Is a turbo mandatory for fuel economy?

[DarkDownDeep]

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?

 

[genscripter]

I remember when I first got my NA IDI, I was told that getting the turbo was a way to get better MPG. Frankly, I think there are many other ways to get better MPG (detailed here: http://www.nickpisca.com/diesel/turbo/the-great-big-list-of-eco-mods-for-6-9-and-7-3-idi-vehicles/ ), because once you put on a turbo, you will want to have fun with the vehicle. With a turbo, it'll pull up hills faster, give you more power, allow for faster acceleration, etc. The last thing on your mind will be "maybe I should drive slower to save fuel."

The best way to get better MPG with an IDI is to keep it at 55mph. It's a lot easier to stick to 55mph if you don't have a turbo.

As for the thinner gaskets, I'd be a bit concerned with deck protrusion.

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IIRC, i think the allowable spec is 0.010-0.036. Putting a thinner gasket in would make it really tight.

 

[DarkDownDeep]

Does increasing compression a tad improve combustion and fuel economy? Does a turbo increase the percentage of fuel burned or does it simply push more air in?
Can the precup design be improved for better economy?

 

[genscripter]

I don't know. Milling new heads and pre-cups sounds like a lot more work than just getting a set of LRR tires, driving slower, installing a overdrive, and swapping for a better gear ratio.


The turbo will increase the proportion of fuel being burned, but you will need to turn up the fuel ratio to get the turbo to spool anyway. It's kind of a catch 22.

Overall, yes, a turbo will give you better fuel mileage, but only if you resist the urge to ham on it all the time and you rig it up to spool up earlier than most IDI turbos are designed to do. At regular flat highway speeds, it won't contribute much boost to make a noticeable difference in MPG. These turbos are designed to max out from 11-15 psi, and usually they don't provide any action until you are under load.

 

[DarkDownDeep]

On that note, what rpm does the idi get the best economy?

 

[Thewespaul]

I disagree that turbos will add efficiency, especially running empty. You are using energy to get the turbo to spool back up every time you slow down and that is a parasitic draw any way you look at it. The only way I could see it adding efficiency is if you were towing a lot on highway stretches, instead of having the foot to the floor all the time you have the extra power with the turbo and you aren’t having to respool the turbo very often that way.

As far as what you can do for getting the most efficient setup, invest in a new fuel system and buy a timing meter, conventionally 8.5* is what people set the timing at, but I would wager a bit more retarded would net some better economy, although sacrifice some performance.

 

[gandalf]

My understanding is that you get the best economy running the engine at 2000-2200 RPM. On my truck, '92 7.3 NA, 4.11 gears, dually CC, that puts me at 60-65 miles speed.

 

[Hydro-idi]

Don’t mess with the compression. Does a turbo increase fuel economy? Maybe but probably not much, because instead of going 30mph up a steep hill naturally aspirated, you’ll be going around 50-60mph instead with a turbo lol. And you’ll probably be running engine wide open in both cases if your towing. You’ll pick up mph, not mpg.
I think a turbo will make a diesel much more efficient, and increase power output by around 30%. A diesel engine with a turbo will be able to utilize fuel output much more efficiently, instead of blowing it out the tailpipe in the form of black smoke as a N/A engine is more likely to do.

 

[chillman88]

I think a turbo will make a diesel much more efficient, and increase power output by around 30%. A diesel engine with a turbo will be able to utilize fuel output much more efficiently, instead of blowing it out the tailpipe in the form of black smoke as a N/A engine is more likely to do.

I think this is the key here. If you can manage to drive slow still, you might gain 1-2mpg as a result of increased EFFICIENCY.

As everyone else here has already said though, once you go from NA to Turbo you'll start keeping up with traffic and there goes your MPG because you'll be USING the power which means using more FUEL too.

 

[genscripter]

I think this is the key here. If you can manage to drive slow still, you might gain 1-2mpg as a result of increased EFFICIENCY.

As everyone else here has already said though, once you go from NA to Turbo you'll start keeping up with traffic and there goes your MPG because you'll be USING the power which means using more FUEL too.

^^^^^ that's the truth. I did the turbo thing because I wanted to get better MPG, but my turbo converted my slow old van to a vehicle that keeps up with California traffic. There is no way I'm going back to the days of creeping up California mountains at 45mph. 75mph all the way, and that ate up my MPG.

 

[david85]

In a word. No.

Fuel savings will be most noticeable at higher engine loading though. For cruising around empty at 55 MPH, you don't even need a turbo...but it sure is nice to have it, hehe.

 

[Macrobb]

For better fuel economy, new IP and injectors, better timing, and crank the fuel Limit screw down a little. Less power, better economy, especially unloaded.
A Turbo nets you power, without sacrificing economy much, and will let you go faster under a given load.

 

[icanfixall]

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.

 

[genscripter]

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.

This is probably the only way a turbo can contribute to better MPG. Either at high speeds with a low gear ratio, or if you are hauling stuff. But for regular highway driving, you can't get the turbo on these IDI's to spool up enough to warrant the installation.

 

[Thewespaul]

Our shop truck will sit at 7psi cruising around 70 mph