Header Tube and Collector Specs "Trends"

[maxracesoftware]

Header Tube and Collector Specs "Trends"

Exhaust Gas Temperature ( EGT )
has a huge overall effect on the entire Exhaust System !
EGT sets up the Speed of Sound FPS + temperature gradient thru the entire Exhaust System !

Compression Ratio effects
Low Compression Ratios : ( High EGT's )
= Larger Tube + Collectors , and Longer Tubes + Collector lengths

High Compression Ratios : ( Low EGT's )
= Smaller Tube + Collectors , and Shorter Tubes + Collector lengths


Fuel Effects
Gasoline -vs- Methanol
Gasoline will have higher EGT temps than Methanol
so that Gasoline Engine will have slightly larger Tube + Collector diameters
and slightly longer Tubes + Collector lengths -vs- Methanol Fuel


EGT Effects
Low EGT's :
= Smaller Tube + Collectors , and Shorter Tubes + Collector lengths

High EGT's :
= Larger Tube + Collectors , and Longer Tubes + Collector lengths


other Effects are :
Header / Exhaust System Coatings, Tube Material, Wraps, Tube thickness

[theyoungone]

Doesn't an increase in temperature increase the speed speed of sound?

I always thought you could get away with a smaller pipe due to this but what you put was the opposite.
Can you explain this for me?

However, a hotter gas takes up more space so it make sense.

[maxracesoftware]

Doesn't an increase in temperature increase the speed speed of sound?

I always thought you could get away with a smaller pipe due to this but what you put was the opposite.
Can you explain this for me?

However, a hotter gas takes up more space so it make sense.

Yes, an increase in EGT temperature does increase the Speed of Sound FPS

since Wave FPS is faster , it needs longer Tubes and Collector lengths
to "Tune-in" the Negative pressure Wave to be approx. centered or "Timed" to occur on the TDC-Overlap Period .

[68corvette]

Isnt there a conflict between Compression and EGT sections?
Or is there some other parameters that reverse the order?

[hoffman900]

Isnt there a conflict between Compression and EGT sections?
Or is there some other parameters that reverse the order?

They’re the inverse of each other as there is more expansion happening due to the tighter “squeeze”.

[maxracesoftware]

Isnt there a conflict between Compression and EGT sections?
Or is there some other parameters that reverse the order?

this is pretty easy , not complicated !

Low Compression Ratios = Higher EGT's ..... Speed of Sound FPS is now faster
Tubes and Collector lengths need to be longer
Tubes and Collector diameters need to be larger

High Compression Ratios = Lower EGT's ..... Speed of Sound FPS is now slower
Tubes and Collector lengths need to be shorter
Tubes and Collector diameters need to be smaller

What you are trying to do is "Time" negative pressure acoustical wave to be approx centered on TDC-Overlap Period

and when i say "approximate" , i mean that even if an Engine has negative Overlap Period Cam specs
it will still benefit from Header Tuned Lengths/Diameters because negative wave pressure helps decrease exhaust pumping losses
as Piston rises towards TDC-Overlap Period

i've seen this effect on my Dyno tests many times

if your Engine Simulation program does not show this ... then its not relating or correlating to real-world results !

[ptuomov]

And the relevant compression ratio here is the expansion ratio to the exhaust valve open? Earlier exhaust valve open works the same as lower geometric compression ratio, all other things constant?

At which point will higher geometric compression ratio start requiring so much ignition retard that, in order to prevent knock, that EGTs will go up again? Probably not so relevant for naturally aspirated engines, but I’m thinking forced induction.

[dhidaka]

So Larry, for those of us without an engine dyno:
1. How is EGT measured?
2. How do we successfully use PipeMax in exhaust design calculations?

[maxracesoftware]

by ptuomov » Fri Aug 28, 2020 3:03 pm
And the relevant compression ratio here is the expansion ratio to the exhaust valve open? Earlier exhaust valve open works the same as lower geometric compression ratio, all other things constant?

At which point will higher geometric compression ratio start requiring so much ignition retard that, in order to prevent knock, that EGTs will go up again? Probably not so relevant for naturally aspirated engines, but I’m thinking forced induction.

So Larry, for those of us without an engine dyno:
1. How is EGT measured?
2. How do we successfully use PipeMax in exhaust design calculations?

ptuomov ....
Header Tube Lengths "Trends" :
The earlier the exhaust valve opens .... then the longer the Primary Tube length
-vice/versa
The later the exhaust valve opens .... then the shorter the Primary Tube length
.... reasons : you are trying to "Time" the negative pressure Wave to occur approx. centered on TDC-Overlap Period

ptuomov and dhidaka , this Picture below should answer your questions :

[ptuomov]

Interesting.

This seems to imply that opening the exhaust valve earlier (which, holding the exhaust valve closing constant, will increase the time available for the pulse travel between EVO and EVC) has a larger direct effect of increasing the tuned pipe length than its indirect effect of shortening the tuned pipe length due to higher EGTs. Is this always true?

[maxracesoftware]

Interesting.

This seems to imply that opening the exhaust valve earlier (which, holding the exhaust valve closing constant, will increase the time available for the pulse travel between EVO and EVC) has a larger direct effect of increasing the tuned pipe length than its indirect effect of shortening the tuned pipe length due to higher EGTs. Is this always true?

the EGT is the System's Speed ( Speed of Sound FPS ) you have to work with,
and the "Timing" of the returning negative pressure Wave @ TDC-Overlap is where huge amount of TQ and HP gains are ,
so the earlier EVO event is ... the longer the Primary Tubes need to be .

a "Hunting analogy" :
the faster the Duck flies ... the more you lead the shot with your Shot Gun

so basically ...
if you shoot too soon , you don't hit the Duck ( TDC-Overlap )
if you shoot too late, you don't hit the Duck either !
if you shoot at the correct time , you hit the Duck , and win the TQ and HP prize !
 

[ptuomov]

Interesting.

This seems to imply that opening the exhaust valve earlier (which, holding the exhaust valve closing constant, will increase the time available for the pulse travel between EVO and EVC) has a larger direct effect of increasing the tuned pipe length than its indirect effect of shortening the tuned pipe length due to higher EGTs. Is this always true?

the EGT is the System's Speed ( Speed of Sound FPS ) you have to work with,
and the "Timing" of the returning negative pressure Wave @ TDC-Overlap is where huge amount of TQ and HP gains are ,
so the earlier EVO event is ... the longer the Primary Tubes need to be .

a "Hunting analogy" :
the faster the Duck flies ... the more you lead the shot with your Shot Gun

so basically ...
if you shoot too soon , you don't hit the Duck ( TDC-Overlap )
if you shoot too late, you don't hit the Duck either !
if you shoot at the correct time , you hit the Duck , and win the TQ and HP prize !
 

Makes sense that if you can measure the exhaust gas temperature for the given camshaft and if the exact header design doesn’t really chance that EGT much, the return pulse from the collector or even open single pipe can be timed that way.

What do you do with turbocharged engines? Those see a constraint at the end of the pipe (the turbine) and send a different kind of pulse back for the overlap. Not the good kind!

The factory solution swells to be primaries about half the usual length for the total exhaust tract and minimum (apparently ideally zero) collector length with primaries pairing right at the turbine entry. But I’ve got no science behind that, just observing some anecdotes.

[maxracesoftware]

Interesting.

This seems to imply that opening the exhaust valve earlier (which, holding the exhaust valve closing constant, will increase the time available for the pulse travel between EVO and EVC) has a larger direct effect of increasing the tuned pipe length than its indirect effect of shortening the tuned pipe length due to higher EGTs. Is this always true?

the EGT is the System's Speed ( Speed of Sound FPS ) you have to work with,
and the "Timing" of the returning negative pressure Wave @ TDC-Overlap is where huge amount of TQ and HP gains are ,
so the earlier EVO event is ... the longer the Primary Tubes need to be .

a "Hunting analogy" :
the faster the Duck flies ... the more you lead the shot with your Shot Gun

so basically ...
if you shoot too soon , you don't hit the Duck ( TDC-Overlap )
if you shoot too late, you don't hit the Duck either !
if you shoot at the correct time , you hit the Duck , and win the TQ and HP prize !
 

Makes sense that if you can measure the exhaust gas temperature for the given camshaft and if the exact header design doesn’t really chance that EGT much, the return pulse from the collector or even open single pipe can be timed that way.

What do you do with turbocharged engines? Those see a constraint at the end of the pipe (the turbine) and send a different kind of pulse back for the overlap. Not the good kind!

The factory solution swells to be primaries about half the usual length for the total exhaust tract and minimum (apparently ideally zero) collector length with primaries pairing right at the turbine entry. But I’ve got no science behind that, just observing some anecdotes.

here's what i've seen on my Dyno tests,
especially on 700 to 800+ cid Engines with 4-1 Headers ( thats a whole bunch of Thrust , because these were heavy Engines )
and even on Craig's A/ND and B/ND SBC 406 to 410cid engines with Zoomies
If you make the Collector length at the worst Harmonic length ... the exhaust thrust will push the Engine forward
during a Dyno test , so that i have to abort the Run, and "Chock" the wheels on the Dyno Engine Stand
to prevent the Engine from moving towards me .

Same with Craig,
if we put on 4-1 Headers in place of Zoomies , and the Collector happens to be at worst Harmonic length, it will move his Engine forward .
this Test i did was new 3-Step Dragster upswept over rear tires ... so the Collector was pointing almost straight back
so we popped-off those Collectors and ran the Primaries like they were Zoomies
and they happened to be at the best Harmonic length ... so that they made very close to his best Zoomies
and did not move the Engine stand forward anymore

So my Theory is :
for Turbo app with a lot of Boost Psi , you would want the "Worst Harmonic length" to be at the Turbo
so you get the highest Boost Psi
.... just my Theory , never tested it yet

Until the Turbo Boost Psi relatively surpasses Atmospheric pressure
it should like the Length to be at around the Best Harmonic lengths

[ptuomov]

“So my Theory is :
for Turbo app with a lot of Boost Psi , you would want the "Worst Harmonic length" to be at the Turbo
so you get the highest Boost Psi
.... just my Theory , never tested it yet

Until the Turbo Boost Psi relatively surpasses Atmospheric pressure
it should like the Length to be at around the Best Harmonic lengths”

Interesting.

I am thinking that before the wastegate is opened, the highest priority is indeed to spin the turbo and make some boost. In the highest boost setting, my wastegate opens by 4800 rpm. In that 2500-4800 rpm range, making the pulses hit the turbine as hard as possible should be productive. Does this mean that I should tune the primary and/or collector lengths to their “worst” lengths at 3650 rpm? I’m not sure.

The reason why I am not sure is that I don’t know whether the worst length means that I’m just screwing up the camshaft overlap period or that I am increasing pumping losses. I would like to increase pumping losses at 3650 rpm if those losses go to spinning the turbine. Hell, I’d use a belt or electric motor at that rpm! However, I wouldn’t want the worst tuned lengths if that means that I am screwing up the gas exchange during the overlap. That would be highly counterproductive, because the main way to get the turbine to spin faster is to burn more charge and getting the overlap pressures to work right does just that.

Now, if we move to say 7500 rpm ie the current peak power rpm, now the wastegate is already open. The system is making all the boost it needs to make / can handle and bypassing some excess exhaust gas. Now, I don’t need any more pumping losses even if they spin the turbo. In terms of the overlap, now I really need the pulses tuned right because with the wastegate open it is very hard to keep the cycle average boost above that of the exhaust back pressure. So I definitely want low pressure exhaust pulse at overlap. But but but... since the exhaust pipe is plugged with the turbine, the same lengths that give me the good kind of pulse at overlap without turbo are going to give me the bad kind of pulse at overlap with turbo.

So, what’s the answer?

[maxracesoftware]

“So my Theory is :
for Turbo app with a lot of Boost Psi , you would want the "Worst Harmonic length" to be at the Turbo
so you get the highest Boost Psi
.... just my Theory , never tested it yet

Until the Turbo Boost Psi relatively surpasses Atmospheric pressure
it should like the Length to be at around the Best Harmonic lengths”

Interesting.

I am thinking that before the wastegate is opened, the highest priority is indeed to spin the turbo and make some boost. In the highest boost setting, my wastegate opens by 4800 rpm. In that 2500-4800 rpm range, making the pulses hit the turbine as hard as possible should be productive. Does this mean that I should tune the primary and/or collector lengths to their “worst” lengths at 3650 rpm? I’m not sure.

The reason why I am not sure is that I don’t know whether the worst length means that I’m just screwing up the camshaft overlap period or that I am increasing pumping losses. I would like to increase pumping losses at 3650 rpm if those losses go to spinning the turbine. Hell, I’d use a belt or electric motor at that rpm! However, I wouldn’t want the worst tuned lengths if that means that I am screwing up the gas exchange during the overlap. That would be highly counterproductive, because the main way to get the turbine to spin faster is to burn more charge and getting the overlap pressures to work right does just that.

Now, if we move to say 7500 rpm ie the current peak power rpm, now the wastegate is already open. The system is making all the boost it needs to make / can handle and bypassing some excess exhaust gas. Now, I don’t need any more pumping losses even if they spin the turbo. In terms of the overlap, now I really need the pulses tuned right because with the wastegate open it is very hard to keep the cycle average boost above that of the exhaust back pressure. So I definitely want low pressure exhaust pulse at overlap. But but but... since the exhaust pipe is plugged with the turbine, the same lengths that give me the good kind of pulse at overlap without turbo are going to give me the bad kind of pulse at overlap with turbo.

So, what’s the answer?

So, what’s the answer?

just need to start doing some testing to find out for sure if it will help you .

Note : all those Tests were in the working RPM Range between Peak TQ to Peak HP + about 300+ RPM higher than Peak HP RPM point
so i don't really know how much Thrust would be available if you were operating much below Peak TQ RPM point ???

Craig's SBC were making 1000+ Peak HP @ 9400 RPM
the BBC engines were making 1671's to 1760 Peak HP N.A.