Nerding out on boat data

[UWSkier]

So, on another forum, I found some cool free logging software and instructions to build a data cable to connect to the ECM on my older Malibu (2001 Indmar Monsoon II). Today I got it out to log some data to troubleshoot an issue I was having with poor holeshot (fixed with new pump I think). One thing I wanted to do was plot RPM vs GPH.

 

So it looks like about 10-10.5 GPH for slalom skiing with this hull. Would love to see this test done with a wetter hull like they're building these days. I know that a TXi tends to spin about 400-500 RPM higher than my boat does to achieve 34.2 MPH.

 

22 GPH at full whack!

 

Red line is moving average.

 

 

[jjackkrash]

So cool.

[Kwoody51]

Would be interesting to see what you see for GPH when plowing water, just below planing speed vs on plane speed.

 

I'd love to carry around this data on a public lake to show all the Wally's that choose to plow water and throw a giant wake vs get up on plane (or drive slower) that they are burning way more fuel than if they'd just go a few mph faster. Just one of many things that drive me crazy when on the lake.

[UWSkier]

One thing I wish I would have thought to do was use RPM mode on my PP and step up in 200 RPM increments from 1000 to 5000. I didn't explicitly go out to plot GPH vs RPM, but that was in my resulting dataset so figured I'd plot it out. Maybe I'll bring the computer along again next time we go skiing and do that after sets are done for the day.

[TomH]

That's pretty cool. My boat pulled 8 hours of barefoot clinics the past two days - and took down ~25 gallons....Mostly kids this go-round/lower speeds, so the GPH probably lines up pretty well with your graph when you figure actual time at speed.

[keithh2oskier]

So what your saying is you burn more fuel the faster the engine spins?

 

Can you track how many gallons that are burned in an average 6 pass set?

[UWSkier]

@keithh2oskier You could. The ECU reports GPH at a given snapshot in time. So you can get a good idea of idle consumption and consumption at 34 MPH steady. The holeshots are a bit tricky. For example, my 34 MPH steady consumption was around 10 GPH, but I have data points from the acceleration phase where I was burning 15 GPH momentarily at 2500 RPM.

 

So you could probably get fairly close. Depends on how you want to time-slice it. At the very least, would want to convert down to gallons per second. The program I'm using takes 5 data points per second by default. Would just need to do the appropriate time slice conversion and add it up.

 

Not sure what year PCM switched to GM power and which MEFI version they used by year, but could probably apply this method to that as well. The software was actually written for Mercruiser but since MEFI is universal, it works great on my Indmar. The connectors are all GM/Delphi standard.

[GMC]

@UWskier thanks for sharing. I've always been curious about instantaneous fuel usage (and when the boats with O2 sensors/converters go into enrichment) but never got the devices to read it.

 

In my years of tracking fuel usage for a couple clubs and various boats my rule of thumb has become 4.25 gallons per boat hour.

[MISkier]

@keithh2oskier, we have always used 1 gallon per 6 pass set at 34 mph as our number. Maybe 1.25 - 1.5 for 36 mph.

[WiscoSkier]

@UWSkier could you share how you made your connector and how you got the software? I have a 1998 response with the hammerhead 365 and would be very interested in how my boat compares to yours.

[UWSkier]

Everything in this thread. Don't forget the diode.

 

https://www.themalibucrew.com/index.php?/forums/topic/52012-lets-talk-mefi/

[Zman]

Would this same data be available using some of the OBD II Scanners on the market?

[Windsurfnut]

I'd love to see at what RPM is your best fuel efficiency

[UWSkier]

@Zman OBDII scanners don't work in marine applications typically. At least not on older rigs.

 

@Windsurfnut best fuel efficiency is when it's on the trailer. :)

 

[BraceMaker]

Nice work @UWSkier - I'm going to bookmark that page and look it over.

Been building people 10 pin metri-pack with LED for years - should be able to make it work with a USB socket as well for a standard cord.

[UWSkier]

Here's a link to a csv output file if anyone's interested in the type of data presented. No IAT sensor on these older engines. ECU instead used MAP sensors to calculate barometric pressure.

 

Please excuse the old date. The CMOS battery in my old Windows netbook is dead and it loses sense of time anytime it suspends. :)

 

https://drive.google.com/file/d/1ysib4TE5qaBzJIld_1i0JTzcbngXpxfw/view?usp=sharing

[UWSkier]

Bit of further analysis shows about 9.2 GPH running around 3350 RPM, which is 34.2. That's with no skier. I'm going to attempt to run a data collection for a morning session of skiing next week. We're public water guys so our runs are longer than 16 seconds, but to calculate for course use, just delete a bunch of data points in the middle until you're happy with the time period.

[UWSkier]

Grabbed some data from the morning ski passes today. Interesting to see the Zbox doing its thing and how that's reflected in the throttle opening percentage, the trailing RPM increases and drops, and the GPH figures. Purely by the data, with my big 250lb behind skiing at 34.2 MPH, I burn 11 GPH in my glide and up to 13 GPH in my pulling phase. This software is f'n cool!

 

Pullout, glide, followed by 14 wake crossings before dropping for a breather.

 

Looks like I was a little lighter on the line after the first few crossings... :)

 

It takes roughly 5 data points per second. I'm skiing on C2. Wonder if the throttle curves would be different on a ZO boat.

 

For some reason this forum software won't let you click on an image to expand it, but if you right click and open in a new browser, it's much easier to read.

 

 

[Windsurfnut]

Love it, and you have a zbox! Much more interesting then my fuel economy request!

Would be great to see more zbox data- abc123 settings, turning up the zbox value etc. if you had access to a zo boat, you could probably tune your boat to behave very very very close.

 

[UWSkier]

I don't know if the software has sufficient resolution to try to perfectly emulate ZO but the data is still quite interesting.

 

Some super quick back of the napkin math would suggest that each pass through the slalom course (holeshot, run-in, course, run-out, drop) on my boat would be about 0.1 to .13 gallons of fuel.

[UWSkier]

Here's a 33 MPH skier without Zbox. Guess my Zbox works.