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-   -   crazy turbo question (https://www.fuelly.com/forums/f8/crazy-turbo-question-8083.html)

sethag 04-23-2008 06:44 PM


There is no way any electric TURBO will do any more than lighten your wallet. Don't waste your money on snake oil products. Its a electric motor connected to a squirrel cage. I think the original use of these was for boat bilge pumps.
I have owned turbos since 1981 and they hurt your mileage more than they will ever help. It's hard to get top gas mileage out of a turbo-ed engine due to several factors.
I too have owned turbo charged vehicles, (and equipment) for years. I would have to disagree with you. I have owned 2 different diesel pickups, one without a turbo, and one with. The turbo charged pickup had much more power, and much better fuel economy.

Like wise, I've been around small and big tractors alike. In farming FE is the name of the game to help keep production costs down. There are tractors from 40hp to 400hp that have turbos. I know of some older 250 hp tractors w/o turbos (big motors) that don't get FE of the same size tractor with a turbo. If turbos hurt the FE, then you would see lots more without.

Almost all of the semis (big trucks) you see on the road have turbos. Why? more power & better FE.

GasSavers_ALS 04-24-2008 07:37 AM

Sethag that was why I made a point to say:


A turbo is used to produce more power from a smaller engine.
The more boost you put into an engine more fuel it uses.

The VW TDI's are prime example where a turbo mated to a diesel engine produces the best of both worlds as they say.
In a gasoline engine a turbo does not produce the efficiency that you see in a diesel engine. In a truck you can decrease the size of the engine needed when you add on a turbo charger. So instead of a 7.5 liter engine you can get away with a turbo charged 6 liter making the same or more power but using 20 percent less fuel during normal operation.

The difference between my Volvo 740 Turbo and a 740 non turbo is my car comes with 160 hp vs a non turbo with 114 hp. Both are 2.3 L in line four cylinders.
Yet the difference in gas mileage is about 2 mpg city and 4 mpg highway better for the non turbo. 25 to 26 mpg highway is about the best a Turbo owner gets. Yet the non turbo owners are getting between mid 28's and 30 mpg.

GasSavers_topher 04-24-2008 07:46 AM

BEEF: Can you map sensor read above 0 vac?

If I were you I wouldn't use an electric turbo they are nothing more than a scam. My friend tried them on his prelude only at the result of nothing other than noise.

You could piece together your own turbo kit for probalby $800. I know I pieced toghether mine for about the price.

GasSavers_BEEF 04-24-2008 04:38 PM

honestly, it was just an idea that I had. my whole car was only 2K so if I were to do something like that I would put a super charger on my truck to get it in the 13s instead. I think all my extra money is going to go to college in the near future. I have a 2yr degree right now and am thinking hard about my 4.

side note: graduated almost 9 years ago so it will be a change in life style for me. last time I was in college I didn't have a wife or a mortgage. man how things change

JanGeo 04-24-2008 06:08 PM

The fan has to be more powerful to produce boost and if you have a air flow sensor instead of Manifold Absolute Pressure (MAP) sensor then you can "blow" more air into the engine and it should work ok to a point where the injectors can't inject any more fuel then you will run lean. eCycle has an electric Supercharger driven by their several thousand watt electric motor and a video on their website showing it running. You can vary the motor speed to control the air pressure and volume and have a dump regulator to prevent over pressure. Another way to do it is to have a tank of compressed air sprayed into the intake with a high pressure nozzle and force more air into the engine along with the air from the nozzle. Good for maybe a 20-30 second burst until the compressor can repressurize the air tank again.

Diesels are a whole other story - my friend has a 8 liter 4 cylinder volvo diesel in his boat that runs about 28psi of boost from the turbo and the boost pressure can go a lot higher (40+psi) for more HP but can't run at higher power levels for long periods of time. All computer controlled btw including shutdown and startup . . . $40,000 for the motor and installation.

GasSavers_Dust 04-24-2008 10:55 PM

Word, a non-turbo kei(660cc engine, 3 speeds, about 45 hp. 110kmph top speed), doesn’t have the power to move a 1000 lb car past a certain point. Give it a better transmission, meaning a fourth gear with room for 145 kmph, and a turbo when needed, and the car will run great, even at 120 kmph. I think that if you gear the car to use the boost, you can benefit from less fuel off boost. Diesels, like discussed in the why diesels run better at idle thread, don’t need to fill up the CC with fuel to get a bang.

dieselbenz 04-25-2008 08:13 AM


Originally Posted by RoadWarrior (Post 96515)
Hum, that would be inches of water, you know it takes nearly 28 inches of water to equal 1psi?

Inches of water over atmospheric pressure.

GasSavers_Glacial 06-09-2008 10:48 PM


Originally Posted by ALS (Post 96446)
I have owned turbos since 1981 and they hurt your mileage more than they will ever help. It's hard to get top gas mileage out of a turbo-ed engine due to several factors.
1. More air pumped into the cylinder more fuel needed.
2. Produce more heat than a non-turbo-ed motor.
3. To work best you need to lower the compression ratio of the engine.
4. More wear and tear on the drive train and cooling system.

A turbo is used to produce more power from a smaller engine.
The more boost you put into an engine more fuel it uses.

I disagree -- actually, turbo motors are much more thermally efficient than naturally-aspirated or supercharged motors, since they use some of the energy normally expelled out the tailpipe to drive a compressor and do work. Lowering compression ratios is only necessary if one wants to run obscene boost. It'd make the engine less efficient off-boost but with the potential to run higher psi with less risk of detonation. There are a few LS1 twin-turbo cars out there putting more than 700hp to the ground on the factory 10.5:1 pistons!

At factory turbo sizing, you're right. OEMs tend to put oversize turbochargers into their turbo models, going for top-end power over economy. But that's only one use for turbocharging.

A small turbo, for example, can use otherwise wasted exhaust energy to reduce pumping losses, which can have a dramatic effect on fuel economy. The effect during highway cruise can be noticeable! Also, a fast-spooling turbo setup will tend to produce lots of low-end torque, allowing the turbo car to run taller gears or be driven in a higher gear, thus reducing parasitic losses from spinning the engine at higher rpms.

Lots to read on this issue!

mpgmike did a writeup with a really good explanation of the issues involved in turbocharging for fuel economy. He slapped a turbo onto an old Plymouth Duster and went from 18mpg to 23!


R.I.D.E. 06-10-2008 04:25 AM

Turbos dont reduce pumping losses.

They increase compression, and add restriction to the exhaust. They do reduce suction but it's more than offset by the increased compression and exhaust restriction losses.

In a diesel more air means higher compression and more power. Its a completely different scenario because the diesel can run at AF ratios of 50 to one,

A turbo allows you to use a smaller engine to provide extra power when it is needed. The smaller engine will increase efficiency, because it takes more power to do the same work, which means you are closer to the sweet spot in your BFSC map without the turbo. Generally turbo engines have less compression than the same engine without a turbo (except diesels) which means less power (unless the turbo is boosting the intake charge).

Turbo's were first used in aircraft to increase the density of the atmosphere when it was inducted into the engine. At 30,000 feet the atmosphere is very thin and temperatures are 40+ below 0 farenheit. A carburetor at that temp is useless, unless you add serious heat to the intake charge. Even fuel injection won't properly atomize fuel at extreeme low temps.

Compare the 1950 Alfa engine of 1.5 liter at 2MPG to a Nascar restrictor plate engine at 6 MPG at 185 MPH.

1/3 the fuel consumption with more horsepower with the non turbo old tech NASCAR engine.

I owned a 95 Buick Riviera, one of the nicest cars I ever drove (but it would put me to sleep). The boost was low but it allowed 0-60 times of 8 seconds and 28 MPG highway (at 70-75 MPH). It was supercharged with a belt driven roots type blower between the intake and the heads.

The Riv is a perfect example of using a supercharger to make good performance out of what would be a dog without the supercharger.
Mercedes uses superchargers to get performance and economy in the same package with smaller dispalcement engines, but the secret is the smaller engine, operating closer to ideal BFSC in normal conditions.

Compare the INDY rules about supercharged and naturally aspirated engines to better understand the comparison of turbo and non turbo.

I know the defference between turbo and supercharging. Pop's B17 was turbosupercharged which allowed that plane to cruise at 30,000 feet, impossible without supercharging. The heat from the turbos also allowed that engine to use a carburetor without having the fuel freeze when it atomized due to the heat of the turbo.


theholycow 06-10-2008 06:36 AM


Originally Posted by Glacial (Post 104974)
turbo motors are much more thermally efficient than naturally-aspirated or supercharged motors, since they use some of the energy normally expelled out the tailpipe to drive a compressor and do work.

I used to think that, but then I realy thought about it and followed the energy around. The kinetic energy in the exhaust is not wasted, so harvesting it doesn't add efficiency. Search this forum for 'egv' or 'exhaust gas velocity' to understand why. The engine has to push that turbocharger by pushing harder on the exhaust stroke. It uses pretty much the same kind of energy that a supercharger uses, just in a more roundabout way; but it doesn't do it at low RPM. Therefore, a turbocharged engine can be sized smaller, provide big-engine power when necessary, but still be efficient when the RPM are kept down.

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