My internal combustion engine is more efficent than 30%

[brewnog]

You've been told this already, but the amount of fuel used at idle is just not a way to compare what the fuel efficiency is like on load. To infer the fuel consumption on load from a fuel consumption at idle is irrelevant, meaningless, negligent, incorrect, wrong, and completely pointless.

 

[Bob S]

...2.5 kva 5.5 HP 163 cc engine at 3600 rpm with 2kw load 15 L will last 6.5 Hours

So that is 38.46 cc/min with approx 2.4kw output (80% generator efficiency??).

The official conversion used in BSFC (brake specific fuel consumption) maps is

100% efficiency ≡ 83 grams gasoline per kW-hr.

See http://en.wikipedia.org/wiki/Brake_specific_fuel_consumption

"Certification gasoline = 18,640 BTU/lb (0.01204 kW·h/g)" = 83 grams per kW-hr

So a 100% efficient 2.4 kW engine should use 3.32 grams per minute, or about 4.5 cc per minute. This implies that your engine is ≈12% efficient.

The BSFC map in the above pdf shows a 40% efficient engine, with a minimum fuel consumption of 206 grams per kW-hr.

See table in above pdf for table of engine efficiencies. In particular note the Toyota Prius engine at 37% efficiency.

Bob S

 

[jambaugh]

"The ultimate proof is in the pudding" ok done a rough estimate if I could drive fairly constantly without too many hills at 60km/h I could do it Atlanta to New York 1418 km if I had a 20 L jerry can on board. It begs the question I will use overdrive on my next test to see if it is any better and will recalibrate one of my load sensors as well but that will be at the end of july now before I can retest any of my theory's.
Oh I can also push my engine to hard knocking without piston damage but the crank takes a beating though.

Unless some one sponsors me I will never get my engine on a dyno.

The drive test may indicate a qualitative improvement (or disimprovement) but you really need some numbers. So if you can't afford a dyno, make one. Probably the cheapest thing to do is fix a setup so your engine is vigorously stirring a big drum of water sufficiently to generate an appreciable load.

To calibrate it,
* measure the volume of the water in cubic meters,
* measure the initial temperature in deg. C,
* run the apparatus for a minute or so but measure the time to the second (100 seconds is a nice round number),
* measure the temperature afterwards and determine the change in temperature.

1 Calorie = 1000 calories = energy needed to raise the temp of 1m^3 of water 1 deg C.
= 4.184 kiloJoules = 4.184 kilowatt seconds.

This will allow you to calculate power output at a given engine RPM with your setup.
Follow this procedure for each run and carry out several runs at different RPM's.

Once you've calibrated the load you can then run the engine at constant load calculated for that RPM. Run it for 30min or so and measure the fuel consumed per calculated Joule of energy output and thus calculate explicit efficiency.

This setup should be quite accurate but the precision depends on your measurements. Try to find the calibration time which gives you a good temperature change but be sure your initial temperature is the ambient temperature, and it will help if you be sure the can is covered as much as possible to prevent evaporation loss. Insulation around the water drum would also help. Also the stirring apparatus should agitate the water but you want to make it turbulent, something like an egg beater or butter churn. But be sure no water sloshes out. (I recall once seeing a fellow tuning up the the outboard on his boat by running it in an drum of water in his back yard.)

Basically this is reproducing Joule's experiment measuring the http://en.wikipedia.org/wiki/Mechanical_equivalent_of_heat"

 

[HowlerMonkey]

Our dyno uses twin eddy current retarders.

https://www.youtube.com/watch?v=5VkDLfmGH7Y

That's only a 1300hp pull but it was enough to go from 0 to 252.9mph in a mile from a standing start.

We're finishing a 2500hp engine for some world record runs.

Engine management systems of today's EFI cars have the ability to display a relatively accurate mpg...unless the manufacturer purposely skews the data to show more favorable mileage.

They use injector pulse width, rpm, grams per second (from mass airflow sensor), gearing, downstream monitoring of exhaust gases, and the fuel trim correction values.

Miles per gallon increases require optimizations in many areas but the hardest area to optimize is the driver.

I've seen guys get 18mpg in a prius because the driver drove in such a way that he defeated any of the benefits of his car's design.

 

[smokingwheels]

Would exhaust manifold temperature tell how efficient an engine was?

My engine which has a cast manifold and I have a normal engine but its got extractors.
Problem..
Can I compare the two?

Test setup:
My engine temperature was about 95 deg C and warmed up and idling, the ambient temperature was 12.9 deg C, wind W25 km/h and wind gusts 43 km/h.
The Second engine temperature was below 88 deg C and still warming up, the ambient temperature was 9.5 deg C, wind W 29 km/h and wind gusts 52 km/h.
I melted 60/40 Solder on the exhaust path about 3-5 inches away from the head with the engines idling after going for a drive to warm them up.

My modified engine took some time to melt the solder the second engine did it really quickly with the flux smoking well.

I was wondering if its because of the extractors being thinner and less surface area would it be hotter?
With more surface area for the cast iron manifold would it run cooler?
Will ambient temperature affect the manifold temperature a lot or not?
The ambient temperature dropped after testing the modified engine.

I have a Video play list if you are interested to see the results from 4 short clips.
http://www.youtube.com/playlist?list=PLA7848D3EF5B27FF3

Solder (60/40) melts at 370 deg F and a soldering iron is about 700 deg F.
My engine with the cast manifold took quite a while to just melt the solder with not much smoke from the flux.

The other normal engine with the extractors did it very quickly and the flux was rapidly turned into smoke in a similar way to a soldering iron from my experience.
I know I need 2 of the same to compare so I need to find a few volunteers in Australia if
possible.

 

[brewnog]

So you're using solder as instrumentation while doing tests on two different engines under two different conditions at idle?

Firstly, thermocouples are the way to measure exhaust temperatures on engine test. You can get them for less money than you probably spent on your solder. Melting solder (and trying to draw a conclusion about the way it melted) doesn't tell you anything, except that the exhaust pipe is hot. It doesn't even give a good indication of the temperature of the exhaust gas!

Secondly, (and we've been through this before, but I'll say it again because it seems to have soaked in like water off a duck's back) performance indicators at idle tell you so little about what your engine is doing that when doing engine development work, we hardly ever take data at idle. It just doesn't tell you anything about what the engine will do under operation.

Thirdly, what do you mean by 'extractors'? The only exhaust extractors I've come across are ventilation systems for taking combustion products out of the test cell.

Finally, what are you trying to determine now?

 

[smokingwheels]

Thermocouples Ok but I would have to get a hole drilled and a fitting welded to my exhaust.

An engine under load is what's needed.

"what do you mean by 'extractors'?" They are smooth mandrill bent tubing providing a rounded flow for the exhaust gasses also usually larger than cast iron counter parts and they are freer flowing.

"Finally, what are you trying to determine now?"
To see if there is a relative difference between the two engines I guess I will have to find a similar engine setup to compare to mine.

I don't have any money to play with, I guess that is what my trouble is and why I don't give up.
Another reason I don't give up is my car has done a trip at 80 km/h one night and got a fuel consumption of around 4.1 L/100 km, worst case is as high as 5 L/100 km this is dependent on the slope of the pavement where I filled up, its about a 3L variation on a full tank from tests I've done since, so I am discounting if I got less fuel when I filled up that night. My consumption would of been around 3.3 L/100 km, I have a witness or two but I doubt if they would talk to me again (x girlfriend and her x husband). That 71 US MPG I serious do not think I can reproduce that ever. I have shelved my engine thing for a few months now maybe a bit longer is needed. But I could try and contact the x husband some how.

 

[jambaugh]

smokingwheels,

If you don't want to build/buy a dynamometer, and you have the engine mounted in a working vehicle, I would suggest you hook up an auxiliary fuel tank (which allows you to measure precise fuel usage), take it on the highway and make a few trips with and without your modifications. To be more scientific you could have someone else do the driving, not letting them know whether you do or do not have the mod installed. Try to drive at constant speed and work up the average mileage with and without the mods. See if there is a significant difference in fuel economy which will indicate whether there is a significant difference in fuel efficiency.

Be sure you use the same type of fuel each time. Look http://www.epa.gov/fueleconomy/data.htm" for information on what variables can affect fuel economy so that you can minimize variations and get good data.

And I'll repeat again what everyone has been telling you:
Performance information at engine idle is useless! You must test the engine under load!

 

[HowlerMonkey]

This one got a LD28 with a turbocharger for a while before going back to gas...and a turbo.

Post is related because it's the same year and model as being discussed.

http://princemakaha.homestead.com/files/IMG00069.jpg