Thread: Fuel Economy Engine

With gas prices being what they are, I've decided to focus my SR16DE engine build on fuel economy. So far, I have a 10:1 SR20DE that I installed the crank and rods of an SR16VE into. Some calculations showed that my compression ratio will be an unacceptable 8.5 or so due to the decrease in swept volume. I would like to get this back up to at least 9.5 but preferrably into the 10-10.5 range. SR16VE pistons will give me about 9.5 and shaving 1mm off the block or head would give me a little over 10.5 with the SR16VE pistons.
Now for the questions, can I shave 1mm off of the block or head safely? I understand that will cause some cam timing issues, and I will fix that with some cam gears. If I can do it, is it better to remove material from the head or the block or half on both?
My other question is related to heads. The car that the engine is going in is an NX1600 that currently has an SR20 swapped in. When this new engine goes in, I will be installing Megasquirt for fuel and timing control. Does the low port head give better mileage (assuming everything else stays the same) than the high port head?
And finally, what header/exhaust combination would yield the best fuel economy? I know we tend to focus on performance (power) in this forum, but I think a high fuel economy build can be pretty cool, too. Thanks for the input!

2" was found to be optimal on a naturally aspirated GA16DE engine, so I'd try 2" for your exhaust piping size. Also, a 4-2-1 header will give you more power from low-mid range RPM. I really don't think the head style in terms of high port or low port will have an effect on your engine's efficiency, and if it there is then it's negligible. If you're going custom ECU I'd suggest looking into running 4 BAR of fuel pressure so you can gain better atomization (more complete burn... better gas mileage).

Your choice of chassis is probably the best choice you could have made, as it's going to be one of the lightest possible. If you can drop more pounds off of it though... even better.

With lower compression you can run leaner. If you are hwy driving this is better for fuel milage. Using newer style injectors like the ones from denso is a good idea too. adding a turbo is always a good idea.

Maybe you can get a custom cam grind for FE?


Although... think about this... Think about all the money you are spending on the project, and how far you plan on traveling with this thing... and then think... is the money you are spending to get better gas mileage going to offset the gas savings in the long run?

Haha I think he is more focused on seeing what he can do with it, just like any good car project should be

Danja has the right idea. This is primarily to see what I can get out of it. The chassis will probably end up much lighter than factory. It was a theft recovery and most of the interior is pretty shot anyways.

Bigtom, what compression ratio should I try for if I were to optimize it for highway driving? And what are these Denso injectors you mentioned?

Thanks all for the input, keep it coming.

well you could get a ecu and havethe engine tuned, and could have it tuned for better gas mileage

Yes, but what about specifics? You can get an engine tuned for anything, it's the whole "what needs to be tuned to what" that makes the real difference.

why not start with the GA16? that's a pretty fuel economy focused engine. if you'll stick to the SR engine, get the G20 tranny(P10 has longest gears and FD).
Honda Insight wheel and tire combo (overinflated)should help you get a little more mpg.
then work on the chassis, get rid of the mirrors, wipers, put some plexiglass over those concave headlights, smoothen out the undercarriage and the bottom of the rear bumper.
Sorry I'm no help with the motor but you'll want a non restrictive I/H/E ( but not 2.5 inch piping or 4-1 header,which will give you no torque at lower rpm), maybe gap out the plugs, and you definitely want to run leaner so get some type of fuel management and lean the bish out, especially under light load

this def. might become the new thing, SR's still longer known for power in the year 2008, but also gas mileage.