Donaldson/Tempest Filters

[N201MKTurbo]

None of this affects me. I have a MP red line of 30” and have no problem hitting it.

[Paul Thomas]

18 minutes ago, N201MKTurbo said:

None of this affects me. I have a MP red line of 30” and have no problem hitting it.

If you buy the improved performance claims, you should save fuel.

[skykrawler]

I switched to Donaldson - didn't know Tempest was making them till I saw the guy at  IA refresher in Richmond.

To me, it's all about cleaner air going into my engine.    That should reduce the silicone content in an oil sample.

[N201MKTurbo]

1 hour ago, Paul Thomas said:

If you buy the improved performance claims, you should save fuel.

How is the restriction from the air filter any different than the restriction from the throttle plate?

[philiplane]

4 hours ago, N201MKTurbo said:

How is the restriction from the air filter any different than the restriction from the throttle plate?

If you restrict the air coming into the turbo due to a poor filter, the turbo has to work harder to produce the MP you want. So it spins faster, makes hotter air, and wears out quicker.

Comparing a cellulose media filter to the others: a Brackett filter will generally cost you 1"  MP when new. A K&N costs about a half inch.

Edited June 27 by philiplane

[N201MKTurbo]

2 hours ago, philiplane said:

If you restrict the air coming into the turbo due to a poor filter, the turbo has to work harder to produce the MP you want. So it spins faster, makes hotter air, and wears out quicker.

Comparing a cellulose media filter to the others: a Brackett filter will generally cost you 1"  MP when new. A K&N costs about a half inch.

You are not getting my point. The throttle plate restricts the airflow through the system. Anything that restricts the airflow through the system is the same. The air filter is no different than the throttle plate. They both restrict the airflow through the system. As long as you get the manifold pressure you need, it doesn’t matter where the restriction is. If there was no air filter (power boost) you would need the throttle closed more to make up for the loss of restriction from the air filter. With a more restrictive air filter, you would need a throttle plate that was more open to get the same MP. In the end it is all the same.

Anybody with a power boost, E, F or J, the air filter doesn’t mean jack, just open the power boost.

[Pinecone]

11 hours ago, N201MKTurbo said:

You are not getting my point. The throttle plate restricts the airflow through the system. Anything that restricts the airflow through the system is the same. The air filter is no different than the throttle plate. They both restrict the airflow through the system. As long as you get the manifold pressure you need, it doesn’t matter where the restriction is. If there was no air filter (power boost) you would need the throttle closed more to make up for the loss of restriction from the air filter. With a more restrictive air filter, you would need a throttle plate that was more open to get the same MP. In the end it is all the same.

For NA, the only time the filter restriction is a factor in the power is at wide open throttle.

For a turbo, you can get the same power, but as mentioned, by working the turbo a bit harder.

[N201MKTurbo]

4 minutes ago, Pinecone said:

For NA, the only time the filter restriction is a factor in the power is at wide open throttle.

For a turbo, you can get the same power, but as mentioned, by working the turbo a bit harder.

I agree with your first statement, but not the second. 

[Paul Thomas]

1 minute ago, N201MKTurbo said:

I agree with your first statement, but not the second. 

I think of an engine as an air pump. If it's harder to get air, I automatically think that the engine has to work harder to get the same output (flow of air). Where is the error in my ways and what is it different for NA vs. Turbo?

[N201MKTurbo]

2 minutes ago, Paul Thomas said:

I think of an engine as an air pump. If it's harder to get air, I automatically think that the engine has to work harder to get the same output (flow of air). Where is the error in my ways and what is it different for NA vs. Turbo?

My point is except at WOT, we chose off the airflow intentionally with the throttle plate. We do this to get some specified MP. Wether we cloak it off with an air filter or a throttle plate, makes no difference.

My turbo system has a fixed waste gate with an upper deck pressure regulator. It maintains the upper deck MP at ~32” with a MP red line of 30”. So as long as the upper deck pressure is above 30” I will never know the difference, the turbo is always working too hard. 
 

There are quite a few different turbo systems. They all have their inefficiencies and compromises. In all of them, the contribution of the air filter is negligible.

[Pinecone]

On 6/27/2025 at 11:37 AM, N201MKTurbo said:

I agree with your first statement, but not the second. 

How so?  If I can get 39 inches of MP at full throttle, I am getting the same airflow.   The turbo is just sucking and blowing harder

[cliffy]

Just as another point of reference from personal experience-

I had the red fuzzy filter for a while and found that after a couple encounters with rain the "fuzzy" was washed off the outside of the screen and a light from behind showed BIG holes in the filtration. 

Went back to the Bracket.  

Take your red filter off sometime and try it. You'll find visible holes- many. 

Red filters in cars don't have the rain impact to deal with.