Airbox mod results
#1
04-07-2017, 06:04 AM
Airbox mod results
I read a post on another forum from a FEH owner who had drilled holes in his air filter box. He reported more power with a MPG increase of 3-4 MPG, along with a louder engine noise.
Sounds good. Who wouldn't want more power PLUS fuel economy.
So I pulled out the stock airbox, noting the soda-straw intake tube that it feeds from. It certainly looked restrictive. Years ago, opening up the air filter housing was a quick way to improve performance, so why not try it?
The housing was very easy to remove once the filter element was out. One or two bolts. On looking at it, I determined the easiest way to add a lot of flow was to cut holes in the flat sides. So I used a 2" holesaw one either side in the large flat part. This is the deepest part of the box on the outboard end as installed. The result looked like you could pass a 2" bar through the box from either side. Including reassembly it took all of 30 minutes start to finish. I kept the circular cutouts in case I wanted to reverse it.
Results: The engine noisy is somewhat louder, but not objectionably so. It's sort of a throaty moan. I'm OK with it.
Power: There is definitely more mid-range torque. Passing is a much safer proposition now, as is merging with faster traffic. Cruising at 75-80 feels comfortable where before it felt like the engine was not happy. It appears the fuel economy at high speeds may be better, judging by the scangauge numbers. Much appreciated.
Fuel economy: Not so much. I'm no hypermiler, but I was getting a reliable 31 mpg with no real effort. Now I do good to hit 30 mpg on a tank. I suspect this is mostly from additional use of the loud pedal, as it's more responsive.
So the net result is better power at the cost of a louder engine sound, and maybe 3% less fuel economy. I call that a net gain, so I'll leave it for now.
If I get ambitious, I may look at making a vacuum actuated valve to open up the airbox when manifold vacuum drops. This was pretty common on 1970s muscle cars. That would preserve the OE sound and the as-designed air inlet, yet allow a lot more air in when you tip into the throttle. I am not sure this engine would generate a strong enough vacuum signal to make that work.
Sounds good. Who wouldn't want more power PLUS fuel economy.
So I pulled out the stock airbox, noting the soda-straw intake tube that it feeds from. It certainly looked restrictive. Years ago, opening up the air filter housing was a quick way to improve performance, so why not try it?
The housing was very easy to remove once the filter element was out. One or two bolts. On looking at it, I determined the easiest way to add a lot of flow was to cut holes in the flat sides. So I used a 2" holesaw one either side in the large flat part. This is the deepest part of the box on the outboard end as installed. The result looked like you could pass a 2" bar through the box from either side. Including reassembly it took all of 30 minutes start to finish. I kept the circular cutouts in case I wanted to reverse it.
Results: The engine noisy is somewhat louder, but not objectionably so. It's sort of a throaty moan. I'm OK with it.
Power: There is definitely more mid-range torque. Passing is a much safer proposition now, as is merging with faster traffic. Cruising at 75-80 feels comfortable where before it felt like the engine was not happy. It appears the fuel economy at high speeds may be better, judging by the scangauge numbers. Much appreciated.
Fuel economy: Not so much. I'm no hypermiler, but I was getting a reliable 31 mpg with no real effort. Now I do good to hit 30 mpg on a tank. I suspect this is mostly from additional use of the loud pedal, as it's more responsive.
So the net result is better power at the cost of a louder engine sound, and maybe 3% less fuel economy. I call that a net gain, so I'll leave it for now.
If I get ambitious, I may look at making a vacuum actuated valve to open up the airbox when manifold vacuum drops. This was pretty common on 1970s muscle cars. That would preserve the OE sound and the as-designed air inlet, yet allow a lot more air in when you tip into the throttle. I am not sure this engine would generate a strong enough vacuum signal to make that work.
#2
04-12-2017, 06:25 AM
Re: Airbox mod results
Update: I think my mpg drop may have been due to a change in routine - more short trips, less highway miles. I'm back to my normal routine now, and I'm seeing 31+ mpg tanks. Yesterday I easily passed 2 slow-moving trucks on a 2-lane road, accelerating from 40 to 70 with a lot more authority - and safety - than before.
So I'm calling it a net gain.
So I'm calling it a net gain.
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