Help with custom headers

[Sid_RallyX_82]

Ok I like the idea of wider power band from a TriY(is that the same as a 4-2-1?), so, how do I lay out the setup for it(if it isn't a 4-2-1)? Also, is there a way to calculate collector size and length? Same for final exhaust pipe?

[sketchman]

That is a 4-2-1 yes.

You could use Charlie's specs he posted up there and buy from coneeng.com. Just the collectors for the Tri-Y/4-2-1 would be around $75 from coneeng.com.

[drddan]

I like these posts

This is good advice!

You can't go wrong with a 4-1 that's longer than it needs to be, 30+ inches. Obviously a 4-2-1 will have multiple torque peaks, but simplicity sake, I'd stick with 4-1. Plenty of other car groups have plenty of great luck with equal length 4-1. Until you have your engine breathing to it's max, having a header fine tuned to a precise length isn't a huge deal, but anything with quality merge collectors is going to provide enhanced flow over those factory manifolds.

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4 to 1 will provide higher peak TQ numbers, depending on the tune length. Try y will give a more broad peak TQ area. Honestly though, the stock setup on these engines is so far from optimal, that it's very easy to make an improvement. A try y with 16" long 1.25" primaries and 21" long 1.75" secondaries, collecting into a 2" pipe for 36" would be about perfect for a 1300cc 2 valve car engine with a target TQ between 3000 and 5500 rpm.
Most low volume, budget minded header builders will stick to a traditional equal length 4 to 1 because it's the best bang for the buck. Collectors are the most difficult and expensive component in a header, and having 3 of them can drastically increase the cost of the header. Check out "Burns Stainless" website for an example of the commitment that goes into a good collector and you'll see why the value is in the 4 to 1 merge. If you were to use Burns collectors to build a try y you'd have 450 dollars invested in just your collectors. I often use Burns collectors when making 1 or 2 headers because it's cheaper than building 1 or 2 of my own collectors.

[navdoc101]

My FMS Header is a 4 - 2 - 1

[bhearts]

With the option of a rear turbo, a header is a great mod for the future. A header will help with a rear turbo, and it will help if you decide to supercharge your engine. So it's good in every situation.

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[Advancedynamix]

Ok I like the idea of wider power band from a TriY(is that the same as a 4-2-1?), so, how do I lay out the setup for it(if it isn't a 4-2-1)? Also, is there a way to calculate collector size and length? Same for final exhaust pipe?

Yeah, 36" 2" exit, after the 36" you should step up to a larger diameter . I prefer to exit into a 2.5" resonator. This provides the tune length you desire, without the droning sound of having a tune length end directly under your thin tin box. I use another resonator, after that one, and a well baffled muffler. If you want a race car sound, go without the muffler. I dont suggest leaving out the resonators. The droning hum is really annoying at freeway speeds in these cars.

[eurotiva]

I can say from experience, a header and rear turbo doesn't work as well as one would think. I've learned it's about velocity not volume.

That being said, my 11 second passes was through a stock festiva exhaust!

[bhearts]

I can say from experience, a header and rear turbo doesn't work as well as one would think. I've learned it's about velocity not volume.

That being said, my 11 second passes was through a stock festiva exhaust!

Wouldnt the header equate to velocity?

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[Sid_RallyX_82]

Yeah, 36" 2" exit, after the 36" you should step up to a larger diameter . I prefer to exit into a 2.5" resonator. This provides the tune length you desire, without the droning sound of having a tune length end directly under your thin tin box. I use another resonator, after that one, and a well baffled muffler. If you want a race car sound, go without the muffler. I dont suggest leaving out the resonators. The droning hum is really annoying at freeway speeds in these cars.

I'm only going to use the header for track days, so, is there any function to header-back? Or should I just dump it under my floor pan? Or out the side? Also, what is "tune length"? What is being tuned? The collector?

[bhearts]

I'm only going to use the header for track days, so, is there any function to header-back? Or should I just dump it under my floor pan? Or out the side? Also, what is "tune length"? What is being tuned? The collector?

The rpm at which peak extraction occurs. Scavenging.

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[bhearts]

But it all had to deal with runner length. Collectors are almost primarily efficiency proposed, where the runners length and diameter determine the torque peak

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[Sid_RallyX_82]

I've read about making a step in the flange to stop reversion. Should I make the holes in the flange the same size as the ports to make the step as big as possible? Also, does the length of the collector affect the torque curve? Or is optimal flow the only concern with collectors? Thanks guys, you've been so much help!

[bhearts]

I've read about making a step in the flange to stop reversion. Should I make the holes in the flange the same size as the ports to make the step as big as possible? Also, does the length of the collector affect the torque curve? Or is optimal flow the only concern with collectors? Thanks guys, you've been so much help!

Yes, very much so. Long runners will have better low torque, and shorter runners better high end torque. But I think the biggest factor for torque would be the runner diameter.

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[Advancedynamix]

The shape of the collector, the diameter of the secondary and the length of the exhaust do affect the tune of the exhaust.
Also, most racing organizations don't allow the exhaust to dump under the car ahead of the rear most point of the rear tire. This is pretty standard.

[bravekozak]

Picture.