Question for you Detroit Guys

[Avenger]

I don't have the exact spec but,

HP= (torque X RPM)/5252 so if my H.S. algebra still works correctly: Torque = (5252 X HP)/RPM

Using the standard numbers: Torque = (5252 X 485)/ 2300 (I'm assuming 2300 RPM for a Detroit pleasurecraft rating)

Torque = 1107 lb/ft.... approximately.

Now let's sit back and watch the engineers beat me up.

 

[neosin]

I don't think anyone doubts the fact that you COULD produce 1700HP from an engine configured LIKE an 8V71. But it wouldn't be a DD 8v anymore because every part in it would be different. It's kind of like saying that all top fuelers use Mopar Hemi's to produce their 5000+ HP. Yes, the engines are BASED on the Mopar hemi design but that's it.

Heck, formula one cars currently use 183 CID, naturally aspirated engines that weigh around 200 lbs and produce 800+ HP. But you could stick 4 of 'em in there, have 3200HP and weigh less than a third of what ONE dd weighs and they would occupy less space! Of course they spin 19000+ RPM to produce that power which might be a bit "buzzy" in a boat!

Based on my experience with building gas engines (though NONE with diesels) I'd expect to see 20 percent more power and efficiency in a DD if you just blueprinted it. This, frankly, seems to me to be about the limit in what is reasonable for these old motors. Going beyond this means essentially redesigning the thing.

LOL you got that right... sound like beez in the engine room hahah

 

[neosin]

That's nice, but one must note that RPM is the killer of efficiency. Power output on engines is close to linear, but the losses due to friction are exponential. This is one reason the low RPM ship engines (150rpm max) get close to that 50% thermal efficiency.

Making lots of power is one thing; making lots of power efficiently is another. A turbo shaft can make a ton of power and weighs very little but it's low compression ratio gobbles fuel.

Your thinking of one big engine that uses weight and balance to make it's power. No way do small boats have the room nor want to use the whole salon as an engine room. So the topic i was on was better power out of smaller engines that would last... Everyone kinda jumped on the fact i said a DD 8v71 could make 1700hp I should of said 1700FPT, That is a little easier to understand in a diesel seeing how horsepower in a diesel is only relative to the speed you want to hold. Anyways...

The engine is an airpump, your looking at a HUGE engine and trying to compare it to a small little dd, I was really just saying these DD's could be rebuilt to be better without giving up life. a DD 8v71N want's to run at full rpm, 2350. That is where it would like to live it's whole life, that is the point it can pump max air. (around that rpm maybe not right at it) My point is you can make a 8v71N a better airpump if you could build it to handle a little more RPM without causing more wear, You'd have to do that with better rings, oils, lighter parts and better balance. Thats all...


500+ cubes making 350hp... I laugh in the face of inefficiency and only ask can we rebuild out DDs to do a little better job? Dare i tell the engineers of 1972 IT COULD BE BETTER! hahah...

 

[neosin]

Guys, I only wanted to know how much torque the 12v71 in the bird produce.

If i had to guess i'd say around 800-1000fp Not sure what the 12v's put out...
And you know us boat lovers have nothing better to do than talk about some wacky ideas! lol

 

[MarioG]

Mike, Can you really get around 20% more power and efficency out of an 871 by blueprinting?? would service life improve or degrade? What would be the ball park cost for the blueprinting assuming your going to overhaul anyways?

Hmm...

 

[67hat34c]

from mikes prior posts regarding balance and blueprinting, the engine would last longer. all you are doing is making it more perfect, no increase in compression or the other stuff that seems to make them wear out. Balanced motor is more smooth and blueprinting makes perfectly round holes and all the exact same size, reduce friction and vibration.

Well professor Mikep, did I get it right?

 

[Brian Degulis]

If only we could get the guys that actually build engines together with the guys that don't but have all the answers.

Brian

 

[krush]

Now let's sit back and watch the engineers beat me up.

but you're exactly correct!

If only we could get the guys that actually build engines together with the guys that don't but have all the answers.

Don't know who that was in reference to, but I've built/repaired/solved what shot rods thru blocks in/etc engines.

 

[Boss Lady]

when you figure out how much it would cost to blueprint a Detroit let me know. LOL I raced cars for quite a few years and I normally had to inspect 6-12 blocks before I found one that did not have core shift. Yes you can make an engine that is more reliable by polishing out stress risers, make the heads flow better, use better components etc. but I don't know how practical it would be to try and do all that to a detroit.

The engineers have their hands full trying to make an engine that complies with the new emmissions requirements, and no one is trying to improve the old detroits, no money in it.

I do know of a new engine that is being built, fewer moving parts, modular design, multi-fuel capable and very small size. A dozen Automotive Engineers have left the big three and signed on board this project, they already have a proven generator application that has already passed 2000 hours continuous duty. The engine has a very high weight to HP ratio and will be used in aviation as well. It is the first new design that will reach commercial service in decades. This is going to be a big rock in a small pond and is a disruptive technology. It will be used in every area from marine, industrial, automotive to aviation. The old piston engine is going to go the way of the dodo bird. I was shown the 800 HP version and it is small than a V6.

 

[neosin]

when you figure out how much it would cost to blueprint a Detroit let me know. LOL I raced cars for quite a few years and I normally had to inspect 6-12 blocks before I found one that did not have core shift. Yes you can make an engine that is more reliable by polishing out stress risers, make the heads flow better, use better components etc. but I don't know how practical it would be to try and do all that to a detroit.

The engineers have their hands full trying to make an engine that complies with the new emmissions requirements, and no one is trying to improve the old detroits, no money in it.

I do know of a new engine that is being built, fewer moving parts, modular design, multi-fuel capable and very small size. A dozen Automotive Engineers have left the big three and signed on board this project, they already have a proven generator application that has already passed 2000 hours continuous duty. The engine has a very high weight to HP ratio and will be used in aviation as well. It is the first new design that will reach commercial service in decades. This is going to be a big rock in a small pond and is a disruptive technology. It will be used in every area from marine, industrial, automotive to aviation. The old piston engine is going to go the way of the dodo bird. I was shown the 800 HP version and it is small than a V6.

Call me ... let's talk shop have a few questions, about to build out a queen bed and need to know some prices from ya

 

[krush]

That new engine, is it this one? http://www.angellabsllc.com/mytengine.html

 

[Trojan]

Why do all the big blocks only run 1/4 mile and then require a tear down? Same HP as a diesel! Why can't you run that BB HP on the street? Why are the BB boat racers always rebuilding. I also ran a fuel rail and still would never put a DD in it. Even if it was the same HP. Its all about weight, weight, and more weight. You can't stop a high speed train on a dime. You can't stop a heavy piston at high rpms for very long ether. All the balance in the world would not make the DD last much more. Obviously none of you super techs have never been in a engine plant and watched the amount of balancing that takes place before that everyday motor is built. All rods, cranks, pistons are balanced and matched. They don't teach common sense in collage. Book building engines doesn't work in the real world. The engineers at DD know more about diesel design and build than anyone on this net. HP at low RPM is the only way to go. Unless your a jet. LOL. Go reinvent the wheel and come back. LOL We also need a new mouse trap to. LOL.

BILL

If you dazzle them with briance, baffle them with BS
.

 

[Pascal]

how much power did they get out of the 671s ? smaller engine... 426cid yet didnt' they stretched it to more hp than the bigger 8v71 ? iknow some of high power versions dont last long but it really seem that there woudl have been room to develop the 8V71

 

[neosin]

I don't know who your really talking about but we get about 100 1/4 mile runs out of our 454s before we even need to do anything to the engine. Used to they had to make pistons heavy to take the stress of combustion. Now days we can make light weight pistons (very light weight) that are 3 times as strong.

Problem with old DD's is it was designed LONG ago... it would be worth rebuilding a DD to new specs and i'd think if you did you'd get one heck of an engine. They kept RPM down on the DD mainly because they didn't have cranks that would hold up, now we have far better metals to build cranks out of. There is no reason why a DD couldn't be rebuilt to get a red line of 3200rpm with a cruise rpm of 2300 - 2500rpm and last JUST as long. This can be done today, It would also be worth it to have some aluminum alloy heads CNC'ed for the beast and that would get you some weight savings and horse power right there with a few changes in the chambers. LOTs could be done with a good DD engine. These 2 strokers are great engines, I might start looking around for some DD 8v71Ns to rebuild... talking about it just makes me want to tinker...

Anyone know where I could get a cheap set of DD 8v71N low profiles? On the cheap!?

Why do all the big blocks only run 1/4 mile and then require a tear down? Same HP as a diesel! Why can't you run that BB HP on the street? Why are the BB boat racers always rebuilding. I also ran a fuel rail and still would never put a DD in it. Even if it was the same HP. Its all about weight, weight, and more weight. You can't stop a high speed train on a dime. You can't stop a heavy piston at high rpms for very long ether. All the balance in the world would not make the DD last much more. Obviously none of you super techs have never been in a engine plant and watched the amount of balancing that takes place before that everyday motor is built. All rods, cranks, pistons are balanced and matched. They don't teach common sense in collage. Book building engines doesn't work in the real world. The engineers at DD know more about diesel design and build than anyone on this net. HP at low RPM is the only way to go. Unless your a jet. LOL. Go reinvent the wheel and come back. LOL We also need a new mouse trap to. LOL.

BILL

If you dazzle them with briance, baffle them with BS
.

 

[Trojan]

You will never get a DD to run with any kind of aluminum head made on this planet. Aluminum will not take the heat or the cylinder pressure. They grow to much. If you didn't drop the pan on your rail between runs, you did not have it rung out and you were not a top dog. No offence meant. I could not afford it ether. I had enough trouble keeping 2 motors going for a switch out. I'm up on the front porch now, could not run with the BIG DOGS. So is my neighbor with his BB funny car. LOL You can make them run, but not for long. You need heavy iron......


BILL

 

[krush]

With the right alloy of aluminum and as long as there are enough bolts to keep it from wiggling to much one could put AL head on a detroit. The al conducts the heat away much quicker, but one has to make sure to not overheat it lol warpage.

Some engineers are idiots (like any profession), but there are also smart ones out there too. Who the hell do you think designed the detroits to begin with?

 

[Trojan]

The right alloy your butt. They were designed and built long before you were even thought of. If it were possible to do it today or yesterday don't you think they would have. Go back to school become a real engineer we have enough wannabees. You need to strike out on you own while you know everything. You were still peeing in your shorts long after the Detroit's were built. LOL Sorry kid didn't mean to ruffle your feathers. You need to gain about 45 years to catch up.
I'm just one of those dumb a-- engineers that everyone talks about and proud of it. Did time in 3 engine plants. Stop by the house and I will introduce you my neighbor who was an engineer for 43 years with DD. LOL
I would introduce you to Milt Cummings of Cummings Diesel a grand son but he passed away 5 years ago. There are lots of engineers on this forum that know more than you or me. Your not going to zoom all of us with your book talk. Keep those ideas coming though. Chuckle! We like everyone here.
BILL

 

[krush]

The 6600 is a totally new 90-degree V-8 diesel engine (I'll talk about how new in a minute), utilizing 4-valves per cylinder and Bosch common-rail direct injection. Also new is the use of aluminum cylinder heads, which incorporate hardened steel valve stem guides, valve seat inserts, and injector inserts. Six head bolts surround each cylinder, which provide more than enough clamping load.

http://www.thedieselpage.com/news5.htm

 

[luckydave215]

There's nothing wrong with aluminum heads on a diesel. All the modern european diesel cars have them. Get your head out of the sand, cast iron is antique just like DD's.

 

[Boss Lady]

Pleasure boats are severe duty applications. We apply continuous full loads at cruise speeds, on road vehicles only apply full loads on steep grades, those new fangled 4 strokers cannot dissipate the heat generated in the marine application as well as the old detroits yet. They also are paying their dues when it comes to new alloys and stuff for crankshafts. Saw a nice new Bubble boat with broken crankshafts only had 100 hours on the boat too. Sorry there Caterpillar but that was what was written on the engine badges. I am confident that the engineers will eventually get this right, but I am sticking with Detroit until they do.