Fuel Efficient Camshafts

[jeff88]

Unfortunate circumstances means doing a valve job on my 2001 Toyota Corolla. While I have the head off, I'm wondering if there are any mechanical mods I can do to aid in fuel efficiency. I know there are "performance" camshafts, but not sure what these do for fuel efficiency. Is there anything available out there or do I need to get a grind to get a better profile? Is it even possible to get a more fuel efficient profile from the Toyota factory cams? I have VVT so maybe none of this is possible?

[Ecky]

If you change anything about the cams, you'll need to have it re-tuned - which could buy you some fuel economy on its own. Most factory tunes prioritize emissions, and leave a bit of economy on the table. Re-tuning may not be possible on the stock ECU, in which case you'd be looking at $1500 minimum in electronics, plus the cost of the tune - and most tuners won't touch part throttle tuning because it's time consuming and difficult.

Typically, a "cooler" cam will, in fact, slightly help economy, and may also improve torque at the bottom of the rev range, by reducing it up top. A cam wouldn't be the first place I'd look though.

Instead, I'd consider the following "engine" mods:
-Block heater
-Balance shaft delete (if it has them)
-Electric power steering conversion (or manual rack)
-A tune
-Possibly a slight underdrive pulley for the accessories

What would probably help even more is taller gearing - a slightly taller top gear can save a ton of fuel on the open road.

[oil pan 4]

Vvt already has fuel economy on the low end and power on the high end.

[jeff88]

Thanks for the replies guys. I have one opportunity while this thing is opened up to make any internal mechanical changes, other things can come later. That's why I'm wondering if there's anything we can do with the head off.

[Ecky]

Originally Posted by jeff88

Thanks for the replies guys. I have one opportunity while this thing is opened up to make any internal mechanical changes, other things can come later. That's why I'm wondering if there's anything we can do with the head off.

You could try a thinner head gasket to bump up the compression slightly. This may slightly alter mechanical timing (more slack in the timing chain taken up by the tensioner).

[cRiPpLe_rOoStEr]

Originally Posted by Ecky

You could try a thinner head gasket to bump up the compression slightly. This may slightly alter mechanical timing (more slack in the timing chain taken up by the tensioner).

Unless the ethanol content of the gasoline is increased, I'd take bumping up the compression ratio with a grain of salt.

[Ecky]

Originally Posted by cRiPpLe_rOoStEr

Unless the ethanol content of the gasoline is increased, I'd take bumping up the compression ratio with a grain of salt.

All else equal, you might get half a percent fuel economy out of a thinner head gasket. Most OEM designs have some safety margin built in with regards to ignition timing, so a quarter or half point of compression isn't likely to cause ignition retard.

[serialk11r]

If the head is off, you can look into raising the compression ratio by milling it. I remember asking a shop a long time ago about doing that to a 1ZZ and they said you can take a decent amount off (but like all engines, you would mess up the timing chain geometry a bit so realistically not much can be taken out). I highly doubt you'll find anything in cams.

2ZZ water pump with slightly bigger pulley will save a little bit of power but you probably won't get your money back for a long long time.

[Ecky]

Originally Posted by serialk11r

2ZZ water pump with slightly bigger pulley will save a little bit of power but you probably won't get your money back for a long long time.

I went up 11% in size on my K24 water pump pulley, and found I had temperature issues. I was surprised the cooling (at idle) was so marginal.

But yes, I agree, it would amount to some savings. Perhaps between compression and the pulley, you'd see 2-3%.

[cRiPpLe_rOoStEr]

Originally Posted by Ecky

Most OEM designs have some safety margin built in with regards to ignition timing, so a quarter or half point of compression isn't likely to cause ignition retard.

Instead of how the ignition timing would compensate for the slight increase to the compression, I was thinking about the EFI enriching the mixture