Supercharger pulley size?

[paul e]

I've been wondering lately why it is that my Dinan Vortech SC system out of the box produced between 7.5 and 8 psi at redline, yet others with whats supposed to be the same kit were producing anywhere from 6 to 7 psi....Why the variation?

Well, maybe this is why...Measure your SC pulleys! I just took a measurement of mine, and it read 82.5 mm, or 3.25". Yet, I just spoke with someone who's pulley measured 3.5". This slight difference results in an impellor speed difference of 2600 to 3000 rpms at redline depending on your drive pulley size. If these are valid measurements, and reflect the kind of pulley size variability common with the shipment of these kits, then its no wonder we are finding differences of up to 1.5 to 2 psi! If it were only a half psi difference Ive been hearing about, I could attribute that to weather differences, as cold weather and hot weather will effect boost produced to a small degree. But the difference between say, 6 psi and 8 psi is larger than I've usually seen attributed to weather alone, when this amounts to approx. 25% of total boost.

Why this variation exists is a bit more puzzling. What does it say about quality control? Perhaps nothing...But it certainly doesnt give us a great deal of confidence with regard to the vendor's ability to communicate accurately what it is we are buying. But then, much as I like Dinan, and respect his know how, I think that their lack of any web presence (I dont care that they have a website...I was referring to the fact that they dont even have an email address to contact them on), the difficulty in getting good technical information from them, and their general 'standoffishness' makes them less than a pleasure to work with...Any time I want to talk to the owner of RMS or Active Autowerkes, I can always reach them, and can always carry on meaningful dialogue...Unfortunately, the same cant be said for Mssr. Dinan.

[gerry_miranda]

Here are the valid Vortech pulley sizes:

P/N 2A036-262 Supercharger Pulley, 2.62", 6-Rib
P/N 2A036-287 Supercharger Pulley, 2.87", 6-Rib
P/N 2A036-312 Supercharger Pulley, 3.125", 6-Rib
P/N 2A036-325 Supercharger Pulley, 3.25", 6-Rib
P/N 2A036-333 Supercharger Pulley, 3.33", 6-Rib
P/N 2A036-348 Supercharger Pulley, 3.48", 6-Rib
P/N 2A036-360 Supercharger Pulley, 3.60", 6-Rib

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Dinan CARB declaration says:

Stage 1 Kit: Kit includes a Vortech V-1S supercharger with a 3.43" diameter pulley and a 5.14" diameter crankshaft pulley with a max. boost pressure of 6.5

Intercooled Supercharger Kit: The supercharger uses a 3.03" diameter pulley and a 5.5" diameter crankshaft pulley with a max. boost pressure of 10 psi.
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Now according to the Vortech chart there are no 3.43" or 3.03" SC pulley sizes. I doubt Dinan will re-engineer SC pulleys when they can accomplish the same thing thru the crank pulley size change which they are already re-engineering. So I dont jnow how accurate their data is....It could have been a typo on their part...but notice how vortech offers a 3.25" and a 3.48" pulley that matches yours and you friends?

How did you measure your pulley? What did you use? Did you measure from the outside most rim or from the innermost rim of the V belt valley ?

[paul e]

Here are the valid Vortech pulley sizes:

Gerry,
>>. I doubt Dinan will re-engineer SC pulleys when they can accomplish the same thing thru the crank pulley size change which they are already re-engineering.<<

I believe your wrong here...Dinan will tell you they use SC pulleys engineered to their own specs, and do not use Vortech pulleys...I believe its the same with RMS.

I measured with a calipur...I measured across the outside lip, however, if you check the belt surface, its hardly measurably different..It feels like a flat ribbed surface all the way across. if theres a difference, its under a mm. And frankly, I dont know how Vortech is measuring theirs, but the difference in methods on this pully is tiny.

And since Dinan sources their own pulley according to spec, its quite possible that if one supplier runs out, they use another, and its certainly not out of the question that the pulleys they us may vary by a couple of mms.

I just like to think this is true, because i just have no other explanation why mine, when it was stock-Dinan, registerd 7.5-8 psi, more than most others out of the box, despite Dinan's own admission in my installation instructions that you may see up to 7.5 psi...I no of no one besides myself who actually met or exceeded this value.

[gerry_miranda]

1) Why do you think DINAN re eng the vortech sc pulley?
2) What dinan part number is etched on your SC pulley? I can compare it with mine?

[paul e]

) Why do you think DINAN re eng the vortech sc pulley

Gerry, because Vortech told me so!