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View Full Version : Pros and cons of supercharging.



taracatac
05-08-04, 03:55 PM
What are the pros (other than HP) and cons of supercharging? A friend of mine is thinking of supercharging his 2000 coupe w/ about 50K miles. Currently it is bone stock. Will reliability and driveablility be affected? This car is a daily driver.

Thanks!

cruzer99
05-08-04, 04:14 PM
Shorter engine life, lower mileage, reliability, limited places for trusted sevice, tickets, etc.

When you supercharge your car you will be driving it harder, it's a fact.
If that is all OK and it's what you or he wants go for it.

powderski13
05-10-04, 05:09 PM
Fun Fun Fun.. For a more reliable S/C look into the Magnuson roots style blower. It offers better low end torque than the centrificals but you will have to replace the hood. The centrificals offer higher RWHP potential at the risk of reliability. You will start breaking stock engine and drivetrain components if you go much over 500 RWHP. Custom tuning is needed for any S/C application to get the AF ratio down to a safe 12.0. Gas milage will also suffer.

SleepieAce
05-11-04, 11:05 AM
Driveability is no different from a stock car until you step on the gas. A supercharger doesn't make boost until you stand on the throttle, so until then it's just a more efficient intake. For that reason my highway gas mileage actually went up. However, it is hard to resist stepping on it every now and then and so city mileage may suffer. So far mine's been reliable...in one year and 5K. However, I don't use it as a daily driver. The Magnusson seems to be the best for daily drivers.

Dave C. '04 Z06
05-12-04, 10:01 AM
There's no way your highway mileage can increase with adding a supercharger. It can only decrease unless you have some sort of clutched compressor pulley.

The engine has to spend the extra fuel to turn the supercharger whether or not your using it.

If it's a centrifugal then it's always creating boost and heating up the air in front of the throttle plate, which is more drag on the motor at part throttle. You only see the boost on your gauge when you step on the throttle because your gauge is connected to your intake manifold. I'll bet if you port it from the outlet of the centrifugal supercharger you'll see 20#s of boost while cruising down the road at 2000RPM.

If it's a "roots" style compressor that replaces the intake, then you don't have boost at part throttle, but you have more mechanical drag than a centrifugal.

So either way you're burning extra gasoline.

If you ran a turbo you may see the same mileage, but no better, because a turbo doesn't drag on the motor.

A supercharger is fun, however. But if you have hypereutectic pistons you better have some money set aside for when they disintegrate.

I agree with the guy who said if you have a supercharger, you will beat on it.

:beer

-Dave C. '04 Z06




Driveability is no different from a stock car until you step on the gas. A supercharger doesn't make boost until you stand on the throttle, so until then it's just a more efficient intake. For that reason my highway gas mileage actually went up. However, it is hard to resist stepping on it every now and then and so city mileage may suffer. So far mine's been reliable...in one year and 5K. However, I don't use it as a daily driver. The Magnusson seems to be the best for daily drivers.

SleepieAce
05-12-04, 10:32 AM
I have to respectfully disagree, just from experience. When you're on the highway, extra belt or not, the s/c is a more efficient intake than the stock one. This is my gas mileage for the recent 240 mile trip from my house to Lexington, KY.



http://www.corvettekillstories.com/photogallery/albums/SleepieAce/The_Car/DSC00293.JPG

That's mostly highway driving, but a little city to get to the highway from the houses. Before the s/c the highest I saw was 28. I don't have a picture of that because it wasn't any big deal back then.

I'm not enough of an expert to argue the reasons, but I'd be extremely suprised if you saw 20 psi from my s/c at any time. If you did I'd be very upset, because that creates a situation where if the blow off valve siezes the engine is gone. With the size pulley that I have on, the max boost possible should be 7psi at about 5800 rpm.

DRTH VTR
05-12-04, 11:37 AM
Just to add my $0.02, nothing is free here. If there is additional load on the engine, it will cost as energy consumption. If that engine load results in better efficiency at the intake end, great. But I don't see how it can. More air in means more fuel in. I just don't see getting a free lunch. I would like someone to explain how better fuel consumption can occur with this scenario. Maybe it is true, but it seems counter-intuitive.

SleepieAce
05-12-04, 12:15 PM
I don't know how or why it works, but most of my s/c friends say the same thing...gas mileage goes up unless you're stomping on it. And it's not putting more air in at normal driving. The blow off valve dissipates extra air. The point is that the engine no longer has to pull the air in on its own...it's being fed to it...

JBsC5
05-12-04, 06:20 PM
Get the magnusum ASE certified supercharger for your 50K mile C5! ..Its a great package and you also get a 36month/36K mile warranty on the engine and the entire driveline...(only an extra 2 hundred and best money spent)

If I had a ls1 engine corvette I would definitely consider a supercharger as the way to go high performance..

JMO and good luck.

Dave C. '04 Z06
05-13-04, 08:57 AM
Hmm...well, certainly that mileage is impressive. I cannot explain that.

Did you get your car tuned after the installation? If so, one believeable explanation for the increased fuel economy is that they advanced the timing for cruise situations.

Is your supercharger a centrifugal or a roots style?

When I said your supercharger would generate up to 20psi, I meant if it's a centrifugal and you have no bypass valve, and you're cruising down the highway, meaning your throttle is mostly closed. The supercharger is still spinning the same speed and sucking in the same amount of air, but it just can't go anywahere. If you have a blowoff valve on the supercharger (a bypass valve more accurately describes it) then it will usually sit at the bypass valve's activation pressure.

However, if your supercharger is the roots style which replaces the intake manifold, then it will not generate boost unless the throttle is open because it can get no air until then, but it does spin and drag on the motor.

I'll have to look into why you're experiencing that high of mileage (unless it was 240 miles down hill all the way! :) ). But it seems to violate the laws of energy physics.

Anyways....superchargers are fun!! :)

Dave C. '04 Z06




I have to respectfully disagree, just from experience. When you're on the highway, extra belt or not, the s/c is a more efficient intake than the stock one. This is my gas mileage for the recent 240 mile trip from my house to Lexington, KY.



http://www.corvettekillstories.com/photogallery/albums/SleepieAce/The_Car/DSC00293.JPG

That's mostly highway driving, but a little city to get to the highway from the houses. Before the s/c the highest I saw was 28. I don't have a picture of that because it wasn't any big deal back then.

I'm not enough of an expert to argue the reasons, but I'd be extremely suprised if you saw 20 psi from my s/c at any time. If you did I'd be very upset, because that creates a situation where if the blow off valve siezes the engine is gone. With the size pulley that I have on, the max boost possible should be 7psi at about 5800 rpm.

G WIZ
05-13-04, 09:10 AM
That mileage is amazing. I am also considering either a supercharger or a NO2 setup. I am also kicking around the idea of an 04 ZO6. NO2 appears to be much less expensive, but I have not yet analyzed the pros/cons of both systems. Which system would lead to less reliability issues with the vehicle?

SleepieAce
05-13-04, 11:02 AM
That mileage is amazing. I am also considering either a supercharger or a NO2 setup. I am also kicking around the idea of an 04 ZO6. NO2 appears to be much less expensive, but I have not yet analyzed the pros/cons of both systems. Which system would lead to less reliability issues with the vehicle?
Either system, if done well, should give you no problems. The good thing for you is that you're in the Dallas area and there are several really good performance Vette shops that can help you out.

Any time you add a power adder of the FI/nitrous type you're going to reduce the reliability of the car somewhat. It can't be helped. By good tuning and being conservative you can make it a very small reduction. A nitrous setup is less expensive, but there's also the continuing cost of refilling the bottle. It's not a huge cost, but it can be a pain...especially if you don't have a performance shop that can do it close to you. As long as you're conservative with what you do, I don't think you'd have too many reliability issues with either. I know one guy who's been spraying his 98 C5 for most of its 80K miles and has no problems. I know another with almost 20K on a s/c with no problems either.

It's all in what you want. I went s/c because I wanted power on demand...without bottle warmers or refilling.:beer

G WIZ
05-13-04, 11:17 AM
I certainly agree on the conservative issue. I do not want to abuse the engine. This will help me decide;

http://www.bewellweb.com/cogans/thinkjerm/games/flash/parachute.swf

SleepieAce
05-13-04, 11:28 AM
Hmm...well, certainly that mileage is impressive. I cannot explain that.

Did you get your car tuned after the installation? If so, one believeable explanation for the increased fuel economy is that they advanced the timing for cruise situations.

Is your supercharger a centrifugal or a roots style?

When I said your supercharger would generate up to 20psi, I meant if it's a centrifugal and you have no bypass valve, and you're cruising down the highway, meaning your throttle is mostly closed. The supercharger is still spinning the same speed and sucking in the same amount of air, but it just can't go anywahere. If you have a blowoff valve on the supercharger (a bypass valve more accurately describes it) then it will usually sit at the bypass valve's activation pressure.

However, if your supercharger is the roots style which replaces the intake manifold, then it will not generate boost unless the throttle is open because it can get no air until then, but it does spin and drag on the motor.

I'll have to look into why you're experiencing that high of mileage (unless it was 240 miles down hill all the way! :) ). But it seems to violate the laws of energy physics.

Anyways....superchargers are fun!! :)

Dave C. '04 Z06
Alright, I talked to a couple guys who know more than me and here are some answers that may help you.;)

First of all mine's centrifugal. In talking to ATI, the impeller design is such that at situations of below 2000 rpm (cruising) the best you can get is a positive pressure on the intake side of the throttle plate. The design is such that it won't actually start pressurizing things until around 2000. My head unit is not physically capable of 20psi, no matter how hard you spin it. Yes it's still moving air, but not the major amounts you would think. In fact, I was told that if it was not designed this way, but just built up lots of pressure on the throttle plate, then cracking open the throttle plate would lead to all that pressure immediately entering the engine and throwing one of the pistons out the bottom.

As to heat, because of the intercooler the IATs are actually the same as...or in the case of really large intercoolers, lower than...stock IATs while cruising. A part of this is the fact that when it's not generating boost it's not really heating up anything much more than normal.

The belt does create a draw on the system, but not a noticeable one until the car is in boost.

All supercharger systems have a blow off valve. The function of the blow off valve is to dissipate any boost in situations where it would be unwanted. In other words, if I use a very light throttle to get the car rolling but leave it in first all the way up to 6000 rpm all the boost will be sent out of the blow off valve before it ever gets to the intake. The only way boost can get to the intake is for the blow off valve to be closed and the car to be above 2000 rpm or so where it's actually making boost. The blow off valve works by using vacuum lines to judge when the throttle is depressed past 3/4. I've had it all explained to me...but its a really long explanation.

For all these reasons, when you're cruising down the highway, the blower is really nothing more than a more efficient intake. Which most times leads to better gas mileage, given that the rest of the engine is stock. Of course if you start upping the cubic inches, etc. all this goes out the window.;)

Now here's the bad news for me.:cry In talking to one guy, he told me that the DIC gas mileage may become inaccurate due to the larger injectors and extras that have been put on. He said most people if they actually run the numbers without using the DIC will get about 2 mpg more. I really think that he's probably right. I'll go ahead and count mileage and gallons next time and see for sure.

Hope all this longwindedness helped.:beer

Norman Clemmer
05-13-04, 11:39 AM
[QUOTE=Dave C. '04 Z06]There's no way your highway mileage can increase with adding a supercharger. It can only decrease unless you have some sort of clutched compressor pulley.

My mileage went up about 1.8 mpg on the return trip from LPE after having the supercharger installed. In my opinion there is no downside of the magnacharger vs. stock.