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Discussion Starter #1
Hi!

You can read a lot on the forum about cold air intakes. There is a lot spoken about the fact that the air enters through the wiper grills providing the filter with cold air but has anyone measured this already? Pressure difference in a closed air filer box (before the filter) and under the wiper grill. Is there no venturi effect with the grill because you have air passing by at high speed under an almost 90° angle with the grill?

On the other hand is it not better to have K&N drop in and enlarge the air feed system in front of the car like they do by bikes (RAM air, see Yamaha, huge HP gain while driving)?

What is the diffence on the dyno with stock air filter with and without the element?

I think if you would enlarge the pipes, make the front intake bigger (design a new wider intake instead of the small one now) you would have a good forced cold air intake with the only minus that you maybe mis the sucking sound of the 4 hungry dwarfs. Btw if you look to sport cars you never see a radiator flat under the body. The body is always shaped in sudge a way that the air is guided. If you drive your open roof you're also not blown away and the wind you get in never reaches the air speed as in the inlet tube of the air filter box. See also F1 cars with their big air intake facing forward.

Maybe my thoughts are wrong but I think it's nice to discuss about :cool:

Rogier
 

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CE's MC40
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4 Posts
Air Box Mods

Good questions! I pondered all of them myself and agree that a larger direct ram-air intake would be the best for performance gains. But...such a piece would, to work correctly, have to be much larger than the stock one and would require some major modifications to the grill and under-hood components. It is not a feasible aftermarket product. I opted for the BMP high flow airfilter kit. The installation was simple. I don't like the fact that intake air will be drawn from under the hood, in spite of the aluminum heat shield that comes with the kit. I did go ahead and drill four 1.325" holes in the abs housing, just above the airbox, that collects air around the wiper dam. I do know that there is a low pressure pocket of air at this location with the steeper the windshield angle the better.

I too pondered the venturi effect that may exist when air is allowed to flow through this area but figured that in the worse case scenario a strip of duct tape over the four holes would restore the sill box to its original condition.

I did notice an immediate improvement in off idle performance as well as a significant improvement in spooled up power. Plus the sound is nice.


Craig


racemier said:
Hi!

You can read a lot on the forum about cold air intakes. There is a lot spoken about the fact that the air enters through the wiper grills providing the filter with cold air but has anyone measured this already? Pressure difference in a closed air filer box (before the filter) and under the wiper grill. Is there no venturi effect with the grill because you have air passing by at high speed under an almost 90° angle with the grill?

On the other hand is it not better to have K&N drop in and enlarge the air feed system in front of the car like they do by bikes (RAM air, see Yamaha, huge HP gain while driving)?

What is the diffence on the dyno with stock air filter with and without the element?

I think if you would enlarge the pipes, make the front intake bigger (design a new wider intake instead of the small one now) you would have a good forced cold air intake with the only minus that you maybe mis the sucking sound of the 4 hungry dwarfs. Btw if you look to sport cars you never see a radiator flat under the body. The body is always shaped in sudge a way that the air is guided. If you drive your open roof you're also not blown away and the wind you get in never reaches the air speed as in the inlet tube of the air filter box. See also F1 cars with their big air intake facing forward.

Maybe my thoughts are wrong but I think it's nice to discuss about :cool:

Rogier
 

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Mini Mod
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9,227 Posts
kidlife said:
Good questions! I pondered all of them myself and agree that a larger direct ram-air intake would be the best for performance gains. But...such a piece would, to work correctly, have to be much larger than the stock one and would require some major modifications to the grill and under-hood components. It is not a feasible aftermarket product. I opted for the BMP high flow airfilter kit. The installation was simple. I don't like the fact that intake air will be drawn from under the hood, in spite of the aluminum heat shield that comes with the kit. I did go ahead and drill four 1.325" holes in the abs housing, just above the airbox, that collects air around the wiper dam. I do know that there is a low pressure pocket of air at this location with the steeper the windshield angle the better.

I too pondered the venturi effect that may exist when air is allowed to flow through this area but figured that in the worse case scenario a strip of duct tape over the four holes would restore the sill box to its original condition.

I did notice an immediate improvement in off idle performance as well as a significant improvement in spooled up power. Plus the sound is nice.


Craig

It's not low pressure.
It's basically neutral or too small to measure until you get to 50MPH.
I've documented this in the past.
 

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Mini Mod
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pressure

Sorry, realized I had posted this on another forum
Testing done with an Alta intake, lots of tape and plastic sheet(ask Randy) and a Magnehelic gauge. 2 runs each test in 2 diffferent directions and average to minimize any effects of the wind (which was < 10MPH that day)

In a nutshell.
You don't see a pressure differential until 50-55 MPH. It's almost .035 psi at 70MPH.
This was obtained by taking a bag( 2 gal trash bag) and taping it in place where the cowl opening is. Inserted the gauge lead in under the cowl grill and driving.

Remove the bag and just run the lead in and repeat. Readings are slightly lower. Remember this gauge is in .035 psi increments so you have to kind of trust my judgement. (This is THE reason I never really posted this info since I didn't want to take a beating from the anal test monkeys out there. You know who you are )
Run this 3 different times with the lead in 3 different places. Results are indistinguishable from each other. One with the lead right next to the filter.

Now the biggie.
I use plastic sheet and a friggin ton of tape to isolate the air box, close to what the OEM air box would be like. Rerun the tests.
Pressures are slightly, approx 1/4 psi, lower than with the open cowl being used.
For me that's all I really needed to see.

Note:
Max reading for the day was right a .06125 psi during an 80mph sprint.

I'm sure there's some cool mathematical ratio to explain the pressure rise. Like this:

45mph nuttin
55mph close to .0175 psi
70mph .04375psi
80mph .06125psi

One thing I didn't test but wanted to that's relative to this thread is; are forward or rear facing scoops better? Just couldn't figure an easy way to make test scoops. As upright as the MINI windshield is, I'm thinking rearward.


And for your further reading enjoyment.
Here's an experiment I did on under hood temps
 

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CE's MC40
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4 Posts
Pressure

Great stuff obe, thanks. Now just so I understand your results, at 70mph there is a .04 pressure differential measured from inside of the car and then to the sill box below the windshield? The pressure was LOWER in the sill box as opposed to the car's interior? If so then that's all good for an air intake location and specially good for a pumped air intake. I'm glad I drilled the four holes in the sill bulkhead.

BTW, thank you for the link to your temperature testing post. I was a little paranoid about allowing the air intake to have direct access to the under-hood temperatures but it would appear that is no reason to be scared!!!


Craig

obehave said:
In a nutshell.
You don't see a pressure differential until 50-55 MPH. It's almost .035 psi at 70MPH.
This was obtained by taking a bag( 2 gal trash bag) and taping it in place where the cowl opening is. Inserted the gauge lead in under the cowl grill and driving.

Remove the bag and just run the lead in and repeat. Readings are slightly lower. Remember this gauge is in .035 psi increments so you have to kind of trust my judgement. (This is THE reason I never really posted this info since I didn't want to take a beating from the anal test monkeys out there. You know who you are )
Run this 3 different times with the lead in 3 different places. Results are indistinguishable from each other. One with the lead right next to the filter.

Now the biggie.
I use plastic sheet and a friggin ton of tape to isolate the air box, close to what the OEM air box would be like. Rerun the tests.
Pressures are slightly, approx 1/4 psi, lower than with the open cowl being used.
For me that's all I really needed to see.

Note:
Max reading for the day was right a .06125 psi during an 80mph sprint.

I'm sure there's some cool mathematical ratio to explain the pressure rise. Like this:

45mph nuttin
55mph close to .0175 psi
70mph .04375psi
80mph .06125psi

One thing I didn't test but wanted to that's relative to this thread is; are forward or rear facing scoops better? Just couldn't figure an easy way to make test scoops. As upright as the MINI windshield is, I'm thinking rearward.


And for your further reading enjoyment.
Here's an experiment I did on under hood temps
 

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MUGEN POWER
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11,372 Posts
hmmmmmmm

I was thinkin even if u didn't gain much due to extra pressure u wud gain due to the fact that u have access to more air and probably colder too:)

no idea if u have tried this but if u have the plastic cowling out like u have to with an Alta and get sum one to put their hand on the pollen vent and rev the engine u can feel it sucking so it must be gud for summut;)
 

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CE's MC40
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4 Posts
What's a "polen vent"? :p


Craig

RedUn said:
hmmmmmmm

I was thinkin even if u didn't gain much due to extra pressure u wud gain due to the fact that u have access to more air and probably colder too:)

no idea if u have tried this but if u have the plastic cowling out like u have to with an Alta and get sum one to put their hand on the pollen vent and rev the engine u can feel it sucking so it must be gud for summut;)
 

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Mentalist
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83 Posts
Check out the attached thread on the NAM site. The idea is to remove the stock airbox and tubes and just attach a huge bare K&N filter directly to the throttle body. It was eventually determined that a K&N RU-1550 filter fits the best. Some testing has shown that the temperature difference may be negligible and is more than offset by the increase in air flow. Better gains than with an Alta intake apparently. What do you think of this?

http://www.northamericanmotoring.com/forums/showthread.php?t=25654
 

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Mini Mod
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9,227 Posts
Revolver said:
Check out the attached thread on the NAM site. The idea is to remove the stock airbox and tubes and just attach a huge bare K&N filter directly to the throttle body. It was eventually determined that a K&N RU-1550 filter fits the best. Some testing has shown that the temperature difference may be negligible and is more than offset by the increase in air flow. Better gains than with an Alta intake apparently. What do you think of this?

http://www.northamericanmotoring.com/forums/showthread.php?t=25654
The ole [email protected] filter experiment.

Effective and ugly.
 

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Mentalist
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83 Posts
Oops, I didn't bother checking whether you guys were talking about an S or a non-S. The [email protected] solution has only been tried on a MCS. Without an intercooler there may indeed be temperature issues because the intercooler isn't there to, um, cool. :rolleyes: I don't believe anyone has tried it on a non-S yet.
 

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Mentalist
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83 Posts
FYI...I did the "hot air intake" (HAI) mod described above and discussed in the thread I attached above. It works great! More pull especially above 3500 rpm, and the supercharger sounds much louder and different. It really screams at high rpms. You can also clearly hear the butterfly valve in the throttle body opening when you first hit the throttle.
 
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