Common rail vs direct diesel injection

[benchmark]

A pal is at the junction of buying a new engine for his boat and the choices are a 200 hp direct injection or a 220 hp common rail engine . I know that common rail is newest technology with some advantages but with it also comes electronic and software potential complications which good old direct injection is free off. 200HP is adequate for his boat so if one should ignore the 20 ho difference, Which engine will you advise and why?

 

[Trundlebug]

Interesting question.

I don't have experience of common rail engines in marine applications, but I do have direct injected diesels.

I would say about direct injected:-

• They're noisier than common rail and indirect engines
• They're very efficient and reliable. Common rail are also efficient, probably more so
• Mine don't have glow plugs or preheat - one less thing to go wrong. Although I think that many common rail engines don't actually need them, they're for emissions purposes only.
• They're probably not as smooth or free revving as common rail

 

[petem]

Personally, I think there's something to be said for the older / simpler direct injection engines that any mechanic with a tool bag can fix.

And also, the quality / longevitiy / cost of the ancillaries, e.g. turbos, superchargers, coolers would be a major factor to me.

In other words, a good direct injection engine is better then a bad common rail one.

 

[[2068]]

Common rail has the advantages of less smoke on startup, smoother running, quieter, more efficient.
The electronic side of things is pretty reliable if installed properly, but if something does go wrong with the electronics, you'll need a dealer with a laptop.

 

[volvopaul]

A pal is at the junction of buying a new engine for his boat and the choices are a 200 hp direct injection or a 220 hp common rail engine . I know that common rail is newest technology with some advantages but with it also comes electronic and software potential complications which good old direct injection is free off. 200HP is adequate for his boat so if one should ignore the 20 ho difference, Which engine will you advise and why?

Give us the make of engines before I comment

 

[Portofino]

Too vague is the initial post .
Need to know the make(s) really and what type of boat to appreciate the anticipated use age .

The biggest general diff of CR vs none CR is the delicacy of the injector tips .

CR are hugely less forgiving due the massive pressures involved with water or any $hit in the fuel .
Of course with decent filtration that issues should not come to light .If it does ,a knackered tip then — bang rebuild .
If it’s modular then just that piston / cylinder liner .

Though having said that most small block ( 200 Hp ) are probably throw away single cast / bored blocks .Either way a lot of €_$_¥ or GBP

 

[jfm]

This discussion feels all mixed up.

Some people are comparing electronically governed injection with mechanically governed, it seems.

The difference between cr and unit injectors (if that's what you're asking - is it?) is the mechanism for creating pressurised fuel at the injector. Both then use electronically governed injection, identically.

The phrase direct injection normally refer to injectors that inject direct,y into the cylinder and not a pre chamber, but that has nothing to do with CR.

you need to clarify the Q, and frankly hold fire on the replies so far that seem to have made different assumptions about what you're asking.

 

[Portofino]

The injector tips indeed whole thing are different ,not identical or interchangeable .

As said more delicate and susceptible to $hit fuel ,—— erh in a boat - mm .

I know you don,t like folks reffering to “ Mr Google “ but sometimes he is more eloquent at getting facts across .:encouragement:

http://www.trucktrend.com/how-to/expert-advice/1211dp-why-diesel-fuel-injectors-fail/

 

[[2068]]

you need to clarify the Q, and frankly hold fire on the replies so far that seem to have made different assumptions about what you're asking.

Assumption is that one engine has marketing blurb about “Direct Injection” being the latest and greatest feature, e.g. Volvo Penta AD41 @ 200hp.

And the other engine is a common rail electronically controlled engine such as a Volvo Penta D4-220.

Exact makes and models of engines would help, though.

 

[volvopaul]

Personally, I think there's something to be said for the older / simpler direct injection engines that any mechanic with a tool bag can fix.

And also, the quality / longevitiy / cost of the ancillaries, e.g. turbos, superchargers, coolers would be a major factor to me.

In other words, a good direct injection engine is better then a bad common rail one.

The term , direct injection engine is where the engine design has a flat cylinder head and the combustion chamber is located in the top of the piston , the injector injects through the head into the chamber inside the top of the piston it has no glow plugs required to enable starting .

An indirect injection engine has a flat top piston which squeezes the compressed air into a chamber located inside the cylinder head , the injector nozzle injects it’s fuel into this , the glow plug tip is located in the combustion chamber area.

A common rail injection engine is a direct injection engine, as far as I know there are no indirect combustion common rail engines , over the years the indirect injection engines produces less cold start smoke but produces less power for the same given cubic capacity.

Back to the OP, what make of motor or motors is he looking at?

 

[benchmark]

The two engines he is considering are a new (old stock) Nanni Diesel 4.390 tdi which I have myself in my boat and I can vouch for but another salesman wants him to buy a T4.205 which is newest technology , common rail and all.

I just downloaded the brochure for the T4.205 and I can see that it is not even 220 hp as he was told but same 200 hp as the 4.390, ...another reason not to trust the salesman banter.

 

[rafiki_]

What is your friend looking to achieve? Does he need a fully emissions compliant engine? Probably not unless the boat is new? To install the CR engine, a you will need a very comprehensive wiring loom and local BUS unless the boat is already set up for a fully electronic engine. This alone will be more than enough to steer your friend to the D I engine.

 

[benchmark]

It’s an older boat from 2004ish and I don’t think emission compliance is a priority .
Whichever way I reckon he will have to rewire a fresh engine loom because his old motor was a Volvo and I doubt if the old loom will be compatible. He has been unfortunate with his old engine and has really been impressed by the ease in maintainace of mine ..hence why he is looking into the 2 above named models.

 

[Portofino]

Still a bit vague , will it be used daily or weekly like a fishing boat or left to rot for weeks on end in the winter ?
What s it in ?
A 20 ftr planer or 40:ft D speeder ??
Alarm bells ringing form me - re moded VW Tdi , or Toyota ! Road engine —- so called “ marinised

Try Perkins

 

[volvopaul]

The two engines he is considering are a new (old stock) Nanni Diesel 4.390 tdi which I have myself in my boat and I can vouch for but another salesman wants him to buy a T4.205 which is newest technology , common rail and all.

I just downloaded the brochure for the T4.205 and I can see that it is not even 220 hp as he was told but same 200 hp as the 4.390, ...another reason not to trust the salesman banter.

Toyota base unit then , plenty of posts on here regarding the woes of the Nanni / Toyota unit to do with overheating, failing injectors, pumps and total failure over the years of this great forum.

Why not consider low hp rated D4 or the later D3 which I’ve not heard any bad reports (yet) .
If he’s on a real tight budget you could speak to Mermaid or Lancing Marine about what they can offer, There is even JCB own Perkins copy engine that’s marinised .
Does it have to be new? What engine does he presently have?

 

[superheat6k]

For my ten pence worth, I will never own a boat with electronically controlled engines, also completely dependant upon the manfacturer's preferred service agent . Good old jerk pump injection everytime.

I will put up with a bit smoky and a bit less efficient for a bit more reliable and no limp home (at 4 knots) mode.

 

[benchmark]

Thanks for all the advice guys, I will show him this thread. :encouragement:

 

[[2068]]

For my ten pence worth, I will never own a boat with electronically controlled engines, also completely dependant upon the manfacturer's preferred service agent

The electronics are not service items: you can do pretty much everything else yourself.
I’m not convinced that the average forumite would have the skills or tools to overhaul a mechanical high pressure injection pump either.

 

[MapisM]

The difference between cr and unit injectors (if that's what you're asking - is it?) is the mechanism for creating pressurised fuel at the injector. Both then use electronically governed injection, identically.

The injector tips indeed whole thing are different ,not identical or interchangeable.

LOL, yeah, of course they are not interchangeable, Porto: not even the builders are the same - some adopted the CR, and others didn't. But all of them, bar none, are nowadays direct injection, and use high pressure, electronically controlled injectors which share the same type of complexities/needs.
As I understand it, in jfm explanation "identically" was referred to this logic, not to the part numbers...
And if so, I think he's spot on.

 

[QBhoy]

I’m on the fence about this one
Whilst liking the techy bit and gadgets permitted with modern common rail and ecu governed engines and he definite efficiency improvements...they are great when working but all the downsides are listed above.
Also on the other side of the fence...having maintained TAMD61 VPs for a decade and more...I simply can’t fault the simplicity and reliability of these.