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Just wondering how much mpg drops with turbo or supercharger, I'm thinking of running low boost levels. The car will be mostly hwy cruising so fuel range is kind of important to me.
 

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Don't know about the S/C cars, but the Turbo with the enhanced upgrade is providing us with around 28-31mpg on a regular basis.
I've gotten as much as a 35.8mpg tank. The last one was 29.6!
Hope that helps a little!!

Did a 600 mile loop trip this weekend and I averaged 32.1 in upper 80's to low 90 degree temps at speeds between 55-70mph.
These cars are such a kick, fun factor & great mileage for a sports car! Yeah!!:thumbs:
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'09 Pontiac Solstice GXP Coupe - (man.) Mysterious / Black - (NIICE) Vin: 000116
'09 Saturn Sky Redline - (auto.) Ltd. Ed. Hydro Blue - (COOOL) 1 of 49
 

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The S/C goes on a 2.4 engine (20% more displacement than the 2.0 Turbo).

In stock form, and with enhancements, the Turbo is probably more economical.

However, both will yield over 25MPG (at this level neither is a gas guzzler...

so, who cares).

Other variables ought to inform the choice between these two.
 

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Running unboosted, i.e. without foot to floor, the way most people drive most of the time, there is little parasitic power loss from a turbo (a mild increase in exhaust back pressure perhaps) while a supercharger is always 'on deck' pulling some power from the engine and not putting anything back until it gets called on.

Based on that, the GXP 2.0 will give netter mileage than a 2.4 with supercharger (or without supercharger, for that matter). Not sure what driving really hard does to the mileage of either, but doubt that is a big concern anyway?
 

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My experience has been unusual thanks to my particular way of driving.

My driving is both city/highway and averaged a solid 19mpg for the first four years of ownership. After the turbo and the tune I've been averaging about 25mpg for the past year but that's probably because I'm not driving as high in the power band since I still haven't replaced my clutch.

At least in the turbo world I think it'll depend way more on your foot than the power adder.
 

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My last tank of 91 octane E15 gas I got 20mpg. That's a good mix of highway/city leaning heavy on the city; also running around 100 degree weather.

Best I've gotten is around 25 on all highway from Oklahoma to Wyoming.

I'm running DDM Stage II with Flowmaster exhaust.
 

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My experience with gas mileage is this, I drove the solstice 2.4 na for 2 years, mileage according to the info center was around 25.5 -26 mpg and I had no problem getting 315-320 miles on a tank full of gas everytime I filled it. Since then, I installed the stage II supercharger,(2 years of summer driving) and the info center still says I get around 25- 25.5, but I have to fill the tank everytime around the 275-280 mark, so I feel that I lost about 30-40 miles per tankful, even though the info center says about the same.
 

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My experience with gas mileage is this, I drove the solstice 2.4 na for 2 years, mileage according to the info center was around 25.5 -26 mpg and I had no problem getting 315-320 miles on a tank full of gas everytime I filled it. Since then, I installed the stage II supercharger,(2 years of summer driving) and the info center still says I get around 25- 25.5, but I have to fill the tank everytime around the 275-280 mark, so I feel that I lost about 30-40 miles per tankful, even though the info center says about the same.
Dave pointed out to me that the increased intake tube size is what makes the info center mis-read from the MAF sensor. It thinks less air is moving past it, so it reads better mpg. I'd say I lost about 4-5mpg adding the S/C, but added at least 20 smilespergallon. So I figure it more than makes up for it.
 

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The first 2x you push the button, display trip mileage, A and B,the next time is how many miles left in gas tank, and the 4th is mpg, there are 8 stages to the info center readings. This is not a good explanation, but the best I can come up with.
 

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Info center does not do a great job of reading actual MPG but does give you an idea ,try it for yourself.If you go on the expressway and stay at a constant speed not really pushing on the pedal to keep speed like on a downhill or somewhat flat road ,you will see the MPG actually increase then stomp on it or just start giving it more gas and the MPG does not really show the difference.Some cars read off the vacuum and figure the MPG and they are more accurate because you can see the difference almost immediately .As far as more MPG I would have to say that the turbo is more economical to drive because it only gives boost when you need it and the supercharge is instant power it is constantly driven off a pulley which not matter how you look at it ,it is using some power from the motor.Don't forget anything that uses the motor to drive it will cost you in gas some how,consider AC it is also driven off the motor pulleys which puts a load on your motor.The law of physics will tell you that you have to use power to power other items and because there is no way to get perpetual motion .Anyone who can get perpetual motion like for instance wind power to drive a generator which would drive a larger generator producing more power that it took to create the initial driven power would be a millionaire.I know it was long winded and for that I am sorry ,just it takes power to make power and there is always a cost to it.
 

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If you set the DIC to Actual Mileage instead of Average you will see the difference on MPG when you give it gas. It takes longer for it to show it on the Average , because it takes longer giving it gas or going up or down hills to affect the Average MPG . If you check the mpg yourself you will find that the DIC is very close.
 

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I'll throw a monkey wrench into this whole discussion.

The method of forced induction is irrelevant to MPG in the 2.4L LE5 motor.
Whether it's a Turbo or a S/C (of which there are many kinds) it uses so little HP during relevant MPG conditions it makes no difference. Roots superchargers have an internal recirculating valve that lowers the pressure across the rotors and effectively removes any drag and centrifugal compressors at such low impeller speeds are also not really loading up the engine. Be it Rotrex S/C or Turbo - Vortech/ATI S/Cs are a little more, but still low at cruise speeds.

What determines the MPG is the Tune.
Having the correct sensor calibration is required for producing an accurate MPG rating on the DIC. This includes correct injector calibration, correct MAF and MAP calibration. Once all of that is on point then any only then will the MPG DIC numbers fall in line. After that you still have the issue of properly reconfiguring the Volumetric Efficiency coefficients table to reflect the new air model condition based on how the compressor has changed things.

I haven't seen every Tune on the market, but of the ones I have seen none of them have put in the changes necessary in the VVE tables to produce the best MPG for the system. Most of that comes from the fact that the generally accepted software used for tuning doesn't even provide a way to display or manipulate these values, and also that those coefficients are so complex and difficult for most to comprehend that they are ignored for all but the higher ranges of the air model.

Unless you are measuring tank for tank and ignoring the DIC on a boosted 2.4L you are likely living with a false sense of MPG performance.

I just started another round of VVE tuning on my SKY since going to the Rotrex C30-94 and I assumed that it would be very close to the C30-74 that I was using before, but I have basically started from OEM due to the compressor profiles being so different. This is the same issue for every S/C type and very much the case for a Turbo. I used to get real deal 32 MPG tank average numbers around town in closed loop and could push 36 MPG in an open loop tune that was useless for boosting, but now currently I'm only up to about stock MPG ratings.

This is not to say that kits available are not well tuned, it's just that they are not specifically tuned for MPG hyper-miler set-ups. You can get good MPG and good Power, but you can't get amazing MPG on the 2.4L with any kind of power expectation. Anyone getting better than LNF MPG ratings with the same power on a 2.4L is either using fairy dust magic or just has a MAF that is out of calibration.
 
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