Head Porting for Fuel Milage

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BLSTIC
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Re: Head Porting for Fuel Milage

Post by BLSTIC »

And it depends on the driving too. High torque at low rpm means you can use a higher gear more often while at low speeds or accelerating, reducing wasted energy (rotating the engine, pumping losses, whatever you want to call it) further.
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Re: Head Porting for Fuel Milage

Post by RDY4WAR »

David Redszus wrote: Thu Jan 26, 2023 11:56 am Raise the compression ratio. That will improve efficiency across the entire rpm range.

Put it on a dyno and plot the BSFC curves.

Drive the vehicle in the rpm sweet spot. (see typical BSFC curves)
Compression definitely improves combustion efficiency, but I wonder to what degree the value. The main reason people chase better fuel economy is to save money on fuel. If the higher compression forces more expensive premium fuel, then it's counter-productive. At least that's my view on it. In such a case, if compression is limited by knock, parameters like swirl and squish velocity become prominent.

I'm curious what benefit could come from a pressure regulating check valve on the inlet side of the PCV system that would allow intake vacuum to pull reduce crankcase pressure. Say you have a 5 psi (~10 inHg) check valve on the inlet side and the engine is cruising with 15 inHg intake vacuum. The check valve would regulate the air flow into the crankcase and maintain a 10 inHg pressure drop in the crankcase. How much impact would such as this have on oil windage, pumping losses, and such? Would it potentially be worth a 0.1-0.5% mpg improvement?

In any case, there isn't much that can be done with the engine to get better fuel economy aside from using a smaller engine.
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Re: Head Porting for Fuel Milage

Post by Tom68 »

BLSTIC wrote: Sat Jan 28, 2023 4:42 pm And it depends on the driving too. High torque at low rpm means you can use a higher gear more often while at low speeds or accelerating, reducing wasted energy (rotating the engine, pumping losses, whatever you want to call it) further.
Have to be careful with that when carb'd, lots of fuel fallout to contend with.

My daily driver's on LP Gas, half the price of Petrol here, similar mpgs, clean oil, 492,000 kms so far.

My work hack is on LP Gas through the primaries and premium fuel through the secondaries, cheap to cruise and still got some get up and go.
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Re: Head Porting for Fuel Milage

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Walter R. Malik wrote: Sat Jan 28, 2023 10:29 am If it uses a carburetor or throttle body injection there should be no sharp corners within and very smooth transitions keeping the fuel in suspension.
Dan Timberlake wrote: Sat Sep 14, 2019 9:45 am
I wonder how many manifolds with beautifully rounded, faired in carb openings are throwing away some drive-a-bility unnecessarily.

Back in 1972 the folks at AMC said this to their SAE buds.
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Re: Head Porting for Fuel Milage

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Tuner wrote: Sat Jan 28, 2023 5:23 pm

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Gotta bigger pic ?
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Re: Head Porting for Fuel Milage

Post by Tuner »

It is in this thread on page 6. Cliff notes = "sharp 90 deg. edges are good" viewtopic.php?f=1&t=58475 I recall this image being posted a few times in the last 15 years and being better able to read it, but I couldn't find the right thread. The search function in this forum is quirky and not effective. I have been trying to find my own posts about the '66 289 Ford 4V spacer with the sharp edges protruding into the flow, the lower half is slightly smaller than the upper half with a sharp edge at the parting line. Removing the lip on an otherwise stock motor caused the car to go from 9.50 1/8 mi. ET to 10.70 and the mileage to drop from 25 MPG to 15. Got another original spacer from a wrecking yard and put it right back to where it was, only change was polishing out the ridge and replacing it. That one experience is about the worst thing I know about tuning engines and carbs.
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Re: Head Porting for Fuel Milage

Post by Tom68 »

Tuner wrote: Sat Jan 28, 2023 8:17 pm It is in this thread on page 6. Cliff notes = "sharp 90 deg. edges are good" viewtopic.php?f=1&t=58475 I recall this image being posted a few times in the last 15 years and being better able to read it, but I couldn't find the right thread. The search function in this forum is quirky and not effective. I have been trying to find my own posts about the '66 289 Ford 4V spacer with the sharp edges protruding into the flow, the lower half is slightly smaller than the upper half with a sharp edge at the parting line. Removing the lip on an otherwise stock motor caused the car to go from 9.50 1/8 mi. ET to 10.70 and the mileage to drop from 25 MPG to 15. Got another original spacer from a wrecking yard and put it right back to where it was, only change was polishing out the ridge and replacing it. That one experience is about the worst thing I know about tuning engines and carbs.
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Re: Head Porting for Fuel Milage

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RDY4WAR wrote: Sat Jan 28, 2023 4:57 pm
David Redszus wrote: Thu Jan 26, 2023 11:56 am Raise the compression ratio. That will improve efficiency across the entire rpm range.

Put it on a dyno and plot the BSFC curves.

Drive the vehicle in the rpm sweet spot. (see typical BSFC curves)
Compression definitely improves combustion efficiency, but I wonder to what degree the value. The main reason people chase better fuel economy is to save money on fuel. If the higher compression forces more expensive premium fuel, then it's counter-productive. At least that's my view on it. In such a case, if compression is limited by knock, parameters like swirl and squish velocity become prominent.

I'm curious what benefit could come from a pressure regulating check valve on the inlet side of the PCV system that would allow intake vacuum to pull reduce crankcase pressure. Say you have a 5 psi (~10 inHg) check valve on the inlet side and the engine is cruising with 15 inHg intake vacuum. The check valve would regulate the air flow into the crankcase and maintain a 10 inHg pressure drop in the crankcase. How much impact would such as this have on oil windage, pumping losses, and such? Would it potentially be worth a 0.1-0.5% mpg improvement?

In any case, there isn't much that can be done with the engine to get better fuel economy aside from using a smaller engine.
Great point RDY… I definitely don’t want to use more than 87 octane.
Heads are off first “ rebuildable core” . Engine already bored .040…. So no larger pistons are available… but bores look good and might work ok.
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Re: Head Porting for Fuel Milage

Post by mag2555 »

Another point that might be looked at that is not engine related and is many times overlooked is rotating weight.
Rims and tires can sap up a noticeable amount of power.
You might not have much choice on tires, but lighter rims might be doable.
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Re: Head Porting for Fuel Milage

Post by PackardV8 »

mag2555 wrote: Mon Jan 30, 2023 10:45 am Another point that might be looked at that is not engine related and is many times overlooked is rotating weight.
Rims and tires can sap up a noticeable amount of power.
You might not have much choice on tires, but lighter rims might be doable.
For true. Taking my life in my hands here referencing electric vehicle experiences, but my own and many others on various fora show a 7% to 15% drop in efficiency when switching from OEM EV tires (which are admittedly built for maximum efficiency rather than traction and handling.) to mainstream performance tires. Going wider and stickier are those at the 15% loss end.
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Re: Head Porting for Fuel Milage

Post by BobbyB »

PackardV8 wrote: Mon Jan 30, 2023 11:33 am
mag2555 wrote: Mon Jan 30, 2023 10:45 am Another point that might be looked at that is not engine related and is many times overlooked is rotating weight.
Rims and tires can sap up a noticeable amount of power.
You might not have much choice on tires, but lighter rims might be doable.
For true. Taking my life in my hands here referencing electric vehicle experiences, but my own and many others on various fora show a 7% to 15% drop in efficiency when switching from OEM EV tires (which are admittedly built for maximum efficiency rather than traction and handling.) to mainstream performance tires. Going wider and stickier are those at the 15% loss end.
Agreed...I have crudely compared this 4x4 ranger against my 95 corolla daily driver...in a coast down test from "the top of the hill at my neighbors house to my driveway... corolla requires significant braking to stop in driveway...Old Blue (ranger) requires significant gas pedal "well before driveway to make it to the driveway... Not so good for the ranger...however the corolla is not very good at being a tractor...Old Blue is!
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Re: Head Porting for Fuel Milage

Post by dfarr67 »

Didn't EngineQuest make some HiPo replacement iron heads for this- at one time?
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Re: Head Porting for Fuel Milage

Post by SoCalDave »

Remove casting flash on the heads and do the same on the intake manifold. That should be the easiest thing you can do to improve power and fuel mileage.
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Re: Head Porting for Fuel Milage

Post by FC-Pilot »

PackardV8 wrote: Mon Jan 30, 2023 11:33 am
mag2555 wrote: Mon Jan 30, 2023 10:45 am Another point that might be looked at that is not engine related and is many times overlooked is rotating weight.
Rims and tires can sap up a noticeable amount of power.
You might not have much choice on tires, but lighter rims might be doable.
For true. Taking my life in my hands here referencing electric vehicle experiences, but my own and many others on various fora show a 7% to 15% drop in efficiency when switching from OEM EV tires (which are admittedly built for maximum efficiency rather than traction and handling.) to mainstream performance tires. Going wider and stickier are those at the 15% loss end.
Spot on Jack. Heck, I can even plot the improvement of fuel economy when inflating my tires above the recommended pressure in the door sticker. I never go crazy with it, and NEVER inflate more than is posted on the tire sidewall.

Admittedly, switching drivers from my wife to myself produces the highest gains in fuel mileage.

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Re: Head Porting for Fuel Milage

Post by RDY4WAR »

The cost becomes a factor in all of this. I have a friend who used to be into the ecomodding. He said he tallied up all he had spent on mods to improve fuel economy, and he never broke even on the fuel cost saved.

Take the wheels for example. Let's say you get an extra 0.5 mpg on a vehicle getting 12 mpg using lighter wheels. Let's say you go low end on the wheels at $150/ea, $600 total. Gas at $3.29/gal for 87, driving 10,000 miles a year.

10,000 / 12 = 833.33 gallons x $3.29/gal = $2,741.67
10,000 / 12.5 = 800 gallons x $3.29/gal = $2,632.00

$2,741.67 - $2,632.00 = $109.67 in fuel savings. At this rate, it would take 5.5 years to break even on the cost of the wheels. Even if it improved it 2 mpg, well off reality, it would still take 1.5 years.

Low rolling resistance tires are the same trap. You'll likely not break even on the extra cost of those tires over the lifetime of the tires.

When it comes to fuel economy, or rather saving money on fuel, you want to spend as little as possible to make it worthwhile. It's like people who trade in a perfectly fine vehicle that gets 25 mpg for a new one that gets 40 mpg. Sure, you might save $50/month on fuel, but you're paying $200-400/month more on the car payment and $50-100 more a month on insurance. It's counter-productive.
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