Hello, I just recently bought a 2004 G35, and was looking to add either a vortech charger or the turbonetics single turbo kit. I have the two questions:

Which would be better for daily street driving?

What kind of gas mileage do you, or people typically get from these power adders??

Thanks a bunch

I had a couple of turbo cars that were great DD. Both got GREAT mileage.However, I want a SC now.

There is a huge debate on which one is better for "street" driving. Here's the pro's and con's for each.

Supercharger (Vortech, Stillen)+easy install+easy on engine internals+less expensive

-not as much output compared to turbo apps-stillen is a roots style that requires a hood cowl

TURBO+more power, especially twins

-much harder to install-not as fuel efficient without exhaust upgrades-twin setups will consume more fuel-heat issues under the hood-much more expensive (twins)

I'm sure there is more for each, but you get the idea. It all depends on your goals. Decide those before you purchase anything.

The gas mileage answer really depends on your tune. It is possible to get better than stock MPG, but most likely you'll consume more fuel. If you're not interested in making tons of power, just want an additional 120+HP at the rear wheels, go with the Vortech. It's easy to install, requires the least additional hardware.

joe603 wrote:TURBO+more power, especially twins

-much harder to install-not as fuel efficient without exhaust upgrades-twin setups will consume more fuel-heat issues under the hood-much more expensive (twins)

Twin set-ups don't inherently consume more fuel. There are a lot of factors that go into the equation, but given similar peak power outputs, its likely the biggest factor is going to be the efficiency observed and the amount of restriction the turbo system represents at the most typical cruising speeds as this is where the greatest portion of operation time will be spent.

joe603 wrote:The gas mileage answer really depends on your tune. It is possible to get better than stock MPG, but most likely you'll consume more fuel. If you're not interested in making tons of power, just want an additional 120+HP at the rear wheels, go with the Vortech. It's easy to install, requires the least additional hardware.

I highly doubt you'll ever get better than the OE mileage in either system. There's no amount of physics that would remove the additional load a supercharger's moving parts places on the motor.

For turbo systems, the turbine will always be a source of restriction in the exhaust. With the right turbo, this can be minimized, but most aftermarket turbo systems are designed without much thought put into fuel economy...

True, but I've seen posts of people with SC that claim to have better mileage than OEM. Not so with a twin setup. There is a fine line between the additional HP that the SC develops and the HP required to turn it. At cruising speed, I would suspect that the engine is spinning fast enough to overcome the HP required to run the SC, and the extra boost increase gas mileage. Of course all of this goes out the window when you stomp the gas!!

joe603 wrote:True, but I've seen posts of people with SC that claim to have better mileage than OEM. Not so with a twin setup. There is a fine line between the additional HP that the SC develops and the HP required to turn it. At cruising speed, I would suspect that the engine is spinning fast enough to overcome the HP required to run the SC, and the extra boost increase gas mileage. Of course all of this goes out the window when you stomp the gas!!

Its easy enough to skew the gas mileage by driving nicer with the S/C then you did before the S/C was installed. The same could be said for turbo cars.

Boost can never increase gas mileage. The compression of air in a turbo or S/C will likely be at 80% efficiency tops. This means that 20% of the energy provided to the S/C's pulley is wasted in generating heat. The other 80% is spent actually compressing air. Unlike a turbo, this will always be happening as the S/C is connected to the crank directly. Some of it is recoverable as it it bypassed, but I doubt that will be a 100% efficient process either.

The engine's speed doesn't overcome the S/C's parasitic drag on the motor either. By design, anytime a compressor's wheels are spinning, it is trying to accelerate the air into the compressor housing to compress it. In order to do this, there must be energy available. While a engine that is rotating quickly may spin the turbine with out energy added to it, it will slow down the motor. Thus, fuel must be burned in order to keep the motor spinning. And as it is now forced to overcome the resistance that was in the motor prior to the S/C and the additional resistance the S/C provides. Thus requiring more energy which means more fuel must be burned. There is absolutely no situation where this is not going to be true. This includes turbos. Though the relationship between the motor and turbo will be slightly different as it will be a function of airflow rather than engine speed.

C-Kwik wrote:
Its easy enough to skew the gas mileage by driving nicer with the S/C then you did before the S/C was installed. The same could be said for turbo cars.

Boost can never increase gas mileage. The compression of air in a turbo or S/C will likely be at 80% efficiency tops. This means that 20% of the energy provided to the S/C's pulley is wasted in generating heat. The other 80% is spent actually compressing air. Unlike a turbo, this will always be happening as the S/C is connected to the crank directly. Some of it is recoverable as it it bypassed, but I doubt that will be a 100% efficient process either.

The engine's speed doesn't overcome the S/C's parasitic drag on the motor either. By design, anytime a compressor's wheels are spinning, it is trying to accelerate the air into the compressor housing to compress it. In order to do this, there must be energy available. While a engine that is rotating quickly may spin the turbine with out energy added to it, it will slow down the motor. Thus, fuel must be burned in order to keep the motor spinning. And as it is now forced to overcome the resistance that was in the motor prior to the S/C and the additional resistance the S/C provides. Thus requiring more energy which means more fuel must be burned. There is absolutely no situation where this is not going to be true. This includes turbos. Though the relationship between the motor and turbo will be slightly different as it will be a function of airflow rather than engine speed.

Actually, I disagree. Here is when it applies. If the power output of the engine at a given cruising speed greatly exceeds the power necessary to maintain that speed, then the engine is actually producing wasted power. This is less obvious in an automatic where slip is available.

A perfect example would be going 35 MPH in 1st gear on a 6MT. The power necessary to maintain 35 MPH is likely in the 30 HP range. At 35 MPH in 1st, the engine is around 6500 RPMs, producing somewhere in the neighborhood of 280-290 HP.

Though this is an extreme case, it is also true at cruising speed. My 05 coupe is at 3k RPMs at 80MPH. My I30 with a smaller, less powerful motor was able to maintain that speed at 2700RPMs (and getting 2-3 more MPG). Now granted, there is more drivetrain loss in a RWD than FWD, but theoretically, it is possible to produce more power at a lower RPM, thereby allowing the engine to operate on less gas.

All you'd have to do is get shorter diff gears

Sentientbydesign wrote:Actually, I disagree. Here is when it applies. If the power output of the engine at a given cruising speed greatly exceeds the power necessary to maintain that speed, then the engine is actually producing wasted power. This is less obvious in an automatic where slip is available.

A perfect example would be going 35 MPH in 1st gear on a 6MT. The power necessary to maintain 35 MPH is likely in the 30 HP range. At 35 MPH in 1st, the engine is around 6500 RPMs, producing somewhere in the neighborhood of 280-290 HP.

Nope. If you are at 6500 RPM in 1st gear and cruising then you are not at WOT. And the peak HP you speak of only occurs at WOT. Thus, you'll be making significantly less power and actually, the torque output at the wheels will be the same. And in actuality, the torque output at the motor will be less than it would in a higher gear at the same speed as the transmission will be multiplying the engine's torque output such that the same torque output will exist at the wheels. So there is no wasted power. Frankly, if you were actually wasting some 250 HP worth of energy, something would overheat as the energy has to go somewhere (Conservation of Energy)

Sentientbydesign wrote:Though this is an extreme case, it is also true at cruising speed. My 05 coupe is at 3k RPMs at 80MPH. My I30 with a smaller, less powerful motor was able to maintain that speed at 2700RPMs (and getting 2-3 more MPG). Now granted, there is more drivetrain loss in a RWD than FWD, but theoretically, it is possible to produce more power at a lower RPM, thereby allowing the engine to operate on less gas.

This is a very different example actually. The engine speed at a given vehicle speed in a car boils down to gear ratios. If you mated a Geo metro motor to the I30's transmission, it would operate at 2700 RPM at 80 mph as well. The big difference is the Metro's motor would require a greater throttle opening as it would need to use a greater percentage of it's available power.

As for the I30 using less fuel, there are several factors that go into this. Engine RPMs is a big factor as higher engine speed means more windage losses in the motor. Bigger motors also have more mass and more parts that contribute to an increased need for energy consumption. Lastly, the engines are tuned differently as well. Volumetric Efficiency will be different for these motors at their respective RPM's and throttle positions. It's impossible to make this comparison without accounting for all these differences.

Very good point. Thank you for the clarification.

So in two instances. Both at the same speed and very similar acceleration, but one in a lower gear and another in a higher gear. Is the engine to blame for the lower fuel economy in the lower gear?

In other words, is the engines movement to blame for the increased fuel consumption?

Sentientbydesign wrote:
Actually, I disagree. Here is when it applies. If the power output of the engine at a given cruising speed greatly exceeds the power necessary to maintain that speed, then the engine is actually producing wasted power. This is less obvious in an automatic where slip is available.

If the power output exceeds the power necessary to maintain steady state speed then you are accelerating. This is assuming no slip condition.

Sentientbydesign wrote:A perfect example would be going 35 MPH in 1st gear on a 6MT. The power necessary to maintain 35 MPH is likely in the 30 HP range. At 35 MPH in 1st, the engine is around 6500 RPMs, producing somewhere in the neighborhood of 280-290 HP.

Being at 6500 RPMs does not mean you are producing 280 HP. If you are going 35 in first gear at 6500 RPMs and the vehicle is going steady state, and it requires 30 HP to maintain steady speed... then you are ONLY producing 30 HP.

Power output depends on the speed and the load. To get your 280 HP you have to be at 6500 RPM and Full load.

And what C-Kwik said is right.

joe603 wrote:True, but I've seen posts of people with SC that claim to have better mileage than OEM. Not so with a twin setup. There is a fine line between the additional HP that the SC develops and the HP required to turn it. At cruising speed, I would suspect that the engine is spinning fast enough to overcome the HP required to run the SC, and the extra boost increase gas mileage. Of course all of this goes out the window when you stomp the gas!!

I don't know as I've never had a S/C, but it, like the AC when it's on, wouldn't the S/C add a drag to the engine. Wouldn't that drag increase fuel usage?

My opinion re: turbo vs. S/C is that the S/C is far more trouble free. I've known several S/C'ed Mustangs that never had problems with the system. If I was to go to FI, it would be with a S/C for about a 90 HP boost.

I just saw a video of a S/C Caddy CTX V running 12.5 at 115. That is fast.

Sentientbydesign wrote:Very good point. Thank you for the clarification.

So in two instances. Both at the same speed and very similar acceleration, but one in a lower gear and another in a higher gear. Is the engine to blame for the lower fuel economy in the lower gear?

In other words, is the engines movement to blame for the increased fuel consumption?

I'd say if the acceleration rate was the same in both gears, then the higher gear would likely use less fuel as engines speeds would be lower overall and a higher throttle position would be used(VE is typically higher at high throttle). However, there are a multitude of variables that could affect the results.

In theory though, if there were no frictional and aerodynamic losses, mass of the engine internals were not a factor and VE were constant, the fuel consumption would be the same in either gear for the same rate of acceleration. But the reality is they are not. And therefore, it is a very difficult question to answer with any real certainty without either accurate testing and/or some complex calculations with known variables. And even then changing the duration and rate of acceleration could vary the results substantially...

I am having a brain thunder reading these explanations . I need a drink . Just answer my question on my other post about what really happens to the vehicles with SC or TT installed?

FI generally puts more strain on your engine and drivetrain components.

Gas consumption is GENERALLY higher with FI as well, due to more fuel + more air = more power.

Toolbothwilley:

Do you have an idea which parts actually start having issues? Any knowledge of anyone with SC who has had problems and what type of problems do they have?

Hey Joe,

How much do SC kits go for? Does anybody else make these other than Stillen? Do you know if it fits on a sedan?

I think I saw the TC kits go upward of $6K.

Their are roots-style superchargers (like stillen) and Vortech style superchargers. Vortech superchargers are a whole different class of superchargers. Roots style superchargers use relatively heavy blades compared to turbos. Vortechs use impellers very similar to turbos. When people talk about how much energy it takes to turn a super, they are talking about roots-style. Centrifugal compressors are very efficient (turbos and Vortech) so please, no more putting Vortech in the same class as your typical supercharger...

Your options are:

Stillen "roots" style SC 4kVortech centrifugal SC 5kTurbotechnics TC 5kJWT twin turbo 9-10kGreddy twin turbo 9-10k

Thats rough estimate prices...tuning will be more.

C-Kwik wrote:
Its easy enough to skew the gas mileage by driving nicer with the S/C then you did before the S/C was installed. The same could be said for turbo cars.

Boost can never increase gas mileage. The compression of air in a turbo or S/C will likely be at 80% efficiency tops. This means that 20% of the energy provided to the S/C's pulley is wasted in generating heat. The other 80% is spent actually compressing air. Unlike a turbo, this will always be happening as the S/C is connected to the crank directly. Some of it is recoverable as it it bypassed, but I doubt that will be a 100% efficient process either.

The engine's speed doesn't overcome the S/C's parasitic drag on the motor either. By design, anytime a compressor's wheels are spinning, it is trying to accelerate the air into the compressor housing to compress it. In order to do this, there must be energy available. While a engine that is rotating quickly may spin the turbine with out energy added to it, it will slow down the motor. Thus, fuel must be burned in order to keep the motor spinning. And as it is now forced to overcome the resistance that was in the motor prior to the S/C and the additional resistance the S/C provides. Thus requiring more energy which means more fuel must be burned. There is absolutely no situation where this is not going to be true. This includes turbos. Though the relationship between the motor and turbo will be slightly different as it will be a function of airflow rather than engine speed.

Pulled from STS' website: "Unlike a belt driven supercharger, the turbo utilizes "wasted" energy leaving your tailpipe. Most of our customers get 1-3 mpg increase in gas mileage compared to their original stock mpg numbers."

http://www.ststurbo.com/benefits

joe603 wrote:Pulled from STS' website: "Unlike a belt driven supercharger, the turbo utilizes "wasted" energy leaving your tailpipe. Most of our customers get 1-3 mpg increase in gas mileage compared to their original stock mpg numbers."

http://www.ststurbo.com/benefits

STS's website has some of the most twisted and misleading technical turbo info I've seen out of any website. Yes, a turbo uses exhaust energy, which is virtually free, but it still poses a restriction on the motor as it requires a pressure differential across the turbine to create the airflow necessary to spin the turbine wheel.

If you want to consider their credibility, consider their statements:

"Approximately 500F lower turbo temperatures. Eliminates the need for a turbo-timer, which allows the engine to run after the car is shut off in order to cool down the turbo and prevent oil and bearing damage."

What they don't tell you here is that you also lose out on 500F of energy that could be used to drive the turbine. This means that for a given boost level using a given turbo, it will require a higher pressure differential as there is less heat energy that can be used to drive the turbine.

"Denser exhaust gasses drive the turbo turbine wheel more efficiently."

More efficiently than what? Notice they don't mention that. Certainly, denser gasses will drive a turbine more efficiently than less dense gas of the same temperature.

"Turbo is closer to the tail pipe outlet. Provides a better pressure differential across the turbine wheel which promotes better flow across turbine."

A higher pressure differential provides more energy to the turbine. what they don't tell you is that the goal of any turbo system is to try and make the same boost/power with a lower pressure differential as it frees up more HP as backpressure will be reduced. The higher pressure differential is needed in their systems because of the location of the turbo.

Keep in mind that STS has changed their technical info quite a bit since I've last looked at their site. I wish I had saved a copy to contrast and compare. It used to contain much more "technical data" to try and compare itself to more traditional turbo layouts. Funny how they seemingly dropped any comparisons to traditional turbo systems when it comes to power and efficiency.

joe603 wrote:
Pulled from STS' website: "Unlike a belt driven supercharger, the turbo utilizes "wasted" energy leaving your tailpipe. Most of our customers get 1-3 mpg increase in gas mileage compared to their original stock mpg numbers."

http://www.ststurbo.com/benefits

I agree with everything C-Kwik said so no point in repeating.

On another note.... It is very unlikely you will get increase in MPG due to adding a turbo charger. Most production turbo cars have a lot lower mpg rating than their non-turbo counterparts. Turbo cars have to run rich due to cooling issues inside the combustion chamber. This is probably the single most important factor that drops the fuel efficiency.

Thanks guys...I'm going Vortech anyway

We won't hold it against you.

joe603 wrote:Thanks guys...I'm going Vortech anyway

That would be my #1 choice too.

Me too! Vortech it is!