How many Mandrel 'U' s

[bigsteviejoe]

Hello

I was wondering if anyone has ever put any thought into buying mass produced mandrel U bends, cutting them to make 2 supplementary mandrel bends, and welding them with straight pipes to make up an exhuast system?

How many U bends do you think one would need to make an OEM routed, performance exhuast system for the Reatta?

[Guest Greg Ross]

2SeaterHal would have to answer this for you,

Hal, "The question that someone did ask"

[padgett]

First keep in mind that the "C" engine is not limited by just exhaust. LoPo cam and restrictive intake are also a function.

If I were going to replumb it would be with a long(er) tube rear manifold and a new crossover pipe with a collector about a foot or 18 inches further along. Of course this would require rear manifold removal befor the engine could be pulled from the top (why it probably has that terrible tailpipe connection now) and a later 2.5" tailpipe to catalyst & rear transverse muffler as now. Is all it really needs.

[2seater]

I agree with Padgett that the engine only has so-so breathing ability unless internally modified, however, reduction of restrictions on the intake and exhaust will help to a certain extent. I have looked at the exhaust and have thought about what could be done. JC Whitney has nice mandrel bent elbows in mild steel or stainless, and I have used them before. The project would be pretty straighforward, especially if you can weld stainless steel, otherwise you end up with a bunch of clamps. If I remember correctly, the 2.5" '91 Reatta exhaust is still available. The elbows are not mandrel bent, but are probably acceptable for our use. The 2.5" exhaust size will allow a 250hp. engine to breath adequately. If you go larger than this, there will probably be a reduction in low speed torque as the exhaust velocity drops too far for effective scavenging. I am still using the stock 2.25" exhaust with my turbo, but I would like to go larger. The 2.5" exhaust should have 23% greater flow capacity. I have seen modified headers like Padgett describes on late model 3800's and it would certainly be possible to make a different rear manifold that will separate the front and the rear completely and join them a little further down than at present. The front manifold isn't terribly bad, at least the little head pipes are pretty much aimed in the right direction, the rear could stand a lot of improvement, more than just opening up the outlet. Regarding that rear restriction, I discovered a 2" hole saw is an almost perfect fit to remove the restriction and the portion of the O2 sensor weld boss that hangs in the stream. It definitely speeds up the process, and only requires minor finishing. A sharp hole saw, slow speed and a lot of coolant is required.