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It has been 3weeks driving with smaller pulley on Comptech supercharger.
Before I mislead anybody, the reason I have done this is primarily to make up the lost boost going through custom intercooler set-up.
With some good help from board members here, I was able to go forward with the project and came out with satifying result(more to come of course).
The diameter of the original blower was 4.75 inches and if I believe correctly(I may have to re-check) new blower pulley came out to be approximately 3.85 inches.
Apparently this would bring impeller speed close to maximum at 9K rpm, which I believe may have been under estimated but I don't want to find out the hardway just what pulley size would the impeller start exceeding maximum speed.
I have taken some photos and wanted to show you, but unfortunately my camera became crazy so I was only able to grab pictures after the installation. One side by side photo of original pulley and new smaller pulley would have been great, but following photo is all I can give you.
You can click the photos and enlarge it with chooseing full size.
Wrong way of comparison, I know..
I like the polished shiny new blower pulley. The fabricator did an excellent job.
I was glad swapping out the pulley was relatively simple.
My mechanic just unscrewed bolts of the bracket and loosened the blower without removing. Apparently that gave enough space to pull out the original pulley.
The new pulley's hole+key hole seemed tad too tight, no biggie, just hair bit of grinding was necessary to push in the new smaller pulley. After the successful installation of the blower pulley, a new smaller belt had to be ordered to make it fit.
After the installation of the new smaller belt, I immediately checked the clearance of the belt and the waterpump pulley. Here before, I periodically pointed out how I didn't like the blower belt running too close to the water pump pulley. I said this was contributing some odd rubbing noise as well as additional vibration.
Check out the photo and try to compare with how it looks in your car.
Well I was so happy that the problematic issue has been solved finally.
As I have predicted, with this fix, the noise that I use to hear at certain rpm was gone.
Immediately upon start of the car, ECU seems to go into learning mode similar to when you reset ECU. I took easy that day but I can sense easily of new found power. My car never felt this good especially above 4+rpm. Later when I finally start to drive normally, I was really happy that my car finally felt significantly stronger than prior to supercharging.
I haven't dynoed it yet but it will be scheduled to be done soon.
Also boost gauge will be installed to see just how much boost I am running right now. Except some MAP sensor contributing to idle issue when very cold, everything seems good and automatic.
Since I am running with different final gear ratio and Toda flywheel, it is helping me to propel the engine to 4K rpm where boost seems to come into a play. Boost seems to be building up smooth and strongly all the way to red line.
I am glad that things have worked out and I am finally enjoying Comptech supercharger like it meant to be.
Already I am being little too greedy and want to cut the pulley size even smaller and limit my rpm operation up to 8K, but that will be acted upon later.
Meantime, I am just going to enjoy what I have to the fullest.
I am not certain if you should try with non-intercooled set-up but it may not be wise until you find some means of cooling the compressed air temperature otherwise you will surely suffer detonation with added heat output.
I will be sure to report back of the dyno session and what boost I am running. Guestimation is 6-7psi at the moment.
Ok what do you know, I get a second chance to take a comparison photo of two pulleys side by side.
As the marking on the pulley says it is about 3.87 inches and stock blower puelly is 4.75 inches.
Looks tiny huh?
