3.6 pulley to a 3.33 pulley

swl987 · May 16, 2008

When going to a smaller pulley on a blower what are all the effects and risks? Such as how much more power, how much sooner will the boost come on, does it affect the a/f, do you get more boost? And how much smaller of a size can you go and still be safe? Any other things you can think of? thanks

the98stang · May 17, 2008

swl987 said:
When going to a smaller pulley on a blower what are all the effects and risks? Such as how much more power, how much sooner will the boost come on, does it affect the a/f, do you get more boost? And how much smaller of a size can you go and still be safe? Any other things you can think of? thanks

For every size down you usually see an increase in about 2 pounds of boost. That will be about a 15-20whp increase on a near stock engine. Your blower will not spool too much faster. If you have a roots blower you will definitely notice the power gain. We all know centrifugals build boost slowly lol. The A/F will be changed, but not drastically. If you can tune the car yourself go ahead and tune it after the pulley swap. You won't blow the engine or anything if it isn't re-tuned, though. You can pulley down to a 3.1 with out changing to a 8 rib set-up. Hell, I run a 2.87 with 6 ribs and I don't get any belt slip or dust. Hope that helps :SNSign:

BennyBlown2v · May 17, 2008

the98stang said:
You won't blow the engine or anything if it isn't re-tuned, though. You can pulley down to a 3.1 with out changing to a 8 rib set-up. Hell, I run a 2.87 with 6 ribs and I don't get any belt slip or dust. Hope that helps :SNSign:

You're also incredibly lucky, and probably don't beat on your car like it should be beat on 6-rib on a 3.12" pulley is where I started getting slip on the street, and on the dyno.

You need to make sure the air:fuel is still in the right spot after swapping pulleys, and if you DON'T have it adjusted it probably will be VERY high (imagine adding 2lbs of boost to an engine with a stock tune, it will run dangerously lean, just like when adding boost to a tune that wasn't setup for that much). Boost will come on sooner, but you probably won't notice it because it will only be like .25psi more boost at 3800rpm or something lol... I think 3.33" is the best pulley you can throw on a non-intercooled vortech kit. I made 423hp/408tq with a 3.33" pulley, longtubes, tb/plenum, and midpipe and catback.

spederman · May 17, 2008

the98stang said:
The A/F will be changed, but not drastically. If you can tune the car yourself go ahead and tune it after the pulley swap. You won't blow the engine or anything if it isn't re-tuned, though. QUOTE]

IDK about that advice. If you dont tune it after that big of a pulley change and arent intercooled either, you'll blow the engine very quickly. Like BennyBlown said, Adding that much more boost is going to lean you out alot.

swl987 · May 19, 2008

I had 9.5 lbs of boost with the stock throttle body. I just put on a 75mm one with a plenum. Now that the air is being forced into a larger opening does that mean the boost will go down a little? Kind of like how a regulator works. I'm just wondering because if I went down a pulley that would be 11.5 lbs of boost roughly. I'm not sure at what levels of boost you need to start worrying.

3.6 pulley to a 3.33 pulley

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3.6 pulley to a 3.33 pulley

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