Mez

Superchargers such as the positive displacement and centrifugal type have a by-pass valve that recirculates air thru the compressor back to the intake so they are not providing any boost or consuming engine power. Thus, they use almost no power at low throttle openings. So, technically it may be "On" but it is using very little power...something like .5 to 1 hp at cruise.

Bill Curlee

I have to disagree!!!! I added headers, ported Throttle Body, VARARAM, & 160 deg stat, to my 06 MN6 Coupe. Prior to the mods, I was getting an easy 25 MPG highway and if conditions were right, maybe 26.

After the mods, mileage SUCKED! I wasn't tuned after the mods. I had a caned tune installed at a national event and the performance was a slight bit better but it did NOT improve the fuel mileage.

I had Chuck at Corvettes Of Westchester tune the car after I got tired of running rich and having poor throttle response. He installed the tune, road tuned the car and did some fine tuning. Talk about an IMPROVEMENT! WOW!

Throttle response was significantly improved! WOT was improved. NO MORE rich black tips and exhaust smell. The best part of all was the IMPROVED fuel economy. Yea, yea yea,, I know. Who cares about fuel economy. RIGHT!
Hell, 80% of the driving that most of us do is part throttle cruising and if you can save a few bucks in fuel, thats a WELCOMED bonus.

My wife and I made the yearly trip to the Cruise In at Bowling Green last spring. The car was FULLY LOADED with luggage and two people. Driving on the highway in light traffic.. We were seeing an easy 28 mpg. I was being extra careful and driving easy and saw 29 for some nice flat stretches in light traffic.

In heavier congested traffic areas, (NYC / Jersey areas) we were still seeing 26-27. SO,,, yes you can have MODS and Fuel efficiency. I never thought I could add mods and get BETTER fuel mileage. I did!

Chuck now has EFI Live AUTOCAL and can tune your car remotely at HOME with the same fantastic results at a very reasonable cost. With AUTOCAL, you use a programmer/data logging tool to add his tune to your car and after you up load the tune, you data log the car and send him the data log file via E-MAIL. He will fine tune the PCM tables using the data log file and send you back a corrected tune for a spot on tune custom made for your engine and mods. Call Chuck and get the details.

Heres a link to his site and the AUTOCAL Check it out!!:

http://forums.corvetteforum.com/c6-c...-sale-now.html


Bill Curlee

wallyj

You could rig a control to the bybass valve on a PD style blower to always keep it open and no boost would build, but you would have major tuning issues. The gentleman who suggested using your right foot to achieve or avoid boost is most correct IMHO.

After I posted this I see Mez already explained this.

PowerLabs

Maybe you should ask Mel Gibson for help then if his movies are where you are getting your information from

Bill Curlee

You asked for specific info and I provided
QUOTE" If anyone has any info on mods they have done and their subsequent gas mileage I would like to hear about it."

What part of INCREASED doesn't equal preserve. Mileage on my car was better than stock so you will at LEAST preserve what you have now! My goal was NOT better fuel mileage either. I just hated the **** poor efficiency and throttle response that I was getting without a proper tune.

Movies are FUN and often filled with fiction. Your NOT going to find an ON and OFF blower. SORRY. You cant suck air thru a roots type blower when it not pumping.

BC

seevi

Since you haven't posted a profile, I'll presume that you engine is stock. Making the car breath better will get you increased performance and fuel economy. I'm not talking big HP numbers, but with an air filter that breaths better, recalibrated MAF and dialed in AFR, you'll get much crisper throttle response and increased mileage. I have a K&N air filter, ported intake and 3" ZO6 exhaust and my highway mileage averages between 31 and 33 MPG.

5knives

Mad Max also had a rabid dog and had to fight off desert mutants for every ounce of petrol. You want that too?

The only mods that may hurt your daily driving mileage would be a cam, gears, and converter. All other mods should assist with engine breathing thus preserving most of your mileage when not on the gas. If you're looking for an on/off power gain, N20 is probably your best (only?) choice. You can be completely stock and then summon 150whp at the flip of a switch. Is that what you want?

No need to get so upset. If your question isn't being answered the way you want but people are still trying to help, maybe you should rephrase it to specifically what you're looking for?

You want more power but don't want to lose gas mileage, correct? I think we all got that and have provided you with a decent starting point. Any in/out breathing mods should keep your mpg close to stock but you have to know that when you're going WOT, your modded mpg will be lower than your stock mpg were. I don't believe there are mods that keep stock mpgs when at WOT. I could be wrong though.

Joe Camel

Sorry but some posts thought I was trying to improve my mileage when I stated clearly I was just trying to keep it or close to it. Yes, mine is totally stock. NO2 is out, as far as I am concerned that stuff isn't for a normal street ride.

Thanks to Bill and Seevi for a couple of helpful posts. Those are what I was asking for.

It's fairly obvious that air isn't going to go through a positive displacement blower that isn't turning. It would need a bypass of some sort. Not all blowers are positive displacement are they? And a clutch like on the AC compressor is possible.

Everything in Mad Max isn't for real? There's a shot across my bow.

Not intimate with the computers in this car but I thought they might be capable or retuning themselves for boost and no-boost conditions, although if I had a blower I probably would set it for a low boost and just leave it be.

I bought my 66 GTO in Denver, 3 deuces. It was barely chugging when I got to the top of Pikes Peak and it died on the outskirts of Phoenix, a quick carb adjustment got me going again. I thought the Vette would retune itself for those conditions?

Anyway, If I had to guess I would have said more horsepower always equals worse mileage but when it comes to freer flowing exhaust or intake I wasn't sure what it would do. I also read in an ad for a blower once not too long ago that it wouldn't hurt mileage, but I found that one hard to believe.

Anyway, thanks for all the input and I would be happy to send a tank of CO2 to anyone I flamed.

Mez

Positive displacement blowers have been used by GM and Ford on various models in the past. I owned 2 Thunderbird Super Coupes and when the by-pass valve is open at cruise, there is like I said about .5 hp loss.

I don't think they use a clutch because air must go thru them. If you stop them, they become a restriction to air flow. Like a turbo charger.

As for the factory PCM, yes they do make adjustments to the fuel and ignition....within a certain a range where the O2 sensors operation.

Once you go to Wide open Throttle, the O2 sensor no longer are used for feedback on the A/F ratio because things are happening too fast. The PCM looks up the fuel and ignition from a series of tables based on RPM, MAP, MAF, air temp, etc. So if you add a S/C, you need to recalibrate these tables to deliver the right a/f ratio at WOT these new conditions.

For more information, pick up a copy of Greg Banish's book at Barnes & Noble.

JoesC5

My factory supercharged Mercedes has the closest thing to an on-off switch for a blower that you will find. The blower has a clutch(just like what is used on the A/C compressor) that is controlled by the computer. Normal driving and the blower is not spinning because the clutch is not engaged. When the computer senses that you want to accelerate more then normal driving, the computer applies voltage to the clutch, it engages, the blower starts spinning, and away you go. There is a seperate duct and valve that allows air to the engine when the blower is not spinning.

The computer controls the on-off of the blower, but I guess bubba could rig up something along the same lines and put a toggle switch on the gear shift for manual control by the driver of a Corvette.

Bill Curlee

Well, you learn something new every day. I stand corrected. Maybe Joe can cobble one of those on his corvette. Sounds pretty simple. How much is that Mercedes?? Im sure that part isnt that much..

BC

BC

Mez

I did not know Mercedes had a clutch on their SC. But then again, they tend to like complex solutions.

I own a Mercedes ML55 AMG. It's rated at 342 hp/375 ft lbs of torque from its 5.5L V8. It has a double overhead cam, 3 valves per cylinder, and 2 spark plugs per cylinder. I open the hood and think to myself "why'?

smurfkiller

the edelbrock e-force blower, the magyy tvs blowers are positive displacement but do offer a bypass valve so when your cruizing your mpg and power levels are stock. sounds like you just need to visit your local speed shop (one with a good rep thats not ust looking to sell you stuff) they should be able to answer all your questions with no b.s.

0Chuck CoW

Yes....Correct. The Edelbrock and the Maggie both work this way...

One thing that customers tend to forget is that in many cases POWER makes for BETTER MILEAGE...

YES IT DOES... Underpowered vehicles or vehicles with heavy "torque management" strategies will tend to do 2 things....

Get POOR mileage...and because the power is insufficient, just simply press the accelerator down futher causing poor mileage.

Think about it... Having more power (within reason) you have to press the pedal less... Less air...Less fuel.... Better mileage.

Rear end changes can actually ADD mileage under most circumstances...


REASON: The extra torque multiplication causes you to be able to use or "take advantage" of more of the engines power than before.

People think "gears raise rpms so fuel consumption goes up"..WRONG.

When you change gears...RPM's go up slightly but, ENGINE LOAD goes WAY down for "normal" driving....

When load goes down, throttle angle goes down, and fuel consumption goes down.

BACK TO TUNING:

Yes, a good tune (especially after a conservative STOCK tune) you should pick up mileage.

You can't imagine how many guys with C4s bought adjustable pressure regulators and cranked UP the fuel pressure to make more power....WHEN, reducing the fuel pressure slightly actually makes better power and mileage....

Same goes for Tuning LSx Corvettes and the like.

Done properly, mileage goes up!

However....MILEAGE IS TOTALLY DRIVER DEPENDENT.

The best most fuel efficient tune will still get less mileage when driven aggressively.

Mileage can go up with a tune....As much as 2-3 MPG....

But, most guys who gain performance and mileage with mods...will offset the gain with more aggressive driving....

Chuck CoW

PowerLabs

Wow... This is fascinating! I have a Mechanical Engineering degree, and I have worked for 3 years in an Internal Combustion Engine research laboratory on fuel efficiency, and I had NO IDEA! They always teach us in school that superchargers are not 100% efficient devices, they require horsepower to drive, and the parasitic drag on the engine costs fuel economy... They tell us that since frictional losses are a function of speed, operating an engine at higher speeds incurrs lower fuel economy... They also tell us that there is this thing called "pumping losses" that happens when you run an engine at part throttle; it has to do work to suck air through the restriction posed by the throttle valve (one of the reasons Diesel engines get such good fuel economy since they have no throttle). God my professors are so stupid
Great stuff. Man, if class-leading fuel efficient vehicles like the Prius, the CR-V, the Mini, the Civic can do 33 to 55+ MPG with tiny 4 cylnder engines and high final drive, imagine how much further they could go on a tank with 4.11 gears and a supercharger! Someone has to tell GM to start capitalizing on this

S'vette

every time I tuned my new car it got better milage and more power. I had 2 Audi TT's and would chip them and get way more hp and tq and got 2 mpg better avg than before. And it was a 4 banger and I avg 27 mpg combined and could still do 0 60 in 5.2, not bad for a 4 banger with a tune. Now if you are always on the power then no you wont get better milage, but that goes for stock cars too.

JoesC5

Isn't that the truth. My Hi-Tech Mercedes gets 21/29 MPG(real world mileage) and my old fashioned Lo-tech Z06 gets 18/29 MPG (real world mileage). Maybe there is something to KISS afterall.

JoesC5

Wasn't trying to get smart with you Bill, just pointing out that there is an on-off blower in use on a factory installed supercharger.

I made the joke about Bubba as there is always a Bubba around that will try anything.

Ragtop 99

Not so much KISS as KILW (Keep it Light Weight)

Vetteinplano

Magnuson blower and this: http://www.lingenfelter.com/sites/li...structions.pdf