RE: Doubled my fuel economy!  
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All Forums >> RC Cars, Buggies, Trucks, Tanks and more >> RC Car Engines >> Car Nitro & Gas Engines >> RE: Doubled my fuel economy!
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RE: Doubled my fuel economy! - 7/23/2007 7:29:24 PM   
lsurber


 

Posts: 251
Joined: 6/22/2007
From: Fort Worth, TX, USA
Status: offline 		It is not exactly an egr but works similarly. It is an internal port!

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RE: Doubled my fuel economy! - 7/23/2007 7:34:12 PM   
Anthoop



Posts: 1060
Joined: 2/3/2007
From: , UNITED KINGDOM
Status: offline 		Yes i see where your coming from and good luck to you.
Have you tried advancing spark timing as you would with an egr system.

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RE: Doubled my fuel economy! - 7/23/2007 7:34:27 PM   
lsurber


 

Posts: 251
Joined: 6/22/2007
From: Fort Worth, TX, USA
Status: offline 		I will be working when I have time to develop, photograph, and document the procedure. Once I can measure, confirm, and repeat results it may be something I wish to patent.

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RE: Doubled my fuel economy! - 7/23/2007 7:36:40 PM   
lsurber


 

Posts: 251
Joined: 6/22/2007
From: Fort Worth, TX, USA
Status: offline 		That is what head shims are for! Ignition is a product of critical temperature and pressure!

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RE: Doubled my fuel economy! - 7/23/2007 7:38:33 PM   
Anthoop



Posts: 1060
Joined: 2/3/2007
From: , UNITED KINGDOM
Status: offline 		Oops yes sorry,talking 4 strokes then.
I take it then that's a yes.

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RE: Doubled my fuel economy! - 7/23/2007 7:42:55 PM   
lsurber


 

Posts: 251
Joined: 6/22/2007
From: Fort Worth, TX, USA
Status: offline 		By the way, I went home at lunch and ran 12 min. and still had a 1/3 tank left. This is on an engine which I am still breaking in.....so it is a little rich.

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RE: Doubled my fuel economy! - 7/23/2007 9:57:46 PM   
hpi apollo



Posts: 2639
Joined: 5/13/2006
From: Georgetown, KY, USA
Status: offline 		i have modded a few engines before, i havent reached double fuel economy but well over a 50% difference, the way i did it was just general sleeve porting, knife edging the rod, cutting a little bit off of the piston skirt, and grinding a groove in the head button directing fuel over the glow plug for a better burn, i did alter the crank timing a bit in both ways too but thats just because my crank allowed me to


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RE: Doubled my fuel economy! - 7/23/2007 10:15:57 PM   
bikeracer


 

Posts: 150
Joined: 7/8/2006
From: , UNITED KINGDOM
Status: offline
quote:

ORIGINAL: lsurber

No,,,, I didn't change the induction timing! I changed the crank-case pressure timing. This decreases the amount of fuel required by allowing a slight charge of unburned fuel to enter from the exhaust back-pressure!


Sounds like sub piston induction to me,thats where the piston skirt uncovers the bottom of exhaust port.If it is, it's nothing new.


Allan

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RE: Doubled my fuel economy! - 7/23/2007 10:45:50 PM   
lsurber


 

Posts: 251
Joined: 6/22/2007
From: Fort Worth, TX, USA
Status: offline 		Well, since it's nothing new,,,, you nailed it! I have never worked on or built any kind of engines other than 4 stroke race engines so this stuff was all new to me! When I had to mod my cheapo engine I saw that notching the skirt on the exhaust side would increase efficiency and decided to try it! I am used to having original ideas so I had to guard it a little until I did some research! Thanks for the info and good engineering detective work on your part bikeracer!

Lee

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       Post #: 34

RE: Doubled my fuel economy! - 7/23/2007 10:47:25 PM   
lsurber


 

Posts: 251
Joined: 6/22/2007
From: Fort Worth, TX, USA
Status: offline 		I still have a few tricks left up my sleeve though! LOL!

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RE: Doubled my fuel economy! - 7/24/2007 1:12:15 AM   
downunder



Posts: 3196
Joined: 10/10/2002
From: Adelaide, AUSTRALIA
Status: offline 		Sub piston induction was used on many engines long ago but the only ones that actually had a slight benefit from it were the piston ported types like the Mills diesels where the inlet of air through the venturi was so inefficient that any extra bit of air helped. With open exhaust engines, before mufflers, the sub piston induction didn't affect them much because the exhaust port was virtually free of gasses and it was only open for a few degrees around TDC anyway. When mufflers came into vogue the exhaust gas was trapped and this would then contaminate the fresh mixture and power suffered.

lsurber, don't get discouraged from trying out ideas just because this one has bombed but you have to remember that even though our 2 strokes are extremely simple they're also extremely well developed. It's only in detail refinements that any extra power can be squeezed out of them and most of this is already done with the more expensive or specialised engines. I know of one for instance that force feeds the lower rod bush with oil instead of relying on splash lubrication from the fuel/oil mist inside the crankcase.

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RE: Doubled my fuel economy! - 7/24/2007 2:27:13 AM   
bikeracer


 

Posts: 150
Joined: 7/8/2006
From: , UNITED KINGDOM
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quote:

ORIGINAL: lsurber

Thanks for the info and good engineering detective work on your part bikeracer!

Lee


No detective work involved,I've had engines with sub piston induction,a Mills .75cc over fifty years ago and such as Oliver Tigers and PAW diesels after that. Webra used to use it on their long stroke .60 aero engine about twenty odd years ago.I've not seen it used for a while though.

If it works,there's no reason not to use it especially if your getting more mileage from your fuel.More power to anyone experimenting I say, certainly makes a change from the "Why won't my engine start/what's the most powerful engine" type questions.


Allan

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RE: Doubled my fuel economy! - 7/24/2007 5:01:49 AM   
lsurber


 

Posts: 251
Joined: 6/22/2007
From: Fort Worth, TX, USA
Status: offline 		I have noticed a very good bottom end, an unwillingness to stall, and significant mileage increase. The idle dropped a little low even with the set screw all the way in. I can fix that with a little slide work though! It idles so low you would swear it was gonna stall out but never does. I have also noticed that you don't see the typical increased idle when leaning it and decrease when richening. It just has a very nice 4 stroke idle all the time even after full throttle hard runs. When I got home I filled the tank and ran it hard for about 15 min. then let it idle to cool down and burn the remaining fuel out! I don't know how long it ran but I had enough time to smoke a camel and drink a beer before the tank ran low enough to start leaning out where I shut it down! Overall it's a keeper with plenty enough power to roast em down low and into mid range!

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RE: Doubled my fuel economy! - 7/24/2007 2:12:11 PM   
2916jr


 

Posts: 880
Joined: 1/1/2006
From: Clevland, TN, USA
Status: offline 		so all your doing is running a tube from the pipe to the crankcase(tube as in fuel line or something)


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RE: Doubled my fuel economy! - 7/24/2007 4:00:38 PM   
lsurber


 

Posts: 251
Joined: 6/22/2007
From: Fort Worth, TX, USA
Status: offline 		No, it involves cutting the piston skirt on the exhaust side!

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RE: Doubled my fuel economy! - 7/24/2007 4:19:10 PM   
RBMike


 

Posts: 401
Joined: 1/18/2007
From: Santa Clara, CA, USA
Status: offline 		I think Honda called it active recubustion when they did it 10- 15 years ago. If I rememeber correctly it cost them power but improved emmisions & milage.

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