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Exhaust upgrade with or without catalytic converter...
looking to add a little growl to the 951...some good cat back options out there, FS, B.B., etc...not gonna mess with the down pipe unless I upgrade the turbo. Maybe in the future.
I’m not expecting any gains from a catback alone, but, would it behuve me to take out the cat, and put in a 200 or 400 hfc? I don’t really want to put in a test pipe, for the sake of smelling heavy fumes....does anyone suggest a HFC? Anyone ever gone this rout?? Thanks guys.
get a "regular" cat... but if your local government allows it, get a "larger" one.
so if your exhaust is a 2.5" see if you can get a 3" in/out cat and use adapters to fit it to the 2.5 pipes.
the cat is a restriction on a turbo car, but stepping up in size should lessen the effects of that restriction by having more cells to flow thru (more flow area).
get a "regular" cat... but if your local government allows it, get a "larger" one.
so if your exhaust is a 2.5" see if you can get a 3" in/out cat and use adapters to fit it to the 2.5 pipes.
the cat is a restriction on a turbo car, but stepping up in size should lessen the effects of that restriction by having more cells to flow thru (more flow area).
catless or ineffective cat REEKS.
good advice. Cool, stock exhaust is 2.5 correct? So get a 3inch in and out with adapter. And get the largest bodied one I can fit under there??
all of the above, thank you, I was thinking 3" pipe and 200 cell cat, but I see V2 has suggested "larger" cat, please elaborate: regular vs. larger. My understanding is stock cat is 400 cell and the recommendation for 200 cell is to improve flow, decrease back pressure.
"regular" means "real" emissions type catalyst - something that wouldn't be specified as a "high flow cat".
so think like bundles of straws...
a 2.5" diameter bundle of regular drinking straws, vs a 3" diameter bundle of coffee stirrers.
smaller bundle with bigger holes, or bigger bundle with many more, smaller holes.
i'd think that you could maintain emissions compliance AND have less restriction.
I'd just take the stock cat off and knock the guts out then reinstall the hollowed shell. You'll see some nice gains while maintaining your stock look and you'll have a full wallet. If you decide to totally upgrade you'll want to go to a true 3 in downpipe and a 3 to 4 inch full exhaust. Over 4 inches is probably not worth the money and exhaust scrapes unless your tracking and looking for Max output.
I currently use the lindsey 4 in big flow exhaust with wastegate dumped to atmosphere. It uses a straight pipe Instead of the cat with a magnaflow muffler. I like the sound of it. Though I may try the borla muffler out someday. From what I understand it has a raspier sound.
"regular" means "real" emissions type catalyst - something that wouldn't be specified as a "high flow cat".
so think like bundles of straws...
a 2.5" diameter bundle of regular drinking straws, vs a 3" diameter bundle of coffee stirrers.
smaller bundle with bigger holes, or bigger bundle with many more, smaller holes.
i'd think that you could maintain emissions compliance AND have less restriction.
thank you V2 I appreciate your ability to explain stuff to folks in visual terms. I live out East and with a "89 951 emission testing is not required.
I'll offer a second opinion since you are asking. Don't take the following as anything other than thoughts - I'm not a greenie and probably line up on the Hank Rearden / John Galt side of the spectrum. So take it for whatever it's worth.
I don't think you'll find the cat-delete worth it, all things considered. Yes you are going to get a HP bump - the turbo will spin up a little sooner too. But after you drive it for three days, the gain will be baked-in and you won't perceive it anymore. You will find yourself less willing to wind it up because it is going to audibly draw the wrong kind of attention (the blue-light kind). And half the fun is winding the 951 up all the time. Finally, it smells like a rotten egg. It's fine when you're going 70 down the interstate, but sit at a stop light or in traffic and it's going to be wafting. Your clothes will smell like it too.
I have a full Fabspeed with sport cat that can be swapped with cat delete via v-band. I can comment from experience on OEM cat, sport cat, and no cat. I would recommend the middle choice. You'll get most of the horsepower gain, eliminate the smell, keep the pedestrians and bikers breathing, and split the difference in the growl you are looking for. I prefer it by far, maybe you will too.
I'll offer a second opinion since you are asking. Don't take the following as anything other than thoughts - I'm not a greenie and probably line up on the Hank Rearden / John Galt side of the spectrum. So take it for whatever it's worth.
I don't think you'll find the cat-delete worth it, all things considered. Yes you are going to get a HP bump - the turbo will spin up a little sooner too. But after you drive it for three days, the gain will be baked-in and you won't perceive it anymore. You will find yourself less willing to wind it up because it is going to audibly draw the wrong kind of attention (the blue-light kind). And half the fun is winding the 951 up all the time. Finally, it smells like a rotten egg. It's fine when you're going 70 down the interstate, but sit at a stop light or in traffic and it's going to be wafting. Your clothes will smell like it too.
I have a full Fabspeed with sport cat that can be swapped with cat delete via v-band. I can comment from experience on OEM cat, sport cat, and no cat. I would recommend the middle choice. You'll get most of the horsepower gain, eliminate the smell, keep the pedestrians and bikers breathing, and split the difference in the growl you are looking for. I prefer it by far, maybe you will too.
Kind Regards, RB
That is the exact route I am going. A high flow cat seems like the very best option. I have a mid 450 hp Audi S4 right now with no catalytic converter‘s. It runs 100% e85 so the smell isn’t that bad. But on regular gas it is pretty horrendous.
I'll offer a second opinion since you are asking. Don't take the following as anything other than thoughts - I'm not a greenie and probably line up on the Hank Rearden / John Galt side of the spectrum. So take it for whatever it's worth.
I don't think you'll find the cat-delete worth it, all things considered. Yes you are going to get a HP bump - the turbo will spin up a little sooner too. But after you drive it for three days, the gain will be baked-in and you won't perceive it anymore. You will find yourself less willing to wind it up because it is going to audibly draw the wrong kind of attention (the blue-light kind). And half the fun is winding the 951 up all the time. Finally, it smells like a rotten egg. It's fine when you're going 70 down the interstate, but sit at a stop light or in traffic and it's going to be wafting. Your clothes will smell like it too.
I have a full Fabspeed with sport cat that can be swapped with cat delete via v-band. I can comment from experience on OEM cat, sport cat, and no cat. I would recommend the middle choice. You'll get most of the horsepower gain, eliminate the smell, keep the pedestrians and bikers breathing, and split the difference in the growl you are looking for. I prefer it by far, maybe you will too.
Kind Regards, RB
thanks RB, I am planning to go the Fabspeed route, when you say full Fabspeed, please elaborate, 3" pipe, 200 cell cat, muffler, what else?
And I assume you are completely happy with the setup, HP and torque gain, not too loud?
thanks RB, I am planning to go the Fabspeed route, when you say full Fabspeed, please elaborate, 3" pipe, 200 cell cat, muffler, what else?
And I assume you are completely happy with the setup, HP and torque gain, not too loud?
Yeah man. I have their downpipe all the way to the exhaust tip. I opted for their sport cat as well as cat bypass. Takes just a few minutes to swap if one wanted to do HPDE or something. The sound is great - love it. Doesn't sound like a boy racer, sounds like a porsche.
10-11-2017, 04:14 PM
Exhaust upgrade with or without catalytic converter...
