Hi Forum, I have to replace my Cats so I figure I might as well get a Hi flow Cat and start modding the exhaust. I was looking at Magnaflow, since it looks like most of you are using that brand, but I don't see anything for an '05 STR. It looks like they stop at '04. So, what would be the best Hi flow Cat I can get for an '05 STR and do I have to do the exhaust at the same time or can I do it a couple of months down the road? I am planning on getting the Mina intake this week as well. Thanks

 

If you are going high-flow, then you are going universal in which case they will all be the same from 03-08. I would recommend an x-pipe at the same time, but its not necessary.

 

I also have an '05 STR, and at 64k miles I expect cat problems before too long. Not to mention the desire for another 10HP. So far, here's what I recall from forum members with STR's:

(bfsgross) Magnaflow hi-flow cats and Tru-X center muffler, 16" resonators and Dynomax VT mufflers. (VT mufflers had early problem with flap, apparently corrected ~Feb/13).
(dvsadam, Rasputin) High-flow magnaflow 59975 cats, followed by magnaflow 11385 (which has an internal x-pipe), out to the stock mufflers.

Other configurations produce cabin drone or raspy noises, but the 3 members above seem well pleased.

 

Cats? What are those....

 

lmao....

 

I looked up Magnaflow 59975 Cats and I see them on ebay and such, but not on the Magnaflow website. I'm assuming they've been discontinued. Do you guys know of a similar model? Maybe a different brand? Thanks

 

I am running the Magnaflow 99675HM which do not require O2 sensor spacers. I would highly recommend doing a resonated x-pipe at the same time. I have the Magnaflow 10790 x-pipe, and would recommend something else.

 

Thanks QuartzSTypeR, I'll order it right away. When you say do a resonated X pipe, are you saying NOT to get the magnaflow 10790 or should i get that one? I'm new to modding so really dont know what works well and what does not. I just figure if I have to buy cats anyway, might as well do the exhaust...at least thats how I'm selling this to the wife. LOL.

 

Try here:

Magnaflow 59975_ Metallic Substrate High Flow Universal Catalytic Converter - Hottexhaust

However, just saw the post from QuartzStypeR, and the 99675HM sounds good, but there have been complaints about cabin noise with Magnaflow unless the hi-flow cats are paired with a suitable x-pipe/resonator. I think QuartzStypeR is warning against the 10790.

 

I'm running the 59975 cats and the 11385 tru-x perforated core resonator to replace the stock res. I still have the stock mufflers and they sound great with this set up. No drone, and lots of compliments on the sound.

 

I run the same setup as dvsadam and am very happy for $$$ invested.

 

Hi Dvsadam, that's good to know. I ordered the Mina intake, 59975 cats and the 11385 tru-x last night. I was going to go with the 99675HM, but after researching, I think the HM stands for heavy metal which is just for 49 states, but the 59975 is OBDII which is 49 states and California...as long as your car isnt registered in California... confusing.I think my car needed the latter. Thanks for the advice...I'll let you know how it goes.

 

Just make sure you get a reputable exhaust shop to do the work. Some members here have had problems after installing the cats due to improper welds or placement of O2 sensors. I've had mine on for over a year and no problems whatsoever.

 

You will need to be aware of possible problems with O2 sensor positioning with 59975 cats. Have a good read of this thread:
https://www.jaguarforums.com/forum/s...59975-a-73220/

 

Robinb, I am looking at this now and will print out a copy for the exhaust shop. The mechanic did mention that I would need to cut outs or something like that per cat for the O2 sensors, so it sounds like he's on top of this. But it sure couldn't hurt to give him this as well. Thanks a lot. I appreciate it!

 

I would not use the 10790. The high flow cats make the exhaust a little raspy, and the 10790 is not resonated and makes the rasp louder where a resonated x-pipe will cut the rasp and give it a better tone. I don't think you will notice a power difference with the 59975 and the 99675HM cats. If you aren't in a strict emissions area, the 59975s are fine if you don't mind the O2 sensor spacers. I am in a more strict emissions area (almost as bad as California) and need to be able to pass strict limits every 2 years so I was advised and opted for the 99675HMs.

 

Decided to do some reading up on the subject - apologies to those who already know all this...

OBD1 and OBDII are 2 methods used for emission control and monitoring engine performance. OBD1 was used up to 1995, OBDII from 1996 onwards. OBDI is concerned with emission control, while OBDII is more sophisticated and uses input from multiple sensors to monitor and report on overall engine operation.

In addition, there are 2 types of catalytic converter. 2-way converters are only concerned with converting carbon monoxide to carbon dioxide and burning off excess fuel. 3-way converters also convert environmentally-polluting oxides of nitrogen to oxygen and nitrogen.

For automotive catalyst converters, the catalyst core is usually ceramic with a honeycomb structure, but metallic foil replaces ceramic in some applications. Metallic cores are used in sports cars where low back pressure and reliability under high load conditions are required.

So today, OBD1 has been replaced by OBDII, and 2-way cats have been replaced by 3-way cats, especially in regions where control is strict (like California). In other places, if a catalytic converter is doing its job properly, a combination of OBD1 and a 2-way converter may still be acceptable.

When I hear a 59975 cat described as "pre-OBDII", I would guess that it is a 2-way cat designed for OBD1 control that could give code errors with OBDII. When I hear a 99675 HeavyMetal cat described as "OBDII", my guess is that it's a 3-way cat with a metal core designed for sports cars with OBDII. Just like my '05 STR.

If the above is true, might that explain the need for positioning O2 sensors with 59975 cats? And is the 11385 x-pipe OK with the 99675?.

 

Robinb, thanks for the clarification. I had it all wrong then. I thought the 59975 was OBDII compliant (49 states AND California) while the 99675HM (heavy metal) was only 49 states. I guess I read it wrong. Do you think installing the 59975 will in any way hurt my Jag? On the sticker in the engine compartment it says "OBDII compliant 49 states and California". Do you feel I should return then and get the 99675 HM's instead? Thank you.

 

There are a few members running the 59975s with O2 sensor spacers that aren't having any issues. It won't hurt your car and you should be fine with them. The basic difference is that the 99675HMs have are more metals absorbing emission output. Chances are you would pass emissions even in California with either choice as long as your car is running correctly.

 

Thanks QuartzSTypeR, I'll go ahead and continue with the 59975's then. I also ordered a Magnaflow 11385 as well. Not sure what that does other than quites the cabin, but I see other members have it and recommended it so I figured I'd get it also. Thanks again!!