Exhaust Flex section

I've been using the braided steel accordion-style flex section, but at the last race it bit the big one due to a soft engine mount. the accordion part tore open and spewed hot exhaust onto the floor right under my feet. toasted the paint on the floor and melted the heels of my shoes. DOH!

http://static.summitracing.com/globa...M-642510-1.jpg



I'm wondering if there's something else that would be better suited and less restriction- like the corrugated stuff?

http://static.summitracing.com/globa.../WLK-40000.jpg

Should I keep with the same short braided flex section, go to a longer one to allow more movement, or change types to the corrugated stuff or something else entirely?
Thoughts?

I would think that the corrugated stuff would be the WORST for flow.

It's no worse than the inside of the braided steel flex sections... Actually, it may be slightly better since the corrugated stuff is mashed into an oval-shape corrugation. it's not nearly as rough as the inside of the braided type.

Quote:

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Originally Posted by Matt93SE

It's no worse than the inside of the braided steel flex sections... Actually, it may be slightly better since the corrugated stuff is mashed into an oval-shape corrugation. it's not nearly as rough as the inside of the braided type.

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Did anyone say that the braided flex sections were good? :)

I think those two things combined really leave a lot to be desired in terms of flow. I can't see how an internally corrugated pipe would be worth it - but I have no data to support that theory, I would never even have considered in a viable option in a test.

Build a better motor mount first.
Then build a softer mounted exhaust system. I use chains to hold it up and a slipped on front joint, retained with BA brake springs. Overlapp the collector tubes about 3in. with a good bit of slop, so that the engine has a few degrees of rotation before using the exhaust as a torque arm.
The flex stuff is just waiting to make problems.

Yeah, I thought about that as well. probably the best idea is to use a slip-fit joint. I was trying to keep everything flanged so they would have to be unbolted-- less chance of it falling apart during a race if you don't have a spring to dislodge in an off. I'll look at where this joint is and see if I can mount everything up so it has little chance of falling off.

One big issue is the header flange is directly below my feet, and the flex section just behind it. I DO NOT want to damage the header by the exhaust hitting something. been there, done that, threw away a $$$ header after it bent around my steering rack, and spent all night in the pits welding up another exhaust to fit a stock exhaust manifold.

Then again, I think it was the flange itself that got hooked and bent the header. :doh:

The flex section may lose a bit of power (would be nice to see some dyno numbers on various types tested just for grins.), but it sure saves wear and tear on headers and manifold studs.


.... and yes, engine and tranny mounts were solved this weekend. I had a tranny mount go bad at the last race and it caused the tail housing to move over 3-4" during cornering. destroyed exhaust, engine mounts, exhaust flex, and pulled the wires out of an o2 sensor. And I missed a 3-4 shift and found reverse at 85. destroyed reverse gear as well. ouchies.

I use a ball & socket flange type connection. If used with coil springs on the bolts it will seall well enough for a race car and still have the flex requied.

Link to one supplier I've used.

http://www.mandrel-bends.com/catalog...7abd384ed750cc

I used a similar style a while back (I think it was an older Chrysler type??) that used a graphite donut to seal against a flared flange. it worked great till the graphite donut wore out, then the springs got loose and it was a rattly noisy mess. an all-metal one looks better, but I might just give the slip-fit a try this time. it's the cheapest and easiest solution since I can pick the parts just up the street.

If I can ever get the paperwork done for the alternate engine I want in STU, I'll be going to a 3" exhaust anyway, so this one won't be in there terribly long...

Thanks for the advice, gents!

Matt:

Why are you over-thinking a fix for your exhaust system? After all, it only failed when you asked it to act as a motor mount. Just replace your engine mounts & replace your busted flex tube w/a new one. And for God's sake, don't even THINK about using that JC Whitney flex tubing!!! If you don't believe Andy, just pick up any HS Physics 101 textbook. :D

not trying to overthink it, just trying to find something a bit more reliable. the braided flex sections don't have a great history in my experience (not just my car), so I was looking for something a bit more robust without losing any more power.

still haven't bothered to fix it. next race isn't until december thanks to cancelled races in Oct and the no-start race in Nov..