custom deader 4-2, pipe diameter?
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First go to this link and save some of the pics to your computer.
You'll need to give some thought as to the wall thickness of the tubing available to you because the OD's I am giving will effect the ID depending on tubing thickness .
The D&D + Two Brothers duals just use a single crossover pipe unlike the merged siamesed collector of the HMF in the link .
Usually a 38-40mm OD for 4-6 inches stepped up to 40-42 mm for the primaries of 18-19 inches total lenght. The 45-47mm or so OD to the mids then 50mm " 2.0 inch " on to the muffler inlet .
If you want to save some time and use the stock header down tubes then after the Y's bring the secondary tubes up to 1 7/8 OD then 2 -1/4 OD mid-pipes all thinnest guage you can get .
Drill , then heat the factory Y's and use a dent puller to bring internal volume up a bit .
I like the mild steel of the stock headers . Gas speed is high with mild steel and they are large enough inside diameter before the Y's . It's the combination of stock collector and smallish ID of the mid-pipes " 1.4 inch " that hurts power the most - IMO
Then make a crossover tube " just about mandatory " of around 75% the size of the secondary tubing .
There's many + 190hp bikes out there using a stock header section with a modded collector and mids .
You'll need to give some thought as to the wall thickness of the tubing available to you because the OD's I am giving will effect the ID depending on tubing thickness .
The D&D + Two Brothers duals just use a single crossover pipe unlike the merged siamesed collector of the HMF in the link .
Usually a 38-40mm OD for 4-6 inches stepped up to 40-42 mm for the primaries of 18-19 inches total lenght. The 45-47mm or so OD to the mids then 50mm " 2.0 inch " on to the muffler inlet .
If you want to save some time and use the stock header down tubes then after the Y's bring the secondary tubes up to 1 7/8 OD then 2 -1/4 OD mid-pipes all thinnest guage you can get .
Drill , then heat the factory Y's and use a dent puller to bring internal volume up a bit .
I like the mild steel of the stock headers . Gas speed is high with mild steel and they are large enough inside diameter before the Y's . It's the combination of stock collector and smallish ID of the mid-pipes " 1.4 inch " that hurts power the most - IMO
Then make a crossover tube " just about mandatory " of around 75% the size of the secondary tubing .
There's many + 190hp bikes out there using a stock header section with a modded collector and mids .
To make it easier you should make the first section right out of the engine (first 6" or so) in one piece that slips on to the rest. That's how a lot of mfrs are making them now. Makes it a lot easier to get on on off.
In other words each pipe coming out the engine would bolt to the bike, then bend down. The rest of the header would then slip on there.
If you really wanted to get creative, you make the parts I am talking about then go buy this from Brock:
Then all you have to do is make a crossover tube and mids to connect your cans like I did. Now I can use any slipon I want.
The biggest problem you will have once you settle on your design will be finding someone to mandrel bend the tubing, or if you can do it yourself, finding the equipment that can bend the uber thinwall tubing. My mids are actually a little heavy since the shop I used couldn't bend the super thin tubing.
In other words each pipe coming out the engine would bolt to the bike, then bend down. The rest of the header would then slip on there.
If you really wanted to get creative, you make the parts I am talking about then go buy this from Brock:
Then all you have to do is make a crossover tube and mids to connect your cans like I did. Now I can use any slipon I want.
The biggest problem you will have once you settle on your design will be finding someone to mandrel bend the tubing, or if you can do it yourself, finding the equipment that can bend the uber thinwall tubing. My mids are actually a little heavy since the shop I used couldn't bend the super thin tubing.
Great info,
So is the restriction in the stock pipes constrained to the secondary tubes and mid-tubes? I find it interesting that other manufactures have smaller diameter down tubes that get larger. I guess that is dictated by the exahaust ports....so may this makes sense.
So I'm gaining nothing but making larger down tubes? Sure be a lot easier to simply mod the stock headers and weld on larger secondary and mid-tubes.
I've got a hydraulic bend but need to buy the appropriate die for it. Sure like that HMF design. It is what I'm shooting for.
I am assuming that Brock's replacement primaries are the same diameter as OEM? If so, I see little reason to use then when I can get stocked used headers for $20.
So is the restriction in the stock pipes constrained to the secondary tubes and mid-tubes? I find it interesting that other manufactures have smaller diameter down tubes that get larger. I guess that is dictated by the exahaust ports....so may this makes sense.
So I'm gaining nothing but making larger down tubes? Sure be a lot easier to simply mod the stock headers and weld on larger secondary and mid-tubes.
I've got a hydraulic bend but need to buy the appropriate die for it. Sure like that HMF design. It is what I'm shooting for.
I am assuming that Brock's replacement primaries are the same diameter as OEM? If so, I see little reason to use then when I can get stocked used headers for $20.
What not just take OEM headers & modify them versus paying $200 a pop for Brock's?(thebbbusa @ Sep. 05 2007,09:02) To make it easier you should make the first section right out of the engine (first 6" or so) in one piece that slips on to the rest. That's how a lot of mfrs are making them now. Makes it a lot easier to get on on off.
In other words each pipe coming out the engine would bolt to the bike, then bend down. The rest of the header would then slip on there.
If you really wanted to get creative, you make the parts I am talking about then go buy this from Brock:
Then all you have to do is make a crossover tube and mids to connect your cans like I did. Now I can use any slipon I want.
The biggest problem you will have once you settle on your design will be finding someone to mandrel bend the tubing, or if you can do it yourself, finding the equipment that can bend the uber thinwall tubing. My mids are actually a little heavy since the shop I used couldn't bend the super thin tubing.
Do you have any pics of your exhaust build?
The brock primaries are larger than stock, so are all other aftermarket headers. They keep the first several inches small to keep the velocities of the spent gases up so it gets away from the head. There are compromises to all exhaust systems. Where one can be designed for power up top, another might be designed for more grunt down low.
As I said, mfrs use stepped headers to keep velocities high. My Two Brothers header looks almost stock, just bigger pipes. Unfortunately my pipes are not stepped as you have seen here. I would suspect there is a slight advantage to stepped headers, but the only way to know for sure would be to do dyno runs back to back with stepped vs. non stepped on the same bike. Even though they are stepped, they are still starting with a larger ID for more flow than the stock ones have.
I would expect that you will spend more on the die you need to complete your project, than would make the whole effort worth it...unless of course you really want to have something special. Mountainmotor fabbed his own up and I did too. I am not sure of my exact power gains, but I do notice a difference in performance. I did it more because I liked the dual can look than anything else. If you want true performance you will need a stepped setup like the HMFs and Brocks.
You could cut the stock headers off and weld on new larger pipes, that's a thought. Thing is, you'd likely have dissimilar metals cause your stockers are iron and aftermarket you're gonna likely use stainless. But that's a thought.
The next point of restriction comes from the factory mid pipes. Once you take one off and look inside you will see why. After this point in the exhaust system I would venture to say there will be very little difference in performance gains or losses between the different can mfrs since most use the same or close core diameter and almost all are straight through.
Here's a link to my Winter Mod project, it's where the pics are.
As I said, mfrs use stepped headers to keep velocities high. My Two Brothers header looks almost stock, just bigger pipes. Unfortunately my pipes are not stepped as you have seen here. I would suspect there is a slight advantage to stepped headers, but the only way to know for sure would be to do dyno runs back to back with stepped vs. non stepped on the same bike. Even though they are stepped, they are still starting with a larger ID for more flow than the stock ones have.
I would expect that you will spend more on the die you need to complete your project, than would make the whole effort worth it...unless of course you really want to have something special. Mountainmotor fabbed his own up and I did too. I am not sure of my exact power gains, but I do notice a difference in performance. I did it more because I liked the dual can look than anything else. If you want true performance you will need a stepped setup like the HMFs and Brocks.
You could cut the stock headers off and weld on new larger pipes, that's a thought. Thing is, you'd likely have dissimilar metals cause your stockers are iron and aftermarket you're gonna likely use stainless. But that's a thought.
The next point of restriction comes from the factory mid pipes. Once you take one off and look inside you will see why. After this point in the exhaust system I would venture to say there will be very little difference in performance gains or losses between the different can mfrs since most use the same or close core diameter and almost all are straight through.
Here's a link to my Winter Mod project, it's where the pics are.
What is the OD on your 2 bros headers? Curious to compare them to Brock's. I will give them a call. Thanks for the info. Oh, what about your stainless tubing? Find it locally or what?
A die on my tube bender is only around $125. I'm always looking for excuses to buy more dies. Good call on the mixed metal. I can weld some mixed metal but certainly would prefer the same throughout.
Hey, btw, where did you source your screen material? I wanted to add black screen to the rear plastic. Looks nice, nice one!
I got my screens on Ebay, and painted them gold. You can get a very similar material at the local home improvement store too. There is also a guy here that makes them, although they may cost a little more.
I don't recall exactly the dim but it is very close to 2" OD at the point where it connects to the mids. I think the down tubes were something like 1.8" or close. Honestly I can't remember exactly...It was last winter.
I would venture to say that the final diameter on the Brocks and HMFs are similar to mine, they just have the stepped section at the beginning.
FYI People also claim that 4-2-1 flows better too. I don't really know though.
I don't recall exactly the dim but it is very close to 2" OD at the point where it connects to the mids. I think the down tubes were something like 1.8" or close. Honestly I can't remember exactly...It was last winter.
I would venture to say that the final diameter on the Brocks and HMFs are similar to mine, they just have the stepped section at the beginning.
FYI People also claim that 4-2-1 flows better too. I don't really know though.
Why weld anything when you can build it slip fit all the way ? That is after upping the size of the secondary tubing of the stock header and welding thin guage steel to the stock collector Y's .
You will need to fabricate a couple of 3 bolt flanges or buy them or cut them off your stock mid-pipes .
If you just want hi-mounts you could just try to buy the mids from FMF - not a typo- FMF - Flying Machine Factory , then use flanges to mount your Yoshes to the exit ends .
Actually the FMF is more of a high exit than hi- mount .
Anyway , carefull on buying too much material and the likes as it might get to where you could have bought a compete HMF exhaust and sold off the mufflers for less cost and obviously less work .
M4 exhaust sells stepped down tubes and the slip fit springs and Burns Stainless has about anything you want to include mandrel bent pieces to help keep from having t do the pie shape piecing and welding to form a curved section together .
Good luck and post pics when finished
