Hi Gear MPG Gauge

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Hi Gear MPG Gauge

Postby roarin_mouse » Sat Jun 25, 2011 4:47 pm

Man, I really like Tuner Studio. This has made tuning so easy. I was thinking that an astute software person could create an MPG gauge that works like this: User would enter the RPM at 60 MPH in high gear. That would then be a constant. Now from the injector flow rate, injection duty cycle, injector dead time (opening time), and RPM, the MPG could be determined and hence displayed. This would only be correct for high gear but that's when we want to know the MPG, right. Comments?
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Re: Hi Gear MPG Gauge

Postby LT401Vette » Sun Jun 26, 2011 1:16 pm

It is on the todo list. I've worked through the formulas in MLV way back.
What it has been waiting for is OutputChannels that are application based, bot controller ini based. I just added the core of that in this week, so this should not be too far off.
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Re: Hi Gear MPG Gauge

Postby jsmcortina » Sun Jun 26, 2011 1:29 pm

The formula is fairly easy (although not necessarily wholly accurate). I'll post what I used later.

I plan on building something into MS3 that will improve the accuracy by capturing the injected fuel figure a little better.

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Re: Hi Gear MPG Gauge

Postby LT401Vette » Sun Jun 26, 2011 2:42 pm

What part are you improving accuracy on? It always seemed to me the biggest error factor is injector open time, usually just the default 1.0 gets used.
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Re: Hi Gear MPG Gauge

Postby jsmcortina » Sun Jun 26, 2011 3:43 pm

LT401Vette wrote:What part are you improving accuracy on? It always seemed to me the biggest error factor is injector open time, usually just the default 1.0 gets used.

The code I've yet to write will sum up the injection pulsewidths before dead time is added. As you say, using 1.0 is "close" but usually not close enough to get accurate mpg.

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Re: Hi Gear MPG Gauge

Postby roarin_mouse » Sun Jun 26, 2011 4:16 pm

This is good to hear.
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Re: Hi Gear MPG Gauge

Postby LT401Vette » Sun Jun 26, 2011 4:33 pm

What has been on my todo list for years now, but I think I have all the ground work in place finally to do it. Make a tool to measure injector open time.
The high level plan is to make a wizard sort, where the engine is held at about a 2000 RPM free spin. The ve's for the run range get altered up and down slightly. By taking measurements of the delta PW and delta AFR, a effective one time could be measured. An engineering approach, but could give a much better open time to use in the tune settings and be used for calculating better net pw's.
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Re: Hi Gear MPG Gauge

Postby jsmcortina » Sun Jun 26, 2011 5:25 pm

Some other ECUs allow an automatic switch from 1 squirt per cycle (per injector) to 2 squirts and derive the dead time by iterating there. I have that in mind to add to a future MS3 release. (I think that the pulses need to be in close succession to maintain the injector timing.)

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Re: Hi Gear MPG Gauge

Postby LT401Vette » Sun Jun 26, 2011 5:31 pm

That might work better if it doesn't cause to dramatic of and effect. I'll play around with it this week.
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Re: Hi Gear MPG Gauge

Postby M30guy » Sun Jun 26, 2011 10:02 pm

jsmcortina wrote:Some other ECUs allow an automatic switch from 1 squirt per cycle (per injector) to 2 squirts and derive the dead time by iterating there. I have that in mind to add to a future MS3 release. (I think that the pulses need to be in close succession to maintain the injector timing.)

James


That's how I figured out the deadtime is by changing the squirts and alt vs sim should give you the same afr if the deadtime is correct. Worked great for me anyways.
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Re: Hi Gear MPG Gauge

Postby subwoofer » Mon Jun 27, 2011 1:06 am

DTA recommends toggling 2-stroke mode to determine dead time, so your plan should work just fine. I don't think there is much to be gained by adding code to split one pulse into two at the same point in the engine cycle, but maybe the MS3 should pull the idle up to 2k or so while autotuning to make sure air and fuel are flowing the right way all the time?
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Re: Hi Gear MPG Gauge

Postby jsmcortina » Mon Jun 27, 2011 3:14 am

I don't think there is much to be gained by adding code to split one pulse into two at the same point in the engine cycle, but maybe the MS3 should pull the idle up to 2k or so while autotuning to make sure air and fuel are flowing the right way all the time?

On my engine at least, the engine runs audibly differently with different injector timing, so it seems very much needed to keep the two injections within a similar time frame in test mode or else you will likely invalidate the test?

The way we schedule sequential injection in MS3, swapping to semi-seq from seq won't work while the engine is running. What I have in mind ought to give a smooth transition from one to the other.

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Re: Hi Gear MPG Gauge

Postby subwoofer » Mon Jun 27, 2011 4:20 am

The reason I suggested a raised idle was to get flow velocities up to the point where injection timing doesn't matter too much, but sensitivity will probably be reduced since pulse length will increase somewhat - thus making the dead time less of the total.

Not knowing the code, I suggested what seemed likely to be easier - from a blackbox perspective.
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Re: Hi Gear MPG Gauge

Postby racingmini_mtl » Mon Jun 27, 2011 6:53 am

jsmcortina wrote:(I think that the pulses need to be in close succession to maintain the injector timing.)

Make sure you leave enough time between the pulses so that there is no issue either electrical, mechanical or hydraulic from the injectors or the fuel supply. You may need to have a user defined interval because you may have major differences in what different setups can tolerate before you start being in a non-linear region.

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Re: Hi Gear MPG Gauge

Postby jsmcortina » Mon Jun 27, 2011 9:26 am

Likely at least 2ms between pulses?

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Re: Hi Gear MPG Gauge

Postby racingmini_mtl » Mon Jun 27, 2011 9:58 am

That's what I would say for petrol injectors but LPG injectors will likely need more than that.

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Re: Hi Gear MPG Gauge

Postby subwoofer » Tue Jun 28, 2011 12:51 am

jsmcortina wrote:(I think that the pulses need to be in close succession to maintain the injector timing.)


Warping the thread yet again: You do realize that this is getting close to what is needed for CR diesel? Specialist Components/Simtek UK is already selling a diesel ECU based on their latest ECU with an added injector driver box, but it is expensive to say the least. I am not a great fan of diesels, but there seems to be a screaming need for diesel ECUs for engine conversions, people are actually converting the engines to mechanical control instead of going through the hassle of trying to make all the integrated electronics behave after removing them from the donor car.
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Re: Hi Gear MPG Gauge

Postby Shotgun » Wed Jul 06, 2011 11:32 am

One method of determining the open time is to extend the injector test wizard from MegaTune. Choose an open time and cycle count, and have the user measure the output and input it to a field. Then choose a different open time and cycle count. The equation is (open + opening)*count = measured_volume. You know count and open from both (or all) runs, so it is just a matter of solving the system of equations to determine the one unknown (opening). I did this by hand, and determined that my opening time was 1.1ms.

On a related note, does anyone know what the "fuel flow" units are in MegaLogViewer? The numbers I'm getting don't seem to match anything that makes any sense to me.
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Re: Hi Gear MPG Gauge

Postby Silverback » Tue Jun 03, 2014 9:20 pm

I was searching for something related and ran across this... both (the MPG calculation and the injector dead time tester) would be immensely helpful, did anything ever happen with either?
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Re: Hi Gear MPG Gauge

Postby LT401Vette » Thu Jun 05, 2014 5:52 am

The MPG gauge (along with power, tq, fuel flow, etc) is in the current stable release of TS.
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