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Too Cheap to paint!
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Discussion Starter · #1 ·
A few years back I converted my car to the FITECH Throttle body fuel injection. Lots of teething issues, many threads, but got it running great. One area I was never happy with was the location of the O2 sensor. The common practice was to drill a hole in pipe #3, clamp on a temporary sensor, and go. It worked OK, but the car always ran rich, uneven cyl temps, i thought there was room for improvement.

FFR MkII primary pipes, originally manufactured by Hooker:

Hood Wood Automotive exterior Bumper Rectangle


What could be a quick solution would be to simply replace the pipes with these by BBK, though at a high cost. A secondary problem is that the BBK's do not match the original headers in length. Most likely with the different vintage. (MKII vs MKIV)

Automotive exhaust Metal Nickel Brass Steel


So, while wanting to get better sampling while maintaining pipe position, I came up with a different solution.
 

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Too Cheap to paint!
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Discussion Starter · #2 ·
So, applying the same concept to my primary pipes, I came up with this. Keeps the O2 sensor in the same exact place as the BBK in relation to the distance from the exhaust port. I purchased the two flanges from a specialty exhaust vendor who does make stainless sidepipes for our cars. I also made up the wooden jig to make sure the work stays in alignment, so re-assembly is proper.

Here is pictures of the final work, and I'll let everyone know how the car runs, and if it made an improvement.

And, true to my nature, I preferred to design my own solution, not just buy something. And, it was half the cost of the BBK!

Wood Metalworking Bumper Automotive tire Gas


Automotive tire Wood Automotive exterior Bumper Bicycle part


Wood Gas Bumper Auto part Machine


Automotive tire Tire Wheel Wood Rim
 

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I hope you don't cause more issues than you solve. You are basically just dumping the exhaust into a square box, then it's forced out again. Any tuning impulses from the headers may have just gone out the door. It'l be interesting to see what happens, one side still has complete exhaust scavenging all the way to the side pipe, while this side doesn't. Hope I'm wrong
 

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Too Cheap to paint!
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Discussion Starter · #5 · (Edited)
Rich,

Interesting scenario, I would not know. It is a direct shot through the "box" back into the sidepipe. But, hoping for a better O2 sensor sampling.
 

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Discussion Starter · #6 ·
EDIT - Put some thought into Rich's comments. While, yes, I am interrupting the flow somewhat from a sound wave perspective, our systems are not a tuned system or fully scavenging anyway. To do that, the pipes must have equal lengths, and sometimes even routed in a way to augment the firing order and promote scavenging. The original Hooker sidepipe systems are built much more for functionality, fit, and appearance, with no true tuning. If a primary header were to be built with equal length runners, and proper orientation, it would be a "bundle of snakes". Almost seems the original system using the "Shorty" headers was almost better!

It's an interesting topic on it's own for discussion. Has anyone built a true tuned sidepipe system?
 

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I think that most headers end up a compromise between true equal length tubes and the need to get them to fit inside the car. Decades ago I worked for a man racing a 280ZX in SCCA w/ no budget limitations. At one point we wanted to try to come up w/ better headers and got into contact w/ a major header manufacturer. I took the car to them and hung around while they mocked up headers using the cut and tack method by cutting pieces from several standard 180 degree bends. The guy was fun to work with and at one point I asked about getting equal length. He said he does the best he can but...the problem is that the length of a tube should be measured at the center of the tube all the way through. Obviously you can't physically do that so he used a tape measure to try to get a measurement along two opposite sides of the tube and average them. That was pretty tedious especially for the last 3 tubes because the first 3 tubes (inline 6 engine) were in the way. Today I imagine a computer could do the measuring much better.
 

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Discussion Starter · #8 ·
I remember NASCAR in the late 70's and 80 with the crossover systems, all pipes equal, and the headers crossed either under the engine or behind the engine. Sure had a different sound.

I also vaguely remember a few tries at a "balance pipe" on a Cobra, tying the two halves together?
 
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