: Stupid ques...(turbo vs supercharger)



Joey'sVee
05-11-05, 01:43 PM
OK...I'm learning here so let me ask a stupid question. I'm pretty familiar with turbos so I was just wondering what is the difference in turbos and superchargers? Don't they both pressurize the combustion chamber thus producing more power? Thanks and feel free to get very technical! :D

LV_V
05-11-05, 01:49 PM
Very basically, a turbo uses the engine's exhaust pressure to spool up causing "boost". A supercharger uses the engine's power through a belt or screw drive to create the boost to the engine's intake.

urbanski
05-11-05, 01:50 PM
difference: no turbo kit (that i know of) is made for the V yet.

lasstss
05-11-05, 01:52 PM
Turbos make more horsepower but are a cluster F to plumb up...Usually turbo drivetrains also last a lot longer too..

jspinetto
05-11-05, 01:55 PM
The biggest difference is how they are driven.

Supercharger = Belt & Pulley

Turbo= Exhaust gases.

Personally I am a big fan of turbo's. I have one on a 2.0L motor and it lays down roughly 500rwhp on race gas.



Controlling the boost on the turbo is also very convenient. For example I can push a button on my boost controller and instantly I can go from 15psi-25psi (or any value I set).



Also with turbo's since they are driven by the exhaust gases, you do not loose power in driving the turbo, unlike a supercharger.



However I am sure someone will be quick to point out turbo lag. Turbo Lag is a symptom of turbos because before that turbine wheel has enough rotating force to compress the air coming into the compressor it has to spin and will take a moment to spin. However this is easily overcome with more displacement.

I could go on, but I think that is enough to get this topic started.

Jonathan

lasstss
05-11-05, 01:59 PM
The biggest difference is how they are driven.

Supercharger = Belt & Pulley

Turbo= Exhaust gases.

Personally I am a big fan of turbo's. I have one on a 2.0L motor and it lays down roughly 500rwhp on race gas.



Controlling the boost on the turbo is also very convenient. For example I can push a button on my boost controller and instantly I can go from 15psi-25psi (or any value I set).



Also with turbo's since they are driven by the exhaust gases, you do not loose power in driving the turbo, unlike a supercharger.



However I am sure someone will be quick to point out turbo lag. Turbo Lag is a symptom of turbos because before that turbine wheel has enough rotating force to compress the air coming into the compressor it has to spin and will take a moment to spin. However this is easily overcome with more displacement.

I could go on, but I think that is enough to get this topic started.

Jonathan

Ah but that nice slow squeeze of power saves the driveline and plays catchup in a hurry. I used to get full boost at 2500 rpm the lag never hurt me a bit. Some guys would get me out of the hole but then I would just walk em.....:D

Katshot
05-11-05, 02:06 PM
I read an article that did a head to head comparison of the two forms of forced induction, complete with dyno charts. They used several different manufacturers for comparison.
As I recall, the blowers did better in the low to mid rpm range but the turbos did slightly better in the upper rpm range. Beyond the power output, there is the obvious difference with respect to mounting. Generally, turbos take up more room because of the extra plumbing.

DgtalPimp
05-11-05, 02:08 PM
Someone here can clean up my comments as I am NOT an expert on either turbos, or superchargers.

With that said here are the differences I see between the two:

Screw supercharger

One of the basic differences also is the "feel" of the boost. The screw type of supercharger will allow you to have positive air displacement at very low revs since the screws are turning all the time. Down side to the screw is they reach there limits of pushing air on the higher revs. (Tech expert insert reason why here).

Centrifugal supercharger
They still use the motor to push the air in the intake, but do so in a turbo like manor (they even look a little like a turbo minus the exhaust side of the turbo. They tend to "come on" with higher revs. (Tech guys jump in this and correct, comment where needed)

Turbo
Make lots of power require the exhaust to force air into the intake. The faster you go the fast you go (within reason, nuking your motor, or running out of fuel (think engine management not empty tank). They also “come on” with higher revs as you need to turn the motor to get more exhaust, and thus you hear about turbo lag. The turbos of today have much reduced the lag you hear about in the older setups, but there is still some. Down side is there are space requirements for the turbo tubing/routing, and heat issues. (Again tech guys jump on this and correct/comment)

All three will need some sort of engine management since you are putting more air in you will need more fuel. Also there are many ways you can setup each type of FA device that can alter the above generalizations I made (i.e. Centrifugal supercharger “coming on” at lower revs). I found that when searching I looked at what is best for what I want and the way I drive. I personally like the torque feel of a screw type supercharger, I am not saying that screws make more torque, I am just saying to me this is the way it feels.

BeelzeBob
05-11-05, 02:38 PM
Not disputing anything said so far....

And some folks may not care about this item at all, but....

Another factor impacting the decision to supercharge or turbocharge is the fact that the supercharger only involves the intake side of the engine. One a method of driving the supercharger is established thru a belt from the crank and/or a jackshaft the supercharger assembly simply replaces the stock intake system. This makes it somewhat easier as an aftermarket upfit as the exhaust and underhood temperature is not affected. This means that the emission compliance is not affected within reason. Since the engine will run the FTP without generating boost the supercharger is virtually transparent. Oxygen sensor response and catalyst lightoff is not affected since the exhaust system is not modified. If you care about emissions, or have to deal with any sort of emission compliance or inspection or are a manufacturer looking to upgrade a powertrain without tearing up an emission compliant engine control system the supercharger makes a lot of sense. If the engine is turbocharged it will have dramatic effects on the emission capability due to the catalyst light off early in a cold start. The turbo sucks up so much heat that it will delay lightoff and make emission control very difficult and certainly invalidate any existing emission compliance on the vehicle. Not that it is impossible to meet the requirements with a turbo but it is much much harder.

A supercharger has excellent low end capability and good response...two things that feel very good on the street. A turbo needs to be sized for the particular RPM range that boost is required...so a large turbo for good top end HP is going to suffer on the low end and a small, responsive turbo for good low RPM torque and response is going to run out of beans on the top end.

Manufacturers and some of the aftermarket tuners are coming up with hybrid systems that are really trick. Some use dual, sequential turbos, one small and one large so that they can be sized for specific speeds without sacrificing power at either end. There are packages that supercharge the engine for the excellent throttle response and good low end torque and then add a turbo that feeds the supercharger. The turbo is deliberately large so that it takes over the boost chores at full output and will actually windmill the super charger. Either of these is fairly exotic and complicated to plumb but REALLY trick for the best of both worlds.

A supercharger will typically stress the mechanical parts of the motor more than a turbo setup. The supercharged engine is going to have more cylinder pressure at low speeds which really puts a lot of load on the rotating and reciprocating parts. The supercharger requires considerable power to drive. An engine making around 440 HP with a supercharger is going to need 60-80 HP to drive the supercharger so the crank and rods and pistons,etc. are all dealing with 520 HP.....not the 440 HP at the crank.

Turbocharger plumbing is fairly complex and adds a lot of thermal load underhood and it is easy to melt things. Putting a lot of hot exhaust plumbing underhood is a real challenge.

One thing not mentioned is intercooling. If you are reasonably serious about HP intercooling the compressed charge will be a necessity. A turbo is typically intercooled by routing the compressed charge to the intercooler heat exchanger. An air-to-air exchanger is mounted in the air stream at the grill to cool the compressed charge and then it is ducted to the inlet system. Superchargers are more difficult to intercool for two reasons. One is the difficulty of structurely mounting the supercharger so that the outlet can be ducted to a heat exchanger and them back to the engine. Secondly, the boost characteristics of a roots or screw type supercharger is not friendly to a heat exchanger. Where the boost from a turbo is fairly smooth the boost from a supercharger has very high pressure spikes that will rapidly fatique (crack) an air-to-air heat exchanger and while it is running it will make a lot of boom-boom-boom-boom noise. Superchargers are typically intercooled by placing a air-to-water head exchanger in the supercharger boost path to suck the heat out of the compressed mixture. The water in the system is pumped and routed via hoses to a separate water-to-air radiator behind the grill to remove the heat from the system. This is harder to fabricate and has more pieces but can be easier in the long run as the coolant for the intercooler is in the small pipes for routing to the radiator but the boosted air from the turbo must travel thru fairly large tubing to avoid restriction. No free lunch either way.

Katshot
05-11-05, 02:43 PM
Here's a couple articles from both camps:

http://www.superchargersonline.com/content.asp?ID=19

http://turbochargedpower.com/Turbo%20vs%20Blowers.htm

Both articles go into pretty good depth concerning the strengths and weaknesses of both systems. In the end, you need to be the judge as to which meets your particular needs best.

RVanEvery
05-17-05, 12:19 PM
another thing not to forget:

The spool of a turbocharger is Greatly affected by load brought onto the vehicle, this is a great reason why in hill-climb events a turbochager is choosen more-so then a supercharger. If you have ever driven/riden in a turbo-6 diesel truck ("big rig") with and without a trailer you will easily see what I am talking about; they have two completely different lag characteristics simply because of the amount of load being put onto the motor.

On the supercharger side, load has really nothing to do with boost, its simply rpm dependant; the faster that motor is spinning the more boost the charger is capable of creating. On a down side (aside from parasitic loss of the pulley system) most superchargers have an increasing boost track, you usually dont see full boost till sometime before redline (also dependant on the charger).

Where a superchargers dyno graph may resemble on constant upward slope, a turbochargers may resemble an extremely steep slope with a hair of drop-off near redline (also dependant on the turbo).

Ultimately, there is a right and wrong turbo/supercharger for every car and each motor along with its use.

jspinetto
05-17-05, 07:35 PM
haha Ryan your funny.

Your car is slow :shhh:

lol

j/k

Jonathan

cts-v ls6
05-17-05, 09:43 PM
The easiest way to intercool is chemically with water or water/methanol injection. There is no heat exchanger required, and the efficiency approaches 85-90% vs. 50-60% for an intercooler. I seem to remember the Buick Grand Nationals cool this way.

2004ctsv
05-17-05, 10:03 PM
This is a great thread. The responses are good (till you get to this one)


I have had both - supercharger on a Buick and turbo on a Saab. You pays your money and you takes your choice. As described above, each excels in its own way.

Without a turbo available for the V, there is no choice to make. Unless you are a very good mechanic.

Tony

Dennisscars
05-17-05, 10:13 PM
turbo = hot :devil:

supercharger = hot DAMN! :lildevil:

RVanEvery
05-17-05, 10:36 PM
water/alky injection is a great method for cooling the charge, but its even better when you combine it with an intercooler. Just dont spray the w/a injection before the intercooler :halo:

Jon...:helpless:....:thumbsup:

4 cylinder 4 life yo. :p :bonkers:

BeelzeBob
05-18-05, 01:21 AM
The water/methanol injection into the intake charge helps cool the charge somewhat and it will help prevent detonation but that is not really intercooling.

The Buick Grand Nationals had air-to-air intercoolers...not the water/methanol injection.

I think you may be confusing two different system for water/methanol/windshield washer fluid 'injection"....

One system sprays the mixture into the inlet charge to help cool thru evaporation and prevent detonation via the cooling effect of the humidity in the chamber. This helps if low octane fuel is being run but it really doesn't "make" more HP. It helps recover lost HP due to spark retard from detonation but if good fuel is on board it will not make more power.

The other, similar system has a spray bar on the air-to-air intercooler so as to wet down the external fins of the intercooler to aid in cooling the charge inside via evaporation. The water/methanol/windshield washer fluid is not injected into the engine just sprayed onto the intercooler surface. This is a very effective way of reducing intercooler temperatures and increasing charge density and making more HP. This WILL increase the HP of the system.

Introducing the water into the charge directly detracts from power as the engine is injesting water vapor molecules instead of air molecules. The less air that is injested the less power is made. If the abnormally high humidity of a water injection system is replacing air that could burn with fuel and make power then it will cost power. So water injection into the charge itself is an iffy situation. Wetting the outside of the intercooler with a spray bar is a win/win situation.

RVanEvery
05-18-05, 07:05 AM
I have never seen great gains from spraying water/alky onto an IC, I haven't even seen great gains from spraying nitrous on the IC (though most dynos are off being that the nitrous always finds its way to the intake...). The subaru sti and mistu. evo both have water sprayers for the IC, the only time I hear about it making a difference is after they have heat-soaked.

Water into the intake charge is great...it will cool the charge down and it GREATLY reduces the combustion temps...resulting in more power. It also leaves room for more boost.