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Michael T

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Dream_Inn

MT, kind of a neat site.  I have to say, I voted on the page that mine burned more (few others had as well).  & as far as 1500 rpm and 14mph, I'd have a hard time doing that! Might as well buy a trawler!!!  On a good day, I'll be right around 0.8mpg (maybe .9 with wind and tide).  I do have smarcraft connected and played a bit, but if you don't have the heart to ignore that fuel burn, then get a smaller boat!! (not geared to you MT)

Michael T

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[Deleted User]

Owning an express cruiser and going at displacement speed is like owning an airplane and taxiing to your destination! )

I will check out that site, it should be interesting.

Sea state affects consumption dramatically with my FV250 with a 5.0 VP GXi. I recently visited Catalina, 72 miles round trip. Heading there I had to beat hard against a 3 foot swell, a swift current and a 15 knot headwind, got 1.7 mpg. Coming back I literally surfed the swell with a tailwind and got 2.2 mpg. I burned 37 gallons total at a cost of $188. Average cruising speed was about 25 mph turning @ 4,000 rpm.

I have a Floscan fuel flow gauge, which is great for adjusting trim to get the best gph reading. They are pricey but well worth the money. When I go to the fuel dock, I know within .2 of a gallon exactly how much she needs to fill up. It's also good for peace of mind knowing what your likely range with a comfortable reserve will be.

Andy

Michael T

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212rowboat

MT- is your new ride going to be equipped with a catalytic converter?

If so, it will also be equipped with o2 sensors... that will make a TON of difference with economy, as the engine can accurately trim to stoichiometric air to fuel ratio of nearing perfect 14.7:1, and also advance timing (safely) to match conditions... that sensor that is missing from the pre catalytic converter FI engines should make a huge difference in economy, and a decent difference in power......

it's kind of a shame merc didn't introduce an o2 sensor prior to being required to w/ the cat- there is no better way to trim fuel than to sample exhaust... the 'puter can guess, which is precisely what it does using the upwind sensors (MAP, IAT, Coolant/engine temperature), but it can/could never find perfection as it can with a downwind o2 sensor, and trim the injection pulse to maintain it..

it's the precise equivalent of running a finely adjusted carb- you can have that rascal as finely tuned as you want it to be, even using a wide band o2 sensor on the manifold to monitor it- but as soon as environmental changes happen, that balance is gone long gone... an FI engine w/o an o2 sensor is only marginally better, but better none the less.. an FI engine that monitors and adjusts trims using the full loop (upwind pre-combustion, and downwind post combustion) of monitoring, and then with the capacity to alter the injection pulse to suite, BAM.... but, there is another BAM coming:

If the 'puter determines the conditions are stable enough, long enough, it will advance ignition timing to match.... if 'cold' timing is 10~15* advanced from TDC, and if the engine is stable running a controlled temperature, and the sensors aren't struggling on either extreme side of their parameters, AND the fuel trims are crossing zero lambda, here comes the other BAM....... BAM!! advancing timing to upwards of a safe 30~40* advanced- promoting longer and more complete burn on each and every power stroke, which translates to more sustainable torque being translated to the crank, which equals more horsepower just before it turns into wake...


this is a question for Al, maybe:

Mother Mopar, in her serendipitous fortune, discovered the advantages of spraying the back of a hot valve with fuel during injection did two things- it cooled the back of the valve, AND, it atomized the fuel into a fog... They would lead you to believe they did this on purpose, but I really think it was accidental, but beneficial as it turned out...

One of the things we discovered while working with the MSB's, is that an upgrade from the OE Seimens injectors of the ere (single hole 'pencil' sprayers; 248cc/min; 23.6# EV6 'red' injectors) to Ford Motor Sports 24#  252cc/min, four hole sprayers) allowed atomization of fuel right out of the injectors mouth- which meant spraying early (fuel sync 6* advanced) was a waste of fuel..... SO.... We ran an experiment, and advanced the fuel sync timing (to a straight up 0*, which is actually catching the valve as it is closing), and we found a couple things out:

first off, the OE 23.6# injectors weren't heavy enough for this purpose- the 24#FMS injectors were barely heavy enough- a set of FMS 27# were plenty big enough- the theory and the happenstance is that duty cycles (how long the injector is open, but not a lot to do with volume passing through- the amount of fuel delivered is directly tied to how long the pulse is to keep them open) were maxed out (above 80% is no mans land, or risk running lean at WOT), and not delivering enough fuel when the fuel sync was advanced to 0*.. they delivered fine when the sync was 6* retarded... We determined we needed a heavier injector capable of spraying needed volume of fuel in a shorter period of time- or, better said: more fuel, shorter pulse... a 27#FMS four hole sprayer suited the purpose..

What we found out flat out amazed us... on a dyno, the engine didn't struggle crossing zero, it put 20# more torque, and four solid ponies on the ground... which makes that a pretty expensive pony, as injectors run around $400~$600 a set (don't skimp on injectors fellas)... what we found later, though, was what really took the cake............... we added no less than 4MPG's to a 2002 5.9L 'magnum' V8 Dodge Ram 1500 4x4.... just to see, and because pulling injectors and adjusting fuel sync can be done in less than an hour, we reverted- and lost the throttle response and economy- put it back together, and both returned...


so, about them questions:

1- what kind of sprayers does merc use? Single hole? weight/volume?
2- what is the base unadjusted fuel sync for a merc?
3- how is fuel sync adjusted on a merc?
4- what is the base (open loop) ignition timing for a merc? Does the PCM advance, and if so, what is the ceiling?
5- is there a way to monitor fuel trims on the fly w/o a scanner?

thanks in advance!

TikiHut2

Drew, that's some tweak data right there. I'd guess the engineers who are all-in on those newest designs might have that kind of detail. I met one at the Miami boat show a few years ago. You'd have had a great time trading notes with him.

Neat site MT but even at best trim my fuel use is about 25% higher than shown mostly due to the difference in the boat they use as a comparable. My VERY portly single engine RV of an express cruiser is nowhere near as nimble as the SR 250br in their comparison. I'm thinkin' it's like comparing Oprah or Mellisa McCarthy to Halle Berry or Jennifer Anniston. The options are heavier but it adds to the "experience". In addition there's is just a lot more to love and when your on board it's a lot softer ride too. The head room is worth every once in fuel consumption by comparison too. The compromise is that she has to eat more to keep her happy. If only she would have been a twin then she'd have somebody to share the load.....

All that random justification aside, a realtime fuel flow sensor tied to a dash gauge of any flavor is truly a huge help to tweak GPH for trim, speed and trouble shooting. As for our single engine option rich FV270 at best trim on plane at cruising speed, avg load in benign conditions it's 15gph at 3800rpm runnning 28mph. Theirs is 12.5gph @ 4000rpm. 4k takes us to 30mph and 16+gph and it falls off dramatically from there.

As had been said, find the sweet spot and be satisfied because it's about the creature comforts when you drive the RV vs the Corvette. Mike

212rowboat

maybe it's in the bush a 'lil, Mike, but- it's not completely in the bush.. just a little in the weeds..

if what I presented holds true for merc philosophy, it is an easy way to increase power, economy, and longevity to that engine.. they have to be individually dialed, as opposed to slapped together like the one before it and the one after it, as it comes down to things like valve spring tensions, parameters of specific spark parts like rotor buttons, or even the tips on individual injectors that changes the spray characteristics to the one beside them- even the tiny differences in fuel pressures from regulator to regulator... it would likely take several hours to dial one in, and I'm guessing big manufacturers are more interested in keeping production moving by using widely functional parameters than dialing one specific power-plant into perfection.. 

Michael T

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212rowboat

I'd guess if they are truly hand built and advertise such, than their reputation is on the line to produce something surpassing the notions of assembly line built engines where more than ten people twirled a bolt here and there along the way.. I'd hope they would dial it in- if for no other reason, the ease of doing so is SO much greater than in the past, where there are sensors/monitors built right in, and whereas before it required dedicated equipment to be attached and then detached to do the same thing....