ENGINE QUESTION FOR MECHANICS

[nabeelah]

Comparing two engines & out of interest only wanted to know why some engines have larger displacement and a bit lower hp while some with smaller displacement have higher hp.
In line 6 ,14L MTU series 60 825hp @2300rpm vs soon to released 16.4L Scania Euro 5 V8 800hp 2200rpm.
Apart from the swept volumes,will there be any significant performance issues?

[Big Jay]

Frank (seapower) will prob chime in here and blow me out of the water but Diesels are highly variable in that dept.

Many of the motors are the same displacement but if the fuel pump is tweaked/changed or the boost is increased they get more HP out of the same motor. Reason for the difference is hull ratings. Helps getting around making different motors for every boat. Also gives the owner options.

Some of them did have problems in the higher HP models. CAT was one of them for a while. The older 3116's had problems in the higher HP models as a result of poor head design.

Combination of guys overloading the boats, running them to the pins, and not having them propped right was leading to dropped valves and a whole host of issues.

Of course maintenance is key. I don't know much about your specific motors but I do know that you should do your research on the good ol WWW to find out more info.

Hope I was of help.

[nabeelah]

Thanks Big Jay,
Waiting for Frank to jump in!!
The scania will be Tier 4 and injectors are the XPI developed with cummins.Much lighter V8 at 1300kgs (previously 1550kg)
I have attached the prototype pics below.

[Big Jay]

After reading your initial question I'd also add that stroke and bore also has a lot to do with it. Some motors are bored more than stroked and vice versa. That has to do with efficiency, strain on the lower end, etc.

There's all a bunch of different factors. You have to remember in Marine applications there's a good deal of variables such as peripheral cooling equipment, hydraulic system pumps, etc. Many times smaller displacement = smaller motor which allows for more peripheral gear. Thus, you fit the same HP into a tighter package.

[blackwell50]

A diesel engines horsepower and torgue are determined by the injectors,turbos and fuel pumps.A large displacement low horsepower engine will outlast a higher uotput engine of the same displacement.Lower horsepower models are commercial duty rated engines for use in application where economy and longevity are critical.These are usually used in commercial vessels that need to make a profit.High hp models are used in yachts and the like where speed is wanted and fuel comsumption is not an issue.For example a cat 3406B makes 425 hp vs a 3406E makes 800 hp.The difference is the injector size,boost levels and fuel system control.the b series is a mechanical engine while the e is electrinically controled.Any more questions will be happily answered.Also block configuration comes into play as well.An inline six typically has a longer stroke than a V8.A longer stroke tends to make alot more torque than a short stroke engine.

[Nomad]

Comparing two engines & out of interest only wanted to know why some engines have larger displacement and a bit lower hp while some with smaller displacement have higher hp.
In line 6 ,14L MTU series 60 825hp @2300rpm vs soon to released 16.4L Scania Euro 5 V8 800hp 2200rpm.
Apart from the swept volumes,will there be any significant performance issues?

Except for efficiency differences (which, among modern diesels are not nearly as great as the variation you have noticed between hp/displacement), hp is a function of fuel burn, and fuel burn is a function of (besides displacement) rpm's and compression -- including boost. So, as a substitute for displacement higher rpms and more boost, and get a less expensive, but generally less durable, engine.