I'm interested in changing out the 3.33 pulley for a 3.12 on my V3 Stillen SC kit which has a Vortech blower.

**Edit: I ended up doing a swap to a 2.87 pulley instead of the 3.12 in the title of this thread.

Here are a couple of pics of 2 different pulleys that I have a question about. the first pic shows the SC pulley that the serp belt turns, the other pic is from behind the blower, far easier access; small belt. The first pulley could be a hassle to access due to how close it is to the blower where the one that is on the shaft directly into the compressor would be easy to swap out.

I just got back from an hour tuning run with my UpRev tuner and he told me that the pulley directly behind the compressor would be the same as swapping out the serp belt one; would spin the blower quicker either way.

I've talked to Stillen (where I bought their whole kit) and they seemed confused and just mentioned going with a lightweight "stock size" crank pulley. I then talked to Vortech and they also were like "we can check into it", etc.

*So my question is what do you SC guys think about swapping out the pulley directly attached to the compressor? Would be so much simpler, or even the jackshaft pulley on the same shorter belt on backside of the blower/bracket?


The 2 pulleys in question:

(serp belt) SC 3.33 pulley


back side blower/compressor pulley:

 

Your tuner is correct; making either the jackshaft pulley (1st pic) or the blower pulley (2nd pic) smaller will generate more boost...either way, you'll need to remove the blower to remove either pulley, so I don't think one is particularly harder than the other, but I don't know the fitment of the stillen setup other than visual....

 

Yes, that would be fine.

It's the pulley on the back of the Jack shaft you would want to change.

don't know what size it is, but you want the next size Bigger.

 

Thanks, I'll have to stop in and get an accurate measurement of it; anybody know off hand? OldMan, it's the brown pulley on the backside that you mean, correct? Is it possible to go with a smaller size on the compressor shaft (purple one) to get the same increased blower rpms? It would be nice to have several options to go bigger here or smaller there, etc.

Thank you, are you talking about the blue pulley in the first pic or the back side of the jackshaft (brown) as the jackshaft pulley? The blue one is on the serp. belt and I think is refered to as the SC pulley, at least according to my install manual (I wish they showed all of the sizes), all new to me.

 

Yes, the brown one. depending on what size it is. this is an off the shelf pulley.

But, the better option is to go larger on the Jackshaft if you have room, less belt slip problems with the bigger diameter.

 

Thanks, that makes sense going bigger may decrease chance of slippage.

 

GET RID OF THE LIGHT WEIGHT PULLEY!!!! If you want a aftermarket pulley get a fluid damper or ATI.

 

+ 1

 

What he said....

 

Thanks, but I don't want the fluid damper; would just stay stock if that were the case.

 

Gotcha, just trying to get you some more boost and making your motor happier at higher rpms.

 

Thanks Conway! Yeah, I don't "need" to install the crank pulley at all and I may decide not to so as to keep the stock harmonic balance, etc.

I look forward to the sc pulley install; should get a nice little bump in whp/tq. According to the tech that I have dealt with at Stillen for a couple of yrs. and did an E-tune or two for me they call this pulley their "9 lb pulley" as in-house testing has shown that their SC kit setup for the HR (using the V3/SCi) with this smaller pulley bumps it up from where I'm at now (7.4 - 8 or so) to 9+ - 10 psi. That could equal maybe 25-30 whp or at least I hope!

 

Best of luck

 

Thanks^, I may just return the crank pulley and call it good. I appreciate the advice from you guys.

 

ya, for what you are doing, the stock crank pulley is fine.

 

Thanks OldMan! I had done many hrs. of reading this and that and trying to get some specific info. for the Stillen SC style of the V3 blower kit and actually even got burned out in a way.

There is a ton of info out there for the V3, but not the Stillen type for the '07 hr dual throttle body like I have and like I mentioned before even talking to guys at Vortech and others I still had a hard time making sure that the pulley they were talking about would fit my setup.

Anyway, when I was talking to the Stillen tech guy about the smaller sc pulley (they don't list it on their site) he told me that they have the one exactly for my kit, but they don't support it warranty wise which makes sense plus mine is now 2 yrs. old anyway. *he did say some good test results that they have had with their "high boost" sc pulley however. He knew that I was interested in the 3.12 pulley and he said he wasn't sure of the exact dia. of it, but it bumps up about 2 lbs. of boost.

I figured that since it will fit exactly on my setup I said I'll take it, plus a new serp. belt. He said would you like the lightweight crank pulley to go with that; my mind was in performance mode I guess and just went with it. I will return it and stay with the stock crank pulley for now.

 

I picked up the car a just an hour ago; did the sc pulley swap (3.33 to 2.87) on the Stillen V3 setup on my '07. Also put new drive and blower belts on.

I have only put a few miles on it and feels normal as far as taking it easy; I didn't know if it would run irratic or abnormal until I get it tuned, but am glad that it runs fine for now.

I'll get some Cipher logs going soon and have my tuner get the new tune asap. Waiting for a new laptop which will be next week before I'll be able to do some data logs. Good to have this swap done and will give the car a bump in whp/tq. *It's the one on the right close to the SC.

 

Very nice! Will be great to see more numbers from HRs with Supercharger setups! Good luck on your upcoming tune!

Hope your fuel system is up to par with the demands for the 2.87 pulley.

 

I got the new laptop Sat. (GD motherboard crashed on my HP unit!) and got UpRev items downloaded; got the Cipher parmeters set and went out for a nice cruise Sun. I tried to basically duplicate the type of driving that I had done 3 weeks ago with my tuner sitting in the pass. seat doing a real time tune (before the pulley swap).

Took it pretty easy at first and would hold it at say 3,500 in 4th and 5th (increasing here and there, but not any high rpms) to get some good readings holding it in different gears, etc. like he had me do before.

The car has run well even with just the recent good tune, but now the tuner has my 35 min. through town and open road data log as he told me to do for him. I did 3 WOT pulls (2nd through 4th) on the way back; the car runs strong and boost definitely hits it and climbs fast! No doubt that the new pulley has added some noticable kick. I'll look forward to getting this first new tune on it and go check it out.

 

I wish I had read this sooner. I did the cog pulley swap and the Vortech Si impeller swap on my HR Stillen supercharger. The easiest upgrade was to the new impeller. I had quite a bit of trouble getting the cog pulleys to fit right and stop shredding cog belts. Looking back, I would have done exactly what you are doing, then swap the impeller next.

The only other thing I would suggest is to start looking for evidence of belt slip. I did not see any until around 15 psi. If you start seeing any slip, take a look at the Timrod radius-rod, and design yourself something similar.

IRRC, I drove the car with no problems at around 13+ psi for a while (450whp/375wtq). When I went for more than that, there was nothing but problems. Good luck man.