Header Theory by Vince Roman from Burns @ PRI

[digger]

What about IR intake with zoomies ?

[GARY C]

I thought it was determined years ago the need to time each primary tubes individual pulse in the collector ruled out equal length tubes?

[mk e]

Gotcha Firedome8, If a V-8 engine was as close to PERFECT in design as mechanically possible i think we can agree that all parts and dimensions for each cylinder ( intake runner, intake port, valve size, port flow/shape, piston crown/shape, cc's of combustion chamber/shape, should be as close to identical to each other as possible. If this was the case, which it usually is NOT, each header primary pipe would want to be equal length one to another. I guess it is possible to change the primary length on a certain cylinder in an attempt to correct an imbalance on the intake side of the cyl. head Mark H.

It still would not want even close to identical lengths!!!!!!

DV

This has gone in an interesting direction.

My understanding is that many development efforts use single cylinder setups for their testing, assuming the results for any number of added cylinders would be identical (other than friction) and testing 1 cylinder dramatically reduces time and cost. Every simulation software I've ever seen makes a similar assumption.

I'm completely on board with Calvin's statements that better flow is normally more important that exactly matched tube lengths....and that assertion can easily be duplicated in simulations by plugging in head+header flow data. Makes sense.

The idea that matched cylinders DO NOT match I think will need some splainin' ??????

[digger]

If the cylinders are connected downstream in the exhaust then each cylinder affects another and probably in different ways so the engine is not simply 8 of the same single cylinder engines

[RevTheory]

I would assume that uneven pulses bank-to-bank play a big roll here.

[mk e]

If the cylinders are connected downstream in the exhaust then each cylinder affects another and probably in different ways so the engine is not simply 8 of the same single cylinder engines

The simulator I have assumes no......the important word being assumes. They say that's based on test data and as I said I know a lot of places like, f1 teams, do a lot of development on 1 cylinder setups.

As someone else said, an 8 cylinder with ITBs and zombies is effectively 8 single cylinder engines......as I'm really struggling with what seems to be an assertion that even balanced/matched it's not balanced/matched and requires exhaust changes.

[digger]

If the cylinders are connected downstream in the exhaust then each cylinder affects another and probably in different ways so the engine is not simply 8 of the same single cylinder engines

The simulator I have assumes no......the important word being assumes. They say that's based on test data and as I said I know a lot of places like, f1 teams, do a lot of development on 1 cylinder setups.

As someone else said, an 8 cylinder with ITBs and zombies is effectively 8 single cylinder engines......as I'm really struggling with what seems to be an assertion that even balanced/matched it's not balanced/matched and requires exhaust changes.

Some things probably work on a single cylinder from a correlation perspective but not all.

I'm pretty sure engmod you get different exhaust traces in each cylinder. It's been a while since I've looked at that

[mk e]

Some things probably work on a single cylinder from a correlation perspective but not all.

I'm pretty sure engmod you get different exhaust traces in each cylinder. It's been a while since I've looked at that

The stuff I've messed with over the years is even spaced or separate or both so I have basically no experience with uneven pulses. Once you connect the cylinders, particularly on an uneven setup as Rev suggested I'm sure something happens......which is why I'm interested in hearing what, and even more interested in seeing the data that supports the explanation

[Newold1]

Asked earlier her, but did Vince at Burns discuss or talk about in his seminar the question of equal length primaries and equal length 4-1 headers?? Users wan't to know!

[GARY C]

Some things probably work on a single cylinder from a correlation perspective but not all.

I'm pretty sure engmod you get different exhaust traces in each cylinder. It's been a while since I've looked at that

The stuff I've messed with over the years is even spaced or separate or both so I have basically no experience with uneven pulses. Once you connect the cylinders, particularly on an uneven setup as Rev suggested I'm sure something happens......which is why I'm interested in hearing what, and even more interested in seeing the data that supports the explanation

If not then I doubt merge collectors and wings in the collectors or collector size would be of any benefit but most perfect header designs go out the window when you factor in that they have to fit in a chassis.

[David Redszus]

The idea that matched cylinders DO NOT match I think will need some splainin' ??????

Quite right.

Long ago I was taught that equal length properly refers to equal FLOW length, not MEASURED length.

Reason being that pressure waves travel along the shortest path, while air particles prefer to travel
along the straightest path.

Consequently, each pipe bend or diameter change will affect pressure waves and wall friction will affect
mass flow. Additionally, exhaust gas temperature will affect sonic velocity and air density.

Pipe pressure sensing at each exhaust port will quickly reveal things we would rather not see.
But the issues are still with us, like it or not.

[vannik]

I'm pretty sure engmod4t you get different exhaust traces in each cylinder. It's been a while since I've looked at that

Correct. Nowadays a very small number of sims do not do each cylinder individually. It just makes too many assumptions.

[ClassAct]

The idea that matched cylinders DO NOT match I think will need some splainin' ??????

Quite right.

Long ago I was taught that equal length properly refers to equal FLOW length, not MEASURED length.

Reason being that pressure waves travel along the shortest path, while air particles prefer to travel
along the straightest path.

Consequently, each pipe bend or diameter change will affect pressure waves and wall friction will affect
mass flow. Additionally, exhaust gas temperature will affect sonic velocity and air density.

Pipe pressure sensing at each exhaust port will quickly reveal things we would rather not see.
But the issues are still with us, like it or not.

How do you determine the flow? On a flow bench? If so, what test pressure? If not a flow bench, what method of testing is used.
Since I started reading hear (before I joined) I did some reading at Elstons web site. I realize optimally you want the minimum of bends,and of those bends you want the radius as large as possible. For me, the rub starts when you are stuck dealing with stock bodied cars. Unless the primary tube is 1 inch, it's near impossible to get the tube straight for any length of time. Same goes for keeping the bends from being sharp. My question is in those cases, is the smaller tube still a better alternative? And then the length question comes up. Do you keep a bend nice and smooooooth and then add 3-4 inches to that pipe, or do you just live with the tight radius and make them all the same?

[mk e]

I'm pretty sure engmod4t you get different exhaust traces in each cylinder. It's been a while since I've looked at that

Correct. Nowadays a very small number of sims do not do each cylinder individually. It just makes too many assumptions.

Are you talking about all setups or just uneven setups?

If all setups what differences are there that you're tracking?

[Jim2527]

This is a pic I lifted from another site. Its a 180 degree C6 Corvette piece. IIRC the owner/welder strived for equal length tubes. Seems like the owner/welder should've sacrificed equal length for smoother bends?