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Discussion Starter #1
Here's the deal, I have the Borla XR-1 longtube headers and I recently had replace the clutch and I noticed the lack of a 'firecone' or merge spike or goilet. whatever you want to call it. The part that allows the 4 primary tubes to make a smoother transition together as they go into the collector.

Primary Diameter These headers are fairly long and when I bought them they were the only stainless header that I could get with a 1 3/4 primary that didnt have a 3" collector. My knowledge of exhaust had lead me to believe that a supercharged 4.6 3v would need more than a 1 5/8 primary and as I would continue to add power to the car the 1 5/8 would be inadequate (currently at 450 rwhp plan to go 550+ rwhp) some calculations go by HP instead of displacement.

Primary length When I had gone to an assortment of websites the calculations for primary length varied but generally were from 30-32 inches depending on where you would want the peak power. but then I put my header dimensions into another calculation it had given me a peak power at 6500 rpm for an N/A motor, but I'm sure that the cylinder has an increased volume of expended gases to evacuate, meaning that the volume of the primary tubes are being filled adequately upon higher boost at 3000+ rpm. I would think that the peak hp rpm might be brought down 500+ rpm, but I'm not an expert.

Equal length headers gain about 1% more power from everything I have read and that unequal length can spread the torque curve a bit more but again nothing in the seat of the pants feel.

Collector Now this is where I am not satified with my Borla's. As I mentioned earlier, there is no "firecone". The lack of this can cost up to 5 ftlbs! WHY THE #$%# wouldn't they put one on there? the only thing I can think of is to maintain collector volume. The collector volume is ok it might be a little short. The angle that the collector tapers down to might not be right but its close.

Ok so after my long winded speech I thought I'd ask you guys about putting in a higher quality merge collector that is of the 4-2-1 design or tri y, while I am considering adding a merge spike. The way I see it...
merge spike = 3-5 ft/lbs
4-2-1 collector = broadens power below peak torque, since my exhaust is oversized this may help alot in the midrange. (5% better midrange means better average torque)

This is my fruit for thought, (I know I have too much time on my hands lol)

below are a couple of links I've found the most thorough discriptions and tests. Thanks for any advice in advance. (I should have bought a better exhaust from the get go)
I'm tired and I can't spell anymore...



The Header Test - Engine - Collector Design - Circle Track Magazine
Header Tech - Tapping Into Your Exhaust System's Capability - Stock Car Racing Magazine
 

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Pretty sure my Kooks 6022's are 4-2-1. I'll have to double-check the build pictures but I recall one in particular when they installed the transmission and I could see right up the collector and only see two holes.

If I find the pic I'll post it here. They are 1-5/8" primaries, BTW, still made 678 rwhp.
 

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you have mass produced headers, it's a probably a cost factor to put the cone and 421 design together...Kooks are very expensive, however like most things in this world, you get what you pay for.
 

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Sorry, I'm tired too and read the op wrong, thought Jimmy was looking for a header that was NOT 4-2-1. Didn't think my Kooks were suboptimimal, even with 1-5/8" primaries...apologies.
 

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Sorry, I'm tired too and read the op wrong, thought Jimmy was looking for a header that was NOT 4-2-1. Didn't think my Kooks were suboptimimal, even with 1-5/8" primaries...apologies.
Kooks are clearly one of the best and referenced in the article...I was always curious why the cost was so much higher, but now I know.
 

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Kooks are clearly one of the best and referenced in the article...I was always curious why the cost was so much higher, but now I know.
I should read the article so I understand as well :winks
 

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When moving from 450rwhp to 550rwhp there are loads of more efficient ways to spend your money. In other words the cost is not worth the gain. Your headers are fine. Worry about a lower IATs or fuel volume or belt control. You'll make 550rwhp easy with today's tech without the most efficient header made.
 

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Discussion Starter #8
Pretty sure my Kooks 6022's are 4-2-1. I'll have to double-check the build pictures but I recall one in particular when they installed the transmission and I could see right up the collector and only see two holes.

If I find the pic I'll post it here. They are 1-5/8" primaries, BTW, still made 678 rwhp.
I'm trying to figure out what would work for my setup. Mass produced headers don't fit everyone's build, but if your headers are 1 5/8 with your supercharger it would help the low end torque and if your headers are a 421 collector, wouldn't that be best for a centri rather than a PD blower? Just my opinion.

My concern is that if my headers are "oversized" for my application. Meaning that they are built with a high rpm in mind, my goal would be to bring the peak power rpm down in the band for a more usable range while gaining power on the peak. Because what good is power if you can't use it.
 

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Discussion Starter #9 (Edited)
When moving from 450rwhp to 550rwhp there are loads of more efficient ways to spend your money. In other words the cost is not worth the gain. Your headers are fine. Worry about a lower IATs or fuel volume or belt control. You'll make 550rwhp easy with today's tech without the most efficient header made.
I'm more concerned about improving efficiency of the exhaust when i up the pulley size later in my build. I am working on lower IAT's with dual air exchanger fans. I also recently moved my battery to the rear so I can run an ice box in place of my battery. As for fuel volume I should have gone with the gt500 pumps from the start. The BAP duty cycle is doing quite well right now. I may go to a return system (I might look at what sqidd has done) also go to 60 lb injectors.
The overall plan on the belt side is to go to and overdrive crank pulley but I'm unsure of which brand to go to for good quality (I have yet to research the differences in dampers) I've read another thread where a guy had peiced Together his own 8 rib system for an eforce. I plan to follow his lead after I encounter belt slip.

I know my headers are good but I would want them to be better when I step up the build. since boost is a measure of restriction NOT POWER. More restriction = less power. I think one of these articles says that a 400- 450 hp engine has lost 60hp due to regular exhaust pumping. I would think that reducing restriction would make more power when you are in a high power situation like 700bhp.

The way I am planning my build, is to upgrade the power in stages. While at each stage improving efficiency before moving on to the next. The 421 collector for me would be right around the same time I up the boost level... Air in, air out :bigthumbsup
 
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