I have extractors and 3inch system on my calais. Will a high flow cat make much of a diff and how much $ CHEERS

na or turbo???? 3" mandrel will cost between 600 to 1K including cat and muffler.

If it is a Turbo, anything you do to reduce back pressure in the exhaust will help power and response. If it is a n/a then i wouldnt expect any gain at all, unless your old cat is blocked up. Mick

A cheap but effective and illegal high-flow cat simply bash the core out of your cat to make it hollow then take it to a exhaust shop and ask them to weld a pipe straight through it so basically you don't have a cat as it flows straight through but the cat body remains as a decoy for Police or random EPA check but just hope to hell they don't get the exaust sensor emission probe out or you will cope it. Some original photos have not been recovered yet.

why bash the ******* out when you can pick up a 2.5" high flow cat for $20 (2nd hand with 3 months use)... (i spose it helps being friends with someone who owns an exhaust shop to get it at these prices too)...

The three things you can do to ya cat is get a hi-flow one, gut your existing one out, op pipe your existing one. The first is the most expensive, however is legal, whereas the others are real cheap, however illegal. A high flow cat pretty much gives u the same gain, however u have to pay for it. Its totally up to the individual, some want to be totally legal, whereas others dont really care. Ur choice..

The three things you can do to ya cat is get a hi-flow one, gut your existing one out, op pipe your existing one. The first is the most expensive, however is legal, whereas the others are real cheap, however illegal. A high flow cat pretty much gives u the same gain, however u have to pay for it. Its totally up to the individual, some want to be totally legal, whereas others dont really care. Ur choice..

ppls, it must be na... extractors on a turbo... explain how? 3" for a non turbo??, it must be losing power i reckon

I've got extractors for my turbo! I havent got any pics to show you but turbo extractors consist of equal length runners meeting up at the flange where your turbo bolts on.

i dont understand hi flowed cats? how can they possibly hi flow them? they are still a honeycomb filter, so it cant make that much of a difference. the only real way to hi flow the cat is to bash out the guts. and you should of got a 3" or a high flowed cat when you fitted your 3" exaust.

Yer in a way I agree with StageIII. It may be a marketing gimmick cos really there all full inside, how does the flow actually get any quicer and when it is explained by someone on Ozper how can you tell the difference? ????? Mines gutted and i cant really tell the difference. Althou I do have a n/a... I couldnt tell the difference with it from the other VL I own which does have one working!!!! Just a thought.

I think the hiflow aspect might be in correspondance to the flange size of the cat both in and out. ie, if you have a 2.25" cat on a 3" exhaust then that would cause some restriction. Bigger the CAT, larger contact surface area, and more exhaust flow in the cat, causing less restriction. I dont think you can buy a 'hiflow' cat from the shelf, as cats are cats,but what hte exhaust shop does is put in a cat from a late model V8 for instance, which is larger than the standard commodore one. They cut and weld the flanges to size, and there you have it, a 'hiflow' cat, which is basically a cat that is from another car but has a larger capapcity and therefore is bigger.

Ive been in a RB30ET Torana that hyas a 3" zaust & was running no cat, he then put a "highflow" 3" cat & you could notice a slight performance loss, but due to emission laws I think it would be worth it.

High performance cat convertors have longer tapered entry and exits to the cat body. If you go to a good muffler shop, ask to see a stock convertor and a performance one, the differences should be obvious. Performance cats also have a larger corss section of convertor core inside....imagine a smaller and larger radiator, or intercooler....the larger one will allow more air through. Regards, Andrew.

gutting your cat is more expensive that a high-flow. example you get caught... $10,000 fine on the spot and possible jail term, is the max penalty... however, if you manage to get away with it... go for it... I had a gutted cat on my car for 2 years. however I find it loses more power... unless you want to go to the trouble of welding up a pipe through it, but I doubt the local exhaust shop would like to risk their business for this... gutted cats lose power, not gain. (unless cat colapsed.)