Is a turbo mandatory for fuel economy?

Macrobb · Apr 18, 2018

DarkDownDeep said:
How can it be more efficient but not increase fuel economy?

It's more effecient at making 185hp(rated HP), and would have better brake-specific fuel consumption. The problem is, when cruising unloaded you probably only need 50HP from the engine to maintain speed, and NA, the engine has more than enough air to burn that much fuel cleanly... so, at that load, the engine will be slightly less effecient with the turbo.
Once you start maxing out the engine power doing something,then the turbo can add more air and burn more fuel effeciently... but the fuel economy of doing that is less. Break-specific fuel consumption would be better at a high load, but that still isn't a huge MPG number, because you are doing more work.

Thatoneguy · Apr 18, 2018

icanfixall said:
My engine build with the turbo got 18.9 mpg doing 75 to 85 mph across the country from Cali to Bowling Green Ky in 2009 for the ralley. Yes... I was using the double overdrive and have 3:55 gears.. So my final ratio was 1.96. At 85 mph my rpm was 1950 or 2000 rpm.. Can't recall but there are pics on this forum somewhere.

Man I need that lol... I am running 4.56 gears on my CCLB... 60 mph im at like 2500ish rpm.

steelheadguy · Apr 18, 2018

Thatoneguy said:
Man I need that lol... I am running 4.56 gears on my CCLB... 60 mph im at like 2500ish rpm.

Yea. Im crossing the country right now with a 4 speed. 75 mph at 2700 rpm. wish I had 5th gear. Whats double over drive? A gear vendor in 5th?

snicklas · Apr 18, 2018

steelheadguy said:
Yea. Im crossing the country right now with a 4 speed. 75 mph at 2700 rpm. wish I had 5th gear. Whats double over drive? A gear vendor in 5th?

A BTS E4OD and a GV

david85 · Apr 18, 2018

I think icanfixall is the only guy here with a taller final drive than me. I'm at around 2.2:1 final drive with my E4OD and 3.08s, while he's under the 2.0 barrier. It's a different experience when the speedo needle is at the highest number and the tach only shows 2000 RPM. And I can still gear down to 3rd (direct) if I have to.

Only real problem I have lately is getting a good quality tire that holds proper balance at those speeds.

icanfixall · Apr 18, 2018

At 85 mph in double overdrive the rig is very quite. Mostly just the sound of the air rushing by the cab. Double overdrive is an E4OD in 4th and the Gear Vendors active. to read up on this GV has a web site showing these speeds and rpms.

nelstomlinson · Apr 18, 2018

A turbo helps you burn more fuel. If you define efficient as ``burn more fuel per cubic inch,'' a turbo makes the engine more efficient.

A turbo can pump some extra air through the engine, and maybe that will help lower your EGT? If you define efficient as ``lower EGT at a given horsepower,'' the turbo might help.

A turbo using waste heat to pump the air into the engine overcomes the parasitic load of pumping air through the air filter. This would give a few more net horsepower for a given gross horsepower, which is another possible definition of efficiency.

I've seen people writing things in this thread which might fit one or another of those versions of ``efficiency.'' It helps the discussion if we define our terms. Exactly what do you mean when you say efficient?

DarkDownDeep · Apr 18, 2018

http://www.ijera.com/papers/Vol5_issue10/Part - 2/J510026268.pdf

PDF Effect Of Compression Ratio On The Performance Of Diesel ...

Hydro-idi · Apr 19, 2018

Just put a turbo on your truck and enjoy the new power it will have. Nuff said lol.

plywood · Apr 19, 2018

Turbos don't spin for free off otherwise wasted exhaust gases or temperatures. It causes back pressure which causes less exhaust to escape the cylinder and therefore less to enter. Unless of course boost pushes air in faster in the rpm...load etc where the turbo is in it's efficiency curve. If you want simplicity in an f100 type truck instead of a 6.2 per the original post....forget it, just go non turbo.

DarkDownDeep · Apr 19, 2018

Hydro-idi said:
Just put a turbo on your truck and enjoy the new power it will have. Nuff said lol.

i guess i picked the wrong forum to ask this. Il go find a more knowledgeable one like diesel bombers

mblaney · Apr 19, 2018

david85 said:
I think icanfixall is the only guy here with a taller final drive than me. I'm at around 2.2:1 final drive with my E4OD and 3.08s, while he's under the 2.0 barrier. It's a different experience when the speedo needle is at the highest number and the tach only shows 2000 RPM. And I can still gear down to 3rd (direct) if I have to.

Only real problem I have lately is getting a good quality tire that holds proper balance at those speeds.

Put beads in your tires... problem solved. I only use beads (actually, airsoft bb's).

FordGuy100 · Apr 19, 2018

Lower backpressure without the turbo will net higher fuel economy while cruising. Having boost while cruising will lean out the AFR but that wont increase power as long as its stiochiometrically lean to begin with.

But there are a lot of factors that play into this. There is a reason why fuel economy tunes will open VGT turbo's up while cruising at the expense of throttle response.

austin92 · Apr 20, 2018

DarkDownDeep said:
i guess i picked the wrong forum to ask this. Il go find a more knowledgeable one like diesel bombers

Check out some Prius forums if you want fuel mileage. These motors are very efficient. I get about 16-17mpg combined driving mildly aggressive with the truck smoking black. I babied it roughly 28 miles at 55mph once and it only took .9gal to fill back up, that’s 31.1mpg...

Sent from my iPhone using Tapatalk

Kiwif150 · Apr 20, 2018

DarkDownDeep said:
It's my understanding that the original 6.9 engines were fairly high compression and the aftermarket turbos were set to a rather mild boost. Is it possible to increase the compression with thinner gaskets and or different heads? I dont want tons of power, just good fuel economy, easy to start. Less things to maintain.
I've looked at the 6.2 detroit also but it seems to be far less reliable. I can't find much info on the 6.9 as far as fuel economy tuning tho.
I just want a light 2wd truck like a f150 or f100 with a super simple motor.
Oh. Also i live 5000 ft up. Is a turbo mandatory for higher altitudes?

Let's get back to the original post.

Firstly if you want a light duty f series pickup with a diesel engine and it has to be a Ford , you're going to have to build it ...... no older factory diesel f100/150s in the US as far as i know.

Secondly at 5000 ft altitude you are going to want a turbo if you are trying to get more efficiency/economy from a diesel due to air density.

Thirdly if you are serious about economy being a major goal just buy a good simple F150 300 I6 and use the money you save over building your hybrid truck to tip gas in the tank...... or look into wmo.

You could spend a lot of time chasing the theory of turbo efficiency or just listen to some "real world" experiences , to be honest the best tool you'll ever have for improving fuel economy is the relationship between your right foot and the "make louder , go faster" pedal

Is a turbo mandatory for fuel economy?

Macrobb

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steelheadguy

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snicklas

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icanfixall

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plywood

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