FAQ: Smaller SC pulley? What Size?

Yes, definitely. It takes a very small change in pulley size to increase the boost. You will pick up about 3 PSI going to a 3.5" SC pulley.

Agreed. A 3.5 is a good 'safe' starting point, and very noticable. I highly recommend an MPS (multiple-pulley system) so when you do start modding more you don't need a pulley puller to swap pullies. It also gives you the option of bolting on the smaller pullies for track time and daily driving with a larger pulley.

You probably won't need to change tensioner pulley sizes with a 3.5 or 3.4.

What would a rough guesstimate as to hp gains be with a 3.5? Basically I'm trying to get right around 300 or so. Then I'll be done modding. This is still the DD. I have the Talon for making crazy numbers and track times with.

One thing to understand is that SC pulley size does not equate directly into a specific horsepower/torque number. This is because the pulley only determines how fast the blower spins, not how much air can enter, burn, and leave the engine. There are cars running 3.5" blower pulleys that make 250 HP, and there are probably some 300 HP cars out there with a 3.5". I've seen about 300 HP on the dyno with a 3.4" pulley, and could probably see 280+ with a 3.5".

On a stock engine, a 3.5" can bump you up 15-20 HP at the crank. For someone with a cam, intake, exhaust, tuning... you could easily make 300 HP and still run a 3.5". The difference is, car with more mods in addition to a smaller SC pulley will have increased torque in the upper RPMs, and if done correctly is actually a more reliable set-up compared to the stock engine with 3.5". The pulleyed stock engine will make a lot of low-end torque (good for burn-outs) but will also be more prone to spark knock.

Ha ha. I get that. I meant given the current list of mods I wrote previously. sorry for being confusing. Also, as far as the pulley itself, I have found them on some of the performance sites, but isn't there a cheaper way? A junkyard pulley, or one from auto zone or advance or something? I keep reading about people who get pulley's for 5-25 bucks and would really like to know where!?!? Is there a stock gm part number for the larger pulleys because they're used in other applications?

Nah, you won't find a stock GM SC pulley in the size you're looking for. Cheapest route is a press-on aftermarket, but I agree with deekster's post on getting the MPS. It's $100, but that's the way to go.

There are a lot of used pulleys out there for sale, but they all fit the MPS hub, and you won't see the hubs for sale very often.

Leave the pulley alone,run Toluene instead.

You can often find used MPS systems along with a few pullies on sites like 3800pro.com, clubgp.com, your local Grand Prix club site, etc. If you find a local Grand Prix club and the members are reasonable you can usually find someone with a pulley puller to help you change it, so you don't have to buy a puller.

By the way hollywood, if you're IN Hollywood, you also have 91-octane piss, unlike the 93-octane that all the boys on here back East have... Thus, you're not going to be able to go as small on the pulley for a given setup.

I can tell you that I'm running a 3.5" with the cooler stat, gutted AB lid, gauze filter and 3" downpipe, with an 'acceptable' amount of KR. Admittedly, I didn't change the heat-range of the plugs because I'd already put new Iridiums in it before I started modding...
But it takes a race-blend of 93 to make the KR go away completely.

He's in WI, lol... Probably has 94 on every corner.

Pity he didn't fill out his Location...

BTW, I thought I read on here a few months ago that the 94 was being replaced with 93.

Maybe it is, at least at Sunoco. It's all gone here in OH, but we can always add a splash of 100 unleaded for the track. It's more like they replaced the 94 with 100 at certain stations in my area.

PS - you too can have the 100 octane stuff if you ever drive to the areas of Tracy, Madera, Modesto, or Sacramento.

AA wrote:

PS - you too can have the 100 octane stuff if you ever drive to the areas of Tracy, Madera, Modesto, or Sacramento.

...or Sears Point

Speaking of which, how much do they charge for 100 unleaded? I'll bet it's a bit less than the $7.50 out at Sears.

I think it's around $6 here. Haven't bought it in a while. In your case, just 4 gallons of 100 per fill up would yield a 93 octane mix.

Correct!

Precisely why I posted those octane spreadsheets... except that it costs me $20 more than you
for the same tank of 93!

With enough modification and tuning, our engines can make lots of power on 91. I remember a guy on the DHP board who tuned his GTP to run high 13s in the quarter with a 3.8" and 87 octane, I believe.

I'm guessing headers, rockers, no cat, and a whole lotta' reprogramming?

Sorry about the location. I updated it. As far as premium, around here it's 93 octane. BUT we also have E85 (105 octane I think I remember hearing someplace). Since I've owned the car less than 48 hours I haven't had time to do to much digging but I will definitely be checking to see if I'm able to convert it. I currently run my Talon on E85 and it's amazing. 30 psi and can't hear any knock for miles. Of course it has a few other "minor" upgrades as well.

I would also just like to throw out there that the Rivi is FREAKIN SWEET!!!! Basically how it all went down was that I liked the way the car looked and felt. I searched for about two weeks for a deal and came across my 98 Supercharged with 144k for $2500. I went and looked at it, needed a new hood, pass headlight, and paint. I am the sales manager at a body shop so this meant nothing to me. The seller of course didn't know that. I drove it and withing 3 minutes of driving the service engine soon light came on. Also upon hard acceleration the car would stumble. I figured it was a misfire, but bitched to the guy about it. We ended up settling on 2k even out the door. Drove it home last night and went to bed. This morning at work I found this site, joined and started reading. Stopped at the parts store on my way home and had them double check the code. Sure enough, misfire, cylinder 4. I picked up a few parts, went home and started working on it around 9:30. I finished up about midnight. The car now has Auto lite 140's, 180 superstat, new auto lite wires, and eliminated stock air box. I cut out the hole beneath the stock box a little larger for increased air flow, and attached a (fake) k&n air filter routing it down into the hole I had cut. I fired it up and it jumped to life. No CEL, no misfire, goes right up to the rev limiter with out any issues, and that SC whine is fantastic. I then proceeded to drive it around for the next hour and a half or so up until a few minutes ago, smoking a civic in the process (added bonus)! This thing is so much fun!

I sold an 03 eclipse that I had lots of parts for and between what I have left and the items I'm going to buy this car should be a lot of fun. It's currently white pearl, I'm going to repaint it white with blue pearl. I have 18" chrome Milani's for it, about 2k worth of stereo equipment sitting in the garage, full LED wireless blue underglow, black out tails, corners, side markers, etc. Black housed halo angel eye prjectors, 12000k HID conversion kit, for sure cat back but preferably headers back, 3.5 SC pully, and last but not least, I'd like to see if I can get my stock sidemount intercooler from my Talon to hook up to it. If so it'll be great news for 3800 SC guys cause dsm guys pretty much give them away ($5-$50)

Either way I'm excited to learn more and play more with this car. It was so much fun, and I haven't done shit yet!

You can retune for E85, you'll need larger injectors and want to find somebody who has tuned a 3800 for E85, but otherwise there's not much more to converting, except that it's permanent - in the sense that if you have retuned for E85, then drive to somewhere you CAN'T get E85, you are gonna have problems unless you carry your tuner and have compensated your old E10 tune for the newer bigger injectors you just added...

You can probably do quite a bit on stock injectors, but you'll max em out pretty quickly.

Yeah, I need to do more research into the available options for tuning these things. With the talon I use Ostrich, an emulator that plugs into the ECU where the chip would be, and then plugs into a laptop. The laptop is my tuning laptop and stays in the car. When E85 isn't available I simply turn the car off, fill it with premium, and load a new bin file I already have programmed and saved to the laptop for pump gas.

Before I had Ostrich, I used a chip. The EPROM ecu's in the 1g dsms are able to read 4 maps on one chip. I had a separate tune for pump economy, pump performance, e85 economy, and e85 performance. I then had a couple wires soldiered on and attached to a toggle switch. If I turned the car off I could toggle between maps. Fill up if needed. start the car. Brand new tune, good to go!

It worked great for a while but I wasn't actually able to adjust anything, it was a set tune which may for some people work out fine. I on the other hand wasn't finished upgrading. So i got Ostrich and can now emulate/tune in real time!

hi, i have a 04 SS Impala, Supercharge,GM. I purchased a 3.4" pulley to replace original , if install pulley will this hurt my engine without modifications.

I wouldn't do it,scan for knock first.Without mods, you maybe just loosing power!!! Retarding timing?

cquintcarlos wrote:

hi, i have a 04 SS Impala, Supercharge,GM. I purchased a 3.4" pulley to replace original , if install pulley will this hurt my engine without modifications.

I do not know how to make the needed mods on a '04 Imp. You can probably find out with a web search.

On a supercharged Riviera, you have to retune the PCM and make some other (mild) mods to get full value out of that pulley. In general you need a scanner that lets you take driving logs so you can see reset the PCM parameters, as well as a tool (usually software for your laptop computer) that lets you make those changes. You need to scan the engien stock first, then make mods and reset the computer one by one. So first you are scanning to see if the computer is already giving the engine "knock retard."

Also in general you will also need to run cooler plugs (maybe autolite 104s) to deal with the additional fuel you will have to program in to get the fuel-air ratio back to correct stoichiometry and to reset the engine fans to come on at 180 deg. F (as well as put in a cooler thermostat).

If you just put the pulley on the engine will start knocking from the extra air, the computer will sense that the fuel-air ratio is off (the knock sensor will fire) and retard the ignition timing, basically negating the pulley's effect except you might notice an extrakick from a standing start. It's the kind of thing where you get that extra kick from the standing start then once you are revved up somewhat the computer starts backing things off as the engine starts to knock.If you push things to the point where the engine knocks anyway, then you'll just grenade it and trade the scraps for a used Yugo. There's more but this should get you started. Just like in school, if you want to pass you are gonna have to do your homework. All of it. You are in for either learning to tune the engine computer or having it professionally tuned, finding out which plugs (cooler) you need to run, and if you want to go smaller than 3.4" a new downpipe and exhaust 'cause IIRC the stock exhaust won't move enough air (it is enough for a 3.4" I am told).

Impala forums include:

http://www.naioa.com/v2/modules.php?name=Forums&file=viewtopic&t=37955

http://www.impalaforums.com/forced-induction/75-04-impala-ss-drop-down-supercharger-pulley-how-small-is-too-small-2.html

Good luck looking.

Albertj

Everything else aside... the Impala has a U bend in the exhaust. Right where the 02 sensor plugs in. For those who haven't seen these in real life, it takes the pipe to pretty much half diameter.
cquintcarlos, look under your car right where the exhaust comes down from the engine, you will see what I mean. A 3.4 without removing the U bend WILL cause you major problems.
http://www.wbodystore.com/grandprix/U-Bend-Bypass-Pipe-p-96.html
The linked part will fix it up. It fits right in.

Well, I took a chance I replaced oregenal pulley from my 04 SS Impala supercharge,GM to a 3.4" . I drove it from phoenix,az to toscun,az. WOW it did wonderfull do problems.