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Old 06-15-2008, 12:31 PM   #1
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Can a turbo charger be used to increase MPG?

I was wondering if MPG could be increased with a properly sized turbo.

Obviously the fuel system would have to be dialed in tightly too, but does anyone have experience with turbo'd 5.0L that have acheived better MPG ?
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Old 06-16-2008, 05:28 PM   #2
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Talking

I was gonna say no because most people would have to play with the new power. Then i was thinking that if you used a fmu and didn't injector swap then you would have a chance.... Interesting... Use the 93 as a test car for us.
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Old 06-16-2008, 06:47 PM   #3
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I give the same response to people who ask me if certain BBK parts will improve mileage.

Sure they will since they are increasing efficiency, but that extra power is too much fun to resist....

I was thinking of making the '93 my driver again and getting rd of the '06 (payment) and a turbo 331 '93 Cobra (would need to lower compresion) seems like fun to me.

I was thinking of using a Boost A Pump instead of an FMU with 24# injectors and maybe 8 PSI...

Then again, a turbo 06 GT would be nice too. Gotta love the interior compared to the older cars.
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Old 06-19-2008, 12:41 AM   #4
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I would say that for a given MAX hp in the same veh. a small CI with turbo could net better MPG than similar Max hp in engine with large CI & NA

yeahh1987-88 tbird turbocoupe mmmmmmm damn I love those cars...
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Old 06-20-2008, 09:44 AM   #5
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ive seen supercharger adds claiming to increase mpg buy like 5-20% and if its true i dont see why a turbo would be any diffrent, if anything maybe even better since its more efficent, but try to keep your foot off the throttle just to hear that turbo spool....its addicting
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Old 06-22-2008, 07:11 PM   #6
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Sure it can yeild substantial improvement in gas mileage. Pull your V8 and put in a turbo 4 cylinder.
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Old 06-22-2008, 09:22 PM   #7
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Turbos utilize free power by harnessing otherwise lost exhaust pulse energy. It takes proper tuning ie:$$, but you can definitely make more power using less fuel if done correctly. It might take some time to make the money back however
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Old 07-02-2008, 11:46 AM   #8
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The power is not completely free. Dyno any car. Now put the turbochargers in with the hotside piping, oil and coolant lines and don't hook up the intake sides. Dyno it again, bet you lose power.

The car will make the same fuel economy when out of boost, and less in boost. A properly sized turbo will not be seeing boost under low and mild throttle application on a street car. Any mpg increase you will get is purely from a better tune.
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Old 07-11-2008, 03:15 AM   #9
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I have noticed a slight increase in MPG with my supercharged Mustangs when cruising down to Fla. and such. Tooling around town though, I can't keep my foot off the gas enough to see an increase. Any increase in power without increase in fuel burn will increase mileage, which is fine with a setup like I have on my Boss Shinda (19# injectors), but my Procharged Saleen has 42#ers and that kills my mileage somewhat. 5% I can see, 20% seems a little far fetched. I suppose I get about 2MPG extra on the interstate when cruising, thanks to the huffer. Incidentally, mufflers and an intake will also help MPG slightly. All in all, a blower/turbo can help MPH as long as you keep of the right pedal, but who wants to do that all the time?
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Old 08-14-2008, 02:42 PM   #10
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Quote:
Originally Posted by 95PGTTech View Post
The car will make the same fuel economy when out of boost, and less in boost. A properly sized turbo will not be seeing boost under low and mild throttle application on a street car. Any mpg increase you will get is purely from a better tune.
x2

The main gas savings of a turbo is at the design stage~ someone deciding to make the car smaller and lighter by using a smaller, lighter 4 cylinder.

As far as installing a turbo on a v8 Mustang as an economy measure...

FWIW, my three year plan is to install a V2-SQ versus big bore 347. The 347 would be a constant guzzler, whereas the blower "should" get better "quarter-throttle-and-below" mpg's. A 1mpg increase will pay for the blower install!

...in 28 years.

Seriously, going 347 would consume more gas always whereas you get the same performance (or better) with the blower... though under full acceleration the blower uses more fuel.
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Old 08-16-2008, 10:28 PM   #11
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Quote:
Originally Posted by 95PGTTech View Post
The power is not completely free. Dyno any car. Now put the turbochargers in with the hotside piping, oil and coolant lines and don't hook up the intake sides. Dyno it again, bet you lose power.

The car will make the same fuel economy when out of boost, and less in boost. A properly sized turbo will not be seeing boost under low and mild throttle application on a street car. Any mpg increase you will get is purely from a better tune.
Here is a little food for thought.

I drive an 88 Thunderbird Turbo Coupe. I've got a good bit of mods wrapped up in it, big turbo, header, cam, exhaust, etc. My average MPG was approx 25mpg with mixed highway/town driving.

Now, the wastegate actuator arm some how popped off the wastegate, and the turnbuckle fell off. This results in exhaust bypassing the turbine, and creating no boost. With no boost, my mileage is approx 18mpg.
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Old 08-16-2008, 11:49 PM   #12
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Now, the wastegate actuator arm some how popped off the wastegate, and the turnbuckle fell off. This results in exhaust bypassing the turbine, .
... Does that mean that the compressor is a big fat obstruction in your exhaust path?
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Old 08-17-2008, 02:42 AM   #13
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Quote:
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... Does that mean that the compressor is a big fat obstruction in your exhaust path?
Compressor is on the intake side, if you mean turbine wheel, then no, it's actually less of a restriction than it would be with the wastegate turnbuckle on. The wastegate opens, and allows exhaust to pass the turbo, rather than go through the wheel. That's how it limits boost.
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Old 08-18-2008, 11:28 PM   #14
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imo... if the engine is not 100% (ring seal etc) the turbo would make up for whatever the engine cannot draw on its own. a naturally aspirated engine relies on ring seal to properly draw in air and fuel. with a turbo, it is not as critical. the turbo is always pushing some air, even if not in boost, constantly feeding the engine. i believe you can achieve better fuel mileage with a turbo but i dont think it would be much... unless its a diesel. just my .02.
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Old 08-27-2008, 03:49 AM   #15
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a turbo will NOT increase your MPG. however a turbo car with 400hp will likely have better gas mileage than a 400hp N/A car.

if you are planning to add a turbo to your existing car to increase MPG it's not going to happen. you'll increase hp, and effeciency but not MPG.
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Old 08-30-2008, 06:02 PM   #16
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Ford is on record as saying smaller engines with turbo's "can" achieve up to a 20% savings over larger NA engines....both making about same HP with turbo model making more TQ. Example....a 250 HP turbo 4 in an Explorer VS a 3.5 V6 (future models) making 260 or so. Or a turbo 3.5 V6 VS a V8. Or Turbo V6 in F150, etc. I also believe Ford was talking about street versions making good TQ and running on 87 with DI. Tuned for TQ and economy.

Anyway...that's what is coming from Ford.
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Old 08-30-2008, 09:58 PM   #17
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A properly matched turbo system can and WILL increase your fuel mileage. How do I know???? I actually speak from experience.

My 85 GT was converted to MAF EFI, and with the stock 302, full 2.5" off road exhaust, stock 3.08 gears, 5 speed, 255lph high flow intank pump and 1.7 roller rockers used to get between 340-350km per tank. That's about 220 miles to a tank, and I never drove miss daisy. This is with a fully functional EFI system and everything hooked up, no smog.

I converted to EFI turbo, with a CRAP C+L maf and 30# injectors. The car NEVER ran right with this maf, and I never got around to changing it. I also never wound up installing the O2 sensors in the system. In this set up, the car used to get between 340-350km per tank. I got the exact same mileage with a 'malfunctioning' and un tuned efi system and through Flowbuster mufflers! My turbo set up had so much more potential, I just used to have a money-vampire GF at the time so she got more spent on her than my true baby (don't give me ####)

On the other hand, my friends 95 GT with GT40 aluminum heads, stock cam, 1.7 rockers, Innovative T61E turbo with a nice custom turbo system, 50lb injectors and 80mm maf, no tune, full exhaust, fully ported Cobra intake and 70mm TB...... he used to get 500km per tank easily (312 miles) and once managed 700km to a tank all highway. That's 437 miles to a tank! I see lots of guys with mild N/A set ups around here talking about 180-220 miles per tank! If you don't get into the boost, it will be more efficient than naturally aspirated. And efficiency is what saves you money.
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Old 11-18-2008, 03:49 AM   #18
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http://www.ststurbo.com/fuel_mileage
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Old 01-10-2009, 01:52 AM   #19
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There is so much speculation and bad information in this thread that I highly recommend discarding all of it for those who really came in here to learn something. Some of the posts are accurate, most of them are not.

Just my 2 cents,

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Old 01-10-2009, 10:14 AM   #20
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i said it before and i'll say it again. adding a turbo will NOT increase your MPG.

however a turbo car that makes 300hp will likely be more fuel efficient than a NA car that makes 300hp.

read maximum boost by corky bell for those who disagree.
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Old 01-10-2009, 12:15 PM   #21
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Yes,It CAN increase mileage if properly installed/tuned..Ive done quite a few and everyone saw an increase in mileage.unless your just building them for racing then you'll see some improvement.Most problem is that with added HP,Driving habits change.Period.
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Old 01-10-2009, 12:37 PM   #22
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Yes,It CAN increase mileage if properly installed/tuned..Ive done quite a few and everyone saw an increase in mileage.unless your just building them for racing then you'll see some improvement.Most problem is that with added HP,Driving habits change.Period.
i don't believe it. when you add more air you also have to add more fuel. common sense, and published sources, say that adding a turbo will not increase you fuel efficiency. proper installation and tuning have nothing to do with it.

take a stock 5.0 with 225hp; say it gets 23mpg. add a turbo and the necessary fuel mods that you have to do (bigger fuel pump, 42lb injectors, etc) and now make 350hp. there's NO WAY the turbo car is going to get better gas mileage. NO WAY.

please explain how adding 40-50% more hp can increase mpg?
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Old 01-10-2009, 03:35 PM   #23
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i don't believe it. when you add more air you also have to add more fuel. common sense, and published sources, say that adding a turbo will not increase you fuel efficiency. proper installation and tuning have nothing to do with it.

take a stock 5.0 with 225hp; say it gets 23mpg. add a turbo and the necessary fuel mods that you have to do (bigger fuel pump, 42lb injectors, etc) and now make 350hp. there's NO WAY the turbo car is going to get better gas mileage. NO WAY.

please explain how adding 40-50% more hp can increase mpg?
There is one BIG thing people seem to be forgetting about...and it's GEARING. While turbo charging alone may not do much for fuel economy, lowering the numerical gear ratio sure as hell will. Most turbo stangs thrive off of the likes of 3.27's gears....while everyone else is going the other direction with 3.73's or greater. So that 5.0 you've just upgraded to make upwards of 350rwhp (compared to a stockers 195rwhp) with a simple gear change can absolutely get better fuel economy....all while being much faster.
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Old 01-10-2009, 04:13 PM   #24
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Millhouse,

To me, this is more about the concept of turboing an engine and not about muddying the water with other concepts like changing the cam, decreasing compression ratio, driving more aggressively, or swapping gear and tire sizes. The question being asked here, in my interpretation is, all else equal will will a well-tuned turbocharged setup on a given engine increase overall fuel mileage?

My intuition tells me no. Any time you introduce a restriction in both the exhuast and the intake, I don't see how that would increase fuel economy. Under partial throttle cruise conditions, I don't think that the turbo is pumping air into the cylinder. So, it's not as if the engine is working more easily to pull air in. I think there would be a net decrease in VE.

That said, I'm not entirely sure VE actually plays into fuel mileage. A certain amount of air with a given AFR should produce a constant amount of power all else equal. If you wanted more air, you could just give a little more throttle in an engine with a lower VE. Do the pistons have to work harder? I doubt it. The biggest restriction in the intake path is not the turbo or even the filter, but the throttle body blade. So a high VE intake would need less throttle to move the same amount of air as the less VE intake using more throttle. If the tune is set so that both have the same AFR, then I don't see how we've gained or lost anything on the intake side.

On the exhaust side, there's a big restriction, and it seems clear to me that the motor is going to have to work harder to push exhaust gases through a turbine. This restriction works to the detriment of volumetric efficiency, but more importantly, it's less mechanically efficient. Now, a higher net force is applied to the piston during the exhaust stroke that would otherwise not be present. This would have the effect of requiring more fuel to generate the same net engine output.

In any case, it seems clear to me that thermal efficiency (TE) and Mechanical Efficiency (ME) is more important than VE. There's no doubt that VE is important in power production, but as for fuel economy, adding air and fuel to go the same distance is never going to increase gas mileage. Please don't misinterpret that because making an engine more volumetrically efficient does not mean it will require more air for a given distance. Only that it will need less throttle to move the same amount of air that the engine requires.

I'm not the most articulate person in the world and don't claim to have resolved this dilemma. I'm just trying to get people on the path of thinking through the real physical concepts involved in answering the question rather than making baseless guesses.

Chris
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Old 01-10-2009, 05:17 PM   #25
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Fastdriver, the problem is...gear ratios can have a huge impact on the fuel economy of the setups in question. While simply adding turbo's may not give you any fuel economy change, the optimum gear ratio for a identical naturally aspirated and turbo charged setups have to be taken into consideration....as the original question was in relation to MPG rather than volumetric or thermal efficiency of the engine.
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Old 01-10-2009, 05:38 PM   #26
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It depends entirely on how you do it. Most turbocharged cars aren’t that efficient, partially because they’re typically low compression. This allows for more boost, but the relative efficiency drops by approximately the square root between the low and N/A compression ratios. If you built a high compression engine with a high torque, low rpm cam, gear it for that, and then control the turbocharger correctly, then you could definitely both improve gas mileage and have higher performance than the stock N/A engine.
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Old 01-10-2009, 07:35 PM   #27
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Quote:
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i don't believe it. when you add more air you also have to add more fuel. common sense, and published sources, say that adding a turbo will not increase you fuel efficiency. proper installation and tuning have nothing to do with it.

take a stock 5.0 with 225hp; say it gets 23mpg. add a turbo and the necessary fuel mods that you have to do (bigger fuel pump, 42lb injectors, etc) and now make 350hp. there's NO WAY the turbo car is going to get better gas mileage. NO WAY.

please explain how adding 40-50% more hp can increase mpg?
You really should learn to read and understand what youve read before you spout off some uneducated guesswork (Or YOUR "Common sense")about some things.. IF you run around with your foot in the floor all day then yes,Gas mileage WILL decline...You WILL be FASTER though. Refer back to the small "Driving habits" comment I made..Because EVERY argument you just miserably failed at comes directly from the driving habits.Do You run WFO everywhere you go all day long?It definitely Wouldnt suprise me with your comments.
If it has to be explained to you then you have ABSOLUTELY ZERO idea of how turbo systems work Plain and simple.But I'll try to shed some basics..A turbo engine in the same vehicle will generally get better gas mileage than NA engines for several reasons.1. A turbo itself has VERY little parasitic drain.2(And most important)Instead of the engine having to SUCK the air/fuel mixture in,It is now FORCED in. No longer making the engine a big vaccum pump/air compressor and better Atomization occurs,Filling the cylinder quicker thus requiring LESS FUEL PER HP.. 3.A higher HP engine will generally get better mileage due to not having to work NEAR as hard to pull the same weight..Why do you think they dont put 4 cylinders in hummers? An engine with more power has to work at a fraction of its ability compared to a lower HP engine working at much greater capacity to pull the same weight.Im not saying it will be true in EVERY SINGLE CASE (refer back to my tuning/install and AGAIN driving habits comment so yes,IF you run WFO then it WILL use MORE fuel.. )But to think a turbo will LOWER gas mileage is just plain naive..Although Ive never seen a HUGE increase in MPG in the ones I have built/installed,(As some claim to have seen)There WAS a gain in OVERALL MPG(NOONE ever LOST MPG under NORMAL driving conditions)..And you can argue all day long,Until YOU actually have the knowledge of how F.I. cars work and how to build and tune them then stick to whatever it is you do because Its def. not mechanics and you definitely have NO CLUE about Forced induction of ANY sort..NO CLUE..
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Old 01-10-2009, 10:15 PM   #28
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Who knows....
turbos can definately make smaller engines make as much power as bigger engines...

so you can have a 1.8 turbo engine make as much power as a 3.0 v6 for example...but get 30+ on the highway in the 4 banger turbo vs maybe 24 in the v6
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Old 01-10-2009, 10:30 PM   #29
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In the sense of turbo vs N/A, take the stock 88 Mustang with a 302, and a Turbo Coupe. For all intensive purposes they make about the same power, one has 4 cylinders, one has 8. I'd say the TC is heavier then the Mustang, but not 100% sure.
The comparison of a turbo to N/A is a tough one. If you're trying to turbo a hobby car, then why are you really worrking about fuel economy...If its a toy/hobby and thats what you are worried about, I'd just stop there because you'll be seriously let down with the amount of money you'll have to spend to have a nice turbo Mustang. Dependent on what your definition of a nice car is....
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Old 01-10-2009, 10:38 PM   #30
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turbos can definately make smaller engines make as much power as bigger engines...

so you can have a 1.8 turbo engine make as much power as a 3.0 v6 for example...but get 30+ on the highway in the 4 banger turbo vs maybe 24 in the v6
Exactly..
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Old 01-10-2009, 10:40 PM   #31
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Originally Posted by my8950 View Post
In the sense of turbo vs N/A, take the stock 88 Mustang with a 302, and a Turbo Coupe. For all intensive purposes they make about the same power, one has 4 cylinders, one has 8. I'd say the TC is heavier then the Mustang, but not 100% sure.
The comparison of a turbo to N/A is a tough one. If you're trying to turbo a hobby car, then why are you really worrking about fuel economy...If its a toy/hobby and thats what you are worried about, I'd just stop there because you'll be seriously let down with the amount of money you'll have to spend to have a nice turbo Mustang. Dependent on what your definition of a nice car is....
You have to remember....back when this was originally posted, fuel was well past $4/gallon. At those prices, even on a weekend warrior....it matters. I limited myself to only weekend duty....as I have issues with laying off the happy pedal and was burning a hole in my pockets due to fuel prices. If they stay low...I'll sure as hell be driving it occasionally again to work(60miles round trip).
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Old 01-10-2009, 11:09 PM   #32
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Millhouse, it seems like you just blew off everything I said to restate your point. Nevermind, I understand what you're saying, and I agree with you, brother. Higher hp drag oriented cars won't need as much gear, and will therefore be at a lower cruising RPM. Hence, that car will have more fuel economy all else equal.

I won't speak for the OP, but that still does little to satisfy my curiosity about whether adding a turbo itself can increase fuel economy. I won't give a definitive answer on the question, but I will say that I did not notice anything impressive in the way of gas mileage in my old twin-turbo. I don't *think* it did as well as my old n/a 302, but it was also a heavier car by about 250 lbs with a different cam and induction package. I'll let you know how the new combo works out, but I have no point of reference to compare it to since I'll never drive it n/a.

So, I'm left without any good reference point.

What I can say is that there are some in this thread arguing their hearts out and getting defensive. Nevertheless, they are off base. Turbocharged vehicles under any boost do not make more hp with less fuel. If you don't believe me, research the term "brake specific fuel consumption" and find average values applied to n/a, supercharged, and turbo-charged engines. N/A has the lowest BSFC every time. Also, the engine will always "suck" air in at cruise, unless you're going up a steep incline or are under an abnormally heavy load. Whether turboed or not, at a normal cruise, the turbo will not produce positive boost in the manifold - there will still be a vacuum.
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Old 01-11-2009, 01:07 AM   #33
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So all of us building the turbo cars out there today and seeing increased MPG are just really being brainwashed by aliens..WE really ARENT seeing MPG drop.Its all a hoax..
Bestowed upon us by "the man" Or wait,wait,Our calculators just Start malfuntioning as soon as We install the turbos..We can no longer figure out an average MPG.Yea,Thats GOTTA be it,No other feasible explanation..Guess the tune messes with calculators ability to divide..
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Old 01-11-2009, 01:18 AM   #34
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I'm kinda late in the thread,
Lets not forget to factor in VE ( volumetric efficiency ) either when in terms of boosting. You can have a turbo four banger like say a EVO 8 and actually get LESS mileage. Then say my good buddies 99 N/A Cobra. They aregueably make about the same power. They weigh within a few pounds of one another as well. I know from experience that once you modify and tune the car. ONTOP of driving like you have commonsense since that it is possible. I think the expression is "Have your cake and eat it too". So I think this is what the original poster was thinking when he made the question. IMO if you maximize what the car does already to do more efficiently. It will in a since get better mileage. If you're asking by simply "slapping" a turbo on there and then expecting it get just simply get better mileage. It doesn't quite work like that at all I'm afraid. - to an extend
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Old 01-11-2009, 07:50 AM   #35
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I would love to see your test data 96tangcobra. And, if your post was directed at me, then you must've missed the part where I stated that I don't know the answer to the question.

Nevertheless, what I posted about cruise vacuum and BSFC is not a guess, it's fact. If you insist, I will even find and post links to demonstrate my points. If your post wasn't directed at me, then disregard.

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