Changing pulley/ boost gain?

[steel1]

I have an SN89 with 3.75" s/c pulley and a 6" crank pulley, I make bout 5-6 psi with HO impeller and fluid cooler. I normally don't rev my 93GT much above 5k so when I do the rpm calculation for the SN series I could reduce my pulley size to 3.50". Does anyone think the pulley change to 3.50" would give me any more boost or is it just a waste of money? I do have a Mr. Freeze meth kit that I haven't installed yet.

[Michael]

It probably won't result in any significant additional boost or airflow. What it will do is put the blower's RPM closer to it's ideal range. If you do see any additional boost it'll probably be between 0.5psi-1psi.

Is it worth it? Only you can be the judge. If you can get the smaller pulley without much cash outlay and can change your old pulley for the new one without a lot of effort, then maybe it'll be worth it. But if the pulley is expensive and you have to take it somewhere to have the work done, then maybe not.

[Duke]

change the crank pulley to a 7'' too with the 3.5'' head unit and run an oil cooler on the head unit and last run good high octane gas!

[steel1]

Yeah I run an oil cooler and always run good quality 93 octane. I think I'll try the 3.5" pulley dirst and see what that gains me.

[JPJP]

The Ø3.5" pulley may have belt slip if you only have a 6 rib set up. Minimal gain at this point past the Ø3.75".

[zray]

I've used many different sized pulleys. The main consideration is blower impeller speed at maximum rpm. I always try to have the maximum EFFECTIVE impeller rpm when the redline of the motor is reached. In my experience you may, or may not, get more than 0.5 lb of additional boost from the next size smaller pulley. But a 0.5 lb. of boost from a system that is only putting out 5 to 6 lbs. is nothing to sneeze at.


But one of main benefits of a smaller pulley from a performance standpoint, is that you will have more boost available at a lower rpm. This FAR outweighs an addition of boost at maximum rpm, whatever that number might be.

Z.

p.s. I need to update my sig photo. The Shelby was sold in June of 2012. I "replaced" it with a '65 K code Mustang and a '66 Galaxie 500

[Duke]

I have a 3.5'' blower pulley on my sn2000 stock impeller 7'' crank pulley which is stock on a 5.0 and im running an oil cooler. i make 8lbs of boost at 5000 r.p.m im only over spinning the blower by 200 r.p.m!

[Joo]

The range of boost of the sn-supercharger with HO-impeller I've seen here in the forum is mainly 5-8 lbs. This difference is I think way too much in order to explain it just with the belt ratio. It would be really interesting to know the amount of overlap too and to see the infuence to the sn-boost.

[Duke]

I can guarantee you that im running a stock impeller! im also running an a.f.m power pipe. Oil coolers really lower temperature therefore more air is being pushed in!

[dvs bullet]

The range of boost of the sn-supercharger with HO-impeller I've seen here in the forum is mainly 5-8 lbs. This difference is I think way too much in order to explain it just with the belt ratio. It would be really interesting to know the amount of overlap too and to see the infuence to the sn-boost.

Is the HO impeller the pink one? Just bought a Sn-93 and am installing it in my wifes 5.0 mustang. The guy i bought it from said it was rebuild with an upgraded impeller, but the impeller looks grey (i thought the pink one was the only upgrade) Plus this came with 2 upper pullies a 4" and a 3.5 what are the boost ranges with a 6" base pulley (fairly stock motor, saleen intake ported e7s and an e303 cam)
thx everyone, sorry for the thread highjack lol

steve

[steel1]

Funny you mention that about the HO impeller only being pink. I was looking at my impeller the other day and although it is gray the vanes at the top are curved just like the "pink" impeller, so I would assume not all HO impelers are pink. I have a 93GT with ported e7s, 1.7rr, Steeda18 cam, Typhoon intake, 75mm Pro-M maf, 65mm tb, etc. and I see 5-6lbs. with 3.75" sc pulley and 6" crank pulley. I'm also running a UPR boostmaster pipe.

[dvs bullet]

Funny you mention that about the HO impeller only being pink. I was looking at my impeller the other day and although it is gray the vanes at the top are curved just like the "pink" impeller, so I would assume not all HO impelers are pink. I have a 93GT with ported e7s, 1.7rr, Steeda18 cam, Typhoon intake, 75mm Pro-M maf, 65mm tb, etc. and I see 5-6lbs. with 3.75" sc pulley and 6" crank pulley. I'm also running a UPR boostmaster pipe.

Thanks, I'll take a look at the impeller but I'm quite sure that its a straight blade. I sounds like we have a similar combo, so that make me think i should do the 3.50" pulley (they are all 8 rib btw). I would like it to be the 7-8 are if possible, i will be fabbing up my own boost pipe and there is a cooler system for it. Just finished the front plate for it (made it out of 1/2 aluminum, and its bolt tensioned) So i will keep you guys posted on how it goes.

Is the 4" upper and the 6" lower the standard pulley size for those blowers? what were they rated at with that set up?

[ed1le]

I have the HO impeller but it isn't pink. However, it's also about 10 years old. All that I've seen new recently appear to be pink so maybe that's something more recent to help distinguish the two?

[dvs bullet]

I have the HO impeller but it isn't pink. However, it's also about 10 years old. All that I've seen new recently appear to be pink so maybe that's something more recent to help distinguish the two?

Huh, maybe what I will do is take a picture of mine, maybe someone will be able to let me know what they think it is

[ed1le]

Let me retract my previous statement, my impeller is a pinkish color. Not sure what I was thinking but it's currently off car so I took a look last night. Sorry for the confusion...Modded Impellor.JPG