Can I Turbo a Stock Diesel?

[newhaul]

I would actually have to go against most of the other posters and say no you can't turbo the m18.
The exhaust manifold is the main reason for my saying no. It is a fully water jacketed manifold which means you have no place to get the exhaust to power the turbo. It is entirely immersed in water. Sounds to me you may need to invest in ( a much cheaper alternative ) replacing the prop.

[kmacdonald]

Originally Posted by newhaul

I would actually have to go against most of the other posters and say no you can't turbo the m18.
The exhaust manifold is the main reason for my saying no. It is a fully water jacketed manifold which means you have no place to get the exhaust to power the turbo. It is entirely immersed in water. Sounds to me you may need to invest in ( a much cheaper alternative ) replacing the prop.

Oh darn, I wanted to sink 20 or 30K boat bucks on it.

[alaskaflyfish]

Aircraft owners who brought their aircraft into my shop for maintenance used to call their turbo chargers "trouble chargers" because of the high cost of extra maintenance and painful cost of replacement parts. Unless you plan on towing water skiers or sailing a high altitude mountain lake I just don't see the cost benefit on a average 27ft boat. An outboard motor transom bracket with you dinghy motor attached would be an easier way to get more thrust if you need it.

[shakey doug]

Has anyone considered exhaust pulsing?

[newhaul]

Originally Posted by shakey doug

Has anyone considered exhaust pulsing?

mentioned in last paragraph of post #2

[Sailmonkey]

Originally Posted by shakey doug

Has anyone considered exhaust pulsing?

It’s been mentioned. And while two cylinders are not ideal, it can still work...sort of.

[Redpcx]

I have a couple points...
It takes more air AND MORE FUEL to produce more power. Make sure your injectors and pump will also provide provide more fuel. ( hint: are these parts also used in a larger hp engine? This would be a sure sign of excess capacity.
2. Does you engine run to redline? If not, you are NOT getting your installed HP. If not, less pitch in your propeller might be a fix. If you ARE running full speed, your prop might be under pitched. If you burn less than design fuel rate, you are NOT using your available hp. More Hp will not be used, at the same rpm. You are going to change the prop if you put a turbo on the engine,. Change it first, as MANY sailboats are overengined and underpropped.

[Lepke]

Adding a turbo to a natural engine can double the hp. Don't forget the bigger shaft, bearings, etc. Then you get to buy 3x the fuel and shorter overhaul intervals for what 1-2 knots in a sailboat.
The solution to a faster speed is a longer boat with a higher hull speed.
I use to ride high speed, twin screw, steam powered ships with 60,000 hp. 30,000 hp would get us 27 knots. It took the other 30,000 to make 7 knots more. Fuel was figured in tons/day. Your parents tax dollars at work.

[Meacenas]

As a lifelong car enthusiast and mechanic, I have to weigh in here. Two things come to mind, the first is the question..why would you spend more than the price of a good higher horsepower rebuilt diesel for just a few more horsepower? The idea that you are just going to bolt on a turbo and go is not all simple. You need so many associated additional parts that the cost of the turbo with needed parts like a custom made intake/exhaust, custom brackets to hold it all, custom oiling for the turbo, new injectors to match the high end of the fuel curve, ignition work, far outweighs the price of your little engine. Even assuming that the basic engine has a strong enough bottom end and in overall good enough condition to handle a few pounds of boost... you are talking about starting at 5 to 8 psi of boost, which given the size of the engine, would definitely strain the whole reciprocating assembly.
The second item..why don't you take the selling price of the engine you have, the turbo money, (min $800.00) the money you are going to spend on all the peripheral parts to make it work ( another 5-800 bucks) and just buy a higher HP engine?

[Dockhead]

For the record, these comments may be more or less accurate concerning spark-ignition (gasoline / petrol) engines, but not for diesels.

There is no such thing as "mixture" in a diesel - diesels breathe air and the fuel is not mixed. No such thing as a "lean mixture" in a diesel.

Turbo diesels do not burn 3 or 4 times as much fuel as NAs. They are on the contrary somewhat more efficient, and the more boost you run, the more efficient they get.

Turbo diesels do not need a lower compression ratio. They don't suffer from premature detonation.

Turbo diesels do not, indeed, live less long than NAs. On the contrary, they are lower stress (for a given power output) than NAs because of the reduction of difference of pressure between intake and exhaust which A64 referred to.

For sailboats, turbo diesels have two overwhelming advantages :

1. They can be much lighter and more compact for a given power output. Weight is the enemy of sailing performance.

2. They have a wider range of variation of power output, so they are better suited for being run at low power for long periods. For example - a 100 horsepower, 2000 cc turbo diesel is far happier running at 20 horsepower (typical good weather slow cruise speed, or motor sailing) compared to an 88 horsepower, 4000 cc engine - putting out only 20 horsepower, the 4000 cc engine will run cold combustion chambers and be at risk of bore polishing.


Turbo diesels, on top of all of this, are much smoother and quieter than NAs.

Turbo diesels have so many advantages, that NAs are almost not made any more. All these advantages cost exactly ONE (count em, 1) extra moving part. You certainly can't buy a diesel car or truck without a turbo, and all large diesels are turbocharged.

I wouldn't have a NA diesel on a sailboat, personally.

Now for all of that, and I'm sorry to say this to the OP, but you can't just buy a turbocharger and slap it on and hope for good results. It does take some engineering to do it right. You would need a special exhaust manifold, you'd have to reprofile the injection pump (and it will need a boost compensator), and the whole system would need to be designed by an engineer. You'd be better off selling the existing engine and buying a more powerful one.

[a64pilot]

Only thing I would add, is talk to the guys who run the big Diesels in boats, and ask them about turbos and expected engine life.
The turbo motors on average have about half the life of a NA motor, reason is cause they are usually run on boost, and run hard. There ain’t no such thing as a free lunch, and you get all that extra power, at a price. The price is accelerated wear. Talk to the people who run the big DD’s.
However as a general rule if you don’t use much of that power a turbo adds, a turbo motor can actually outlast its NA brother, but then of course you have to answer the question of what the turbo is for if your not using it.
Turbos do add quite a bit to maintenance, and if they are maintained, they will be very reliable, but if you don’t keep them clean and overhaul them on schedule, and the center section bearing wears out, then the compressor and maybe the turbine will contact the housing, and your buying a new one, not overhauling the old one.

I see the appeal of both turbos and common rail, but I want something that I can fix with a screwdriver and a hammer, the simpler, the better. My ideal is something like a Gardner, but I don’t have nearly enough boat for one.

[kmacdonald]

When you get over about 50HP per liter displacement you give up engine life unless of course you aren't using the extra HP. All the diesel manufacturers have performance ratings for their engines. Deere uses M1 thru M5. M1 is for continuous duty and M5 is for pleasure use only at less than a thousand hours a year and less than 35% load factor. M1 is unrestricted--------WOT 100% of time. A turbo diesel is a little more efficient, a fresh water after cooled turbo is more efficient, and a raw water after cooled is even more efficient. Each time you step up in efficiency you increase maintenance are reduce engine life. A larger displacement NA diesel will DRAMATICALLY outlast a small displacement tubocharged, after cooled diesel of the same HP. Don't take my word for it, read what a Cummins Dealer has to say about it here: https://www.sbmar.com/articles/engin...ngine-loading/
https://www.sbmar.com/articles/engine-life/
There is a wealth of FACTUAL information on his site.

[kmacdonald]

I would guess that more than 95% of the diesels in pleasure boats die from catastrophic events caused by lack of maintenance and poorly designed exhaust systems. A lot, if not most, exhaust manifolds, elbows, combo manifold-heat exchanger are not fail safe and destroy the engine if they fail catastrophically. The new exhaust manifold-heat exchanger combos are so expensive that they certainly won't get replaced pro-actively so I would guess the trend will get even worse. The NA vs turbo may be a mute subject.

[Lepke]

My engine experience is mostly commercial engines. Lots of Detroits, but Cat, Cummings, FM and others. My boat 671 DDs are rated about 200 hp. But the same block is rated to 450+ hp with turbos. The turbo engine has lower compression pistons. My engines already did 20,000+ hours before I rebuilt them. They should get another 20,000+ hours (long after I'm dead). Me, running the turbo version usually get 7,000 hours. Most operators 3,000+. My DDs can use about 4.5 gallons/hour at their continuous rating. The turbo engine can use 30 gallons/hour.
That's just one example that I can match with DDs printed material.
The engine longevity killer is exhaust gas temperatures. People running recreational and commercial turbo engines wot or close to it, greatly reduce the engine life between rebuilds. And I've owned and rebuilt enough engines to see this many times.
There are a lot of turbo engines because there is a demand to fit more hp in a smaller space. I remember when a big tug engine was 1200 hp. Now the same tug will have 4000 hp. You can't fit in a natural. The frequent overhaul cycle is just a cost of business.

[Dockhead]

Originally Posted by Lepke

My engine experience is mostly commercial engines. Lots of Detroits, but Cat, Cummings, FM and others. My boat 671 DDs are rated about 200 hp. But the same block is rated to 450+ hp with turbos. The turbo engine has lower compression pistons. My engines already did 20,000+ hours before I rebuilt them. They should get another 20,000+ hours (long after I'm dead). Me, running the turbo version usually get 7,000 hours. Most operators 3,000+. My DDs can use about 4.5 gallons/hour at their continuous rating. The turbo engine can use 30 gallons/hour.
That's just one example that I can match with DDs printed material.
The engine longevity killer is exhaust gas temperatures. People running recreational and commercial turbo engines wot or close to it, greatly reduce the engine life between rebuilds. And I've owned and rebuilt enough engines to see this many times.
There are a lot of turbo engines because there is a demand to fit more hp in a smaller space. I remember when a big tug engine was 1200 hp. Now the same tug will have 4000 hp. You can't fit in a natural. The frequent overhaul cycle is just a cost of business.

For those who don't know what Lepke means with "DD" -- it's Detroit Diesel, a peculiar and interesting type of diesel engine. A TWO STROKE engine which is charged by a mechanical supercharger. The turbo versions had both mechanical supercharger and also a turbocharger. 1/7 the life (3000 hours) for turbo version vs. 20,000 hours for a non-turbo (I won't say "naturally aspirated" because all DD's have the mechanical supercharger) sounds bizarre to me, but I have to take Lepke's word for it because I don't have any practical experience with those engines. Greatly increased fuel consumption is also bizarre -- normal diesels certainly don't work that way -- but I supposed Lepke knows Detroit Diesels a lot better than the rest of us.