Cold air induction and Increased HP

This was probably discussed before but I could not find the thread.
I just had an Air Flow Performance Injection installed on my Lycoming and instead of a filtered air box my buddy rigged up an unfiltered cold air intake with a filter bypass for ground operations. It looks like a slightly less tall air box with the same basic violin shape....just no filter to impede air flow.

So my question to the horsepower guru's out there is.... Does this setup increase HP significantly by taking away the filter resistance to direct air into the system? That is the idea of course, but has there been any testing done to prove this one way or another?

Should the shape be the same "bowl" as a FAB? or should it just be a snorkel-like inlet?

Does there need to be a ramp in the violin bowl directing air up into the vertical intake? or should the ram air be allowed to just "pool" in the air box?
Any thoughts or recommendations are appreciated.
Ron

patterson said:

Does this setup increase HP significantly by taking away the filter resistance to direct air into the system? That is the idea of course, but has there been any testing done to prove this one way or another?

Click to expand...

Depends on the filter media area and material, and how dirty it might be. With enough filter area, pressure drop across the filter can be very low.

I've done a low restriction filtered airbox...

http://www.vansairforce.com/community/showthread.php?t=44856

....as has Chris Z:

http://www.n91cz.com/

"cold air" name

BTW, normal Lycomings run the induction tubes thru the oil pan; the hot oil warms the induction air a bit. "Cold air" systems bypass the oil pan. This is not the same as a filter bypass, which is what you are contemplating.

In theory cold air sumps should give a denser air charge and more power.

I was having an interesting discussion with a very well known and loved engine builder in the USA recently and his Dyno results showed virtually no difference on the 360's but a noticeable gain on the 540's. Almost tempted to send mine over to him

I can only assume this is due to a size of sump thing and the air spends more time in a bigger chamber so the improvement is bigger? I have not studied this at all, in fact not given it any thought since then.

Dan?..any idea's ?

The rule of thumb is about 1% power increase for about every 10F drop in IAT at the port. Ideally, temperature measurements should be made in the port if the manifold design results in significant heat transfer to the charge air.

Assuming AFR is maintained at the same point, you must see a power increase as IAT drops.

Thomas @ g3i once told me the temp rise of a stock 540 sump was 1.5 deg. F.

Just some rough calculations, but if the average 2 inch induction tube on a O 360 is 18 inches long, the total volume of 4 induction tubes is about 226 cubic inches. An O 360 inhales 180 cubic inches of air per rpm. At a liesurely 1800 rpm's , its inhaling 180 cubic inches of air 30 times per second. That is 5400 cubic inches of air per second. It does not seem the induction air could pick up much heat at the speed it would be traveling through the induction tube, over 100 feet per second. That would be about one sixty sixth of a second any discrete cubic inch of charge air would spend in the induction tube absorbing heat

brad walton said:

Just some rough calculations, but if the average 2 inch induction tube on a O 360 is 18 inches long, the total volume of 4 induction tubes is about 226 cubic inches. An O 360 inhales 180 cubic inches of air per rpm. At a liesurely 1800 rpm's , its inhaling 180 cubic inches of air 30 times per second. That is 5400 cubic inches of air per second. It does not seem the induction air could pick up much heat at the speed it would be traveling through the induction tube, over 100 feet per second. That would be about one sixty sixth of a second any discrete cubic inch of charge air would spend in the induction tube absorbing heat

Click to expand...

I'd agree but can always measure it to know for sure. Cold air and ram air rather than haphazard cowling air should be worth a couple ponies at RV speeds. A good ram air system should be able to recover around 1 inch hg at 180mph. Most RVs are already set up to take induction air from outside the cowling for the lowest temperature. Flow bench tests on large K&N cone filters show almost no measurable loss at typical Lycoming flow rates of 200-300 cfm- like less than 0.5 inches of water which is about .037 inches hg.

measurment consideration

If you do go to the effort of measuring the temperature rise through the sump, Consider other factors.

A suggested test would be test the intake air to ambient delta T. with the sump and then another test with the "cold air induction" system.

Just measuring one without the other would mean very little to me.

There is certainly some (hopefully small) amount of heat that can still be picked up without the sump due to exhaust and cyl/head cooling air.


I have been interested in this data for a while but so far i am empty handed.

Perhaps the difference in gains are not as much to do with the temperature at all. Perhaps it is an improvement in volumetric efficiency through a less torturous path to the cylinder?

Alan was deadly serious about their observations to the point where he said it aint worth worrying about on the 4's, but definitely on the 6's.

Like many things, it may not be what it seems to be.