exhaust upgrades

[jimustanguitar]

It is time for an exhaust in my Reatta. I have made a few before for some oval track cars, so I was going to try making some tube headers for my Reatta. I know that each different design of header has different applications just like how there are different intake manifolds for different RPM ranges, so I was wondering what design would work best in the Reatta, I know that is a high RMP animal compared to what I have worked with in the past. Should I make long tube headers that wrap around the engine and go back to an X-Pipe, or would it be more effetive to make shorty headers and route the exhaust over the transmission like from the factory and just improve on the Y where the two manifolds come together? I have no idea what to decide, because all of the cars that I have made parts for before were RWD V-8 style cars with lots of room and huge displacements. I would like to run dual exhausts, so if I joined the two manifolds in the stock location, I would seperate them again for dual cats and mufflers. Let me know what you think or suggest. Has anyone tried side exit instead of rear?? Thanks for the info.

[Barney Eaton]

Hal (2seater) has been working on a twin turbo 3800 and should have the ultimate exhaust problem. Anything less should be "duck soup". You can do about anything you want but there are always compromises.

When you go for side exit exhaust, you drop the pipes below the floor pan and greatly reduce your ground clearance. Presently there is one pipe running through the small tunnel, you could get two in there but why not run one big pipe to the rear and split it? There is no room for extra converters or mufflers in the front or middle of the car.

Do the math on the cross section area of a pipe and you will see that a 3" pipe has almost twice the area of the 2.25 that came on the Reatta. So a single 3" pipe will flow almost the same as two 2.25 and it will fit in the space better.

[padgett]

Keep in mind that a big part of the reason the manifolds are shaped the way they are is so that the engine can be removed without removing the exhaust manifolds. The front manifold and crossover are not bad but the rear is not so good. For a decent exhaust I would probably make something like a tri-y for the rear and bring the crossover out to junction with the rear manifold about 24" down. This would also require a new head pipe and collector.

[Guest EDBS0]

This is what others have done for the series II 3800. Same routing, over the trans.

[Rattaboy]

I heard a '91 Riviera pull into a parking area a few days ago. It was making non-stock sounds, had a pair if heavy looking exhaust tips, one per side. I ask the young man driver what he was running. He said only the converter and had made a new tail pipe which he split. He reved it for me and the sound wasn't all that bad. I think someone on this forum suggested that some time back.

[2seater]

It sounds like you have all of the knowledge necessary to make a decent system, but be wary of making it too large or low end torque will suffer. From the little bit that I know and some studying of zero loss exhaust systems, the rule of thumb is 2.2 cfm of flow per horsepower and flow through a straight pipe should be approximately 115 cfm per sq.in.@ 20.3" of water, or 1.5 in of mercury. I tested the stock catalytic converter and it flows 223 cfm at that test pressure, and it doesn't matter which way it is flowed. I don't know if a high flow cat. really does what it says, the matrix would have to be larger in cross section or a different design for better flow. If actual flow for the cat. were listed, it would make selection easier and Dynomax is one of the few muffler manufacturers that list actual flow and horsepower ratings. If you look at their website, you will see there is a huge difference in flow capability depending on the design, even in the same size case and pipe diameter.

[Guest imported_Flash]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">

This is what others have done for the series II 3800. Same routing, over the trans. </div></div>

Robert,

What parts supplier are these from?

Thanks.

[Guest EDBS0]

From ZZ Performance. Note Series II will not fit Reatta (I think)?