brassplyer

When exhaust from the factory started running through a cat like the pic does it flow any better than single exhaust or was going to duals after the cat strictly cosmetic?

Eric P

cosmetic , dual cats was the answer

DWAVette

No cats even better!!!

sunflower 1972

Simple answer. NO.

C3 Stroker

Simply cosmetic as stated above. Glorified single exhaust.

Mdbirk

Because duel exhaust looks awesome!!! But......

dyno test 420HP V8, 2.5" dual exhaust vs 3" single exhaust. Both combos are also tested with turbo mufflers vs flow-through (Magnaflow style) mufflers.

brassplyer

Any insight why they didn't do that from the beginning? How much can a cat and a few more feet of tubing add to the cost of manufacture?

69427

Cats use precious metals in their construction that are damn expensive (google search says about a thousand dollars an ounce), and one big cat is most likely less expensive than two smaller units.

Regarding the dual pipes and mufflers after the cat, I suspect Chevrolet figured the noise compliance from two big mufflers was worth the money, (Chevrolet never spends money unless it has to) and the two pipes (and large mufflers) were one of the few methods available back then to keep from losing any more of the already short supply of horses in the engines back then. Remember, an exhaust system is a series of resistances to flow. It is not just one piece of the system that causes all the restriction to exhaust flow.

ctmccloskey

I changed the Catalytic Converter due to issues with the original. I replaced it with a Unit from Summit that flowed almost twice whet the original cat was capable of. It warmed up faster and helped my C4 get 30 mpg while using the emissions system. By using the new catalytic converter my exhaust system sounds great as the exhaust system has a cat back Chambered Pipes System. It sounds ferocious even for a L98 engine. The aftermarket HI Flow catalytic converters were less than I thought, mine was a bit over $200.

Since I keep the car with regular plates I have to keep the emissions system fully functional.

augiedoggy

Seems to me that depending on how restrictive the cat is it might still have some benefit and act like an X pipe?

C3Highway

Based on documentation from Chevrolet back in the day, the dual exhaust pipes running from just behind the cat to the tailpipes did help reduce back pressure some, but not a great deal. The seventies catalytic converters created so much back pressure that the rearward dual pipes could not really make up for it to a significant degree.

Two cats would have added a great deal of expense back in the day. Not so much today. The original seventies cats were large, heavy, low flowing, very hot running and quite expensive. As such, Chevrolet couldn’t justify doubling the expense of fitting each C3 with two monster cats. However, they also didn’t want one tailpipe showing at the rear of the Corvette. The 2-1-2 exhaust system was the compromise they came up with.

By comparison, today’s cats are quite good at their primary function but are much better flowing, smaller, lighter, cooler, and far less expensive. If Chevrolet had today’s cat technology back in the seventies, they may well have installed two cats per car and continued with the two sets of full length pipes of previous model years. The HP would have rated higher as well for all engines.

It is fascinating that practical flow experiments have shown that full length dual exhaust pipes tend to reduce back pressure still further if the two can share exhaust flow at some particular point.

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1979 L82 M21 FE7
Classic White / Doeskin

ctmccloskey

There is now a market for High Flowing catalytic converters and I doubt that any of the hi-flowing catalytic's will cause back pressure. The difference on my C4 was amazing as the body was 50% larger and still fit down there. The C4 runs great and gets good mileage with absolutely ZERO Drone..

augiedoggy

I swapped out a completely gutted cat (leaking) with a high performance unit on my old dodge ram 5.9L truck and it actually improved power curve

TommyFox

I deleted the cats on my 96 GTS Viper, it pepped it up noticeably.

augiedoggy

I guess like anything it depends on the combination of parts and what works best in what situation. I didnt push the thing with high rpms or anything but The torque /acceleration just seemed noticeably stronger after replacing the hollowed out cat which did have an exhaust leak. The truck had 35" mud tires and 4.56 gears but even with the gears the old 5.9liter magnum was no bullet.