4re

GT Owner
Mark IV Lifetime
Le Mans 2010 Supporter
Feb 15, 2006
4,192
According to Whipple, each 1/8" pulley diameter reduction is about 1psi. So, the 4/8" difference in your two alternatives is roughly 3-4psi. My perspective is that if you want to go to the Whipple, you might as well get your bang for the buck so I'd go for the 3.25. Torrie can advise accordingly, but you will likely need a MAF scaling device such as the MAFia as well... or you will risk the ECU seeing a value that is out of range.
 
NorthwoodGT

NorthwoodGT

GT Owner
Jun 12, 2009
1,215
Michigan
pete- I will look at my pulley when I get a chance. car is on the 2nd level of parking solutions at the moment. can't remember which one that car has but all I can say is that it works! (very well) lol
 
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