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  1. #41
    Platinum Member Platinum Member Jassman's Avatar
    Join Date
    Oct 2000
    Quote Originally Posted by HabanaJoe View Post

    Thank you for the report, I figured as much.

    I find it funny how all these stories of Duramax greatest, big Hp and long life come to the surface everytime the word "diesel" pops up!

    How did these stories start, where do people hear about these? Ray from Raylar came on the other diesel thread and said (I'm not quoting him here), that it's going rather slow with Duramax developement, not as planned.

    I know everyone just repeats what they read, but how/where do these "stories" get out there?

    Advice - Anyone that wants to really do a diesel project use the Cummins B as a base engine, you'll go further quicker & cheaper!
    Why the Cummins B vs the Yanmar 480hp version. I did a 43 Nortech with those motors and ASD-8's. Boat was great and did a top end of 74.8. I liked the boat but had a higher top end number in mind before the build, but reading some of the other top end numbers, I believe Nortech did a great job. The boat that I have now is a lighter 43 Nortech vacuum bagged version w/700's/6's. Would this lighter hull by about 800lbs (approx now13500) given any significant benifit to the top end numbers. Also why so down on the Duramax diesel applications. Lighter, more reving closer to a BB gas, and I can get 3 in the bilge vs 2 of the straight 6'rs. Thanks for a great and very interesting thread. Jeff

  2. #42
    My Boats:
    32 SeaCraft
    Join Date
    Jun 2004
    Freehold, NJ
    Jassman, sorry again about your Dad, lost my father-inlaw a year ago last week. My wife was really upset last week and the pain does lessen but you never forget and you don't want to!

    Diesels - The Duramax, I think it's a great engine as is the Navistar. The problem lies with the fact that people don't really understand the stress of a diesel compared to a BB. They think they can make a little, very light built diesel run like a big bore Cat on steroids. I've have tried, sunk many dollars into the little V-8 diesels, had corporate backing (Navistar) and we couldn't do it to make it better than a gas engine.

    Example (I like to tell long stories): the crank on a Duramax is similar to a gas engine, two rods per journal, the fact that the journal is now twice as wide as an in-line to support the load is bad. Also, look at number of main bearings, 5 on a V8, 7 on an in-line.

    A big Hp gas engine (my numbers could be off here) with a blower runs a static compression of say 8:1 with 20lbs of boost? The Hi-Hp Duramx we're talking about is 11:1 compression and runs in excess of 50 lbs of boost (our race B's hit 80 lbs of boost), you could snap the crank in half, these are Top Fuel kinds of loads. If your gas engines can't take those loads than a Duramax will certainly not either.

    Also, why can't a diesel spin real fast? A gas engine can get Hi rpm's from it because you put a volitale mixture into the cylinders and then send a spark at the speed of light to ignite that. The more fuel & the better control over spark - the faster in goes. The diesel as you know has to fire a fuel load into the cylinder and that fuel is pushed by hydraulics, which can't compete with light speed. So, no matter what, it is very hard to get all the fuel into the cylinder at one time so it ignites and does not come in too early to dentonate or end too late in the cycle to be wasted. All the advancements in electronics have helped greatly but it still takes time to inject fuel where as a gas engine already has it in the cylinder. The faster it spins the less cronological time you have to inject fuel.

    So, in racing diesels I've seen two approaches to higher rpm's and have only tested one of them, some people use both. Use 2 fuel injection pumps with two injectors (solid heads no water passages) or put a fuel mixture into the air stream as a pre-igniter for the injected load. The later gives higher-rpms but detonates like hell. The first - impractical but costs are high and you would have to cast new heads with water passages in them for production engines.

    Again - the Duramax is a great engine but will not be better than a gas engine if you crank the hell out of it.

    My reference to the "B" was if you wanted to make a Hi-performance engine I think the "B" is a better place to start. From a stock stand point to put in a boat, I don't think it makes much difference. I like the "B" 4 valve cylinder heads better and think you could flow more air with them than a Yanmar just buy looking at them - only an opinion not fact based.

    Also, Nortech with what they did with the Yanmars and Arneson's - BRAVO!!! A Great job, I commend them.

    I think your asking an opinion question about weight verus speed? Lighter should be faster, but I think it's balance with the added weight of diesels. Also, remember in rough numbers diesel weighs 7 lbs gallon and gas weighs 6 lbs per gallon so if you carry 150 gallons you added 150 lbs to the boats as well. I also think it's prop speed, I debate this with RIK but he is right, there are trade offs to keep a good cruise, stay on plane etc verus balls out racing? I think another factor is strake width the Buzzi boats were designed to carry a heavy load, most boats are not designed to carry that extra weight???

    I have a question for you, I don't see the sense in a what a few miles an hour makes to a V-bottom that is going across a inland style lake or a down the river??? No matter what, a little cat with some outboards for the most part will come charging by you. The reason I got into this as a child was -

    quick story - back in the early 70's when they raced in Point Pleasant I took out my dad's Chris Craft dory and went right out onto the race course and raced around with Billy Martin and those guys after the race started - I know crazy, unsafe, I was 12 years old - but I was hooked!!!! My father went to beat my ass silly and then started laughing and said well your safe, give me the keys & your a dumb F**king kid!

    Back to above, the ocean equalizes everything and a few mph's don't matter so much when your flying through the air. My attraction to this sport was racing in the open ocean, mile after mile, I don't see what difference 75 mph or 80 mph really makes when running up the river but for a short drag race? I have the luxury of being in NJ so I have an ocean. I used to challange everybody in our Super Hero 34 diesel to race me from Sandy Hook to AC, never lost that race (never went past Belmar and they refuse to play anymore) and they could smoke me in the bay all day!!!!

    Anyway, that's why we have NHRA, NASCAR, CART & SCORE something for everyone!

    Joe Gere
    Last edited by HabanaJoe; 02-12-2008 at 11:27 AM.

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