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For the past couple months, I have been running around with a 3.2" blower pulley on my JRSC'd K20A2-swapped coupe. It ran extremely well, so I was interested in seeing what the slightly smaller 3.0" blower pulley would do.

So, a gentleman in Texas (tmartin) swapped pulleys with me, and I was off to test.

Here's the results.

Once again, the car didn't make much power at 50 degrees across the RPM range.

Made 290whp/193wtq at 50 degrees across the board.

Ended up dialing it back to 45 at 5,000 RPM, back to 40 degrees at 5,700 RPM, and the whole way down to 35 degrees at 6,700 RPM.

The car also liked timing, but was weary of adding any more, as I already have what I consider to be a lot in it already.

Here was the final numbers.


And 3" pulley vs. 3.2" pulley.


And the final pressure graph, vs the old one.


It definitely picked up power/tq in the midrange, but not so much up top. There's just all kinds of heat at that range.

Final numbers were 307whp/208wtq.

In conclusion, I would have to say the car definitely feels a good bit quicker in the midrange. It is worth the money to swap it out? I'd have to say "no" in most cases, assuming you already have the 9psi pulley. I happened to get everything I needed for nearly free, so it worked out alright for myself.

I do see it causing issues later down the road when ambient temps warm up in the summer here in the Northeast.

- Derek

EDIT: Here's a video of the tuning session.

http://www.youtube.com/watch?v=2LCBYluPkUE
 

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now if u were running an after cooler set up, would that be a different story???? would it be worth it if u have some type of aftercooling ???
 

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Discussion Starter #3
now if u were running an after cooler set up, would that be a different story???? would it be worth it if u have some type of aftercooling ???
I don't see why not.

- Derek
 

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I think its worth it - in some areas you are making 20 lbs of torque more.

that by it self maybe worth the cost.

D - now we just have to see about heading towards the 400 mark - haha
 

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I think its worth it - in some areas you are making 20 lbs of torque more.

that by it self maybe worth the cost.

D - now we just have to see about heading towards the 400 mark - haha
That's what I was about to say. The midrange looks really solid.
 

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Discussion Starter #6
That's what I was about to say. The midrange looks really solid.
Hmm, maybe I just had higher expectations of increased pressure. ;)

Like I said, the car is a blast to drive.

- Derek
 

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Im going the same route and putting the smaller pulley on. I will be off to Jeff Evans for tuning in March. Will post updates.
 

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Wait, isn't the JRSC a positive displacement supercharger? If so, why does boost rise with rpm, all the way from 5 to 10 psi? Or is this the replacement, the Rotrex?
 

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I have a 02 rsx-s with almost the same set it is quite fun,the 400 whp is a nother story in its self."I think it will be very hard on just the blower now throw some spray on it and now we are talkin":up:
 

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Wait, isn't the JRSC a positive displacement supercharger? If so, why does boost rise with rpm, all the way from 5 to 10 psi? Or is this the replacement, the Rotrex?
He's talking about the Eaton unit still. Regardless if its positive displacement or not, it is still pulley driven. There is still a charger ratio based on the pulleys. If the crank spins faster the crank pulley spins faster, it'll spin the blower pulley faster which in turn spins the blower faster, so rising with rpm is natural. Or maybe I'm wrong.
 

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you are right the faster the crank spins the faster the blower turns the problem with a roots blower is at high boost levels the roots heat up wich makes the air less dense, Also I was just taking to jackson racinfg and the say the ep3 intake is a liit better for fuel delivery due the shorter runner design,but you will lose some in the bottom end.
 

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Discussion Starter #13
Updated first post with video.

- Derek
 

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Wait, isn't the JRSC a positive displacement supercharger? If so, why does boost rise with rpm, all the way from 5 to 10 psi? Or is this the replacement, the Rotrex?
Has to do with efficiency based on the head and air displaced by the charger. It didn't really raise, it was just a lil more smooth. Could be the differences in the cam angles between the two.
 

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very nice.. next step will be to hit it with a 50 shot :up:
nice marketing videos by the way....
 

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i am running the same set up
k20a2 with a3 cp
3.8 blower pulley
62.2in gatorback belt
making 7-8 psi
idle pulley rsx 2.5

so far i am pushing out 272whp 174tq

if i run a K20a2 co with 3.2 what belt should i use? What belt are you using? are you still on stock tensioner or the jrsc?

do you think i wll gain switching to a2cp with 3.2?
 

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You're not running the same set up as D rob when he was using his JRSC.

he was running an a2 crank pulley with no ac, he used a 46 inch 6-rib belt.

he also used a modified oem tensioner and not the JRSC manual one.

no one will know if you will gain anything, you'lljust have to try and see.

switching to an a2cp with a 3.2 will yield you the same result, give or take, as you're getting now.
 

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hummm interesting. so i am fine with this set up then if i want to go down to 3.7 pulley it will be the same psi as 3.0 pulley with a2 cp?
 
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