Filter Size Effect on MPG

[cRiPpLe_rOoStEr]

Originally Posted by XCRN

No idea why, but thats the numbers I got.

Fewer temperature and charge air pressure, leading fewer fuel to vaporize.

[XCRN]

Originally Posted by cRiPpLe_rOoStEr

Fewer temperature and charge air pressure, leading fewer fuel to vaporize.

Right, but I would not think a 10 degree difference in the intake temp would increase mileage nearly 10%. Peak IATs were the same, just took longer the one log to get up to temp being slightly colder that day. If that small drop in IAT made that big of a difference I need to do a lot more work to dropping my IATs since I have been typically running 40-50 degrees over ambient with light cruising. My coworkers 1000hp CTS-V will run that hot only under boost so something is not quote right with my intake setup and there are possible major gains to be had.

This weekend if the wind finally quits I am going to do some back to back at 50mph and see what happens then. And if I notice the increase again in the smaller filter, I might go one set further and try a stock sized throttle body over my 92mm aftermarket one I have.

[Drifter]

Originally Posted by XCRN

Right, but I would not think a 10 degree difference in the intake temp would increase mileage nearly 10%.

There is a lot of noise in the data from one tank to another. Outdoor environmental conditions can have a dramatic effect. My bicycle has a power meter and I try to ride at a steady 180-200 watts most rides. On the same route, that might be 12-14 mph in a severe headwind or 22-24 mph in a tailwind. Those conditions are obvious, but a lot of the time there is a slight crosswind I can't perceive and end up looking at my tires wondering if they're losing air and that's why I'm goin 16-18 instead of 18-20..

Peak IATs were the same, just took longer the one log to get up to temp being slightly colder that day. If that small drop in IAT made that big of a difference I need to do a lot more work to dropping my IATs since I have been typically running 40-50 degrees over ambient with light cruising.

It is probably worth doing further testing. Normally higher IATs should lower pumping losses since your throttle will be open more for the same power output, but they might reach a point where they cause your computer to pull timing to prevent detonation.

Were you driving with the A/C turned off for both tests?

[cRiPpLe_rOoStEr]

Originally Posted by XCRN

Right, but I would not think a 10 degree difference in the intake temp would increase mileage nearly 10%.

Temperature alone is not the only reason for the lower fuel consumption.

[Blacktree]

Drifter has a good point. Real world conditions introduce many variables to the equation. You need a pretty large sample size (i.e. multiple tanks of fuel) to even out those variables.

[oil pan 4]

Originally Posted by Drifter

K&N filters are fine. They're neither magical nor demonic - they simply offer a different set of compromises than factory filters.

According to independent tests for a GM Duramax application, the K&N drop-in filter traded 3.13% lower filtration efficiency for 27.13% less resistance at 350cfm compared to the AC Delco filter: https://www.nicoclub.com/archives/kn-vs-oem-filter.html






That AC Delco filter costs $18.30 on Amazon. The equivalent K&N costs $69.99 plus ~$10 for a lifetime supply of air filter oil (you can use dish soap or simple green to clean). The AC Delco has a 45,000 mile change interval so in that application it takes about 200,000 miles for the reusable K&N to pay for itself from filter changes alone.

That's a diesel and its running wide open all the time.
I would figure out a way to put a bigger paper filter on before I went with a K&N. Which is what I did.

[oil pan 4]

Gasoline engines tend to like warm air. I ran a thermostatically controlled air intake set for 94F. That made the carb run a lot more consistently and a lot better in cold weather.
Diesels like cold air above 20 to 50F. It really depends on the engine, turbo and intercooler setup. Every engine is different basically have to test it to figure out what your diesel likes. If the engine is breathing in near freezing cold air (after the intercooler) its more than likely hurting mpg.