Stock main cat restriction
Thread Starter
Instructor
Joined: Jul 2005
Posts: 228
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Stock main cat restriction
How restrictive is the stock main cat converter on an L98? I've read several places that it is highly restrictive. The reason I ask is the factory cat is the freer flowing monolith brick design found in modern cats opposed to the old inefficient pellet converter design. Would an aftermarket cat be worth the investment a for power increase when re-doing an exhaust system?
Team Owner
Joined: Dec 1999
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Some aftermarket cats will flow better, but they may not help a lot unless you improve the rest of the exhaust. The pre-cats can be removed, and a cat-back exhaust system will also help.
Do you have to have the car smog tested?
Unless you do the work yourself, most muffler shops will not remove a working cat much less replace it. If they get caught, the feds may hit them for a 5-figure fine.
Do you have to have the car smog tested?
Unless you do the work yourself, most muffler shops will not remove a working cat much less replace it. If they get caught, the feds may hit them for a 5-figure fine.
Thread Starter
Instructor
Joined: Jul 2005
Posts: 228
Likes: 13
I already have a 2.5" catless front y-pipe, rear Y with crossover and Dynomax Super Turbos. I'm keeping a main cat mainly to cut down on drone and resonance. I don't need it for inspection. If the factory cat is actually restrictive, I thought I might replace it with a Dynomax Super Converter with I was re-doing the exhaust. If the difference is minimal, I'll save the money and reuse the stock one. I also plan on porting the stock tubular manifolds.
Safety Car
Joined: Apr 2011
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if its a late model stock-like Cat, I'd leave it. They are not that bad. The OLD ones were somewhat different, yes they were bricks BUT they were not as fat and the brick was longer...a bit tougher to pass gas.
Late model designs are using a different substrate design that has as much effect but they are very freeflowing...so well that there is no benefit to taking them off.
I never say the bag of peanuts type cat on a C4...
Your old pre-cats were the REAL problem. Mains were never that bad. Pre-cats were like having a carrot shoved up each nostril.
Late model designs are using a different substrate design that has as much effect but they are very freeflowing...so well that there is no benefit to taking them off.
I never say the bag of peanuts type cat on a C4...
Your old pre-cats were the REAL problem. Mains were never that bad. Pre-cats were like having a carrot shoved up each nostril.
