5.3 twin turbo, are catalytic converters needed for a street car?
05-23-2017, 04:18 AM
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5.3 twin turbo, are catalytic converters needed for a street car? I am building a 5.3 twin turbo set up to install into a 2003 BMW M5. I have the turbo downpipes made, getting ready to finish off the exhaust. Are cats really needed? I am getting conflicting information from searching.
I plan on driving it daily, weather permitting. (It's not my daily driver, but I will drive it as much as I can.) Basically, it's not a drag car. Just a fun car.
I plan on installing very quiet mufflers on the back with cut outs for when I don't want to be quiet. I want to be able to control the loudness.
Here are the converters I am considering using.....
I plan on driving it daily, weather permitting. (It's not my daily driver, but I will drive it as much as I can.) Basically, it's not a drag car. Just a fun car.
I plan on installing very quiet mufflers on the back with cut outs for when I don't want to be quiet. I want to be able to control the loudness.
Here are the converters I am considering using.....
05-23-2017, 07:51 AM
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The link I provided is to what I understand is a high flow cat from Magnaflow....
05-23-2017, 10:20 AM
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I guess I should add that I do not want the strong gas smell. I removed the cats from my old SC'd 2001 M5, and the smell was just too much. I added some race cats and it worked fine.
Will the turbos make a difference?
Will the turbos make a difference?
05-23-2017, 01:57 PM
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If you want to make power reliably...forget the cats.
And unless it's very badly tuned or you're regularly sniffing the exhaust....I wouldnt worry too much about any smells.
And unless it's very badly tuned or you're regularly sniffing the exhaust....I wouldnt worry too much about any smells.
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05-30-2017, 12:45 PM
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E85 isn't really an option. It's not plentiful around me, plus I plan on driving the car long distances for car meets. (8 - 20 hour drives)
05-31-2017, 12:14 PM
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If you're worried about the smell and also want to maximize performance, you're on the right track. Use a/the high flowing cat/s and place the cutout/s prior to the cat/s.
If the smell is your biggest concern and it's a must for you, then yes you need them. Otherwise, it sounds like you're scott free to eliminate them in your state.
It will be stinkiest during warm up, when the AFR is richest, the engine's cold, and you're not moving too much. Lot's of unburned HC's in the exhaust. Once it's warmed up, it shouldn't be too bad, but does still have that lawn mower smell (sans the fresh cut grass).
If the smell is your biggest concern and it's a must for you, then yes you need them. Otherwise, it sounds like you're scott free to eliminate them in your state.
It will be stinkiest during warm up, when the AFR is richest, the engine's cold, and you're not moving too much. Lot's of unburned HC's in the exhaust. Once it's warmed up, it shouldn't be too bad, but does still have that lawn mower smell (sans the fresh cut grass).