Cold Air Intake hogwash

[Whaler27]

The ”cold air intake“ claims have been discussed a lot over the years. During one of those debates I tried unsuccessfully to find a diesel forum thread that described very extensive testing that measured resistance, filter efficiency, load resistance, and other filter characteristics. Today I stumbled upon the test results which had been copied into another hosted site. Since I don’t want to lose it again, and I think folks here would be interested in the data, I’ve pasted it in below.

The study was done by Arlen “Spicer” looking at Duramax options. Those turbo diesels move a lot of air. I think the data developed during these tests is useful across brands and engine types.

For those who want the quick summary: Factory air filters probably do a better job of protecting your engine. Any resistance they provide has little or no adverse impact on performance.

Sponsored

 

[yokramer]

Its a cold air intake if it is moved to a location to bring in cold air, otherwise its something else.

 

[Whaler27]

Its a cold air intake if it is moved to a location to bring in cold air, otherwise its something else.

Yes, but the CAI kits invariably include the manufacturer’s aftermarket filter.

Anybody who flies crappy little single-engine planes with normally aspirated engines has felt the horsepower-robbing effect of rising air temperatures. Reduced air density means the engine is getting less oxygen per given volume of ingested air. Having said that, the difference in air temp/density achieved by the CAI systems is very small in vehicles moving aver 20 or 30 mph, and any air temp/density fluctuation is dwarfed by the influence of a turbo or supercharger.

 

[yokramer]

Yes, but the CAI kits invariably include the manufacturer’s aftermarket filter.

Anybody who flies crappy little single-engine planes with normally aspirated engines has felt the horsepower-robbing effect of rising air temperatures. Reduced air density means the engine is getting less oxygen per given volume of ingested air. Having said that, the difference in air temp/density achieved by the CAI systems is very small in vehicles moving aver 20 or 30 mph, and any air temp/density fluctuation is dwarfed by the influence of a turbo or supercharger.

These days putting an intake on is pretty much useless unless you are doing a bunch more as well. The stock intakes no longer are massive restrictions like they were 20 years ago. And on top of that when you start changing full intakes and exhaust you start getting into needing to tune for the new ones.

If you want sound without anywhere from minimal improvement to actual losses install whatever intake you can afford, otherwise put in a quality filter in the stock box and dont worry about it.

 

[ScottyKenneth]

I usually just go get a K&N and throw it in where the stock filter is. Done! No need for extra pipes spending like $300/$400. Waste of $.

 

[58Willys]

Cold air intakes and less restrictive filters are two different animals. Yes, both get more air into the engine. The big question is can the PCM and accompanying sensors compensate for the added air and provide sufficient fuel to create more power? Is the exhaust system capable of handling the increased volumetric efficiency? I don’t know the answers to those questions, but they need to figured out before dumping a bunch of money on these “upgrades”.

 

[Jtphoto]

The only true CAI for a Jeep is a snorkel and not all of them are built equal. Ramming more air down the tube may help intake but if the computer is not programmed to compensate (as already mentioned) does it really make much difference. My experience with Jeeps with 3.8L, JK3.6 and JL 3.6 is they don’t make any difference in performance only noise.
Realistically the factory intake over the front fender does a pretty good job of pulling in cooler air rather than hot engine compartment air.

 

[kah.mun.rah]

I get a lot worse MPG with my CAI. With the awesome sound it makes I constantly have the skinny pedal to the floor.

 

[Jtphoto]

At one point I had a tractor type bowl pre filter on my snorkel. It was OK on the trail and city speeds but on the highway it was worse on fuel.

 

[croppz]

Engineers have made intakes on modern cars so efficient that installing an aftermarket one is just purely for sound anymore. Especially on turbocharged cars. Unless you’re running a larger turbocharger needing more airflow, there’s no real benefit to throwing one on IMO

 

[Whaler27]

I usually just go get a K&N and throw it in where the stock filter is. Done! No need for extra pipes spending like $300/$400. Waste of $.

That achieves no measurable performance benefit, but it will introduce more contaminates into your engine.

 

[ScottyKenneth]

Yea you are right prob. I will just leave it as is.

 

[Whaler27]

Engineers have made intakes on modern cars so efficient that installing an aftermarket one is just purely for sound anymore. Especially on turbocharged cars. Unless you’re running a larger turbocharger needing more airflow, there’s no real benefit to throwing one on IMO

The Spicer tests attached here were done over 20 years ago.

In the turbo diesel discussions one of the engineers did the math showing approximately when the factory filter inability to flow more air would adversely affect performance. If memory serves, it was somewhere in the neighborhood of 700 horsepower, and that was back in the days when factory engines were still in the 200s and guys were doing all kinds of tunes and other mods to get over 400 hp with commensurate gains in torque. My stock 2024 F350 diesel makes 500 horsepower and 1200 foot-pounds of torque. Guys are are still spending big money to install aftermarket filters and cold air kits (which is especially silly on a turbo diesel that runs that level of boost.)

 

[Whaler27]

These days putting an intake on is pretty much useless unless you are doing a bunch more as well. The stock intakes no longer are massive restrictions like they were 20 years ago. And on top of that when you start changing full intakes and exhaust you start getting into needing to tune for the new ones.

If you want sound without anywhere from minimal improvement to actual losses install whatever intake you can afford, otherwise put in a quality filter in the stock box and dont worry about it.

With the exception of the Hemi, I doubt you can do enough to a modern Wrangler engine to create airflow demand the stock filter won’t allow.

The research detailed in this thread is more than twenty years old. I doubt OEM filters have been a performance-limiter within 25% of OEM horsepower in more than 40 years.

 

[Traveller128]

On the 3.6, there is a difference in power, you can see it on a dyno graph or when tuning. But, it's in the upper RPM range where the stock filter starts to restrict a bit. It's 8-12 HP, but it's there.

Normal driving, we saw a little bump in economy with ours. I'm blaming the better air inlet shape to the throttle body not using an accordion pleated area at the turn, but instead a tube tapering to the diameter of the throttle body as it turns with no pleats. This is an improvement in flow quality, works really well on the V8 Mopars also, people figured that out back in 2008/9.

Filter area with the Mishimoto is over 40% larger than the stock filter. Ours has a dry element that's washable. No gauze, it's a multi-layer synthetic that filters a lot better than oiled gauze but is less restrictive because of the area increase. Mishimoto uses the factory lower airbox, so air comes in the same as stock.

Having said that, I do not feel that all of the air filter arrangements out there will have the same effect. Many are for looks. Oiled gauze is for street cars, dusty conditions will let small particulate through. I have a long history of working with gauze/oiled since the early 80's.

You can easily bolt on an intake without doing a tune. We're talking a small percentage of improvement here, 10 HP more at the wheels is under 5%, which a stock ECM can compensate for. Will a tune improve gains? A little. You'll get a volumetric efficiency bump up high that a tuner can take advantage of. But a tune will improve it everywhere from bottom to top and regain lost power the OEM tune is moderating for torque limiting. The key is, you need an intake that drops inlet temps a bit or doesn't cause an increase in them over stock. If the temps are higher than stock, it will mitigate the flow gains.

With a tune, you'll see it optimized for the install, including exhaust and intake if you modified them.

Sponsored