Gen 4 Catalytic Converter Question

[Brian E]

09 Viper.
Looking at removing oem cats and installing high flow cats to reduce side sill heat.
Do the oem cats have 2 oxygen sensors installed on each side, or is there just 1 installed in each of the oem cats per side?
Looks like the Bellanger high flow cats are manufactured to accommodate 1 oxygen sensor for each side.
If the oem cats have 2 per side, what do you guys do with the wiring for the second oxygen sensor?
Any benefit in upgrading to the cats with metal substrate for an unmodified street driven car?

[Steve M]

My experience with high flow cats in a nutshell (I went with the Belanger metallic substrate high flow cats from Jon B):

1. With the stock PCM, they threw a code (catalytic converter efficiency). It took about 3 drives to show up, but it definitely did. It didn't bother me because I don't have to pass plug-in emissions of any sort, and I can tune it out with HPTuners (and I did). Not everyone has those same luxuries.
2. The metallic substrate cats are substantially louder than the factory cats they replaced. I'd say about 3-dB or so, but I don't have any measurements to back that up.
3. They do run a bit cooler than the factory setup, but the sills still get very warm to the touch.

To answer your questions, yes, the OEM setup has two oxygen sensors installed per side; one before the cat (for monitoring/adjusting fuel trims), one after it (to monitor catalyst efficiency). So 4 total sensors.

The pre-cat oxygen sensors are installed in the collector of the OEM exhaust manifolds - those will both stay regardless of what you put after them (the OEM cats or aftermarket ones). The second oxygen sensor on each side goes after the primary cat (the ones under your feet) - there is no sensor after the secondary cat (the ones around the corner in the sills). The single oxygen sensor bung after the cat on the Belanger high flows replicates the factory setup, so you'll still be running all 4 O2 sensors even after the high flow cat install.

The benefit in going with the metallic substrate cats would be for some additional exhaust volume, and maybe a bit better performance. I'd say the performance upgrade is likely negligible over a ceramic core high flow cat, but again, I don't have any data to back that up. Maybe have a listen to a car with the metallic high flow cats before you pull the trigger to make sure you like the exhaust note they produce. Even with the stock mufflers, it is a different type of sound that's hard to describe. Harsh is a good word to describe it, but it isn't so unpleasant that you can't get used to it. Under normal cruising conditions, they sound just like stock, but under load (WOT), it gets pretty rowdy.

There are multiple things you have to consider if you are going down this path:

1. Metallic vs. ceramic substrate (your choice)
2. Flex section (like the factory setup) vs. no flex section (your choice)
3. What are you going to do when/if it throws a code? It can be tuned out with either HPTuners or the Arrow/Prefix PCM, but that is another substantial cash outlay if you don't have one of those options already.

If you opt for no flex section (I did), you will no longer run the front exhaust hanger. If you do include the flex section (more $$$, but they can do it), the front exhaust hanger will stay in place.

Overall, the install isn't bad, but it will take a while if you are doing it yourself. Just make sure you get the exhaust tips aligned properly - take plenty of before pics, both with the car completely cooled off, and with the car up to full operating temps. You'll notice how much the exhaust tips move between those two conditions, and that's what you'll be trying to replicate. It helps to have an extra set of hands to take the side sills off and put them back on when you are getting the tips in the right spot.

If you have any other questions, fire away.

[Brian E]

Thanks so much Steve. Just the information I was looking for.

[FrgMstr]

Overall, the install isn't bad, but it will take a while if you are doing it yourself. Just make sure you get the exhaust tips aligned properly - take plenty of before pics, both with the car completely cooled off, and with the car up to full operating temps. You'll notice how much the exhaust tips move between those two conditions, and that's what you'll be trying to replicate. It helps to have an extra set of hands to take the side sills off and put them back on when you are getting the tips in the right spot.

If you have any other questions, fire away.

On positioning, I would like to add, I found it easier to simply get out the measuring tape and jot down measurements of where the tip was positioned once the sills are off rather than eyeballing it. I have changed out exhaust about 20 times over the last 10 years going back and forth between a road to track and back setup.

Also, I had V-bands installed on mine. Makes changing out so much easier.

StraightPipeVBand.jpg

[viperBase1]

On positioning, I would like to add, I found it easier to simply get out the measuring tape and jot down measurements of where the tip was positioned once the sills are off rather than eyeballing it. I have changed out exhaust about 20 times over the last 10 years going back and forth between a road to track and back setup.

Also, I had V-bands installed on mine. Makes changing out so much easier.

StraightPipeVBand.jpg

That's cool. Those look like the V-Band clamps I just upgraded to.

Got 'em off Amazon. LINK

Real happy with these new V-Band clamps. They're super beefy ..like they belong on a big V10 Viper.

The originals I had were pot metal crap.

[FrgMstr]

That's cool. Those look like the V-Band clamps I just upgraded to.

Got 'em off Amazon. LINK

Real happy with these new V-Band clamps. They're super beefy ..like they belong on a big V10 Viper.

The originals I had were pot metal crap.

Also, you can see the catbacks and cats on the floor behind the Viper in the picture. Installed the flange directly onto the cat then the Corsa catbacks. Works very well.

The cat is 2.75" and the catbacks are 2.5". If I had it all to do over again, I would have gone 3" all the way through. Live and learn. (Motor still made 666rwhp with cats and catbacks on. About to install the straight pipes again and have it tuned to see what we get out of it with no restriction.)

And yes, that looks like exactly the same V-band clamp that is on mine. I have never had issue with those leaking or turning once torqued down.

And FYI, here in Texas we are allowed one fault on the OBDII test and still pass inspection. So no rear O2 sensors. I just wrapped those up well and tied those up out of the way in case they need to be used again.

[JonB ~ PartsRack]

Great Infos above, plus this:
If you choose the ceramic substrate cat vs the metal substrate cat you will have a deeper tone/note. More muscley.

You will operate somewhat quieter than Metals, but by no means QUIET.

You also choose 2.5" or 3.0"

And the biggie: We can provide a ceramic cat that is NOT likely to throw any codes....especially if you replace old Oxy sensors after 18 years!

JonB@PartsRack.com

[FrgMstr]

Great Infos above, plus this:
If you choose the ceramic substrate cat vs the metal substrate cat you will have a deeper tone/note. More muscley.

You will operate somewhat quieter than Metals, but by no means QUIET.

You also choose 2.5" or 3.0"

And the biggie: We can provide a ceramic cat that is NOT likely to throw any codes....especially if you replace old Oxy sensors after 18 years!

JonB@PartsRack.com

I bought mine from you. Metal. And the Belanger headers as well. Not too high pitched...

[JonB ~ PartsRack]

Some Like It Loud !

Thanks for the purchase and the vid....