ERA FIA Cobras Exhaust Upgrade

fastd · #1 (**permalink**) 12-13-2009, 09:27 AM

Has anyone upsized the stock ERA 2" side pipes on an FIA with positive results? I am replacing my undercar exhaust; I am still going to install a muffler (Flo-Pro) and am wondering whether to go with 2", 2.25" or 2.5" pipes...

Rare Iron · #2 (**permalink**) 12-13-2009, 09:34 AM

Highest flowing oval mufflers = Dynomax Ultra Flows. You can get them in bright 304 stainless also. Let me know the length & configuration (offset/center, offset/offset, etc.) & I'll give you a part #.

tkb289 · #3 (**permalink**) 12-13-2009, 09:51 AM

fastd,

Are you planning to still have the full under car exhaust setup?

For my ERA FIA (still under construction), I am planning to go with the under car exhaust as well, but with a setup that will exit just ahead of the rear tire.

What I am after is something a bit quieter than the FIA race exhaust, but with a bit more volume than the full under car exhaust system

I am very interested to see what diameter pipes and muffler you wind up using and how you like it. Let us know what you come up with. Thanks!

- Tim

fastd · #4 (**permalink**) 12-13-2009, 10:06 AM

tbk289,
I am looking for the same things you are.

I currently have the stock ERA undercar with 2" Dynomax mufflers that go all the way out the back to the chrome tips.

I am changing the carb from a 750 cfm 4160 with vacuum secondaries to a 600 cfm double pumper 4150 HP. It was recommended that I change out the exhaust also; I always wanted them to exit in front of the rear times, so now is a good time.

I will still use a muffler. I have come to find that there is a lot of science involved in the exhaust.

I think I am going with a 2.5" pipe. As for the muffler, a Flo-Pro was recommended. I have noticed a pretty broad cfm range that mufflers produce, however, it is not easy (so far) for me to find what cfm and decibel ratings most mufflers carry. I am working on trying to figure out what the optimal cfm requirements for my set up would be and then try to piece it together. I think the bottom line is that bigger is not better; you trade off bottom end torque to top end hp...best one can do is try to find a happy medium - requires a determination of how you really want to drive your car, street, track.

tkb289 · #5 (**permalink**) 12-13-2009, 10:50 AM

fastd

Sounds like you have the right approach. I am sure there are a few guys here that have made these calculations or have enough experience to recommend a setup. For cfm calculations, there are most likely parameters based on carburetor, motor size, compression ratio, camshaft, cylinder heads and exhaust manifold. A lot of variables to be sure. The other aspect that is more esthetic is the 'quality' of the exhaust note ... some mufflers seem to sound better than others, but that is subject to personal preference. It will be interesting to see what is recommend and why.

tkb289

fastd · #6 (**permalink**) 12-13-2009, 06:27 PM

tkb289,

Any recent build pictures to post?

tkb289 · #7 (**permalink**) 12-13-2009, 10:54 PM

fastd

Thanks for asking ... nothing since the last update to my build thread for 2136 ... The car went to Connecticut Custom last month and they will start the body prep and paint early next year, hope to have some photos then.

No recommendations yet from the exhaust experts ... must all be out shopping for the holidays

tkb289

Rare Iron · #8 (**permalink**) 12-14-2009, 05:37 PM

Quote:

Originally Posted by tkb289

fastd

Thanks for asking ... nothing since the last update to my build thread for 2136 ... The car went to Connecticut Custom last month and they will start the body prep and paint early next year, hope to have some photos then.

No recommendations yet from the exhaust experts ... must all be out shopping for the holidays

tkb289

What exactly are you asking for advice on? Tone, highest flowing cfm mufflers? Are you looking for undercar or sidepipe advice?

DanEC · #9 (**permalink**) 12-14-2009, 05:48 PM

I picked this up on the Forum - Chuck Brandt's build site http://www.chuckbrandt.com/

Towards the end of his build he replaced the ERA undercar exhaust with one of his own configuration and exited it in front of the rear wheels. Lots of good info and photos of it.

I want something larger than 2 inch undercar exhaust on my car also. ERA was pretty noncommital in trying to increase it so I just ordered the headers and I'll see what my local custom exhaust shop can come up with once we see what clearance the rear tires allow.

Dan

Jim Holden · #10 (**permalink**) 12-14-2009, 05:54 PM

On the original cars, I've seen exhausts that were routed under the rear differential similar to that done on XKEs. In a discussion on this topic up at ERA, someone commented that all of the orignal small block street cars came with exhaust systems that exited just in front of the rear wheels. My recollection though is of seeing cars some 45 years ago with rear exhausts that swept under the rear and angled up. Ground clearance was tight, but no more so than that on an XKE.

So, how were the original exhaust systems routed? Anyone know?

Jim

fastd · #11 (**permalink**) 12-14-2009, 06:35 PM

Rare Iron,

Was looking for advice regarding the right match of engine to exhaust; moving forward with 2.5" pipe (exiting if front of rear tires) with Flo-Pro glass pack exhaust that flows around 480 cfm.

mickmate · #12 (**permalink**) 12-14-2009, 07:03 PM

Some of the guys on here have used ovalised exhaust tubing to increase cross sectional area without making the system any taller. That helps some with flow and ground clearance. The original small and big block street cars had the undercar exhaust with a muffler under the seats and a dog leg up over the rear suspension to rear exiting tailpipes.

Rare Iron · #13 (**permalink**) 12-14-2009, 07:22 PM

Quote:

Originally Posted by fastd

Rare Iron,

Was looking for advice regarding the right match of engine to exhaust; moving forward with 2.5" pipe (exiting if front of rear tires) with Flo-Pro glass pack exhaust that flows around 480 cfm.

What's your engine CID & HP? As far as flow rates, all will yield different results because of everybody's different test beds. When I was at Tenneco (Dynomax/Walker/Thrush) we did all our flow testing @ 20.3" H2O, & we tested ALL the competitors. I can give you a pretty good lowdown on how the different mufflers tested.

Also, are you going to use the car to bomb around the street, or all-out racing? Do you want the car quiet, loud, or middle-of-the-road? Also, where are you going to position the mufflers? Is there room for ovals, or tube-type mufflers? Any info you can provide will narrow it down.

-Eric

fastd · #14 (**permalink**) 12-14-2009, 07:26 PM

Rare Iron,
351W, 375-400 hp (flywheel). Occasionally track, mostly cruising around the street; like it quiet enough not to upset the neighbors; will run exhaust under car with muffler, exiting in front of rear tires. Looks like the most I can get out of round tubes is 2.5"; tube-type muffler won't fit, using oval.

Rare Iron · #15 (**permalink**) 12-14-2009, 07:43 PM

Quote:

Originally Posted by fastd

Rare Iron,
351W, 375-400 hp (flywheel). Occasionally track, mostly cruising around the street; like it quiet enough not to upset the neighbors; will run exhaust under car with muffler, exiting in front of rear tires. Looks like the most I can get out of round tubes is 2.5"; tube-type muffler won't fit, using oval.

Dynomax Ultra-Flow Stainless 2.5". How long of a muffler body will fit? (longer = quieter - you have a choice between 14" or 20"). Also, what will the required configuration be? Offset in/center out, center/center, or offset/offset?

fastd · #16 (**permalink**) 12-14-2009, 07:47 PM

14", I think it is offset in, center out (or the other way around).

*13* · #17 (**permalink**) 12-14-2009, 08:23 PM

How loud is the exhaust now? I run the STD sidepipe glass pack exhaust from ERA. The car isn't really that loud until I pull open the butterflies. I usually get the car out away from homes before I bring the RPMs up.

Quote:

Originally Posted by fastd

Rare Iron,
351W, 375-400 hp (flywheel). Occasionally track, mostly cruising around the street; like it quiet enough not to upset the neighbors; will run exhaust under car with muffler, exiting in front of rear tires. Looks like the most I can get out of round tubes is 2.5"; tube-type muffler won't fit, using oval.

fastd · #18 (**permalink**) 12-14-2009, 09:09 PM

*13*,
I would say that the current set up is "pleasant" in terms of loudness. I can handle a few more decibels...

*13* · #19 (**permalink**) 12-14-2009, 10:00 PM

Of course it's all a matter of taste. I hope you find the perfect solution! Let us know what you end up with.

Rare Iron · #20 (**permalink**) 12-15-2009, 08:39 AM

Quote:

Originally Posted by fastd

14", I think it is offset in, center out (or the other way around).

Dynomax Ultra Flo 17283. 4-1/4" x 9-3/4" body cross section, 14" long shell, 2-1/2" in/out & it's offset/center. These will flow in either direction also. This muffler combines bright 304 stainless skin, plus 409 stainless other parts, so it's ALL stainless. Dynomax gurarantees them for life also.

You have other choices in oval mufflers of course: Flowmaster, Spintech, Magna Flow (a cheaper knock-off of the Ultra Flo welded series), Borla, etc. But in a 2.5" muffler, NONE of them will flow higher scfm. These are surprisingly not all that loud either.

Good luck in your search!