Complete engine rebuild: Anything to consider for max efficiency?

[NoD~]

Hey gang,

I have 2x 90's 1st gen neons laying around... smashing the two together to make one good one. One of the shells is my old race shell that I got down to about 2200 lbs race weight. I plan to thin it out a bit more, lower it, aero mods galore, and shoot for the moon.

I am going to rebuilding the entire engine. I'm hoping somebody can give me some tips on achieving maximum efficiency out of my 2.0L SOHC engine.

The bottom end is a bit of a mystery... the engine was hydrolocked. I do have another block, either way, but regardless, new rings, seals, and bearings all around. I'm sure there is some jedi magic to be had with doing the rings... any suggestions on type/gap/etc? What about the hone job, is there a grit that is going to be better specifically for maximum MPGs, or is hone still going to be about the ring type?

I will probably go through and smoothen out some things like the water pump section to get rid of some of the bad cast. I know, probably miniscule, but if every bit counts, why not?

I believe the head has a mild port and polish job right now. It may have been milled down a bit as well, I can't remember for sure. The head is likely in great shape still (haven't pulled it off yet, but can see in the intake ports... head was rebuilt probably 30K miles ago)

Anywho, just fishing for ideas since I'm going to be tearing this down completely and haven't ever considered maximum fuel efficiency when rebuilding in the past.

[bandit86]

Get a camshaft that has no overlap. Smaller oil passages to run thinner oil, lighter valve springs, larger pulley on water pump. High compression probably helps too, it does for power,

Then convert it to diesel

[BLSTIC]

Ok so you are building an engine for economy. So what you want is maximum efficiency at an accessible load/rpm point. Most engines have peak efficiency from 2000-3500 rpm and high loads. Manufacturers are pretty damn good at doing that. If your peak torque is currently higher than about 3000 rpm, altering your cam timing can move it slightly. Also getting the right headers can help with that, as can induction pipe lengths (no, seriously, a tuned intake pipe can alter full load torque by as much as 10% at a specific rpm).

Porting won't hurt if you are just removing casting marks and valve stem bosses. A 3 angle valve cut might be worth a shot.

Compression *will* improve efficiency, if you can stop it pinging. Technically it's the expansion ratio that you are after.

To help with pinging you can remove any really sharp edges in the combustion chamber to reduce the likelihood of hot spots.

Special piston crown coatings are rumoured to help, but I know nothing about these.

Long story short you are building a high performance engine tuned for low and mid range operation...

[serialk11r]

Originally Posted by bandit86

Get a camshaft that has no overlap. Smaller oil passages to run thinner oil, lighter valve springs, larger pulley on water pump. High compression probably helps too, it does for power,

How about instead of getting new cams, retard the current intake cam to reduce overlap and VE ala Atkinson cycle engines?

Got the idea from MechE grad student at FSAE, their motorcycle engine (GSXR600, revs higher than 12000 rpm :O) and restrictor weren't getting along very well.

[ecomodded]

Ceramic bearings, put them anywhere and everywhere you can find a set that will fit your motor.
You will want some fuel injectors that have smaller fuel holes with 1 or 2 added holes to aid in the atomization of your gas.
+ a bigger badder coil

[Ryland]

Balance your engine so it's as smooth as possible.
Are there any smaller more efficient engines that fit the Neon that might be a better choice to start with? I know you already have this one, but if you can get a whole engine for $200 or so from a junk yard and have a better base to start with, then why not?

How about an electric water pump and cog belt to the alternator?

[oil pan 4]

For a gasoline engine you can always try file fitted rings or zero gap rings.
The higher compression is a good idea.
Try to stay close to .002 inches of clearance on the rod and main bearings that way you might be able to run thinner oil.

Go with the newest generation of injectors that can be made to fit your car.
Check the wiki.

[Frank Lee]

I think a proper cam choice is #1; then do the standard blueprinting stuff. I wonder if it's worth it to try a 2-ring pack?

[drmiller100]

as high a compression ratio you can possibly get away with.

due things like deburr the combustion chamber to run higher compression.

disable one intake valve.

run lower ratio rockers.

I've thought about trying to run .100 rocker clearance, but it might be hard on valve stems.

every serious mileage vehicle has HUGE compression.

consider building a custom tune which gives LOTS of fuel when MAP gets anywhere near atmospheric, and running even more compression.

[Grant-53]

The Neon 2.0L is a factory high performance type engine and Mopar may have some manuals for massaging these engines for class racing. Polishing and balancing will help any moving parts. Make real sure of the valve timing to avoid piston collision. Verify the electric sensors are correct for control module and well grounded.