ratman

if you had to do it again, would you still go with the alum hull vs fiberglass? what do your engine trans combos weigh? great seeing more diesel projects being built. i hope to do one next year after i sell one of my properties...rm

pstorti

Hi Joe, I already have through hull exhaust, does have 2 90's an internal and external flappers, its underwater at idle speeds so can't be to careful, when I went from thru prop to thru hull helped planing speed, mpg, and top end, had to put some mufflers on though the diesels don't make an enjoyable sound.

Here is part of the install requirements for the Cummins 6.7, they require an 8" exhaust if it is wet! That is huge, only on the 550hp version though the 480 can use 6" wet exhaust.

Engine Model QSB6.7550
After-cooling SW
HP SAE(Metric) 542/(550)
Rated RPM 3300
Usage Rating** HO
Wet Exhaust Size Min 8"
Dry Exhaust Size Min. 4"
Sea Water Supply Min. 2"
Fuel Supply/Return Min. I.D. #8 JIC 37 Flare #8 JIC 37 Flare
Air Inlet Area Per Engine (Sq.In.) 294
Battery Size Min. CCA/MCA (12VDC) 1100/1375
Battery Size Min. CCA/MCA (24VDC) 550/688
Battery Cable Size Min. #00

HabanaJoe

Hi how are you sounds are if the boat is running well!

I'm not talking about after the turbo, I'm talking about before turbo on exh and after turbo on intake. Your exhaust pipe sizes because they are so short really don't affect much, yes the bigger & straighter the better but more in general about making a engine run better. When you have to add more aftercooling because intake temps are too high look at why, if you open things up boost will drop as boost drop temps go down hence aftercooler becomes more effective as it has less heat going through it.

You would be surprised how much heat the aftercooler can generate because of restriction, lower that and the temp drops.

So I'm saying nothing in particular just remember basics before you start changing things, examine root causes to the problems first.

pstorti

Ok I get it, not much I can do about those parts of the system, the turbo is bolted to the exhaust manifold, and after the turbo to the aftercooler on the intake side there is only a short pipe with a 90 in it, it would take major $$$ I think to improve on either of those systems. I will have to yank the intake pipe off at some point and see if it would be easy to make a better one. I have gotten a lot better performance out of them by making adjustments to the aneroid, and improving fuel delivery using a lift pump.

HabanaJoe

Lift pump makes a big difference, no matter how you look at it the fill port on a plunger (your engines are mechanical pumps right?) is only open for so long time wise, the faster the engine turns the shorter the time it's open.

That is why when you look at mechanical fuel injection pumps they have a limit as to how fast the engine will turn. The governor has zero effect on that meaning if you bypass, lockout or remove the governor link to the fuel rack the faster you turn the pump on the stand the fuel delivery will start going down past a certain point and continue downward. That is why the engine goes flat, nothing to do with turbos, governors or anything other than fluid dynamics to fill the plunger cavity - it simple can not produce more power past that point and in fact the Hp drops like a rock.

By adding an extra or higher pressure fuel pump you can keep the fuel galley full of fuel and increse the pressure slightly. The next thing is to increase the spring pressure on the fuel pump return fitting or restrict it, the more spring pressure the higher the fuel pressure before it allows return, that will also increase HP higher up in the rpm range without messing with anything internally.

Do you have any knowledge of the older Detroit Diesel 2 stroke engines? The cylinder head had a numbered fuel restriction fitting on the fuel return galleries. If you just had an engine rebuilt and it won't start for anything you always checked to make sure the restrictor fitting was in, without it you had almost zero fuel pressure in the galley around the injectors - no pressure no run! As the DD went into higher HP models the restrictor sizes would change as well because the higher HP engines needed more galley (fuel rail) pressure.

Didn't mean to digress just it's funny how all things new or old are still based around the same principles and if you understand them you can make anything run better and better.

dlange

I always enjoyed the "vise grip " technique on our 6-v92t
Detroit. Increase back pressure to injectors and hazaa. More power!

HabanaJoe

That's what I like to hear - Bravo!

pstorti

I have one of these 95GPH at 15psi, my engines only use 16-17GPH each wide open, picked up 2 mph installing this with no other mods.

http://www.fassride.com/shop/fuel-ai...ium-series.php

I can change the spring on the lift pump to present higher fuel pressure to the mechanical pumps on the engines, do you think it would make more power doing that? The fuel line feeds into the engine fuel filter which has a little plunger on it to prime them when you change filters the lift pump makes this obsolete and you actually cannot even push the plunger down it is rock solid now. The excess fuel leaves the filter housing passes through a cooler and goes back to the tank. I hadn't thought about increasing the pressure any more we (me and the FASS tech) were concerned we would have to much pressure at 15psi I actually have a spring that gives lower pressure but they ran fine at 15 so I left it alone.

In my case would restricting the return lines be needed, if so how do you do it? The lift pump has its own return also for excess fuel not taken by the engines.

I am also thinking about putting a plate under the wastegate diaphragm (2-3mm) to increase the pressure required to open it and let the engines make a little more boost at WOT, not sure if the injection pump will keep up though, I am still under warranty though so I haven't messed with the max speed adj screw or the full load set screw ... yet.

HabanaJoe

Can you draw a diagram of how all your lines fit together, I hear what you say, but can't see it in my mind?

Boatlesss

how can you afford to use the xpower drive for an application with a diesel? seems the cost is close to 90K when the alternatives are less than half of that and are proven to last