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Old 06-03-2003, 21:42   #1 (permalink)
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Question Exhaust- Should I run twin or single cats - need advice!

Hey all,

I booked my car in for exhaust system for the NC (v8)....

Firstly, I have a choice a genie or hi tech extractors....which is best?

Also, should I run twin or single cats....what is better for flow and power etc...the guys reckons single with a y pipe is the way to go which is fine by me cos its cheaper than running two cats!!!

thanks

hot eb
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Old 06-03-2003, 22:10   #2 (permalink)
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legally you should be running two, so they're closer to tha engine. that way they heat up quicker and they stay hotter, copz they're supposed to...

i'm told the standard cat is a 1.4 litre(my hm headers came with 1.7 litre cats) and isnt that bad for flow, so tell em to keep the standards.
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Old 06-04-2003, 00:28   #3 (permalink)
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Running twin cats is the way to go, and I am sure the only legal way. The problem with the standard cats is their inlets are really small from memory only 1 3/4". Aftermarket ones are generally 2 1/4" or 2 1/2" which is much better for flow.

Also I run genies on mine and they are great quality. Their flow is great while keeping the primaries small enough not to loose low down torque.
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Old 06-04-2003, 03:26   #4 (permalink)
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Quote:
Originally posted by EDXR8
Their flow is great while keeping the primaries small enough not to loose low down torque.
There is alot of debate on this topic, Does anyone know for sure that if your exhaust system is too free flowing that you will loose low down torque, or is this cods wallap?
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Old 06-04-2003, 05:15   #5 (permalink)
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I have twins all the way to the rear axel with a balance pipe and I haven't seen any loss of torque at the low end with this setup. But I will say I have hear both sides of the story with the exhaust setup and if I was to do another car, it would be twin again.
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Old 06-04-2003, 06:15   #6 (permalink)
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Nearly every mustang or ford magazine has tested this at sometime and they alwas find a slight loss in torque if the exhaust is too big. The main effect is if your primaries of the extractors are too big, over 1 5/8" for a stock to mild engine. The rest of the exhaust does make a difference too, but not as much as the extractors. I remember reading an article where they tested different systems on an 185kw EL XR8 and found the best was a single 2 1/2" system, closely followed by a twin 2 1/4" system. Going to 3" actually cost the a couple of kw down low and gave no power increase up high.
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Old 06-05-2003, 03:06   #7 (permalink)
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Quote:
Originally posted by EDXR8
Nearly every mustang or ford magazine has tested this at sometime and they alwas find a slight loss in torque if the exhaust is too big. The main effect is if your primaries of the extractors are too big, over 1 5/8" for a stock to mild engine. The rest of the exhaust does make a difference too, but not as much as the extractors. I remember reading an article where they tested different systems on an 185kw EL XR8 and found the best was a single 2 1/2" system, closely followed by a twin 2 1/4" system. Going to 3" actually cost the a couple of kw down low and gave no power increase up high.
Interesting article that....so maybe single cat is the way to go?!?!?!
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Old 06-05-2003, 03:10   #8 (permalink)
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Quote:
Originally posted by hot_eb
Interesting article that....so maybe single cat is the way to go?!?!?!
No, you still use twon cats, but then a y piece after that leading to a single 2 1/2" system. Personally, I have never seen a Ford 5.0L EFI V8 done with a single cat.
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Old 06-05-2003, 03:22   #9 (permalink)
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oh ok, sorry I misunderstood you.....thanks for clearing that up
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