Why Racing Beat Header design?
Senior Member
Joined: Jun 2007
Posts: 270
Likes: 0
From: ireland
Think that's what I'm goin to end up doing myself. Loads of room under the FD to play around with. Just to get the engine running I made up a 20 inch primary into 3 inch with one silencer at the rear. Not as loud as I thought but still going to need to brought down a bit. They do make a sweet sound with a free exhaust.
Little video of the first start and it moving under its on power for first time in nearly 5 years!!
Little video of the first start and it moving under its on power for first time in nearly 5 years!!
i'm planning on making mine modular, and go to the dyno and see what the engine likes.
i want to buy 3, 4 foot sections of pipe, and cut one in half. this gives me the header 32", header + 2 feet, ~50", header + 4 feet, ~70", and then header +2 foot + 4 foot, which is 90"
that's 4 runs on the dyno...
once you get to the approximate length you can fine tune it a little.
i'm hoping mine wants a shorter header, so i can run more muffler, but i guess we'll see
i want to buy 3, 4 foot sections of pipe, and cut one in half. this gives me the header 32", header + 2 feet, ~50", header + 4 feet, ~70", and then header +2 foot + 4 foot, which is 90"
that's 4 runs on the dyno...
once you get to the approximate length you can fine tune it a little.
i'm hoping mine wants a shorter header, so i can run more muffler, but i guess we'll see
Joined: Aug 2002
Posts: 2,614
Likes: 31
From: Freeland, MI
Joined: Mar 2001
Posts: 31,835
Likes: 3,233
From: https://www2.mazda.com/en/100th/
i don't see what the infrared gun tells me anything that the dyno sheet wouldn't... i wanna try 4 different lengths, and lay the dyno plots on top of each other.
How its done is while its on the dyno under load you measure the exhaust at certain points. I don't really remember much after that, I need to dig up some old material but I think its a bit more a lost art.
But the way your doing it sounds simple and effective. I would not just run each length 1 time, I would run it multiple times and take the average since each run I doubt would yield the same hp/tq reading.
Then again, that costs extra $$$$$. SO always race as big as your budget allows I guess...
Joined: Mar 2001
Posts: 31,835
Likes: 3,233
From: https://www2.mazda.com/en/100th/
this.
I'm not super familiar with the practice, I learned it back when I had dynamometer and airflow courses. The gist is that you can tune your exhaust by finding the hot spots to determine where an X pipe or Y pipe would go or help aide in fine tuning your runner length. I think this is an older practice with carbs.
How its done is while its on the dyno under load you measure the exhaust at certain points. I don't really remember much after that, I need to dig up some old material but I think its a bit more a lost art.
But the way your doing it sounds simple and effective. I would not just run each length 1 time, I would run it multiple times and take the average since each run I doubt would yield the same hp/tq reading.
Then again, that costs extra $$$$$. SO always race as big as your budget allows I guess...
I'm not super familiar with the practice, I learned it back when I had dynamometer and airflow courses. The gist is that you can tune your exhaust by finding the hot spots to determine where an X pipe or Y pipe would go or help aide in fine tuning your runner length. I think this is an older practice with carbs.
How its done is while its on the dyno under load you measure the exhaust at certain points. I don't really remember much after that, I need to dig up some old material but I think its a bit more a lost art.
But the way your doing it sounds simple and effective. I would not just run each length 1 time, I would run it multiple times and take the average since each run I doubt would yield the same hp/tq reading.
Then again, that costs extra $$$$$. SO always race as big as your budget allows I guess...
so tuning the carb and getting the engine running was really great, the P port was pretty adamant about what it wanted, and after a bit of consternation about why the jetting in the carb was different than the jetting on the piece of paper from 1979, i just let the engine tell me what it wanted.
so the exhaust is the same way, i'm just going to let it tell me what it wants, and hope there is enough room for muffler
or if you want the funny version, the PP is a balancing act between what it wants, what i want, and what the neighbors want. for instance the neighbors like mufflers, the engine doesn't, and so i have a silencer for the neighborhood, the engine doesn't mind the neighbors are happy, and i'm happy.
Old [Sch|F]ool
Joined: May 2001
Posts: 12,865
Likes: 572
From: Cleveland, Ohio, USA
1979 fuel is a lot different from 2014 fuel, too.
I have heard of putting a dual exhaust on a V8 and then spraying it with cheap paint and then blasting around the block, then you put the crossover pipe at the midpoint between the two burnt spots. The only problem with that theory is that, on every car I have ever worked on (that is to say something made of metal instead of theories and thought exercises) you put the crossover just behind the transmission because there's no room in front of that because the trans is in the way, and there's no room behind that because the driveshaft needs that space if you want the rear suspension to move. The perfect spot is meaningless if you can't actually PUT it there.
I have heard of putting a dual exhaust on a V8 and then spraying it with cheap paint and then blasting around the block, then you put the crossover pipe at the midpoint between the two burnt spots. The only problem with that theory is that, on every car I have ever worked on (that is to say something made of metal instead of theories and thought exercises) you put the crossover just behind the transmission because there's no room in front of that because the trans is in the way, and there's no room behind that because the driveshaft needs that space if you want the rear suspension to move. The perfect spot is meaningless if you can't actually PUT it there.
Joined: Mar 2001
Posts: 31,835
Likes: 3,233
From: https://www2.mazda.com/en/100th/
i did paint mine, i think the amount of paint it burns off is more a function of time than anything else... either that or the "perfect spot" is moving rearwards and down.
the exhaust is also visibly sagging.
1979 gas is different, the average 12A with stock jets will lean misfire on 2012 gas, it runs ok, but the emissions numbers are higher than they should be
the exhaust is also visibly sagging.
1979 gas is different, the average 12A with stock jets will lean misfire on 2012 gas, it runs ok, but the emissions numbers are higher than they should be
or if you want the funny version, the PP is a balancing act between what it wants, what i want, and what the neighbors want. for instance the neighbors like mufflers, the engine doesn't, and so i have a silencer for the neighborhood, the engine doesn't mind the neighbors are happy, and i'm happy.
Rotary Freak
Joined: Jul 2003
Posts: 2,199
Likes: 9
From: Oakville, Ontario
1979 fuel is a lot different from 2014 fuel, too.
I have heard of putting a dual exhaust on a V8 and then spraying it with cheap paint and then blasting around the block, then you put the crossover pipe at the midpoint between the two burnt spots. The only problem with that theory is that, on every car I have ever worked on (that is to say something made of metal instead of theories and thought exercises) you put the crossover just behind the transmission because there's no room in front of that because the trans is in the way, and there's no room behind that because the driveshaft needs that space if you want the rear suspension to move. The perfect spot is meaningless if you can't actually PUT it there.
I have heard of putting a dual exhaust on a V8 and then spraying it with cheap paint and then blasting around the block, then you put the crossover pipe at the midpoint between the two burnt spots. The only problem with that theory is that, on every car I have ever worked on (that is to say something made of metal instead of theories and thought exercises) you put the crossover just behind the transmission because there's no room in front of that because the trans is in the way, and there's no room behind that because the driveshaft needs that space if you want the rear suspension to move. The perfect spot is meaningless if you can't actually PUT it there.
Eric
will one of these approx. 4 to 5 feet from the motor still choke a pport? I was going to throw it on to take some of the obnoxious sound away. 4 inch pipe. My header has 18 inch primaries.
