Supercharger vs. Turbocharger

[gibsonj4]

There has been a couple posts about supercharging vs. turbocharging. I just thought I would write a short comparison between the two routes. Please correct me mods if I mis-state anything.

Supercharger

A supercharger compresses air using a belt driven system and sends the compressed air into the combustion chamber generating more power and a quicker burn. There are two main types of superchargers. A Roots supercharger (such as on the LSJ) runs off the engines' crankshaft power via a belt such as the serpentine belt or it can also be chain driven on some applications. Vortech also makes centrifgal superhchargers which look like turbos. These types of blowers work very similar to a turbo spooling but the spool is off of the engine power from a serpentine belt again. There is also a third (Contributed by IMA) type of supercharger called a twin screw or lysholm. It is very similar to a roots type in that it has two rotors inside its housing and it also has a long snout. The difference is a roots blower builds boost in a manifold or plenum while a twin screw builds boost internally as the charge of air moves though the lobes of the screws so that by the time the air is ready to leave the supercharger itself you have full boost. The twin screw is much more efficient thermally and in terms of parasitic loss.

There are several pros to purchasing a supercharger:
-A blower makes power throughout the power band because it makes boost as soon as the rpms rise.
-Superchargers CAN be cheaper but not always depending on the application.
-Supercharger are somewhat easier to install and the whole setup can be considered simpler than a turbo.

The Cons of supercharging a 4-cyclinder are:
-Parasitic loss: since you are using power to make power, then some crank horsepower will be lossed which in turn results in a loss of whp.
-The supercharger is limited by the size of supercharger and the pulley size. Smaller pulley = more boost = more power.


The Turbo
A turbo charger is similar to a turbocharger except a supercharge spools exaust gases above atmospheric pressure and sends them into the combustion chamber to create a quicker burn by adding more fuel to create more power. There are many benefits to going turbo instead of supercharging OUR size engine.

Matching the Turbo
There are several factors to selecting a turbo to fit our engine size. First, is it internally or externally wastegated? The wastegate releases built up pressure from the turbo to prevent detonation and the engine basically blowing up. An externally wastgated turbo uses exactly what it says, and external wastegate to expel the surplus of compressed air. An internally wastegated turbo, such as Garetts "Disco Potato," are being used for the new turbo kits for the 2005-2006 cobalt LS trim levels. The problem is that boost creep can occur when not enough exaust gases pass through the turbo housing and boost rises quickly. This can cause engine damage if you have weak internals. Also, the wastegate can get stuck and cause major dmage/problems where the excess pressure may be released and the engine gets overboosted.

Trim and and A/R
The trim of a turbo is the ration between the turbo's inducer and exducer of the turbine wheel and the turbine wheel. More importantly is the A/R. The A/R or aspect ratio is the ratio for a turbo housing size vs. the inlet of the turbo. Larger A/R makes the turbo spool later while the smaller A/R spools quicker. A small A/R turbo is better for our engines allowing it to spool quicker and supply power quicker at low RPMs.

Components List:
This is just a short list of components. There is a great turbo how-to on ecotec forum written by a former member NJHK. The major parts for a turbo include:

-The Turbo
-Intercooler
-Intercooler piping
-Wastegate (if externally wastegated)
-BOV (Blow off valve)
-Downpipe
-Turbo Manifold with a fabbed or production flange for the turbo.
-Larger injectors
-Fuel Regulator
-Tuning (Piggyback, Standalone, or a Suite such as HPtuners)
-Boost controller (not essential)
-Wideband or an A/F gauge.

Pros of the Turbo:
-A turbo can be fitted to an engine. There are thousands of turbos out there with different A/Rs, trims, etc. and you can really customize your power goals and where you want your turbo to make power.
-They don't take as much power away from the engine and run off exaust gases not by power from the engine crankshaft.
-Power levels are not as limted as a turbocharger is.

Cons of the Turbo
-A turbo can be badly matched to an engine resulting in "turbo lag" where spooling takes a long time and power is delivered late in the powerband.
-Turbos don't make power throughout the entire powerband like a supercharger does.
-Turbochargers are a bit more complex than a supercharger system and can be more difficult to install.
-Turbos are tempting to crank up the boost with a boost controller resulting in a number of things such as blowing a hole in the intercooler or worse running lean resulting in detonation.
-Turbocharging systems can cost more to maintain and purchase.

I hope this answers some questions posted by people on the forum. This is just brief overview of the Supercharger vs. The Turbocharger I'm no expert but this may help some make an educated decision on which route to take.

Tuning Options
AEM - Fuel / Ignition Controller (F/IC)
MegaSquirt - Electronic Fuel Injection Computer by Bowling & Grippo * * ©2005

[IMADreamer]

Good write up. I'd change a few things though.

Instead of saying explosion in the combustion chamber I'd just skip that. lol You really don't want an explosion in the combustion chamber because that is essentially detonation even if it occurs at the right time. What you want is a REALLY fast burn in the combustion chamber and you want the flame front to spread out evenly. It is extremely common to call it an explosion though so it's no big deal even though that's really not what it is.

Also there is a third type of supercharger called a twin screw or lysholm. It is very similar to a roots type in that it has two rotors inside its housing and it also has a long snout. The difference is a roots blower builds boost in a manifold or plenum while a twin screw builds boost internally as the charge of air moves though the lobes of the screws so that by the time the air is ready to leave the supercharger itself you have full boost. The twin screw is much more efficient thermally and in terms of parasitic loss.

[gibsonj4]

I fixed a couple things and also added your info about the lysholm. You should u a FAQ and these two could be stickied might shed some light for people who don't know anything about FI.

[shannonz]

Thanks a ton guys, that helps a lot! I have an '06 LS model and i want more power out of it, but i'm confused as hell about what to do with it...i'm learning pretty quick what's what, but i'm still trying to decide what would be the best (and safest) for my car. If you have any suggestions for brands, that would be appreciated i've heard quite a bit about the "turbonator's," but idk if they are reliable or not...

[dduffy2005]

Originally Posted by shannonz

Thanks a ton guys, that helps a lot! I have an '06 LS model and i want more power out of it, but i'm confused as hell about what to do with it...i'm learning pretty quick what's what, but i'm still trying to decide what would be the best (and safest) for my car. If you have any suggestions for brands, that would be appreciated i've heard quite a bit about the "turbonator's," but idk if they are reliable or not...

IMO the turbonator's a waste of money that could've been spent elsewhere. I say save your money and buy a CAI (cold air intake). You'll find most people on here have either the injen CAI or the GMPP.

[gibsonj4]

Yeah I sent a PM about the F/I route to thje user

[shannonz]

lol ok thanks! i'll look into that stuff...

Originally Posted by dduffy2005

IMO the turbonator's a waste of money that could've been spent elsewhere. I say save your money and buy a CAI (cold air intake). You'll find most people on here have either the injen CAI or the GMPP.

[Chester]

my overall opinon...superchargers should power V-8's and Turbos should power the 4 cylinders

[burzumaske20]

eh I say any american car should stick with a supercharger and any import crap vehicle should stick with a turbo

[IMADreamer]

Originally Posted by burzumaske20

eh I say any american car should stick with a supercharger and any import crap vehicle should stick with a turbo

That's one of the stupidest things I've ever heard.