Turbo vs. Naturally Aspirated

Me and two employees were talking today as we finished mowing a section of pipeline. The other two guys are running JD 5425's, turbocharged. My MF 583 is NA, which I like. I am of the opinion that a bigger, NA engine is cheaper, less things to go wrong, and would last longer. What's y'alls opinion?

John

I'll side with you.

sure a NA diesel wont go down because of a turbo failure, but they wont get the fuel economy either.

It's kind of an apples and oranges comparison for either, if designed properly. Often, when a company takes an existing NA engine, and puts a turbo on it, they beef it up along the way. Lower compression pistons - that might be a anodized and use plasma Keystone rings, bigger piston pins, piston-skirt oil cooling, stronger rods, bigger cooling system, etc. If done right, one can last just as long a the other. Turbo version does more work and is built to endure it. In fact, sometimes the turbo versions last longer because they don't suffer from being overheated and overfueled, and lugged, resulting in cracked heads. That is very common in some non-turbo automtotive diesels.

Now, is a NA cheaper? Well yeah, usually since it costs less to build. But many times a smaller turbo engine takes the place of a larger NA engine - so that cuts down somewhat on the price difference.

Less things to wrong? One less turbo on the NA, that's all (for many systems), and turbos can last a very long time.

Turbo diesel is the fuel efficiency leader. A particular advantage when idling and while under light load.

We used to pull the same load with two tractors--(4x16" plows) AC 185 301 cu. in. NA 6 cyl. AC 6060 200 cu. in. turbo 4 cyl. Basically the same engine with two cylinders chopped off. The 6060 had more power and burned less fuel.

Yeah, but many NAs have "gone down" because the the pump got turned up in efforts to make more power, and then exhaust port temps got so hot the heads cracked. Turbos can last three times what a typical engine lasts between rebuilds - if not abused. And, if you've got a tractor at high elevations, a turbo offers incredible gains. That's why they used to be called "altitude compensators."

Follow me OVERALL I aggree with jd. Just too many things favor the turbo today. Mainaly fuel economy. More air with the fuel just more work for the money.. But you bought what you wanted..I hope you the best but I have seen about 4 diffrent people try that pipeline bushhog contract and they just pay you enough to keep you broke unless you have reall good luck.
Again I hope it works out for you . you will find if you stay in it you will need a brown tree cutter type bushhog and a heavy tractor to hold up.

I think it depends on the particular engine and the application it's used in. There's lots of NA engines that get excellent fuel efficiency. A NA Perkins held the fuel economy record for years. Dave

The only absolute is, there are no absolutes.

There's all sorts of examples of N/A engines that last virtually forever, are extremely fuel efficient, and relatively inexpensive to build/re-build.

Likewise, there's all sorts of examples of Turbo-ed engines that sip fuel, make great power, last just as long as the N/A counterparts, and over the long haul, are cheap to produce and maintain.

That may explain why they still build examples of BOTH....

me persnally i would take a turbocharged engine over a NA any day. with a turbo you get more power and better power under a load because the cylinders are getting more air which also makes for a better fuel burn which in turn gives you better fuel economy. yes there is more things to go wrong but as long as you keep clean oil in the engine the turbo would out-last the engine.
thats just my opinion taken from experience and what i have worked on at school as far as turbocharged engines
M Puller

My personal opinion is that a NA engine of the same horsepower is more than likely to have lower lifecycle maintenance costs than a turboed machine of the same power for the simple reason is there are more things that can go wrong with a turboed engine and more parts to wear.

The operating proceedures are also different and if, for example, you don"t follow the correct shutdown proceedures you can cause the turbo to be damaged. It"s in the operator"s manual but I wonder how many people read that and follow it.

I recently bought a turboed machine and went down to NM from MT to pick it up. How many people know that when you trailer a machine with a turbo for any significant distance, you need to block the exhaust exit to keep the turbo from windmilling without lubrication?

I think there is a place for turboed machines where power to weight ratio is important.

Tractors don"t fit that requirement. Turbo"s are a cheap way to increase horsepower for a given engine size (displacment) but you have to engineer the whole machine for the increases loads and temperatures that boosting causes. This allows you to cheaply derate the engine for the lower power application or you can put different components in the derated engine if that"s cheaper. I think lower manufacturing cost is what drives the OEM"s to turbo"s. That"s why the manufacturers use them so extensively; it cheaper for them and can keep their initial cost low and thus price their machine more competively.

Opinions are like belly buttons; everybody has one. This is mine on this subject for whatever it"s worth.

A turbo engine will run smoother,use less fuel and run just as long,probably 3 times longer than the older engines.Plus put out more power.One of the reasons for the longer life is that better stuff is used to make valves in a turbo engine.
If you put an aftercooler on the engine it even runs better.Much smoother,burns less fuel and runs longer.
Buying a turbo is a lot cheaper than rebuilding an engine.The old Non Turbo engines smoked a lot,werent made of as good of stuff,and didnt put as much power out,and burned a lot more fuel.
Diesel engines have a long life,but the turbo helps them have a longer life as long as everything is maintained right.
They make new turbos nowdays that last a lot longer than the old ones did.I dont know if they make them for tractors or not,but they probably do.
If you want to get the most out of a turbo you need an aftercooler I think.Also an air to air aftercooler is even better.Plus the right injectors to set it up right.
Old 220 Cummins engines got about 3 miles to the gallon and smoked badly every time you pushed down the gas.Put a turbo and aftercooler on them and the right injectors and they got 5 or 6 miles to the gallon and only puffed smoke when you got down on them hard.Nowdays a N-14 450 HP can get 7 MPG and has air to air and a computer and doesnt smoke at all when you get down on it unless there is something else wrong,plus can go close to a million miles with the right maintenace.
Thats a huge improvement over a 220 that needed overhauling at about 150,000 miles.
Years ago,you could turn a 290 Horsepower Cummins into a 400 horsepower Cummins engine and get way better fuel mileage.The aftercooler helps almost as much as the turbo on fuel consumption.

Besides power-to-weight, altitude is big factor.

A non-turbo diesel loses 1% of it's power and efficiency for every 328 feet above sea level.

Take a car or tractor at 10,000 feet - and that's a 30% loss if no turbo is used. I.e. turns into a real dog.

A turbocharger DOEs raise the "effective compression ratio", so it is harder on engine parts. That being said, a decent one is meant to take it.

How many on these forums would rather have their Dodge-Cummins diesels without the turbos?

How many are complaining because the turbos (and sometimes intercooled) 5.9s did not last as long as they should have?

On the other hand, how many have complained about the non-turbo 6.2 diesels as being gutless and short-lived?

None of the above claims really has anything to do with having a turbo or not. It's about general engine design.

My 92 Dodge with the 5.9 (intercooled-turboed) has near 400K and never had a new turbo. My 94 Ford 7.3 IDI has 320K and also never had a turbo.
My 86 Blazer with a 6.2 has a Rajay turbo that's been on three engines so far - with a total of at least 400K miles and the turbo is still tight.

My point being, they usually last a long time if not abused.

Interesting discussion. I never made the connection about the altitide thing, though it's not a big deal here in the deep south. I know the turbo or actually supercharger made a huge difference on early warplanes.

The pipeline contract is actually going well. We have an ongoing spray / mow contract with this company, so it's mowed every 3 years. With a spraying in between, the biggest tree I've mowed yet was a 3" Chinese tallow (popcorn tree) We have a small batwing, a 7' Brown tree cutter and my tractor in front of a heavy 7' Bushog rotary cutter. We also have a three man crew cutting creeks, fences and wet spots we just can't cut with the tractors. My MF 583 is the lightest set-up and I have the best luck cutting wet areas. I back into a lot spots, always in 2wd. If I start spinning, I lock the diff for a second or two. If she dont pull through, I put her in 4wd and drive out forward. Aint been stuck yet! Thanks for all your input.

Not all engines have to beefed up to handle a turbo.

Jdemaris has it right, The whole reason back when turbos were new was to cope with high altitudes ... turbo diesel can in most cases make more power then a N/A, Reasoning behind this is power is created by adding fuel and air. With an N/A engine you can cram all the fuel into the world in the cylinders but without enough air your just going to melt your pistons and other components. With a turbo diesel you can at way more fuel then the N/A and have alot more HP.

It would be interesting to know if a turbo engine can use less fuel then the N/A and still make the same HP both engines with the same displacement. Maybe someone can get into the technicality of that

1. if you add a turbo to a given engine, you can usually count on a 20% increase in power.
2. The engine will burn cleaner under load.
3. The engine will need different pistons, chrome rings, oil cooled pistons, an intercooler, oil cooler, the turbo and oil lines.
4. The engine will need a system to dump boost when unloaded to prevent the creation of harmful nitrious oxides.
5. New John Deere tractors are now favoring smaller 4cly turbo engines over the larger 6cyl engines because of fuel costs.
6. Turbo engines are harder on oil and usually have bigger filters, oil capacity and more frequent oil change intervals.
7. Turboed engines will usually wear out faster than non turboed engines but do more work in smaller sizes.
8. NA engines are still favored in areas where support and parts are hard to get.

A turbo is a plain simple reliable device. Keep the oil clean and don't blip the throttle reving the engine just before shutdown.

Respectfully, you will notice I said "...of the same horsepower..." If th engine"s design point is at 5000 ft altitude, you can size the displacement for that design point and it will have a bunch more power at sea level.

But sure the altitude lapse rate for a turbo sized at sea level, in general, is less than that of an NA engine sized at sea level. In fact if the compressor outlet pressure is held constant by a control system, there is no altitude lapse.

The turbo makes some things easier for the manufacturer but the owner has to pay for the operating and maintenance costs and my point is the more moving parts, the more that can go wrong and it will happen on the owners nickle.

And I was refering to tractor applications not trucks. With trucks, power to weight is an important factor.