Honda, Higher compression = better mpg?

[serialk11r]

Originally Posted by Phantom

Also the Sky-active engines are cast iron so they will hold heat longer. At least last I read unless they decided to change and go the weight saving route.

What? I've never heard of the Skyactiv engines being cast iron anything... I'm pretty sure they're all aluminum.

[cRiPpLe_rOoStEr]

Originally Posted by serialk11r

What? I've never heard of the Skyactiv engines being cast iron anything... I'm pretty sure they're all aluminum.

The gassers are all-aluminum, but nodular iron is still prevalent for Diesels.

[serialk11r]

Originally Posted by cRiPpLe_rOoStEr

The gassers are all-aluminum, but nodular iron is still prevalent for Diesels.

Oh, you were talking about diesel. Over here in the US we don't have many of those :P

Yea the Skyactiv diesels are aluminum to save weight (probably doesn't hurt that cooling is less of an issue too), and the reduced compression ratio reduces the strength requirement.

[cRiPpLe_rOoStEr]

Since it leads to an easier cooling it also reduces the NOx amount. A win-win deal...

[Cobb]

Back in the bad when I worked at a machine shop it was common to stroke an engine. THis is grinding off the back side of the crank journal so the rod move up and down more in the cylinder. Then again these were engines made right after the non leaded gas revolution so their compression ratio was like 8 to 1 and we bumped it up to 9.x to 1 or as much as 11 to one. Makes a hell of a different in torque, acceleration and the heat an engine will produce.

For the smaller "rice burners" they just decked the head a few thousands.

[IWantHX]

Well the d16z6 in my car has a lot of miles and I was wanting to rebuild the engine regardless, just trying to see if a little increase in compression could help with fuel economy while cruising. I guess Ill just rebuild it at around 10-10.5:1 (compared to the stock 9-9.5:1) and just see

[redpoint5]

Originally Posted by IWantHX

Well the d16z6 in my car has a lot of miles and I was wanting to rebuild the engine regardless, just trying to see if a little increase in compression could help with fuel economy while cruising. I guess Ill just rebuild it at around 10-10.5:1 (compared to the stock 9-9.5:1) and just see

How do you know the engine needs a rebuild? As others have pointed out, specific tests must be performed to determine a rebuild is necessary. How many miles are on the motor? I've had a Subaru 2.2L go nearly a quarter million miles, and it was still running fine when it was rear-ended and totaled.

I applaud your "build it and see for myself" attitude, but unless you have plenty of money to burn I would find out more before jumping into the project. That said, please report your findings here if you do end up doing the rebuild. Your results whether positive or negative are valuable information to share with everyone.

[Phantom]

Originally Posted by serialk11r

What? I've never heard of the Skyactiv engines being cast iron anything... I'm pretty sure they're all aluminum.

You were right the Skyactiv are aluminum I have corrected my post to reflect so.

The engine I was thinking was the Ford Ecoboost 1L:
"The engine block is cast iron instead of aluminium for up to 50% faster warm-up, at the expense of additional weight." Ford EcoBoost engine - Wikipedia, the free encyclopedia

[tim3058]

I've heard raising compression helps efficiency as well. On the '93 DX/VX I had the head on my d15z1 shaved and got a 3-angle valve job at the same time (had the car apart anyways).

Unfortunately I did a lot of other upgrades at the same time so no before/after mpg results, but the seat-of-the-pants felt nice after - was very happy with its ability to stay in lean-burn on small hills and headwinds (didn't have to step on it). Passing power was decent for such a small engine - the d16z6 car I now have doesn't seem much better FWIW.

[IWantHX]

I dont think the engine NEEDS rebuilding, just wanting to do it for knowledge and to know I have a fresh engine, but wondering if higher compression pistons (can be had from other oem d16's for pretty cheap) can help with both low throttle cruising mpgs and for a little more passing power