Yesterday the 03 STR custom Magnaflow exhaust was completed with the installation of Magnaflow hi-flow cats and...WOW! Holy Moly! I can only describe the super quick throttle response and power as an exillerating super quick snap of RPM and ensuing gush of power, all this whilst my too worn (97k) blower belt was slipping and smoking. My heart skipped a beat cause I had not the faintest of what to expect. During hard acceleration the exhaust note changed (before hi-flow cats) from an authoritive mature deep drone to a rasp like bark. Light to moderate pedal during cruise emits a much quieter comfortable note. For those who haven't followed my custom exhaust build, this is it: Magnaflow hi-flow cats, 2 1/2" pipe to Magnaflow X-Pipe, to Dynomax glass packed tube mufflers (straight through) to Magnaflow mufflers (straight through design), exiting Mina Gallery Porsche style dual pipe tips. The beast has awoken and will be enhanced with a Mina Gallery 1.5 pulley and EuroToys low temp thermostat.

 

Was there any sign of blockage in the removed cats?

 

Nice job bfsgross! Be the predator Are you setting off any codes now?

 

JagV8, I didn't have the opportunity to inspect the stock cats for failure which may have been the case? The difference of flow is hugely noticeable and the short time to reach high RPM is of biblical proportions (LOL)...night and day. I'll check the stock cats on Thursday but I couldn't describe a humongous difference attained without any less enthusiasm. Panthro, no codes.

 

I think what JagV8 is getting at is if you had blockage in the old cats then it might have been constricting performance quite a bit. That would make your recent changes seem all the more spectacular. I've seen this happen on some turbo cars with light-off catalysts.

Bob S.

 

Bob,

I had this happen to me a number of years ago. After replacing the converter I had to change my driving style as I adapted to the loss of performance over time. That said, the Magnaflows sound like a good product. For those in some states like CA for example, you may not be legal with high-flow cats so you should check your state's emission laws before running out and buying the high-flow cats.

 

Bob - thanks, it was indeed what I was wondering.

Either way, the other (one / few) reports of the Magnaflows was also positive.

 

So when are you going to post an audio clip of those bad boys?

 

hey sounds nice. what is the part number for the Magnaflow hi-flow cats, are they plug and play for the o2 sensors or do u have to wield the fitting for them in.

 

Though on thursday I'll take a peek at the stock cats; when visually comparing stock cats vs hi-flo cats you'll see a demonstrable difference in the size and transparency of the core. I've peeked in good working order stock cats and wondered how exhaust gases were able to escape. The Magnaflow cats are a short step away from a flow through muffler design if you get my drift. That's how "unclogged" or open they are. California forbids highflow cats. I know for sure the Magnaflows are not allowed to be installed there. Lets not forget: Anyone who's installed hi-flow cats are almost always surprised by the resultant immense loss of restriction compared to stock.
On a "Well how does she move?" note: Driving the 42 miles to the office today was a hoot. The newfound crisp and quick throttle reponse and "git up and go" was almost too intoxicating. I found it almost unbearable not to mash the pedal and see what she'll do, held back by a worn and slipping blower belt that squeals under full throttle. Imagine what is to be gained when its replaced along with a 1.5 pulley next week. From a dead start the right rear tire instantly lights up when stabbing the throttle! I know there's ney sayers here that will contest what I write next, but I might as well give away now my response to those who doubt me, so here it goes: "Your STR is out of tune. You need a new fuel filter, air filter, plugs, the cats are clogged, you need a less restrictive exhaust, you need to clear out stored/learned "old fogy" adaptive driving from ECU! I'll bet she'll do noticeably better than Jaguars 5.3 seconds 0-60. I'm guessing 5.0 or lower. And now I'm much more confident in the event of a stop light brawl. I'll try to get pics and a sound track.

 

But given his mileage it's posible that if someone like me with 15K miles put these on their car the change might not be so dramatic.

I have a truck that has 120K miles on it and I just found out one of the cats rattles when it's cold. It doesn't have the power or response it did at 90K so I'm thinking a new set of cats and a fresh muffler might make a difference. It already has a Magnaflow muffler on it.

So some caution with expected results might be in order for a STR.

Bob S.

 

+1 to all that

 

Bfsgross, you remind me of me: Knowing you've got a bad supercharger pulley system you still slapped on an alternate modification and felt her out. Be easy on that gas pedal until you get her sorted out please! :-D

The Magnaflow cats are as close to gutted as you get... with close to 100K on your STR I'm guessing it was a combo of junked up cats and the the new magnaflows which is getting u the crisper throttle response. I'm volunteering myself to begin with a base dyno before modding. I think it'll be helpful for all.

P.S. Which porsche style tips did you get off of mina? Link?

 

Bobby, I'll post the part number tomorrow. You can go to Summitt Racing to view and purchase the Magnaflow hi-flo cats. I believe they were $135/each? No, the O2 sensors aren't plug and play. The exhaust tech welded in the O2 recievers just before cats. Thursday, I'll inspect stock cats for cavitation of the core's catalyst. I'm sure you guys heard a 1998-2003 DOHC 32 valve Mustang Cobra with hi-flow cats and an x-pipe leading to Borlas or the like? Well, this custom Magnaflow exhaust build sounds very similar. Start her up when cold: she emits an authoritive high idle raspy rumble. Step on the gas and she's impressively crisp and responsive emitting an authoritive raspy bark. Let her go through some gears to a cruise and she's suprisingly quiet with a hint of rumble. While cruising at say 65 mph give enough gas to cause a downshift and she's barking again; stepping briskly away from 65 to 90 mph in short time. Bring her to a cruise and she's quiet again. Very sexy, sweet, but surprisingly powerful.

 

Thanks Chris, for validifying the results of my custom Magnaflow exhaust. Judging from the dramatic change, you and JagV8 are likely correct on my cats being clogged from the get-go. Mina Galleries gave me what I thought was their only Porsche style tips? Chris, speak to Chris of Mina and tell him to give you the same tips sold recently to an STR customer. If I was able to out-pull an 09 Camaro SS from 75 mph to 120 mph while leaving a safe margin, I can only imagine what could have been with a properly functioning free flow exhaust and a fresh fuel filter. Come to think of it my STR now sounds like that SS Camaro and if you haven't heard the SS Camaro, it has a bad *** bark. My motive is to increase the force inward with a smaller pulley, then outward from a well ventilated supercharged engine. With the exhaust and fuel now figured out, on deck is the smaller pulley and low temp thermostat. From that point an ECU tune... I'm guessing my STR is producing nearly 425 hp. With a 1.5 pulley, perhaps 450 hp? With an ECU tune, maybe 475 hp @ 490 ft/lbs torque. Let's see what Chris digs up?

 

welcome to my world

 

Riski, ChrisSTR, and I, through our unplugging of exhaust and forcing feeding more air and fuel, came to realize how Jaguar de-tuned the STR as a means to keep her tamed as a touring sport sedan. A few relatively affordable (and expected) mods awakens the beast irking to be released.

 

Lol don't forget this is the guy who snapped the gas pedal off the mount when he first got the str!

I'm curious to hear what this thing sounds like.... You MIGHT even convince me to eventually play with the exhaust on my sl...

George

 

LOL! Hey George, I bailing wired the gas pedal for all these months and had the donor installed the other day. What a difference the new (formerly new) gas pedal feels (not kidding). I swear the original gas pedal was on the way out prior to meeting me.
If you've heard a DOHC 32 valve Mustang Cobra with Bassani X-pipe and flow through mufflers...this is how my STR sounds. It's a chilling-thriling bark during hard acceleration, considerably quiets down when off the gas or during cruise. When cruising at 75 mph and the pedal is depressed enough to cause a kick down the bark comes out again till an upshift or relaxing the pedal. The increase in throttle response and power is amazing too. Though I love it for short trips I'm not sure how long I can go with such an aggressive note during long hauls. To quiet her down a notch, I may replace the Magnaflow mufflers with a pair of Dynomax Mufflers (2 baffles) that I have laying around. At 49 with thinning hair I'm beginning to be concerned of my identity. If your considering opening up your MB exhaust with a similar system, think about your listening comfort zones first. I definitely recommend hi-flo cats and an x-pipe but choose the muffler accordingly.

 

@bfsgross

I'm curious why you chose to switch to Dynomax intermediate mufflers instead of the
Magnaflow?