Wednesday, February 14, 2007

Turbocharing vs Supercharging

This posting of mine was taken from my response on a 7-series thread regarding the differences between a turbocharger and supercharger in relation to a V12 engine. I am posting it here because the general concept applies to all engines regardless of size and cylinder count. Hopefully this information will shed some light on the true differences between the two forced air induction methods used to create more power in combustion engines.

"The main difference between a turbocharger and supercharger is the form in which the turbine is spun. A turbocharger uses redirected exhaust gases from the engine to spin its fan while a supercharger uses a pulley and belt attached to the existing pulley/belt system on the car.

For this reason it (usually) takes a turbocharger longer to produce "boost" because it needs to wait for the flow of exhaust gases to spin the turbine fan. By basic reasoning this takes longer because exhaust is the byproduct at the end of the entire combustion process. The supercharger has almost no "lag" because its turbine spins the moment the engine RPMs rise because it is, in a sense, directly attached to the crank.

The general rule of thumb, and I stress general, is this: if you have a small displacement motor that produces little torque it is generally better to turbocharge because you don't directly drain the engines low-end power having an extra pulley and accessory attached that is always running. There is more wear and tear on the engine when running at lower speeds. If you have a high displacement engine with more available low-end torque you can supercharge because the amount of energy the supercharger demands at low engine speeds doesn't hinder the available power of the engine. At high RPMs the effects are the same for both systems.

Once both systems 'spool' up to their configured boost pressure you essentailly get the same result. This is all assuming you're running a turbine style supercharger (resembles a standard turbo). If you decide to run a top-mount twin (or single) screw supercharger, like those found in the 2003+ Mustang Cobra (among other cars), the use of low RPM engine power is the same but the boost delivery is more direct. It is a more direct boost injection because the supercharger is bolted directly to the intake manifold, rather than running boost through an intake tube to a remote location. If you want that "supercharger whine" you would opt for the twin-screw and if you want the "turbo hiss" you would go with the turbo-turbine supercharger, or just a standard turbo.

The reason many manufacturers have been twin-turbocharging their large displacement V12s is a result of space restrictions on the top of the engine and wear and tear during normal driving. With the development of new bi-turbo technology all but eliminating turbo "lag," the space saving and power saving benefits of running a twin-turbo setup are enticing.

Proper bi-turbo setups run two turbochargers. If the engine only has one intake for both banks of cylinders the turbo's are configured to provide the same boost pressure at different RPMs so they compliment eachother and nearly eliminate the dreaded boost "lag." If an engine has two separate intakes, such as the BMW V12, one turbo is used for each bank and configured to boost at at the same time with the same pressure.

When separating the turbos it makes it impossible to have them compliment eachother thus giving in to boost "lag." The partial solution to this problem comes from the displacement of the engine. Because the V12 engines push such a massive volume of exhaust per bank (6-cylinders worth) the turbos can be configured to maximize boost at low RPMs and maintain that throughout the rev range; again, nearly eliminating turbo "lag."

The latest amazing turbo development was made by Porsche and is implemented in their 2007 997 Turbo. It is called VTG (Variable Turbine Geometry) and basically adjusts the pitch of the turbine blades inside the turbocharger in real-time to account for changes in engine speed and exhaust volume. This allows the turbos to produce their maximum boost pressure at almost all engine speeds without compromise. You can be assured this technology will soon be applied to nearly all new turbo systems, eliminating turbo "lag" forever, both in single and twin-turbo configurations.

Wow, that was long. Hopefully you guys read it and become experts on turbos and superchargers."

- Mitch G

Tuesday, February 06, 2007

Cedar Grove - Issaquah Home For Sale

I am finally ready to put my house on the market! It has been a long time coming and I am very pleased with the result. A short list of the features includes new stainless appliances, flooring, millwork, countertops, bathrooms, light fixtures, interior paint and hardware. There is free community water, a mountain view and propane heating.

The address is 23415 SE 160th Place, Issaquah, WA 98027.

For more information on my home and its features you can click on the title above to take you to the official MLS listing or this link here to view the home information. My real estate agent, Jin Lee of Skyline Properties (425) 591-1042, produced this short video tour of the house to make the previewing process easier:

- Mitch G

Monday, February 05, 2007

Mainstage Comedy Club Review

It was a fantastic late night show on Saturday at the Main Stage Comedy & Music Club in Seattle. Patricia Allen (co-owner) outdid herself with a sensational venue, top-notch performers and a true-to-Seattle theme. The drinks were well made, the full menu (so I heard) was prepared with care and the performances reflected the best comedians Seattle has to offer. Each portion of the experience was light on the wallet and for complete Saturday night entertainment in the "Emerald City" that is saying something. It was equally impressive that a handful of walk-in comedians showed up when they heard the club had opened; their extra talent lit up the stage and provided an evening of true ab-crunching laughter.

There are a few items left to be addressed regarding the venue itself such as proper dining tables, exterior lighting and signage along with other smaller miscellaneous items. I spoke with each of the three owner/managers of the club and each expressed their undying commitment to build the best entertainment venue on the Greater Eastside. I feel they have a fantastic start.

I will be going back for my birthday celebration on Saturday the 18th of February, we shall see how things are after two full weeks of operation. If anyone is interested the official "Grand Opening" is this coming weekend Thursday-Saturday with live stand-up all night long.

Again, best of luck to Main Stage Comedy & Music Club in Seattle; a much needed and welcomed addition to the Seattle entertainment scene.

- Mitch G

Friday, February 02, 2007

Main Stage Comedy & Music Club, Seattle

My good friend's mother is opening a new comedy and music club in downtown Seattle. The club is called "Main Stage Comedy" and is located across the street just west of the Key Arena's main entrance. For now the club will only be open on the weekends but promises to provide a classy, contemporary entertainment venue for all of the Seattle area's residents as well as professional-level national performers.

I will review the venue after I visit this coming weekend for the two-night opening event. I will be there Saturday the 3rd for the 10pm stand-up show. Main Stage's myspace page is here and has a plethora of extra information for show-goers and performers alike. You can also purchase tickets for shows online through Ticket Master.

Best of luck to Main Stage and let the show begin!

- Mitch G