Header theory:
10-14-2012, 09:35 PM
#378
does this look familiar?
"Headers can increase power two ways. First by reducing the restriction to exhaust gas flow caused by a production cast iron exhaust manifold. A header allows the exhaust gases to exit the combustion chamber more easily allowing more air/fuel mixture to enter. The second is by taking advantage of a pressure wave phenomenon that occurs inside the header tube and utilizing it to create a low pressure area in the exhaust port during the overlap period of the valve timing events.
Pressure wave tuning is discussed at great length in the book "Scientific Design Of Exhaust & Intake Systems" by Phillip H. Smith and John C. Morrison. When an exhaust valve opens and the exhaust gases begin to exit the combustion chamber under high pressure, a pressure wave is formed that travels at about 1400 feet per second; this is much faster than the exhaust gases, which move at about 300 feet per second. How that pressure wave is managed can greatly affect the performance of a header design".
Its a good book but most of it is related to the recip engine with overlap and a lot of it says you have to experiment with your own engine/car set up. It does give some good advice.
I am STARTING with 1.75 inch primaries and a 3 inch collector. I dont know where i will end up.
heck back in the flathead ford days--people insisted that the exhaust pipe tip had to be the same height as the exhaust valve ( port in our case).
Has anyone measured the rx8's?
"Headers can increase power two ways. First by reducing the restriction to exhaust gas flow caused by a production cast iron exhaust manifold. A header allows the exhaust gases to exit the combustion chamber more easily allowing more air/fuel mixture to enter. The second is by taking advantage of a pressure wave phenomenon that occurs inside the header tube and utilizing it to create a low pressure area in the exhaust port during the overlap period of the valve timing events.
Pressure wave tuning is discussed at great length in the book "Scientific Design Of Exhaust & Intake Systems" by Phillip H. Smith and John C. Morrison. When an exhaust valve opens and the exhaust gases begin to exit the combustion chamber under high pressure, a pressure wave is formed that travels at about 1400 feet per second; this is much faster than the exhaust gases, which move at about 300 feet per second. How that pressure wave is managed can greatly affect the performance of a header design".
Its a good book but most of it is related to the recip engine with overlap and a lot of it says you have to experiment with your own engine/car set up. It does give some good advice.
I am STARTING with 1.75 inch primaries and a 3 inch collector. I dont know where i will end up.
heck back in the flathead ford days--people insisted that the exhaust pipe tip had to be the same height as the exhaust valve ( port in our case).
Has anyone measured the rx8's?
10-15-2012, 12:44 PM
#381
I didn't know that about the exhaust tip and the valve.
I think I shall try that on the boat motor I'm building.
A 521" engine with a 1.88 ex valve and a 4" exhaust.
Did someone say "nozzle".
I could just put a reducer on there and
you can bet it would speed up things. Just not my boat.
I think I shall try that on the boat motor I'm building.
A 521" engine with a 1.88 ex valve and a 4" exhaust.
Did someone say "nozzle".
I could just put a reducer on there and
you can bet it would speed up things. Just not my boat.
Last edited by Richard Paul; 10-15-2012 at 05:32 PM.
10-21-2012, 08:36 AM
#385
got the stuff--need more parts-- i changed my mine about the v band clamp, so i am getting a SS collector ring and pipe extension (pypes from Summit racing), and o2 sensor harness extender from Casper.
Planning on using a 8 inch collector ( after the merge).
At least I will have a standard type collector bolt pattern and good gaskets will be easy to get.
Planning on using a 8 inch collector ( after the merge).
At least I will have a standard type collector bolt pattern and good gaskets will be easy to get.
10-27-2012, 08:38 AM
#387
well no long tube header for me. No one in this one horse town can work with me and the closest shop that can is 100 miles away. Thats too far for me to work with.
I have added a better collector and extended the collector to 6 inches long, i have smoothed the angles of the header/midpipe/catback transitions. I am using 3 inch all the way from primary pipe back. So It should be a little better.
Here are some pics--before the final welding and install:
https://www.rx8club.com/attachment.p...1&d=1351344875
https://www.rx8club.com/attachment.p...1&d=1351344875
https://www.rx8club.com/attachment.p...1&d=1351344875
after this is installed I will get more pics and performance data.
Hopefully next week. --sigh.
I have added a better collector and extended the collector to 6 inches long, i have smoothed the angles of the header/midpipe/catback transitions. I am using 3 inch all the way from primary pipe back. So It should be a little better.
Here are some pics--before the final welding and install:
https://www.rx8club.com/attachment.p...1&d=1351344875
https://www.rx8club.com/attachment.p...1&d=1351344875
https://www.rx8club.com/attachment.p...1&d=1351344875
after this is installed I will get more pics and performance data.
Hopefully next week. --sigh.
11-01-2012, 08:57 AM
#388
header/collector has been welded. Midpipe taken to the shop today.
It is a short tube header--grrrrrrrr, but it does have a true 3 inch merge collector on it--so it may help a little.
The system will also have good gaskets available--for a reasonable price!
I hope I can install this w/e.
Not exactly what I wanted--but you have to take what you can get sometimes.
It is a short tube header--grrrrrrrr, but it does have a true 3 inch merge collector on it--so it may help a little.
The system will also have good gaskets available--for a reasonable price!
I hope I can install this w/e.
Not exactly what I wanted--but you have to take what you can get sometimes.
11-09-2012, 09:42 PM
#390
my exhaust is finished and installed. It is good. No numbers yet.
Yet and I hate to say this but----somethings you dont need numbers to know that it is better. it is obvious.
numbers to follow when I get a chance.
my system consists of
1- aftermarket tubular header with a true merge collector. primary pipe 1.75 inch, collector 3 inch
normal lenght. air pump stuff deleted
2- mazsport midpipe with 1st resonator removed and midpipe now has a more straight line. using 3 inch header/pipe collector.
3- RB catback with flange removed and midpipe extended--to make a one piece connection.
It is a true 3 inch exhaust from header to exit.
Obvious--I repeat obvious power gain from just the oem header with mazsport midpipe and rb catback. The gain can be felt from about 3K upward. Believe me or not--i dont care.
It is also a sound that I have not heard before--and I like it. Just a little loud for me but in cruising its fine.
Yet and I hate to say this but----somethings you dont need numbers to know that it is better. it is obvious.
numbers to follow when I get a chance.
my system consists of
1- aftermarket tubular header with a true merge collector. primary pipe 1.75 inch, collector 3 inch
normal lenght. air pump stuff deleted
2- mazsport midpipe with 1st resonator removed and midpipe now has a more straight line. using 3 inch header/pipe collector.
3- RB catback with flange removed and midpipe extended--to make a one piece connection.
It is a true 3 inch exhaust from header to exit.
Obvious--I repeat obvious power gain from just the oem header with mazsport midpipe and rb catback. The gain can be felt from about 3K upward. Believe me or not--i dont care.
It is also a sound that I have not heard before--and I like it. Just a little loud for me but in cruising its fine.
11-10-2012, 07:39 AM
#392
lol--you can do it!
http://garx8club.com/v3/download/file.php?id=4630
this was before I added the heat shielding.
http://garx8club.com/v3/download/file.php?id=4630
this was before I added the heat shielding.
Last edited by olddragger; 11-10-2012 at 07:41 PM.
11-11-2012, 06:15 PM
#393
lol--you can do it!
http://garx8club.com/v3/download/file.php?id=4630
this was before I added the heat shielding.
http://garx8club.com/v3/download/file.php?id=4630
this was before I added the heat shielding.
11-11-2012, 08:11 PM
#395
txs ...
here is a better view:
https://www.rx8club.com/attachment.p...1&d=1352686099
https://www.rx8club.com/attachment.p...1&d=1352686140
The resonator does not touch although it looks like it in the pic.
As I first stated this is without my heat shielding.
I saved about 20 lbs and it has more power--hands down.
Full 3 inch.
I may end up putting another very small resonator on this system.
here is a better view:
https://www.rx8club.com/attachment.p...1&d=1352686099
https://www.rx8club.com/attachment.p...1&d=1352686140
The resonator does not touch although it looks like it in the pic.
As I first stated this is without my heat shielding.
I saved about 20 lbs and it has more power--hands down.
Full 3 inch.
I may end up putting another very small resonator on this system.
11-23-2012, 05:37 PM
#400
I have learned a lot during this journey.
The difference a thin wall versus a thicker wall pipe can make.
Where you place a resonator in the system makes a LOT of difference, a possible reason why a single muffler setup ( big enough diameter) has the capacity to increase exhaust flow rate over a dual set up on our car, still exploring resonance, benefits of heat wrap NOT related to heat, the collector design DOES make a difference, most tube headers do NOT have equal length tubes and thats not that important, reversion off the oem center port, efficiency of muffler design, importance of proper resonator packing , J tube resonators and more.
I am tidying up my system now but there is definitely a power increase--it was worth it.
The difference a thin wall versus a thicker wall pipe can make.
Where you place a resonator in the system makes a LOT of difference, a possible reason why a single muffler setup ( big enough diameter) has the capacity to increase exhaust flow rate over a dual set up on our car, still exploring resonance, benefits of heat wrap NOT related to heat, the collector design DOES make a difference, most tube headers do NOT have equal length tubes and thats not that important, reversion off the oem center port, efficiency of muffler design, importance of proper resonator packing , J tube resonators and more.
I am tidying up my system now but there is definitely a power increase--it was worth it.