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Ram air for IO-360-M1B vs. snorkel

QuixoteAg

QuixoteAg

Well Known Member
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I have an IO-360-M1B engine on order for my RV6.
My lower cowling was for an IO-320 with a ram air opening

What would produce better power / less stress on the engine / better fuel flow and breathing?
A - Modify or buy a new lower cowl to use Ram air into the engine
B - Use a snorkel and Modify or buy new lower cowling to be smooth (I received notice that Vans is having to redesign the snorkel system because Lycoming changed FI vendors)

Thoughts?

Thanks
Chris
 
QuixoteAg said:
A - Modify or buy a new lower cowl to use Ram air into the engine
Click to expand...
No doubt version A... the better would be what we strangely don't see much in the RV world, real ram air, as was used on older Mooneys or racers, amongst others: ram air going straight into the throttle body (or carb), an eventual teed filter being used below say 1Kft or in dusty/sandy conditions.

The snorkel and its meandering is just air torturing ;)
 
Dan 57 said:
don't see much in the RV world, real ram air, as was used on older Mooneys or racers, amongst others:
Click to expand...
Thats a good question. Rod Bower had one where you would gain an inch to an inch and a half of manifold pressure.

Tim
 
Lots of opinions, not much data.

We have (or had) a few folks who installed Y systems, with a horizontal feed and a snorkel, so they could see MP with either. There wasn't much difference, certainly little enough that it's really not a choice between straight in or snorkel, but rather, a matter of detail design when installing either.
 
The M1B inlet (in the oil sump) is quite a bit above the air inlet on the updraft Van's cowling. Just go buy the Sam James Bottom cowling, specifically designed for true ram air, using their inlet filter. Otherwise, if you retain your current bottom cowling, then you have to do a whole bunch of mods to either the inlet piping to S curve down to the inlet and have to modify/make your own filter system. The trade off is a 500-750 dollars to sell your cowl and get the Sam James or a whole bunch of work to make what you got fit your cowling/engine combo. Airflow Performances has some bolt on elbow configurations. SkyDynamics has some as well. They made my intake tubes for the M1B engine (before there ever was that model). They may have some configurations of intakes that are used on Pitts and Acro aircraft that could be bolt on.
airflowperformance.com

Aircraft Fuel Injection For Lycoming Engines Certified and Experimental

Leading manufacturer of experimental aircraft fuel injection. We also overhaul Bendix fuel injection, Romec pumps and flow dividers. Stock all types of Lycoming fuel system parts and accessories such as fuel nozzles, electric pumps, brackets, spacers etc. We have about any aircraft fuel...
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Products

skydynamics.com skydynamics.com
 
Some data, RV-8 IO-360M1B with the AirFlow Performance 150C fuel manager and Van’s new snorkel:
- 8500’, atmospheric pressure 21.92
- Density altitude 9950’
- WOT
- Calibrated Manifold Pressure 22.4”

The data consistently showed ~0.4” manifold pressure increase across data runs.

I do not have data on drag reduction/increase of the snorkel cowl vs the ram air cowl.

I suggest a study of Rod Bower results before pulling that trigger.

Carl
 
Snorkel cowling looks cooler than scoop
Ram air equals more pressure, thus more power. However, don't think there is a free lunch here. More air means more fuel and higher fuel flows to get the gain. If you have it then you can use it. If you don't have it, then you get what you got at alt. Many studies on this and the engine is going to require a specific fuel consumption given a certain amount of air introduced into the cylinder.
If you want to go faster, lighten and clean up your airframe. Or reduce cooling drag.
A good read is Ken Paser's book on his Mustang 2 clean up. Lots of MPH out there for the willing.
 
For the snorkel arrangement, a good inlet at the left cooling intake ramp is "almost" as good as true ram air. With a filter in the intake cooling ramp, it all depends on the design and size of the filter. If you have some radius around perimeter of the filter rather than square edges, it will help some. And of course put the biggest filter you can get in there.

For true ram air, there are a few ways you can go. One is through a "Y" fitting with two butterfly valves, so you have an alternate filtered air source in the cooling ramp and direct ram when the butterflies are switched. Airflow Performance sells a nice Y fitting.

Another way to go for ram air is similar to the Rod Bower system. I am in the process of spooling up to make an improved ram intake with a conical filter and housing similar to the Bower system, but with a better alternate air path through the filter. Instead of intake through Reed valves taking in hot lower cowling air, I have an annular bypass duct as an integral part of the ram-air butterfly valve housing on the front of the filter canister. When the ram-air butterfly is closed, the air turns radially outward and in through the front of the filter canister. I think this is really going to work nicely.
As soon as I have the prototype assembled, I'll post some pictures.

If you are interested in this new ram air system, hang in there, its going to be another month or so. Send me a PM and I'll put you on the list.
 
DanH said:
Lots of opinions, not much data.

We have (or had) a few folks who installed Y systems, with a horizontal feed and a snorkel, so they could see MP with either. There wasn't much difference, certainly little enough that it's really not a choice between straight in or snorkel, but rather, a matter of detail design when installing either.
Click to expand...
Two decades ago, one of my friend did testing on 200 HP RV-7 and had no measurable MP difference between the two just like Dan reports.
 
Aden Rich said:
Snorkel cowling looks cooler than scoop
Ram air equals more pressure, thus more power. However, don't think there is a free lunch here. More air means more fuel and higher fuel flows to get the gain. If you have it then you can use it. If you don't have it, then you get what you got at alt. Many studies on this and the engine is going to require a specific fuel consumption given a certain amount of air introduced into the cylinder.
If you want to go faster, lighten and clean up your airframe. Or reduce cooling drag.
A good read is Ken Paser's book on his Mustang 2 clean up. Lots of MPH out there for the willing.
Click to expand...
more air only makes more power with more fuel. got that. but shouldn't make ram air the engine more efficient? if the engine has to do less work to suck the air through the system?
 
Up to a certain point the ram is going to help you. However, how will you derive more power if you don't add fuel to the air to combust? Air is just air and if you took the fuel out the combustion process, your engine would be a higher CFM air compressor, able to process more air flow because there is air being forced into the induction. Now that you have more air going into the cylinder on the intake stroke, you can get some better combustion if there is some unspent fuel in there due to more CFM of air present in the chamber. But beyond that, you have to add more fuel in there to combust with the higher amount of air to gain the power, thus fuel flows will probably go up.
My snorkeled 360 engine used 9,5 gph at cruise at 8K and all my EGTs were within 10-15 degrees at ROP (rich of peak). I had gone through the process of swapping out injector nozzles sizes to get each cylinder to burn the optimum amount. MP would be around 21,5./22. My carbed 360 in my Pacer burns 10 at the same height and EGT spread is 125 degrees with about the same MP. You would have to check calibration on all these instruments to get real scientific but you get the point.
If I had ram air on the injected engine that would give me a higher MP, I would have to add more fuel to realize the gain in HP available to be produced at that MP. I am not saying there is some efficiency gains to be had, just that beyond that, you will burn more fuel. My engine had Lycon cylinders on it and I spoke to Ken a great deal about that he told that all his mods to make more HP is creating the potential for more HP, but you won't be burning 7 gallons an hour and making more HP at ALT. You will be burning more fuel to get that HP and turn it into speed.

There is no free horsepower.
 
Many variables that could affect the best answer. I have an RV-6 with an angle valve engine, SD intake/sump, AFP FM200 and B&C starter. I wanted a snorkel but the intake, FI servo & starter combination meant it was very difficult to get it to fit. I ended up with a RAM inlet. The cowl started as a standard RV-6 item with scoop. The scoop is likely to need adapting to fit your sump/injector, you will likely have to bulge the front profile to fit the snorkel inside. Cowl reshaping is never a quick task. I don't know how much RAM benefit I see over a snorkel.
PeteCowl 1.jpgCowl 12.jpgInstalled 2.jpg
 
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