Engine and Transmission Tech

Anyone know a good online source? My preference is 14 gauge aluminized, that's what I have now. Looks like straight tube is easily available, but can't seem to find 14 gauge aluminized bends -- looking for a couple of U bends so I can cut the angles I need.

Finding plenty of 16 guage but that seems thin.

Also seeing pretty good prices on stainless kits with straigh, U bends, 45's etc. but what gauge is good for stainless exhaust? Most seems to be in the 18 gauge range; some 16 gauge.

I buy stuff like that from summit racing

Aluminized steel exhaust tubing is easy to bend with heat. Make your own one piece exhaust. I have been doing it for years and generally it takes less time than loading a car on the trailer and taking it to an exhaust shop. Results come out better. Here is how you do it. You need a a pipe vise or something similar that can hold one end of the tube about waist high or slightly higher. You need another exhaust tube slightly smaller than the tube you want to ben so that it slides inside the tube you are bending. I suppose larger slid on the outside would work as well. Then you need a good torch, a pair of welding gloves and a good assistant. Mock up the bend you want as a template. You can bend a wire, tape together pvc plumbing fittings, whatever. You just need something to reference without letting the pipe cool off between referencing. The torch I have is a plumbers propane tank with the bib tip. You can't do it with one of those little tanks and tips you see at Home Depot. You need to get the pipe red, but not so hot it melts. Start heating where you want the bend to start. You need to get it red all the way around the pipe. Once you get a good red section around 1.5" wide, have your assistant start pushing down or pulling up to get the bend started. It will only bend at the red. Bend slowly. As the pipe starts to bend, keep chasing the flame in the direction you want the bend to continue. The red will move as you move the heat and will continue to only bend where it is red. This can be done in one slow continuous bend. As soon as you move the flame away from the bent area the red fades in that spot, and moves along the bend radius. The part that bent already cools quickly and the bend sets. It really is easy. Grab a spare length of tubing and give it a try. Figured this out from necessity. Had to bend a 2.25" exhaust up and over the rea axles on my BMW 2002 race car. Not enough room to bend it the way it needed to go because of the low ride height and the fuel cell directly in back of the rear center section. Had to ben 45* up, rise 3", flatten out, and then do the same thing on the other side. Had less than 18" to start and stop the entire thing. No problem bending it with heat. No way in the world to make it work with the pre bent pieces. I have also made headers this way, by starting with 4 equal lengths, a header flange, and a collector. Kind of fun twisting them into place.

Todd, do you have any pictures of the finished product?

Heating to cherry red will burn off the aluminum coating so there will be no corrosion protection in the heated areas.

Jim

Sorry no pics. The way I did it did not burn off the coating. I'm sure it pissed it off a little but the coating did not "burn off" Matters non the less as I hit it with exhaust coating anyway, or in the case of the headers, shipped them out to be coated once I built them. There are videos on Youtube of asian guys building bike exhausts with this method. They use an acetylene torch and only heat one side. Those torches burn hotter than a propane torch.

I watched a couple of the videos. The bend radius they were able to achieve wasn't very tight but it looked like they didn't get much ovalization of the pipe they were bending. I'm not sure they could do a 2 1/2" pipe on a 4 1/4" radius without a mandrel bender. Most of us need something tighter than a 10" to 12" bend radius when building an exhaust. On the system I'm going to be building I will need two 2 1/2" diameter 135* bends on a 4 1/4" radius to make it work.

16 gauge tubing has an 0.63" wall thickness. Are you building an exhaust system or a roll cage? That will be more than adequate for any exhaust system. That's why 16 gauge mandrel bends are readily available.

The old style mandrel benders had a string of balls on a steel cable that they would pull back through the tube as the bend was being made in order to hold the ID constant. Don't see that much in an amateur environment.

Jim

16 gauge tubing has an 0.63" wall thickness. Are you building an exhaust system or a roll cage? That will be more than adequate for any exhaust system. That's why 16 gauge mandrel bends are readily available.


Probably 0.063" wall thickness...

"Probably 0.063" wall thickness..."

Yeah, that. What's a decimal point among friends? ;-)

My point still stands. .063 is plenty thick for an exhaust system.

Even #304 stainless exh. pipe is stronger than mild steel exh. Unless your running a turbo,18g. ss. should be adequate.
2 cents, Art.

This is what I used - stainless straights and bends. Price has gone up about $50 sinçe this time a year ago but it's still a good deal at $190 ($145 when I bought it) with more than enough material for a dual exhaust. I believe it is a metric gauge but measured out to a few thousands shy of 16 gauge.

[www.ebay.com]

Rob,
Are you going to incorporate an x-pipe or an h-pipe?

I did the exhaust over the winter and did an X-pipe.

Rob, Did you have an X or H pipe in the previous installation? Was there any drone?
I have 2 1/2" dual pipes without any connection between them to a Dynamax two in-two out muffler,
and I have a drone in the 2100 rpm range. I have added two homemade helmholtz resonators to the exhaust,
but that hasn't entirely subdued the moaning. I am considering redoing an expensive exhaust system during the winter,
but only if I feel confident I will get the result I desire.
Thanks,
Dennis

Dennis

Where is the muffler located? I have found that pipe length after the muffler can dampen the drone somewhat. Mufflers are often located beside the fuel tank limiting the amount of pipe after the muffler.

FWIW, I have a resonant spot about 2K rpm with the exhaust system pictured ....possibly an engine specific resonance and somewhat independent of the exhaust configuration..

My muffler is at the very back of the car due to the TR6 having the exhaust tubing through a central tunnel.
I have a resonator just off the headers in each pipe, but that isn't the whole answer apparently.
From your picture Graham, I suspect only a larger muffler pair would remedy the situation. I think
I should just get used to it, as the sound is ideal most of the time.
Now, as to whether that 2 in/2 out muffler is stifling performance....I guess too bad!
Oh, I did find that my spark advance was a little retarded at cruise, and advancing it helped,
but just not enough.
Thanks,
Dennis

After 25 years on the road, I finally got rid of all droning. Here's what worked for me. The system is all mild steel except for the 10" long stainless steel tail pipes coming out of the mufflers. Headers have 1-7/8"diameter, 30" primary tubes and 3-1/2" collectors. From the collector flanges, 2-1/2" pipes run to a 2-1/2" Summit Racing X pipe at the rear of the transmission. Connected to exit end of the X pipe is a 2-1/2" Summit Racing H pipe kit, however the side outlets of the H pipe kit point out board, not inboard toward each other. Attached to each of the H pipe side outlets are 32" long Helmholtz resonator tubes made from 90* bends I got at AutoZone. Attached to the straight through exits of the H pipe kit are 2-1/2" tubes that run to 2-1/2" Flo-Pro mufflers. The final piece of the system is the previously mentioned tail pipes. The Helmholtz resonators seem to have made the whole car feel smoother and quieter.