Engine re-build, eco-style. Home project.

[bandit86]

Go super high compression but don't ever race it, hard on head gaskets A heavier flywheel will make the engine run smoother.

[caferacer51]

To save me thanking you all individually, please accept my thanks on a whole to all those who've posted!

It seems like there are certain paterns building up;

Keep intake stock (ie not polished)
Keep the exhaust smooth (but dont f*ck about with it)

I can get the polishing mops on the combustion facing internals

Heavier flywheel, but lighter rods/pistons

Plus I've been reading up on the 14 degree timming advance alteration too.

With regards upping the compression, is that as simple as a head skim, or are shaped pistons or longer rods...?

[ConnClark]

If your going to change the weight of pistons, rods, and fly wheel you better have the engine balanced.

I'd look into titanium valves too. Saving valve train weight will reduce losses overcoming the inertia of the valves. This will help most at higher rpm.

[some_other_dave]

I don't know if this is still the case, but a decade ago titanium valves were a Very Bad Idea on anything but race motors built for very limited duration (like 3000 miles or less). Titanium loves to gall on just about everything, and the valve keepers were real trouble sites.

You would want to deal with airflow management inside the engine as well. Those pistons moving up and down make a good bit of air move around inside the case, and the crank and rods churn it all around as well. So doing stuff like "knife-edging" the crank, and making sure the air has good ways to flow around things, will help cut down on power lost to moving the air around. Drawing a vacuum on the case helps that as well, but it costs you power to pull the vacuum.

The oiling system in the stock motor is likely intended to provide more capacity than a low-RPM eco-driven motor would need. So downsizing on the pump can help reduce the power used to drive it, without risking the engine. Especially if you make sure that the oil passages are port-matched to each other. (We have seen significant mis-matches in the aircooled VW world, and matching the passages in the pump and the case to each other has helped.)

Coatings can help as well. I am told that an oil-shedding coating on the parts of the bottom end that don't need oil on them helps reduce the power lost to flinging oil around inside the sump. Friction-reducing coatings can be used in some areas as well.

Most of the changes I am talking about are going to give very very small results, likely less than 1% improvement each. They are likely past the point of diminishing financial returns until fuel costs get into the truly absurd levels. But they are interesting as an exercise.

-soD

[stovie]

i'd say try for max torque at as low a rpm as possible and then get higher gearing with it. I've also heard that cryogenically treating your engine could increase your FE by 50%. I'm pretty sceptical about that but everything i've read said that crogenicly treated parts have 50% or less friction then they had before, so maybe it well cause the engines supposidly lose 30% of the energy to friction.

[Danncomm]

I have read many times years ago about using ceramics on the head and piston tops to help reduce heat loss in the combustion chamber during the combustion stroke helps to improve mileage. I have not read much about it lately. It does make sense, if you can keep a little more heat during the power phase of the cycle you get a slightly better improvement in power and mileage. Maybe studies have shown that it isnt durable or worth the investment, I have not heard. Maybe something to look in to.

[Frank Lee]

I've personally rebuilt several engines. Were I to do this, I would look at pretty much a stock rebuild... unless I was going all-out, then I'd consider destroking first, deboring second, or maybe even cylinder deletes. I would not spend more to get light rods as that mainly comes into play at high rpms. I would have the head trued for a nice straight gasket surface and teensy compression ratio bump. I'd have a nice multi-angle valve and seat job done. I'd port match head to intake if needed. I put a windage tray in. I would consider a heavier flywheel if my driving style would be to short shift a lot; it would be especially useful paired up with a higher trans regearing. I would re-cam with a grind that's optimized for lower rpms, and also play with cam timing if that's what the cam grinder suggests. I haven't been ambitious enough yet to try to fab up some nice small diameter long tube headers(cuz the commercially available ones are all about high rpms) but that might help too. Coatings and such... who knows, I've never had that done, but if I did I'd probably do the piston skirts first- actually some of the new hypereutectic pistons come with it.

[Christ]

A bit OT, but Frank, I had this silly idea that since most headers are designed for high rpm, high load applications, using a header designed for a gas engine on my n/a diesel (which is always at WOT, remember), would yield some results.

I'm gonna try it, anyway, with a full 2" exhaust...if it doesn't work out, I can always go turbo later.

[Christ]

Back on topic, the OP should consider diesel engine swaps which normally would bolt to the transmission, such as the 2.0 diesels found in escorts and lynx models. The time/money you spends rebuilding a gas engine could easily build mount adapters, linkages, and the simple wiring necessary.

[Sularus]

a process developed similiar to shot peening, but at a much smaller level, reduces friction and is safe enough for all parts of the engine, including bearings.
WPC - Metal Surface Treatment / Micro Shot Peening

an article discussing WPC vs. Shotpeening
Shot Peening & WPC Treatment - Metal Improvement Company - Turbo & High-Tech Performance Magazine