has anyone stuffed duals under a single exhaust car? i have an 81 SOB (semi old bugger) that i just got a smokin' deal on some MSDS headers. i have read some threads on duals vs. single exhaust, so i decided duals might be the best way to go. anyone have experience doing this to an older car?

 

I have headers on my 79. They go to a y pipe into duels all the way out the back. Not sure of the diameter, a little smaller than 2.25 maybe 2.0. Two 2.0's flow a total of 4, which will flow more than a 3inch single.




Car sounds mean, dyno'd at 203 rwhp!

Stephen

 

I don't think that's how that worrks. You need to take the restriction/friction of the side walls into account so, it's no double but problaby somewhere close the a single 3" pipe.

Also, you don't want to restrict each bank too much. To me, 2" is too small for each side. 2.25 or 2.5 is much better.

 

Here's mine in the '82 https://rennlist.com/forums/928-foru...r-my-82-a.html

I've changed it a bit, but love it.

Rod

 

I did one on an 84.

https://rennlist.com/forums/928-foru...-to-duals.html

 

Here, too. See sig. Dual cats, 86.5 mids -stock, or Carl's or fabricated, and an 86.5 final muffler. Or just tips if you want loud.

 

Rod, Landsteer,
Nice job!

Rod, did you see some good hp gains with your setup??

CapeCod, how bout your setup, noticeable gains?
I've thought about something like this for the 79, but not sure if the low power 220horse US motor will benefit that much. I'm sure the 300hp Euro really wakes up to exhaust mods!!

 

Landseer, did or do you have any problems with heat? after the center pipes split to go around the trans?

 

That's the patth all 86.5 -up, exhausts take. So there are heat shields out there if heat is a concern.

 

Its all about the cross section area, only reason I know of to go from a single to a dual pipe is if your requirements call for a larger diameter than its convenient to bent.
.

 

does single have a different tone then duals do?

 

I'm not sure. When I put an X on my 91 Mustang with full dual exhausts, sound changed a lot from the factory H, more of a growl that I like a lot, but that's also the in the car sound and I've been told its both much louder and different from behind. The Y I put on my 85 Euro S 928 is different sounding, and MUCH louder with a single chamber Magnaflow, more roar than growl.

When you start talking about the tone you have to listen to some different combinations, since all the elements change the tone.

 

No, I have no problems at all with heat radiation. I drive it almost everyday, including really hot weather. Its probably not a power making system. though the pipes are bigger than stock, as Porken advises. Its on the quiet side and is compliant, but with the insulation out of my interior it sounds perfect for me as I go through the gears. Thats what matters.

I bought a pair of mid heat shields from a later car that I was going to modify to fit under the magnaflow mids, but didn't need them because my whole system sits just a little lower.

However, I was thinking about moving this system to the 85 platinum car. Its automatic. I would need to apply some sort of heat shield on the passenger side to accomodate the trans cooler lines.

While we are on the subject of heat, I also moved an 84 stock system onto my 85 to pass inspection. It has smaller diameter downpipes and apparently less cat cross sectional area than the 85. Fits right up. Problem was heat. On the 85 the temp gauge was running significantly hotter than I expected it would. When I switched back to the old stock 85 system (it has a few small perforation leaks in the downpipes) the temperature gauge dropped back to where it should be. So, constriction can build heat --- something I know to watch for in the future if a car starts running warm.

Remember, my 84 dual system wasn't designed for power. I had a completely cobbled-up system that needed to be replaced, no source at the time for a stock replacement, and extra money in my pocket. Duals weren't necessary, but I really like the look. If you drive up behind the car you can see two shiny bumps way up underneath, the twin mids.

If I do another one, I'll change 4 things.
Either open-up the cast iron, else switch to 85/6 SS header pipes (larger)
Use some sort of crossover configuration, probably homemade
Use high flow cats
Reconfigure the discharge to the last muffler. The pipes are too wide apart where they exit the bodywork. I'd cut them off and weld in a pair with a jog to bring them tighter together. There wasn't room to fit the dual in/out magnaflow a little more forward and use tips to go through the body cutout. I had to go with the muffler tips being the final discharge.

The reason I bought the expensive aftermarket 85 downpipe/cat was I didn't think I could afford a muffler shop to build the downpipes and add cats inexpensively. At that point, I needed cats / one car, no other exhaust to switch to for inspection. The right shop could have probably built the downpipes themselves and an X followed by high flow cats for about the same money and it would have had less restriction. But for ease of installation and pretty good value and quality, the Eastern system was a great selection.


All that said, duals vs singles, the single pipe system would have been more economical and quite adequate.

 

Smaller pipe is only a restriction when the flow rate is high, as in the combination of high rpm and WOT. With lower rpm a smaller pipe might actually be much closer to an ideal size for the flow, supporting higher velocities and better scavenging. Heat rise could actually be the smaller pipe creating more power at lower rpms, like 3k vs 5k.

 

Mike, you must be an engineer.

Electrical? Civil?