header collector question

[jacksoni]

--- Header Collector Specs (Conventional Straight Tube) ---
Diameter= 3,278 Tuned Lengths= 17,9 best and 9,0 or 35,8

3rd Harmonic = 35,8 inches long ... more bottom-end Torque
4th Harmonic = 17,9 inches long ... highly recommended , best Torque Curve
5th Harmonic = 9,0 inches long ... reduced Torque , more top-end HP sometimes

[Belgian1979]

--- Header Collector Specs (Conventional Straight Tube) ---
Diameter= 3,278 Tuned Lengths= 17,9 best and 9,0 or 35,8

3rd Harmonic = 35,8 inches long ... more bottom-end Torque
4th Harmonic = 17,9 inches long ... highly recommended , best Torque Curve
5th Harmonic = 9,0 inches long ... reduced Torque , more top-end HP sometimes

Yes, the 4th harmonic was what made me think about it.

[jacksoni]

For street car you should be looking at the total length:

-- Total Exhaust System Tuned Lengths (Primary ends to TailPipe end) --
Best HP/TQ Tuned Collector Lengths= 17,9 , 35,8 , 71,6 , 143,2 inches long


So 143.2 or double that.

[Belgian1979]

It's 149,06" from cyl 1 to tailpipe.

[1989TransAm]

Actually from where and to where do you start measuring your collector ? I started from the end of the primaries to the flange.

Does your collector have a cone/spike in it. If so you need to take that into account.

[Belgian1979]

Actually from where and to where do you start measuring your collector ? I started from the end of the primaries to the flange.

Does your collector have a cone/spike in it. If so you need to take that into account.

No, it's just a plain jane older header. Four pipes welded in a collector. The center is welded shut.

[swatson454]

For street car you should be looking at the total length:

-- Total Exhaust System Tuned Lengths (Primary ends to TailPipe end) --
Best HP/TQ Tuned Collector Lengths= 17,9 , 35,8 , 71,6 , 143,2 inches long


So 143.2 or double that.

Unless you can find a reasonable means to separate the tuned length from the rest. Is a terminator box or an empty muffler case possible on your car?


Shawn

[bigjoe1]

Every one is really OVER THINKING this this topic real bad-- On full street exhaust set ups, there will be very little or NO DIFFERENCE. SORRY



JOE SHERMAN RACING

[hoffman900]

Every one is really OVER THINKING this this topic real bad-- On full street exhaust set ups, there will be very little or NO DIFFERENCE. SORRY



JOE SHERMAN RACING

It matters in road racing and circle track applications where requirements are similar (past the driver and have to meet noise regulations).

For full exhaust, assume the collector extends to atmosphere... so you're looking at the entire tailpipe length.

[MadBill]

2X
Unless steps are taken to 'de-couple' the rest of the system from the collectors (e.g. with Vizard-style terminator boxes) the engine will experience a very different tune than projected by an open header calculation. E.g., if a 9" or 18" open collector tunes perfectly for your application, putting a tapered adapter on the end and necking it down to 2-1/2" for the next 4 feet then running it through a muffler changes everything. If the system continued at 3" into an open can (e.g. Flowmaster type) muffler, then if the total length matched one of PipeMax's alternatives it should be pretty well set.

[Belgian1979]

What is a terminator box

[digger]

on a dual exhaust street system for a 250 bhp inline 6 i saw huge losses right at the bottom end (10%), in midrange (12-14) % and peak (10%) simply moving the x-pipe too close to the engine (from 550 mm from end of primary to 400 mm from primary). the AFR were a lot richer (until tuned) indicating the lower airflow through the engine but the engine seemed to not nose over as fast.

the twin system has a catalytic converter, resonator for each pipe and then a dual in and out muffler (not sure if the pipes are linked inside the muffler) complicating what is going on.

at some point i'm thinking i will run a y-pipe positioned at the 3rd harmonic (800mm) and run a simpler single pipe system

[MadBill]

What is a terminator box

There are a number of detailed threads here on S/T under the search term 'terminator box', but briefly, it is a large volume empty exhaust chamber or open Flowmaster-style muffler fitted to the end of the tuned collector, upstream of the muffler and tailpipe, that tricks the engine into 'thinking' the system is wide open. With a properly designed system, even very high power engines can see less than a 1% power loss vs. true open headers.

[1989TransAm]

If using two termination boxes each has to have a volume at a minumum the displacement of the motor to be fully effective.

[Belgian1979]

wow that is quite large. There is no way I can fit something like that under there.

So based on the comments I assume that there is not going to be any use to an extended collector.