2024 CX-5 Turbo Air Filter Box Test - Yikes

[AL Cx5]

Today I installed a WIX Filter Minder, FM, a gauge that measures the pressure drop across the air filter box inlet to the clean air side of the filter media.

I installed a WIX part # 24801. It took longer to find my 11/16" drill bit than to install the gauge.

If you have wondered when the filter needs to be changed, this product has been around for many years on heavy duty trucks and equipment. I've used one for 18 years on my truck to determine the air filter condition. It also indicated the air inlet to the filter box was undersized. We fixed thar issue on my Cummins turbo diesel.

I still have the OEM air filter that came on the car with 5,700 miles. I ordered a new air filter tonight to have a clean air filter comparison.

It appears Mazda is using the same air filter box on the turbo and NA engines but change to a deeper filter media on the turbos. Deeper filter pleats will pass more air.

Normal city driving the FM gauge didn't move. At WOT it measured 15" water column total pressure drop from the inlet to the filter and through the filter media.

I'll pull a steep hill nearby on I20W at 70 MPH on CC and let her eat. It will be interesting to see if this indicates the filter box is over powered under normal driving conditions.

The practice of using the same air filter box NA and Turbo is not all that uncommon. Ram used the same air box on their 3rd Gen 5.7 Hemi and 5.9 Cummins Turbo Diesel. We notice the same deal, the filter minder went to 15" pressure drop driving normally. Over the years folks have found ways to improve air flow through this box. I settled on a 3" hole in the bottom to tubing that increases to 4". I inserted a backdraft damper in the 4" and tuned the box so the damper starts opening at 4 PSI boost. Without this damper, we lost some low end torque. This damper acts like a variable runner inlet found on some NA engines. I tested with and without the damper and found the damper helps when under light load, solo.

I like the design of the Mazda air inlet keeping water out of the box and allow cool air in. I would have blamed the filter media first if I didn't have experience on another platform. We tried K&N drop in filters and didn't see any change in MPG or the FM. When we opened up the air box, we saw and felt a difference. Maybe the Mazda box inlet is undersized.

A 4000 RPM NA 2.5l at 0.05 bar pulls 157 cfm.
Turbo at 4000 rpm at .9 bar pulls 285 CFM or 45% MORE air than it's NA cousin.

The inlet tube to the air box is 3" diameter. Velocity NA is 3,205 FPM, Turbo 5,816 FPM. Again 45% higher velocity. The air changes direction several times to allow water particles to fall out. Holes are in is duct to allow water to exit. 5800 FPM entry velocity sounds very high. It is blasting dust particles across the box into the media. I found bees and flies in the media and no heavy dust in the bottom of the box like I've seen on some NA air boxes.

Velocity through the filer media is much lower and may or may not be the problem. I might order a "high volume" air filter to run as a comparison to a high filtration filter.

The first pic is driving around town, didn't move the gauge and the second is WOT in second gear to 5000 RPM measured +15" wc pressure drop.

 

[AL Cx5]

My short interstate drive, entering the highway 2 times, pulled a steep grade on CC at 70 MPH didn't move the Filter Minder. The car averaged 29.3 MPG on this short trip, including in town driving to and from the interstate, to give you an idea how easy I was taking it.

I believe the OEM filter box is just fine for daily driving conditions. A turbo at WOT will suffer some performance loss.

I'm going to investigate if a 3" backflow damper can be installed in the box without to many modifications. I'll post up if this works out.

 

[Odrapnew]

FYI that doesn't measure pressure drop, it measures static restriction (reference to atmosphere)
Also, depending on where you place the gauge can affect the reading as well.

But, use of a restriction gauge is very smart, you don't have to guess if it's dirty or not.
Check the gauge every once in a while, when it hits about 25", change filter.

 

[AL Cx5]

FYI that doesn't measure pressure drop, it measures static restriction (reference to atmosphere)
Also, depending on where you place the gauge can affect the reading as well.

But, use of a restriction gauge is very smart, you don't have to guess if it's dirty or not.
Check the gauge every once in a while, when it hits about 25", change filter.

The way I see it, it measures the static pressure on the clean air side of the filter, if the gauge is mounted in the clean air plenum.

The static pressure at this point includes the pressure drop from the dirty air inlet, duct and filter media.

On another platform we added an additional opening in the dirty air plenum and saw no pressure drop in the filter minder at high boost. Before adding this opening, the filter minder would show 25'' after the engine was at high boost and high rpm

I doubt I can wait to 25" wc pressure drop to change the filter. More like 6 to 8". Filters are cheap compared to fuel....

 

[Odrapnew]

The way I see it, it measures the static pressure on the clean air side of the filter, if the gauge is mounted in the clean air plenum.

The static pressure at this point includes the pressure drop from the dirty air inlet, duct and filter media.

On another platform we added an additional opening in the dirty air plenum and saw no pressure drop in the filter minder at high boost. Before adding this opening, the filter minder would show 25'' after the engine was at high boost and high rpm

I doubt I can wait to 25" wc pressure drop to change the filter. More like 6 to 8". Filters are cheap compared to fuel....

If the inlet is designed well, downstream static pressure and 'true' pressure drop should be the same.

Regarding the 25" restriction, I meant that as final value, which would be about 10" above what you have with a clean element. 10" rise is fairly typical for recommended filter change.

Also, with fuel injection, you'd be hard pressed to see a fuel mileage change even with a plugged filter. ECU will adjust fuel based on air flow. You might see a power drop, but that takes quite a bit and I bet the turbo can compensate for a plugged filter (at least to some point).

My motorcycle for example is fuel injected and I actually ran the OE filter until the bike wouldn't start because it was so plugged. Replaced filter and power was back, but zero change in mpg.

 

[AL Cx5]

Gotcha.

The FM stays at zero on normal driving. It went to 15" wc at WOT. I stay out of wot exxept to test and tune the Ecu.

So when the FM is say above 5" its getting time change the filter for me.

Seems like if power is down from a plugged filter, the engine has to rev to a higher rpm to make up the difference and down shift sooner. Both will impact FE.

Stayed tumed, I have an easy turning vane mod to our clean air duct. This increases low end torque and has better FE. I'm on rev 1 and will do some testing shortly...

My cost was 0, I used some scrap material...

 

[AL Cx5]

Update:

I installed a new air filter, no change on the FM at WOT, 15" wc vac.

Removed the air filter. Wot was 11" vac or 4" pressure drop across the new filter. See pic below.

That points to pressure drop across the air inlet and dap, dirty air plenum.

 

[ColtX-5]

Nice piece of test gear! I never knew such a thing was available.

 

[Conrad 16.5]

My 2003 diesel pick-up came with one on the stock airbox.

 

[AL Cx5]

My 2003 diesel pick-up came with one on the stock airbox.

Yep, my 06 has a filter minder. Only 270K mi on the clock...

 

[Odrapnew]

Update:

I installed a new air filter, no change on the FM at WOT, 15" wc vac.

Removed the air filter. Wot was 11" vac or 4" pressure drop across the new filter. See pic below.

That points to pressure drop across the air inlet and dap, dirty air plenum.

View attachment 329640

Good test.
Also shows how relatively little restriction there is in the element itself compared to the full system.

 

[AL Cx5]

Good test.
Also shows how relatively little restriction there is in the element itself compared to the full system.

Exactly! Sure is nice to see someone gets it!

After I'm finish the intake tube/turning vane mod, I'll look at how to allow more air into the DAP, dirty air plenum side. I'm going for the low hanging fruit. This one is showing a lot of promise.

On my 5.9 Cummins, we just add a 3" pipe in the DAP. I added a common backflow damper to this mod because we lost some low end torque. On my last trip towing 10,000 pound 28' car haul trailer I zoned out on CC and the truck down shifted going up a steep grade. RPM went near red line and boost was over 20 PSI before I turned off CC and let it up shift. The filter minder only went to 5" vacuum under this extreme condition.

We tune the DAP OEM inlet by installing a simple blast gate. I'm able to monitor boost and video when the backflow damper opens. It starts to open a 4 PSI and is fully open at 6 PSI.

This means the 3" opening in the DAP was doing it's job, allowing a lot more cool air to feed the engine.

Armed with this knowledge, I hope I can modify the CX5s DAP. It's doesn't have a nice flat spot like the Ram air box to cut a hole.

 

[chlronald]

Does it mean the airflow at WOL is restricted for turbo engine? Will an aftermarket intake do any good?

 

[AL Cx5]

Does it mean the airflow at WOL is restricted for turbo engine? Will an aftermarket intake do any good?

An aftermarket intake may help. I'm NOT willing to put a cotton/oiled filter on my engine and sacrifice engine life. Also, the quote CAIs get air from UNDER the HOOD. How can that be a Cold Air Intake!?

So the air is hot, the engine is not protected from sucking up water and it has poor filtration. Should I say more? I'll take the hit at WOT before I'd ever install one. Someone stop me from ranting and get booted from this forum!!!

Below is only and example. I'm sure there are a dozen more of the so called COLD Air Intakes...

https://d1th1shy3lujuj.cloudfront.n...x-5-short-ram-intake_tft8-8s.jpg?t=1715093599

I have a solution I'm working on. I bought the lower part of the air filter box, DAP and some parts to get more air flow into the box and not sacrifice the engine. This is tried and proven on Cummins turbo diesels. We found that we lost some low end torque when opening up the air box at partial throttle. We installed an inexpensive damper that opens when the air box exceeds a set amount of vacuum. It's not a slick looking bolt on with impressive and possibly manipulated WOT numbers. It works better and protects the engine as well.

If this mod works, folks like this mod and want to see WOT vs. CAI, set up a GoFundMe and I'll buy one of these so called CAIs and put the CX 5 on a chassis dyno and do a comparison. I have first hand experience on my CTD with the above mod. The Filter Minder on the CX 5 will tell if air flow increases and has less pressure drop. I'll log the engine as well. You guys determine who gets the CAI. I'd throw it away...

I hope to get this completed and tested over the weekend. I'll post results.

ONE MORE THING about CAIs. They always post HP gains at WOT. Great, but I operate at WOT less than 0.01% of the time. What happens at 30%, 40% throttle? The short answer, NO GAIN over a stock intake. I'll step down from my soap box now.......

 

[Odrapnew]

Does it mean the airflow at WOL is restricted for turbo engine? Will an aftermarket intake do any good?

I think a turbo engine would be less susceptible to a restricted element than naturally aspirated.

Assuming the turbo is not undersized from the start, if you have a little more restriction from the intake, the turbo could spin a bit harder (or wastegate blow off less) and maintain same air flow into the engine. You'll likely create a bit more heat, so it won't result in same power as a non-restricted.

That's a big, general statement, so don't take it as all fact.

 

[AL Cx5]

I think a turbo engine would be less susceptible to a restricted element than naturally aspirated.

Assuming the turbo is not undersized from the start, if you have a little more restriction from the intake, the turbo could spin a bit harder (or wastegate blow off less) and maintain same air flow into the engine. You'll likely create a bit more heat, so it won't result in same power as a non-restricted.

That's a big, general statement, so don't take it as all fact.

I agree to a point.

I improve FE by 4.5 mpg by installing a turning vane and smooth bore in the first 90 after the air filter box. Less restriction helped. I started a thread showing my progress.

Turbo work best with low intake restrictions. More restriction, slower spool up, higher exhaust temp, lower FE. Notice how drag cars stick the turbo facing forward so as the car goes faster it pushes the air into the engine.

On my Cummings turbo deisel we improved FE by 30% with a tune and bolt on mods. We have improved intake flow across the rpm range. We added turning vanes, more air into the air filter box and other tweaks. We have a community of folks who work together, sharing ideas and helping all who want more FE.

 

[N7turbo]

I have a smooth silicone hose and see no change in fuel economy. Just as a data point.

 

[AL Cx5]

I have a smooth silicone hose and see no change in fuel economy. Just as a data point.

Noted.

When you add a turning vane I'd like to see that data point. The design wraps the tv metal around a through bolt that is has double nuts and locktite. The bolt squeezes the 90 and TV as well. It's not going anywhere.

Roi is darn high, using an existing elbow, about $30 in materials..

We need another data point with a TV....

 

[N7turbo]

What about the other bends in the airflow, such as in the snorkel? Most are 90 degrees and don't have turning vanes in them. Those are the ones which would really benefit, much more so than gradual, smooth elbows.

 

[AL Cx5]

Snorkel, is this where the air and water are separated before entering the filter box?

It could benefit too. I'm hesitant to mod this. I want the air to make some directional changes to drop out water. And the velocity is lower vs the TIP.

What sticks out on the TIP 90/reducer coming off the air filter box on the turbo, the air is reduced again. The reducing section in on the out side radius of the previous 90/reducer. So a high density stream of air at increasing velocity runs through this reducer 2nd reducer. The TV I added diverts a portion of the air away from this reducer.

I see why Mazda did it this way. The is just not room to do it properly. The turbo inlet pipe is just one compromise after another. Obviously they concentrated on the hot side and did a bang up job with the exhaust manifold.

I tested a 2nd air inlet in the air filter box. I'll post up later on this post...