I've done an after-market hi-flow cat before with 3 inch to flowmaster all mandrell on my last f-body. I am thinking about upgrading my '91s dual cats to dual hi-flows plus a flowmaster muffler to improve performance and sound.

My current ride came with dual cats to a 3inch outside diameter(factory) pipe to the muffler. The cats and muffler are all original and the car has about 72,000kms on it. The equipment still looks new on the outside but I am wondering if years and not kms matter ? The car's build date is April '91 so the car and exhaust is roughly 11 years old with no visible rust.

If I was to replace this stuff would dual hi-flow cats (eg: Random Technologies) make a diff over factory style cats ? I figure the flowmaster muffler is a no-brainer so would go with that.

The RT cats are pricey though -- about $250 CDN apiece ouch !!$$$$ I suppose if I have to replace them then I have to fork out regardless the question is do the RT cats really work better ?

Any one out there tried this, seen it, read about it before ?

thx in advance,
RP.

 

Since Im cheap..Ill just wait for one of them to go then get the whole system at once..Though the aftermarket cat can make a difference,not enough for a SOTP difference..Ill say youll save money and be happier if you do it all at once..I went from a 2.5" intermediate/Superturbo mufflers(500+ CFM) to a 3" Ultra flow(100+ CFM) muffler and it made a big diffence (higher RPMs)..The 3" Dynomax intermedaite cost a bit more than $100 Canadian

BTW I dont know anything,have any experience or have seen nor heard the combo you were asking about..lol

Daz
Heddman headers
gutted cat
Dynomax 3"(mandrel bent) 2 piece intermediate
Ultra Flow welded
Stainless steel tips

 

Rich, first of all $250 is a good price for a descent hi-flow cat. I paid $300 for my Carsound one a couple years ago. Put it this way, GM wants $550+ for an OEM style one...now how does $250 sound?!?

If you wanna save some coin, why not get rid of the two cat setup and just get one single hi-flow to replace the stockers? I don't think you really gain much from the dual cats anyway, since they join back into one intermediate pipe again right after they exit.

 

Why do you want to replace the converters?

 

Hey IROCKER you are right $250 x 2 is alot better than $550 x 2 for dual cats. The car is setup for duals, air tubes, y pipe, etc so I don't know that I can do a single on the cheap. Also, GM rates this car as 10hp more over single cats -- fact ? fiction ? I coudn't say but it does run strong.

Hey AcceldZ how is the weather in Ottawa ? I was looking at installing a flowmaster I am getting tired of the stock sound of the exhuast -- nice as it is. Then I read about cats breaking down after so many years regardless of mileage so wondered if I replaced them with hi-flows would it lead to better e.t.'s, emissions, exhaust note, etc when put together with a flowmaster 80 ?

Hey Daz, thx for the info this is the first I'd seen anyone attach actual cfm ratings to exhaust mods. Pretty cool.

RP.

 

It's supposed to rain all weekend. I asked the "why?" because you will probably spend $500+ on converters and gain about 3 or 4 HP. The stock GM converters flow resonably well for being OE pieces. If you really want a good set of converters for a decent price, find a wrecked '99+ GM truck with one of the LS1 based engines. The converters on those outflow all the aftermarket converters. Aftermarket converters also usually light off at higher temps than OE converters which makes them less efficient.

As for an exhaust, I suggest the SLP 2 on the left kit. That is, if you don't mind having 2 on the left The sound it makes is like music. It never drones, resonates or gets annoying. CruzN BruzR has a Flowmaster 80 series on his IROC and it sounds pretty nice as well. Personally, I hate my Flowmaster exhaust and so do all of my neighbours. I have the Force II kit which comes with a 2 chamber 30 series muffler. I just found out last month that the 30 series is actually a race muffler typically used on dirt track cars. The American Thunder kits are the ones that come with the 80 series mufflers.

 

this is why i am glad i have an older car. the first thing i did when i got the car was to rip the converter off. i would never even consider purcahsing "performnce" emissions equipment...i would just get rid of the cats. Now, after waiting 6 weeks for canadian tire to get another one for me, i have 2 hooker aerochamber mufflers (2.5" offset in, 2.5" center out) ready and waiting to go on my car. i am taking off my dynomax "cat-back" system (maybe tomorrow), the crappy factory y-pipe and running a short dual exhaust system right off my flowtech headers, as soon as my best friends dad can help me install it (he's a mechanic and has his own shop with a hoist). i am using the mandrel bent pipe from my cat back system. hey palric, wanna buy a dynomax super turbo muffler? its warrented for life and i have the original box and receipt....the muffler is less than a year old.