Fast Fred's OMC Mod 50 secrets Thread #2

[formeone]

this my new project hopefully can make work with braod power band

[Tim Kurcz]

Sure hope all that weight pays for itself and doesn't roll you over in the process!

[Powerabout]

You need to be using a gps receiver that can receive differential(waas as you would call it in the US) data to be anything close to accurate over a short distance otherwise max speed could be way off

[formeone]

yaaa you rite tim,,, gave myself a hernia lifting them,,,lol,,,, think need extra 5hp just cause of weight,,, more just looking at it as a challenge to see if can actually get a set of pipes to work on these motors,,,, and go from there ,,,just a challenge,,,,

[David Mason]

Dave,

Was the course at Whitney Point longer than the course at Alex (Pineville)? When you came down to Alex ('02?, '03?) we were running a surveyed one mile course.

A lot larger, by feel and looks. I think someone said it was a mile and 2/3, i dunno the actual measurment. It was long enough to make me burp the throttle in the 750CCMR to ensure it did not burn up. That was a lot of WOT running. I am surprised the mags held up as well as they did on the 44's. They made the course shorter once 850CCMH came up, but it was still a large course, they said it was a mile at that point, but it still felt longer. Did a quick calculation with some mod buddies, and given the distance on the GPS in the first turn (all the way around) it was longer than the entire straight away in Huntington IN race course.

[Tim Kurcz]

Only pilots here know what the wide area augmentation system is......

[Mark75H]

Let me pose a question ... wouldn't std GPS "inaccuracy" result in lack of repeatability of results rather than significant greatest speed errors that consistently repeated regardless of location and time?


Separately wouldn't speed and course (as on a one mile loop) likely to be accurate, just not accurately reported as to exactly where on, above or below the surface the course is? ... esp since we would be talking about a repeating circle ... traveling in all 360°


I have not known GPS reported speed to significantly vary compared to other accurate references ... radar and timed surveyed measurements but I have seen it be off in regard to location by 100 ft ... but traveling 500 ft away ... it was still off 100 ft in the same direction ... and accurately measured the 500 ft change


I will not believe that a GPS can't tell the difference between 40 mph and 60 mph

[Mark75H]

OK, you made me do my homework ... this is what I learned:

in general, maximum errors will be larger than those observed. This is due to the fact that large errors are brief and unpredictable.

This means that once in a while, but not very often, you will get a reading that is so far off you will know it has to be wrong.

Speed observed by GPS is very likely to be highly accurate if repeated at different times and locations ... those are the conditions involved in my post about the team GPS'ing several classes/speeds

[Powerabout]

Mark 75
Your postion jumps around as it will with std gps just look at a fixed position on a plotter.
The way it works out your speed is from your postion change
The data you see on your screen is damped so it makes sense.

It may just average out with your application?

I notice that the guys with handheld units at our yacht club on yachts, quiet often have unbelievable max speed.

Average speed of course is believable

Sun spot activity is bad at the moment and getting worse so it hickups a lot now.

There are a few handhelds now that receive waas data.
Boating/shipping uses it as well as other sources of differential data.
The Air Force warned last year that they expect blackouts this year due to lack of satellites ( replacement supply is years behind)
I guess the last place that will get blackouts though will be the US ( and anywhere that gets bombed)as you paid for it.

[F77]

Alittle off the GPS topic for a minute, need input on location for the probe for a pyrometer on a 49ci. Starboard side of the exhaust outlet in the adaptor housing just below the powerhead gasket? Thanks Chip