: Size of pulleys on stock STS-V??

02-16-10, 11:25 PM
Does anyone know what the diameter of the supercharger pulley and lower pulley are for our STS-V?? I contacted D3 interested in purchasing a stage 2 power pacakge and spoke with a salesman that knew nothing about our vehicle. He could not even get me an answer to the simple question above. I can understand if this was D3 patented info but I was asking for stock vehicle information.

I want to calculate the supercharger peak efficiency based on the graph eaton publishes for the M122 supercharger. Before I increase the crankshaft pulley (which D3 has two sizes) I want to know exactly what point the supercharger rpm starts to peak and how far above maximum the increased crankshaft will take it. Obviously spinning the supercharger above it peak efficiency rpm will result in excessive heat therefore one would want to know if meth injection, upgrade heat exchanger, additional reservoir, or fans will provide adequate cooling.

Don't get me wrong D3 sells great packages for people who just want hp but before I put additional performance accessories I would like to know how it is going to affect my engine and not just take a performance shops word that everything will be okay even after 50k to 100k miles.

02-17-10, 03:25 AM
I went by D3 and spoke to a guy (I don't recall his name) and he showed me around the place. I was told that the supercharger is spinning at close to max speed stock. He told me to get the most gains from overspinning the supercharger, you need to modify the supercharger cover. What happens when the supercharger is spun harder is that the airflow gains turbulence and actually narrows the width of the airflow going into the engine. He said that the cover is modified to gain efficiency in the airflow. Methanol/water injection is used to cool the impeller blades of the supercharger to minimize thermal expansion of the blades and help cool the air going into the engine. He showed me a customer car that had the stage 2.5 installed. Intake, supercharger cover, upgraded intercooler radiator, increased coolant reservoir and methanol/water injection. When I asked exactly what is done to the supercharger cover and other specifics he was not forthcoming stating that was proprietary information which I can understand because the amount of R&D involved.

This is the car I saw while I was visiting.

YouTube- D3 Cadillac STS-V Stage 2.5 Upgrade

I decided to leave mine pretty much stock except for a tuned PCM to get better throttle and transmission response.


02-19-10, 10:05 AM
I guess no one knows the diameter of the supercharger pulley and lower pulley. It seems that most on this board just throw an intake, exhaust, and tune on the car and call it a day. Coming from a CTS-V I was hoping more people here enjoyed modifying their cars for added performance.

I'll find out myself this weekend as I have some special things planned for the STS-V in the near future.

02-19-10, 11:16 AM
Good Morning,
I was reading where a guy wanted to know the size of the pulluys on the STSV, I am ashamed to say I don't know either. I would think that one should know this sort of thing. Particularly if I plan on doing any SC upgrades. I have
read on the CTSV forum these guys know. Maybe because it's a Chevy engine, No excuses. I should know. I will be checking out the size asap. He is also right that I am just throw parts and tunes at the car without really knowing any particulars about the drive train. I just thought of something, I have the shop manuals for this car, I will look there first. It maybe a little more accurate. I should post to his thread as well. Gentalman please forgive my ignorance concering this matter. Sometimes it takes a baseball bat to wake me up. That post sure did. I will post this very same to his thread.

02-19-10, 06:15 PM
With a total production of *maybe* 12,000 Supercharged N* LC3's between the XLR and STS-V -- That supports a lot of why there aren't larger numbers heavily modifying this powertrain. Its expensive, and without all the proper R&D it would nickel and dime you to death.

Tune, intake, exhaust --enough for me on a DOHC engine... Now if it was a LSx -- thats another story!

02-19-10, 09:33 PM
Based on compnine.com there were 2,503 STS Vs and 2,188 XLR Vs produced for model years 2006 through 2009. I looked up VINs that I found on cars.com to see how many STS Vs and XLR Vs were produced each year (results inlcuded in the table below). If the compnine site is accurate less than 4700 4.4Ltr SC engines were produced and sold. Looks like the high gas price and recession really killed the market for these vehicles.

Build by Year


2009 96
2008 459
2007 642
2006 1,306



2009 239
2008 392
2007 410
2006 1,147



2009 335
2008 851
2007 1,052
2006 2,453


02-21-10, 11:48 AM
nice info