Do I really need a catch can

[texasboy21]

Maybe there is a misunderstanding, in 35 years of building engines or modifying them I have never, ever heard or experienced reducing back pressure actualling increasing it. I don't need to study exhaust velocities to know that removing cats and increasing diameter of pipes increases airflow and reduces back pressure.

I'm not trying to be a jerk, I also Googled it and nowhere could I find a website where they stated improving exhaust airflow also increases back pressure so maybe they're all wrong?

This might be a good read for some. There is a common confusion between exhaust gas velocity, scavenging, and back pressure.

http://www.gomog.com/allmorgan/exhaustbackpressure.html

Basically, with too large of a diameter pipe the velocity slows, the exhaust scavenging is greatly reduced (or even reversed), and the engine power is reduced. This loss of power isnt from an increase in back pressure, or lack of back pressure, it is due to the reduced exhaust scavenging.

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[Loki-GT]

You do understand that there are velocities to exhaust pressures that are being released through an exhaust manifold .. headers need to be designed according to these velocities for a proper flow rate . Just going bigger does not mean you are evacuating these flow rates with out creating back pressures into the intake ,, 35 yrs ,, there are 2 velocities of pressure at each exhaust cycle .

Yes I'm very aware, I am still wondering how increasing airflow through the exhaust which is what was being discussed increases back pressure, I know going bigger isn't always better and yet you still didn't answer the question.

In MOST engines, removing the exhaust manifolds and installing the proper headers and proper exhaust system will reduce back pressure, this is simple and accurate.

 

[Loki-GT]

This might be a good read for some. There is a common confusion between exhaust gas velocity, scavenging, and back pressure.

http://www.gomog.com/allmorgan/exhaustbackpressure.html

Basically, with too large of a diameter pipe the velocity slows, the exhaust scavenging is greatly reduced (or even reversed), and the engine power is reduced. This loss of power isnt from an increase in back pressure, or lack of back pressure, it is due to the reduced exhaust scavenging.

Agreed, of course there there are differences, all I can do is respond to the words he used. He said increasing airflow increases back pressure then defended the statement, I believe that statement is inaccurate. Not trying to get into a scientific debate, just asking for a clarification of the statement, how does increasing airflow through an exhaust system increase back pressure?

 

[Brian V]

Yes I'm very aware, I am still wondering how increasing airflow through the exhaust which is what was being discussed increases back pressure, I know going bigger isn't always better and yet you still didn't answer the question.

In MOST engines, removing the exhaust manifolds and installing the proper headers and proper exhaust system will reduce back pressure, this is simple and accurate.

Proper as in dimensionally tuned headers and proper exhaust . Sorry for an6 misunderstanding on my part . Have you looked at the OP s pics of the valves . These raise questions as to the exhaust he is running and not the pcv system . Ford has updated the baffle plate and added port injection for the 2018 302 engines .

 

[Loki-GT]

Proper as in dimensionally tuned headers and proper exhaust . Sorry for an6 misunderstanding on my part . Have you looked at the OP s pics of the valves . These raise questions as to the exhaust he is running and not the pcv system . Ford has updated the baffle plate and added port injection for the 2018 302 engines .

Yeah I saw the pics, not looking pretty it's one reason I avoid E85, too much fluctuation in quality and the need to run detergents once in a while. The 5.0 already had port injection, for 2018 they added direct injection but my guess is this is what you meant.

 

[bootlegger]

Yeah I saw the pics, not looking pretty it's one reason I avoid E85, too much fluctuation in quality and the need to run detergents once in a while. The 5.0 already had port injection, for 2018 they added direct injection but my guess is this is what you meant.

Technically, if you aren’t running top tier fuel, you probably should add a detergent every few tanks.

 

[TGGT]

I Have already answered this .. go study exhaust velocities and tuned headers .

Yeah thanks. I have. I’m not interested in some bs war of words on some car forum. We’ll agree to disagree on this one

 

[TGGT]

Alright look. Everyone is way over thinking this. Here are the facts. It is my car and no one here has done anything but look at some pics I posted. The car is burning oil. It is coming from the pcv system. A catch can will improve or prevent this condition. The deposits on the valves are from oil.

If anyone one wants to get into some back pressure vs cam timing vs reversion vs fuel additive issue please do so in a different thread. Thank you

 

[Loki-GT]

Alright look. Everyone is way over thinking this. Here are the facts. It is my car and no one here has done anything but look at some pics I posted. The car is burning oil. It is coming from the pcv system. A catch can will improve or prevent this condition. The deposits on the valves are from oil.

If anyone one wants to get into some back pressure vs cam timing vs reversion vs fuel additive issue please do so in a different thread. Thank you

Excellent points sorry for crapping on your thread, I personally would love to get an E85 tune but where I live there is no major supplier of quality versions of it except at the race track.

 

[GT Pony]

Alright look. Everyone is way over thinking this. Here are the facts. It is my car and no one here has done anything but look at some pics I posted. The car is burning oil. It is coming from the pcv system.

Where was the cylinder you scoped located in relation to the PCV port on the intake manifold? Did you scope the cylinder farthest away from the PCV port to see how the valve deposits compared? If the cylinder farthest way has the same level of valve deposits as the closest cylinder, then the majority of the deposits could be from the fuel.

But it can't hurt to run a catch-can. I'm just suggesting a way to determine if the deposits are mainly from oil or fuel.

 

[TGGT]

Where was the cylinder you scoped located in relation to the PCV port on the intake manifold? Did you scope the cylinder farthest away from the PCV port to see how the valve deposits compared?

Interesting point. I guess I’m not so sure on what cylinders the pics are from, but I will say this. When I put the CJ mani on I noticed a small amount of oil in all of my intake ports. Also when I pull the pcv line off of my manifold it drips oil. Not much but if I shake the line it throws oil every where. I’m kind of curious if the cobra jet manifold pulls so much air that it has a siphon effect. That coupled with the crank case pressure generated by 8 pistons moving at 7,000+ rpm is how I believe oil is winding up on my valves and in my cylinders

 

[bootlegger]

Alright look. Everyone is way over thinking this. Here are the facts. It is my car and no one here has done anything but look at some pics I posted. The car is burning oil. It is coming from the pcv system. A catch can will improve or prevent this condition. The deposits on the valves are from oil.

If anyone one wants to get into some back pressure vs cam timing vs reversion vs fuel additive issue please do so in a different thread. Thank you

I was only addressing your concern about intake valve deposits. I spent 3 years in detergent development, so it is one topic I know well. As far as burning oil is concerned, have you noticed it on your dipstick? Have you had to add much oil? I am at 3k miles, and have only added maybe half a quart.

 

[TGGT]

I was only addressing your concern about intake valve deposits. I spent 3 years in detergent development, so it is one topic I know well. As far as burning oil is concerned, have you noticed it on your dipstick? Have you had to add much oil? I am at 3k miles, and have only added maybe half a quart.

One and a half quarts in 4,500 miles

 

[bootlegger]

One and a half quarts in 4,500 miles

That is what I would consider borderline excessive.

 

[Zinc03svt]

I’m at 2700 and dip stick oil level has not moved. As OP stated the deposits on the valves are from excessive oil being pumped through pcv. He never stated how many miles he ran on pump before going E85. Corn is not going to carbon coat valves like that detergent or not.

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