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I've gone through a partial restoration of the body and engine and refitting the exhaust I'm considering gutting the cat. I worked on VW'S in the late 70's the factory had us gut the cat's because of many various reasons including overheating and surging after gutting them we changed the jet's in the carb to a richer mixture plus the cars gained more power at the time. So what do you guy's think? 1984 928. Do you think there's as much restriction as the old cat's had?
Why not just remove it instead of gut it? It would be a lot less work to remove. In addition, if you ever decide to sell your 928 to someone living in a more ecologically friendly locale, you can send along the undamaged catalytic converter.
The CAT is only part of the restriction with the early cars. Look at the collector leading to the CAT.....and the manifolds are not all that great either.
Gutting the CAT on these is somewhat pointless since you are leaving behind the horrible "Y" into the CAT. Instead, remove the piece all together and have a Y pipe made to replace it.
Or better yet, ditch the manifolds and find some 85/86 SS units to replace those cast iron boat anchors, then have the custom Y made.
There used to be some "bolt on" Y's available. Not sure if they are still available.
Can you guy's point me in the right direction for a y pipe. Speedtoys I don't think you want this the PO did some weird welding to the thing I don't know why. How do you adapt the y pipe to the single pipe collector with the round doughnut gasket? Here's a couple photos. I got a new cat from ebay doesn't even come close to fitting. They refunded my money and told me to keep it.
I saw a y pipe for sale on the motorsports web site $ 700 bucks. I'll just reinstall the cat.
Local muffler shop, might be surprised on the price. That plus the 85/86 manifolds are the best bang for the buck performance upgrade for a US 16V car.
Local muffler shop, might be surprised on the price. That plus the 85/86 manifolds are the best bang for the buck performance upgrade for a US 16V car.
I see 928 intl has them for a 100 bucks each. Why is this a good upgrade and will the cat bolt up to them without modification?
I see 928 intl has them for a 100 bucks each. Why is this a good upgrade and will the cat bolt up to them without modification?
They flow better, but kinda pointless unless you plan on improving the flow after the manifolds. If you're only going to do one or the other, start with the Y collector.
I see 928 intl has them for a 100 bucks each. Why is this a good upgrade and will the cat bolt up to them without modification?
The cast manifolds are heavy but they have a nice shape inside. If you are installing a Y-pipe (or anything with larger down pipes), just grinding the 47mm outlet of the 16V manifolds to the 52mm 32V gasket size will notably increase power.
08-27-2018, 08:14 PM
To gut or not ot gut the cat
