Question for Al, and other saavy mechanics/engineers

212rowboat

I'll add this to attempt to discourage you from attacking engine side:

one of the favorite mods novice rodders do to FI engines in hopes for significant gains is a bigger throttle body.. some bore out OE tb's and use larger blades... they then make claims such as 'added response to throttle' and 'higher top end'... and they are right... but, I could do the same thing with my right foot that they did boring out the tb- by just pressing it further down... on the extreme top end, they would have an edge over my foot because you can only go to wide open- and if their wide open is a larger intake, then they have more air being introduced into that FI engine than I possibly could, BUT, who runs the roads at wide open throttle all the time? and, they haven't taken into account the volume vs. velocity rational, which sometimes if not more often gives an advantage to the smaller opening that provides greater velocity, and therefor matches volume..

in your case, and after reading that link about your systems fuel delivery, there ARE several things you could do to increase power output.. you could use larger injection ports.. you could dial up higher pressures... you could increase the lift and duration of the fuel pumps camshaft lobe.. any and all of those would increase fuel delivery, and coupled with better air induction, give you more power, but only manifest by increased RPM's within a certain range.. unless the timing of the injection was altered (which it can be by working with the springs inside the injection valve), you'd be not increasing power per revolution much..

the trick that modern diesel trucks use to their advantage is electronic controlled injection, high pressure common rail fuel systems, and piezo injectors... put it in these terms:

a 6.0L powerstroke diesel uses heui injection off of a common low pressure rail.. they increase pressure at the point of injection.. the way to increase their power is to increase the air (to even the ratio) while spraying more juice.. a stock engine may be capable of producing 400# of torque... one with a worked fuel system may be capable of 900#... and after $$$$ investment.. adjusting fuel timing and duration is a computer function they have control over electronically- where as yours is mechanical and controlled by adjusting spring weights and tensions..

a 6.4L psd uses piezo injection off a common HIGH pressure rail... the injector has a tiny crystal in the piezo stack that shrinks instantly when hit with electricity, and allows fuel past.. the rail has a ridiculous amount of pressure on it, and the crystal responds stupid fast.. since the crystal can actuate so quickly, and taking advantage of the high pressures- MULTIPLE injections per injection stroke can take place... it can inject even ON the power stroke, adding fuel on the descending piston, further increasing the torque.. for very little investment $$, a programmer can be introduced to increase the output- stock = somewhere in the neighborhood of 600#tq, programmed and with no other significant alterations, you can bump one of those engines to over 1k#TQ.... I registered 1281# on mine, with a few other mods..

with your engine, and with the mods easily or rationally done, you stand to increase your power but only marginally - or about the equiv of the novice rodders who bore out a throttle body... what you CAN do, though, is increase the volume by dialing it up some (adjustment), not sweating the duration, and increasing the volume of air (larger turbo?), ALONG with making use of the added torque by re-gearing... re-gearing at the prop or through the gear box... you could find sufficient torque to turn a larger pitch or a higher ratio gear (lower numerically), and obtain speeds/performance at lower engine speed/less consumption... AND, have higher top end... but... you would also wreck your maneuvering speeds unless you feathered the controls/gearbox, which isn't good for them I'd wager.   you could spend some serious coin, though, and rework the entire fuel system at the point of delivery, implement an electronic control module such as a megasquirt, and see some serious gains, and only gained where you want them... i.e. not much more punch at idle or under 900ish RPM, but a serious and noticeable punch at around 1kRPM and exponential increases all the way to redline or black smoke- whichever comes first.. :-)  

TikiHut2

Love the outboard idea but (I think I just felt the earth shift on its axis) is RY actually endorsing a GAS engine instead of a diesel alternative??? 

212rowboat

....try this one...

i'd wager the prop is matched to the gearbox which is matched to expected engine production... I'd guess IF you increase the torque, you could safely increase the pitch of the prop or the gear ratio of the gear box, or both...

Michael T

Yeah Mike, the sound you hear IS RY finally realizing that a gasser with stern drives is getting real close to the "economy"of heavy diesels with fixed (V drives) and that if RY wants to actually have any real performance with his diesels he'll have to boost them which means he'll just have a "souped-up" real expensive, costlier to manitain and heavier rig that's more prone to fuel problems (crappy fuel) than the gassers with their ethanol woes. Too funny. Oh yeah, and the gassers have Axius too. Did the math - purchase price, weight, fuel issues, fixed drives, axius guidance, "mileage" differences, length of ownership and "miles per year" to break even when considering the new 360 - not even close. A friend who is looking at a new sea ray called me on my calculations, then did his own, He's ordered Mercury 8.2 Magnum H.O. ECTs.  In fact I get such good mileage with my Mercury gassers that I can afford to put my boats in the heated covered storage that they deserve! :-) MT