Power Truck

 

 

Centrifugal superchargers are turbo like in design, centrifugally forcing air to compress by the use of single

2008 Silverado sees 535 wheel hp with only two modifications.

2008 Silverado sees 535 wheel hp with only two modifications.

compressor impeller rotating at around 120,000 rpms. Unlike turbochargers which are driven by a turbine impeller in the exhaust stream (connected to the compressor impeller via a solid shaft that allows them to spin together), the centrifugal supercharger is driven using the engine’s accessory belt, and internally either has a pulley & belt system or a lubricated gear drive system with around a 20:1 gear ratio.

So for every revolution of the engine, using this gearing system, we get 20 revolutions of our superchager. As the engine rpms rise from 3000rpms to 6000 rpms for example, the supercharger rpms rise from 60,000 rpms to 120,000 rpms, and so typical of this type of supercharger performance, effeciency, airflow, and boost pressure rise exponentially (Rather than linearly like a blower) with rpms giving a very peaky power band with nice high rpm power.

Below is a chart I made for my own car displaying the expected power band comparison between my stock Eaton MP45 supercharger @ 11psi, vs. a Vortech G-Trim supercharger geared to peak out at 18psi.

 

Centrifugal @ 18psi vs Positive displacement @ 11psi

Centrifugal @ 18psi vs Positive displacement @ 11psi


The stock chart (blue line) is based on a typical dyno-graph for a C230 Kompressor, the modified line (red) is based on a Vortech G-trim compressor map. You can clearly see the relatively flat power delivery of the Eaton supercharger that delivers 11psi from idle to redline. You can also clearly see the gradual boost build of the Vortech supercharger where it delivers 11psi at 4800 rpms (where the 2 lines cross) and keeps building boost pressure up to a peak of 18psi at 6300 rpms, giving a potential power loss below 4800 rpms compared to my current setup, but a net power gain of over 130hp at redline.

Although this kind of supercharger may not make much sense on a small displacement engine (that needs low rpm power boosts typical of a positive displacement roots style twin screw supercharger), this kind of supercharger makes for a great match for larger displacement V6 and V8 engines that already have enough torque (and traction problems) at low rpms, but desire more horsepower and greater acceleration at higher rpms.

A great example of such installation is a 2008 Silverado truck sporting:

“The already healthy stock V-8 5.3L engine was given a boost-a rather big Procharger blower boost to be specific. To better handle the additional pony power and torque made by the supercharger, an Auburn ECTED electronic limited slip differential with General 4.10 gears was a necessary modification because we’ve seen this Silverado move with the quickness! For a throaty rumble, a Gibson three-inch exhaust system also came together to round out this Chevy‘s performance. The HOT Motorsports crew managed to put 525 hp down to the tires, which will certainly surprise more than a few jokers looking to go toe to toe with this speedy single cab.”

Considering the fact that the factory 5.3L V8 makes 315hp @ 5200 rpms and 338 ft.lbs of torque @ 4400 rpms; then an increase of about 288 crank hp for an off the shelf supercharger kit (probably running about 13psi of boost) and an off the shelf bolt on exhaust system is quite impressive. Not bad for a weekend’s worth of install time. What’s even more interesting is that there is probably still more power left on the table, as by my calculations a 3.58” (or 3.5”) exhaust would’ve been a closer match for the truck’s requirements for a single exhaust system at those power levels.

The truck also has a great assortment of suspension, exterior, and interior modifications, be sure to check it out the complete article.

Find the full articles here:

2008 Chevy Silverado – Procharger Supercharger – Truckin’ Magazine