Hello there fellow magna doodlers,

Just wondering, for those people who have modified their car in any manner here are some polls so i can use for info as well as other members.

Poll 1 - Have you changed your catalytic convertor to a higher flow one. If yes what size did u use and what are you comments in regards to performance and fuel consumption. By the way what is the standard magna cat convertor piping size (into and out of).

Naturally Aspirated ones only not those who force feed their baby!

I have investigated this a number of times now, and came > < that close to getting it done but time and time again I have been told here and by people in the business, unless you are pushing some decent ponies through that engine bay then the stock Cat on the third gen Magna is more than adequate for most general mods and to save your $250... it is more your highly modded cars (ie. turbo's and s/c's) where the high flow cat is possibly going to be of any real benefit aparently.

i was goin to change mine wen i got the exhaust done but he said it already had good flow so i never upgraded, will be getting a 3" one soon as the turbo's are on

i got a really high flow cat sitting in a box - racing use only.....

in these pics you can see the differance between a std and high flow ......high flow realy doesnt make that much differance unless trying to get a kw or 2 spend your money on extractors and some high flow mufflers this will be money well spent

i intend on getting it when i buy my paceys ........ may only be an extra kw or 2 but pick up an extra kw here and there all of a sudden ur 10 more kw's clewar than u was b4 and thats a noticable difference

I think you'll find there's no use upgrading the size of the cat unless it matches the size of the exhaust piping. ie: 2.25" piping into 3" cat into 2.25" piping would give absolutely no benefit over a 2.25" high flow cat.

The gasses can only flow as well as the most restrictive part of they system - in the scenario above, the 2.25" piping is the restriction.

I might be wrong - but I'm pretty sure the idea is to keep the diameter of the piping as uniform as possible.......

If your poll had the option - I'd select "Replaced with 2.5" higher flowing unit"


By the way what is the standard magna cat convertor piping size (into and out of).

Stock piping is 2.25" into and out of cat (as far as I know), and the most popular size for upgraded exhaust (in N/A applications anyway) is 2.5" into and out of cat.

I havent changed mine but have been given wat sounds like good advice.
To change the piping after the extractors and before the cat convertor to 3 inch
mandrel piping. Stock piping is too restrictive in that area and by doing that,
supposedly there is no need for Pacemaker extractors.

the cost = $160

What do you think??

I havent changed mine but have been given wat sounds like good advice.
To change the piping after the extractors and before the cat convertor to 3 inch
mandrel piping. Stock piping is too restrictive in that area and by doing that,
supposedly there is no need for Pacemaker extractors.

the cost = $160

What do you think??

To me that just sounds....wrong?

Compare the cast stock headers against pacemakers (or any aftermarket headers) and I'm sure you'll see theres a lot of difference. I don't understand why mandrel bends would do much, since its not that bendy in that section (I think this is the section between the flex and the cat?). But 3 inch where the hottest gasses are is a good idea. I might use that :)

I think I will watch this poll/thread with interest.

Mainly due to the comment that was made by VRX-II (IIRC) in regards to sprintex saying that the standard cats often develop restrictions... Interesting. (and the fuel filter was mentioned as well - would be good to get some more information on this...

I had a chat to my local exhaust guy on the weekend too, and there is a few differences between highflow cats - the truly good ones don't use a ceramic matrix, they use stainless steel (?)... Costs about $250 fitted, but appparently very good.

Cheers
Heath Young

I just had a chat to various exhaust places with one in particular mentioning installing a hiflow cat to the VRX/Ralliart etc would make next to no difference.

Then another place said yes, it will make a difference but gave me 3 options for 3 different grade Hi Flow Cats...

Me wonders if this issue with hiflow cats is just a myth?

I put a 2.5 inch hi flow cat on my magna just over 2 years ago now. I do have to say that I have felt the difference since day one. When I got the cat back done it felt restrictive from 3500 rpm upwards and felt like it was struggling at times. Ever since I put the cat on, I have never had a problem yet.

Mind you, I have a 3.5 ltr, but I couldn't see that much difference with the same on a 3 litre.

I did all my own work by bying a high flow 2.5' Cat of the net. It cost me all up about $160. Welden in some flanges. A BIG DIFFERANCE I SAY