Improving intake airflow (2.5T)

[N7turbo]

I installed an upgraded Turbo Inlet Pipe a couple of months ago. After the install, I started wondering how to improve the rest of the air path.

From the snorkel inlet, the air makes 5 or 6 turns before making its way to the turbocharger. I can't help but think this affects air velocity and overall flow, so the best solution would be to eliminate all the turns and provide a straight path for the air. Look under the hood of a Mercedes and you'll see this isn't a new idea—they run a hose/pipe from the snorkel straight back to the engine, with MAF sensors and filters just before the turbo. Where I'm stuck is what filter solution would work with a straight pipe that doesn't suck. I say that because K&Ns will increase contaminants reaching the engine, and the conical AEM DryFlow flows less than the stock filter according to @sinistriel@. We need something bigger or which flows better, mated to a 3D-printed snorkel that bolts to the stock location, eliminating all bends. If anyone has 3D-printing knowledge I'm serious about getting a working prototype on the car for testing as long as we can find a suitable filter.

 

[sinistriel@]

The AFE panel filter definitely flows more (according to MAF g/s) than stock and more than the Corksport SRI did for me. I don't recall saying it flowed less than stock, if I did I miss spoke.

 

[Koko_Bandit]

Many 3D 'home' printers are limited to ~10" x 10" x10" build volume or less. It would also require the use of ABS or other high temp material. There are companies that offer 3D printing services and have machines capable of larger build volumes. Shapeways is one for example.

The part will need to be designed with 3D printing in mind. A straight tube should not be a hurdle, but the mating ends could provide a challenge.

 

[N7turbo]

The AFE panel filter definitely flows more (according to MAF g/s) than stock and more than the Corksport SRI did for me. I don't recall saying it flowed less than stock, if I did I miss spoke.

Sorry, I'm referring to the conical filter on the short ram. I will edit for clarity.

 

[Lazy2.5]

I think the engineers would have done just that if it made more sense to do so. Even my tuner agrees that the stock intake system is very good (Better than aftermarket).

You can probably get slightly more airflow with your idea, and a lot more sound (Which would be cool, though not necessarily useful,) if you really did fabricate something custom for your vehicle.

Have you looked into getting your ECU tuned? Daniel Routley at DRTuned does a fantastic job. I think his work will give you the "fix" you're looking for.

I'll take a look at your suspension thread, because I'm curious what you've done on that end. My 316,000KM original struts and springs are getting tired - I will eventually look into getting Bilstein B4 Struts and Tanabe lowering springs for my "6".

 

[skid00skid0]

The stock parts no doubt use Helmholtz tuning, both to even out the torque through the rev range, and to make intake noise quieter and more pleasing.

I don't think there's much gain to get, and the lower end of the powerband, as airflow demands double at peak RPM.

Having said that, I've modified almost all my motorcycles, and a good number of cars...

 

[Lazy2.5]

The stock parts no doubt use Helmholtz tuning, both to even out the torque through the rev range, and to make intake noise quieter and more pleasing.

Not exactly a quiet intake on the 2.5

I don't think there's much gain to get, and the lower end of the powerband, as airflow demands double at peak RPM.

Can you please rephrase this for better understanding?

 

[N7turbo]

The stock parts no doubt use Helmholtz tuning, both to even out the torque through the rev range, and to make intake noise quieter and more pleasing.

I don't think there's much gain to get, and the lower end of the powerband, as airflow demands double at peak RPM.

Having said that, I've modified almost all my motorcycles, and a good number of cars...

Yeah.

Mazda's design is good, but I think there is room for improvement. You could say that if Mercedes thought this airbox idea was better, they would have done it.

On their V-engines, they run dual intakes from the snorkels, through hoses, then through an air filter on each side before going into the turbo. It's less user-friendly when it comes time to replace the filters but it's their way of packaging everything.

 

[skid00skid0]

Can you please rephrase this for better understanding?

The faster the engine spins, the more air flows thru the intake system. Since the system flows 'enough' air at redline, at lower RPM there will be no significant resistance to airflow, so no power gains will be seen.

And there may be specific RPM ranges, where (with a user-modified system) resonances actually DO increase power over the stock system, but at other RPM, power will be lower due to 'anti' resonances (out of phase resonances).

 

[N7turbo]

The faster the engine spins, the more air flows thru the intake system. Since the system flows 'enough' air at redline, at lower RPM there will be no significant resistance to airflow, so no power gains will be seen.

"Enough" depends on your perspective. Mazda cuts power intentionally above 4-5K and tunes airflow for low RPMs so airflow needs aren't what they would be with a tune. I think the stock intake is quite restrictive from the perspective of a motor running naturally at its potential on a premium only tune with free flowing air in and out. I've addressed part of that with the TIP, now it's time to complete the run to the snorkel. If only we had a downpipe available, that would also help.

And there may be specific RPM ranges, where (with a user-modified system) resonances actually DO increase power over the stock system, but at other RPM, power will be lower due to 'anti' resonances (out of phase resonances).

There could be, but they should be minimal with a smooth, straight pipe. And they can be tuned around. If I can get this project going I'll record MAF readings as the prototype evolves to quantify the changes.

 

[Lazy2.5]

"Enough" depends on your perspective. Mazda cuts power intentionally above 4-5K and tunes airflow for low RPMs so airflow needs aren't what they would be with a tune. I think the stock intake is quite restrictive from the perspective of a motor running naturally at its potential on a premium only tune with free flowing air in and out. I've addressed part of that with the TIP, now it's time to complete the run to the snorkel. If only we had a downpipe available, that would also help.

There could be, but they should be minimal with a smooth, straight pipe. And they can be tuned around. If I can get this project going I'll record MAF readings as the prototype evolves to quantify the changes.

I've noted engine behaviour above 5000rpm. The ECU will often detect pre detonation and pull timing. Not much that can be done to improve that.

 

[N7turbo]

If you're running premium fuel, there shouldn't be knock.

 

[Lazy2.5]

If you're running premium fuel, there shouldn't be knock.

I am, but there still can be cause for it regardless. It's dependent on so many factors outside of fuel choice or quality.

Premium fuel for example, wouldn't prevent the knock sensors detecting a bump in the road or flopping engine mounts, a hard corner, poor air quality etc while you're accelerating.

I usually don't see timing being pulled due to knock when being gentle on the throttle.

 

[skid00skid0]

If you're running premium fuel, there shouldn't be knock.

U.S. gas is of fairly poor quality...

 

[PulsarKF]

U.S. gas is of fairly poor quality...

That is not true. Our fuel is on par with any other country. The US and Canada measure the octane differently from other countries.

 

[PulsarKF]

The faster the engine spins, the more air flows thru the intake system. Since the system flows 'enough' air at redline, at lower RPM there will be no significant resistance to airflow, so no power gains will be seen.

According to @AL Cx5 Results in regards to the 2.5T specifically, the OEM air box does not flow enough air at redline. It is satisfactory for the NA engine however.

 

[N7turbo]

I am, but there still can be cause for it regardless. It's dependent on so many factors outside of fuel choice or quality.

Premium fuel for example, wouldn't prevent the knock sensors detecting a bump in the road or flopping engine mounts, a hard corner, poor air quality etc while you're accelerating.

I usually don't see timing being pulled due to knock when being gentle on the throttle.

How are you monitoring? I'll start using MazdaEdit soon.

 

[Lazy2.5]

That is not true. Our fuel is on par with any other country. The US and Canada measure the octane differently from other countries.

@N7turbo is right. European gas for example is of superior quality to NA market.

 

[Lazy2.5]

According to @AL Cx5 Results in regards to the 2.5T specifically, the OEM air box does not flow enough air at redline. It is satisfactory for the NA engine however.

I'm not sure what is the point of high rpm flow on a Skyactiv engine, especially the turbo. In my experience tuning the NA engine, I've rarely been able to coax the engine past 5000rpm without seeing the engine pulling some timing (-1 deg.). Once you get a turbocharger in the mix, it only fortifies this reality.

To take an engine so carefully designed around low-mid range driveability, and give it a high flow air intake design makes little sense.

 

[N7turbo]

I'm not sure what is the point of high rpm flow on a Skyactiv engine, especially the turbo. In my experience tuning the NA engine, I've rarely been able to coax the engine past 5000rpm without seeing the engine pulling some timing (-1 deg.). Once you get a turbocharger in the mix, it only fortifies this reality.

To take an engine so carefully designed around low-mid range driveability, and give it a high flow air intake design makes little sense.

That is because the engine is handicapped by the 87 octane friendly tune.