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Old 05-07-2008, 08:43 PM   #1
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Engine rebuild maximum fuel economy

I understand little about this whole subject hopefully some of you can clairify, High compression usually yields higher mpg, due to some crazy thermodynamic efficantcy? and also turbuilance in the intake atomizes better to inprove fuel economy, and minnimize "hot spots" x amount of ignition advance is also better why basically if you were building an engine for fuel efficantcy with money not being limit running on gasoline what would you do how would you design pratical and fantasy approach both appreciated.

thanks Jason metro2089@yahoo.com
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Old 05-08-2008, 10:06 AM   #2
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Quote:
Originally Posted by metro2089 View Post
I understand little about this whole subject hopefully some of you can clairify, High compression usually yields higher mpg, due to some crazy thermodynamic efficantcy? and also turbuilance in the intake atomizes better to inprove fuel economy, and minnimize "hot spots" x amount of ignition advance is also better why basically if you were building an engine for fuel efficantcy with money not being limit running on gasoline what would you do how would you design pratical and fantasy approach both appreciated.

thanks Jason metro2089@yahoo.com
Punctuation and spell check--then someone will probably reply. If you don't mind.. good practice for me as an English major

what you meant to say:

I understand little about this whole subject. Hopefully some of you can clarify. High compression usually yields higher mpg, due to some crazy thermodynamic efficiency? Also turbulence in the intake atomizes better to improve fuel economy, and minimize "hot spots". X amount of ignition advance is also better, but how come? Basically, my question is, if you were building a gasoline engine for fuel efficiency with money not being a limit, what would you do and how would you design it? A practical and fantasy approach are both appreciated.

is this what you mean to say?
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Old 05-08-2008, 10:24 AM   #3
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Avoid cheap rebuild quality cast iron rings, and get moly faced rings for lower friction and longer life. Thermal coatings may help but cost $$$.
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Old 05-08-2008, 12:36 PM   #4
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Around 10:1 compression, so you don't have to run premium, flat top pistons, weld in quench pads in the combustion chambers (if the head doesn't already have them). Clean up the head casting some. Also, maybe higher fuel pressure and cleaned and balanced injectors.

I'd also like to start with a civic HX head (or some other VTEC-E), since it switches from 12v to 16v, and the head already has quench pads.
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Old 05-09-2008, 10:31 AM   #5
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-Polish only the exhaust port, do not port the head.
-Stock cams or cams that are ground to make power lower than stock.
-Polish valve faces, combustion chamber and piston crown to a mirror like finish.
-Exhaust header with straight though exhaust system (the exhaust system takes actual thinking and must be sized appropriately with the displacement).
-Compression should be around 10:1 for aluminum heads and ~9.2:1 for iron as these are the upper limits for pump regular gasoline (dependent on other factors but this is a general rule).
-Moly rings as stated above.
-Very tight clearances so you can run nice, thin 0w-20.

Break-in can make or break an engine with economy. Don't do the easy on it for 400 miles BS. After a couple of light warm up to operating temps and cool downs to ambient take it out and have a healthy run-in with a healthy combination of almost to red-line ~80% throttle runs and engine braking from the top of a gear (preferably 2nd) down to 1.5-2k. Make sure it's done in the first 20 miles.

If you do it right this will make for very nice economy. I built an engine following these guidelines and the engine runs powerful with good economy. I did a couple things differently that let me go with 11.2:1 on pump regular gas but it got direct injection and a slew of other items...
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