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Just after I changed my filter tonight, I read this!!!!
Just after I changed my filter tonight, I read this!!!!
Factory filters... To change or not?
- Thread starter cangreylegend
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When CP-E was designing their cold air intake for the mazda 6, they flow benched the stock intake system.
Us mazda6 guys asked if them if they could flow bench the restriction with various "airbox" mods in place.
One of these mods was of course a drop in K&N or SnB filter. We didn't have one handy, so we just removed the filter entirely and flow benched with, and without the airfilter. The results were the airfilter being completely removed, made roughly a 6% difference in the restriction of the stock intake system.
Performing other airbox mods (like removing the resonator, flapper, tray...resulted in over a 30% difference in flow. At least in the mazda6, the stock airfilter isn't a source of any restriction whatsoever...but the whole rest of the system sure is.
Us mazda6 guys asked if them if they could flow bench the restriction with various "airbox" mods in place.
One of these mods was of course a drop in K&N or SnB filter. We didn't have one handy, so we just removed the filter entirely and flow benched with, and without the airfilter. The results were the airfilter being completely removed, made roughly a 6% difference in the restriction of the stock intake system.
Performing other airbox mods (like removing the resonator, flapper, tray...resulted in over a 30% difference in flow. At least in the mazda6, the stock airfilter isn't a source of any restriction whatsoever...but the whole rest of the system sure is.
When I was at the True Flow facility getting my intake system put on they pretty much verified this. True Flow uses the factory airbox, a foam (Uni) filter, and a modified free flow intake tube. They told me that the factory filters flow every bit, plus some, of the air needed to supply the engine. They said the horsepower increase comes from the air tubes, not the filter. While they feel their filter is superior to stock in filtering capabilities, they had nothing bad to say about flow of the factory paper element.
Btw, my application is a 2003 Chev 2500HD with the 8.1/Allison.
Btw, my application is a 2003 Chev 2500HD with the 8.1/Allison.
The only time I could see a drop in air filter adding any type of power would be...
1) The stock air system is not restrictive, and the paper element is one of the primary sources of intake restriction.
2) The stock filter is extremely dirty.
Think of it this way. If you've got a garden hose, and suddenly add a 3 inch diameter section in the middle of it...is it going to increase the flow of water through the hose? Or is it just going to freak your neighbors out?
Do the reverse however, a 3 inch diameter pipe with a garden hose segment in the middle....
Here's a real world example of the discussion at hand.
This is the mazda 3 intake and exhaust system. That HG giger looking piece on the left is the primary intake ducting. Think adding a drop in filter to that mess of convaluted bends does anything to the airflow? Doesn't do a darn thing.
1) The stock air system is not restrictive, and the paper element is one of the primary sources of intake restriction.
2) The stock filter is extremely dirty.
Think of it this way. If you've got a garden hose, and suddenly add a 3 inch diameter section in the middle of it...is it going to increase the flow of water through the hose? Or is it just going to freak your neighbors out?
Do the reverse however, a 3 inch diameter pipe with a garden hose segment in the middle....
Here's a real world example of the discussion at hand.
This is the mazda 3 intake and exhaust system. That HG giger looking piece on the left is the primary intake ducting. Think adding a drop in filter to that mess of convaluted bends does anything to the airflow? Doesn't do a darn thing.
And here's another real world example:
http://memimage.cardomain.net/member_images/12/web/384000-384999/384791_10_full.jpg
The filter for this 3.8L engine is about 4"X6" the same size as they use on the 2.2 Cavoliers. There is a snorkel on the front of the airbox about 2" in diameter that pulls air from behind the head light.
A freer flowing filter will make a difference on this car. Also most american cars look more like this then the Mazda 6.
-T
http://memimage.cardomain.net/member_images/12/web/384000-384999/384791_10_full.jpg
The filter for this 3.8L engine is about 4"X6" the same size as they use on the 2.2 Cavoliers. There is a snorkel on the front of the airbox about 2" in diameter that pulls air from behind the head light.
A freer flowing filter will make a difference on this car. Also most american cars look more like this then the Mazda 6.
-T
Keith,
In your example...the filter is already oversized for the intake inlet. I don't see how it would really effect flow, or show any dyno results unless the filter it was replacing was dirty.
Remember that dyno runs generally will show a 2-4 whp difference just between run 1 and 2. Which is exactly what most people claim is a hp increase from the drop in filters.
If you actually dyno'd the stock filter, then replaced it with a K&N, then dyno'd immediately after, you'd most likely see a dyno loss. Of course K&N dyno's theirs first....
The main restriction in the intake you showed me, is that ribbed rubber tube. Those ribs usually extend into the tube itself, causing tubulence, and interrupting the airflow on the way to the TB. Replace that with a smooth pipe, and you'd see a power increase, as well as possibly smoother throttle response.
Actually the best system for your particular application would probably be something like this...
Get an extra stock airbox, and cut out the bottom and right sections, then use a conical short ram filter in the center of the box, and run a straight pipe to the TB.
This would smooth out the airflow, remove the ribbed restriction, and the stock airbox would provide insulation for the conical filter against engine bay heat soak.
In your example...the filter is already oversized for the intake inlet. I don't see how it would really effect flow, or show any dyno results unless the filter it was replacing was dirty.
Remember that dyno runs generally will show a 2-4 whp difference just between run 1 and 2. Which is exactly what most people claim is a hp increase from the drop in filters.
If you actually dyno'd the stock filter, then replaced it with a K&N, then dyno'd immediately after, you'd most likely see a dyno loss. Of course K&N dyno's theirs first....
The main restriction in the intake you showed me, is that ribbed rubber tube. Those ribs usually extend into the tube itself, causing tubulence, and interrupting the airflow on the way to the TB. Replace that with a smooth pipe, and you'd see a power increase, as well as possibly smoother throttle response.
Actually the best system for your particular application would probably be something like this...
Get an extra stock airbox, and cut out the bottom and right sections, then use a conical short ram filter in the center of the box, and run a straight pipe to the TB.
This would smooth out the airflow, remove the ribbed restriction, and the stock airbox would provide insulation for the conical filter against engine bay heat soak.
I don't see how a 4x6 filter can flow more then a 2.5" dia circle. Most air filters are twice that big for an even smaller engine. The ribbed hose has a larger diameter then the Throttle body. My engine has apporoxmately 270hp, do you think a 4x6 filter is big enough?
I used to have a box similar to what you posted with a 4" ID x 6" long K&N filter, I now have a much bigger paper filter. Most would say it is still too small.
-T
I used to have a box similar to what you posted with a 4" ID x 6" long K&N filter, I now have a much bigger paper filter. Most would say it is still too small.
-T
Thats what I was trying to point out. Its not a 2.5 dia circle. Its more like 1.8-2.0 internal diameter, and those ribs are effecting the maximum effective diameter as well, and inducing turbulence to the incoming air stream.
I'll try and find a flow chart if I can on the effect of those ribs. Its pretty depressing what it does to the intake charge
Actually I can measure the inside of the ribbed tube, I'd say it's much bigger then 1.8-2.0" in diameter.quote:
Originally posted by crossbow:
Thats what I was trying to point out. Its not a 2.5 dia circle. Its more like 1.8-2.0 internal diameter, and those ribs are effecting the maximum effective diameter as well, and inducing turbulence to the incoming air stream.
I'll try and find a flow chart if I can on the effect of those ribs. Its pretty depressing what it does to the intake charge.
-T
How deep is the box filter, how many pleats? Whats the inside diameter of the pipe? We can use physics and math here
.
Remember I was estimating that because of the turbulence caused by the ribs, that the maximum theoretical internal diameter of the pipe would be less, due to the loss of efficency caused by the ribs.
Aka if the internal diameter was 2 inches (lets say for arguements sake). Its not going to flow the same as a straight 2.0 internal diameter smooth pipe. More like a 1.5-1.75 pipe.
Remember I was estimating that because of the turbulence caused by the ribs, that the maximum theoretical internal diameter of the pipe would be less, due to the loss of efficency caused by the ribs.
Aka if the internal diameter was 2 inches (lets say for arguements sake). Its not going to flow the same as a straight 2.0 internal diameter smooth pipe. More like a 1.5-1.75 pipe.
I see what your saying, but I still stand by my belief that an intake like this can benefit by a freer flowing filter. I will get some pics and measurements for physics sake.quote:
Originally posted by crossbow:
How deep is the box filter, how many pleats? Whats the inside diameter of the pipe? We can use physics and math here.
Remember I was estimating that because of the turbulence caused by the ribs, that the maximum theoretical internal diameter of the pipe would be less, due to the loss of efficency caused by the ribs.
Aka if the internal diameter was 2 inches (lets say for arguements sake). Its not going to flow the same as a straight 2.0 internal diameter smooth pipe. More like a 1.5-1.75 pipe.
-T
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