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1-3/4 vs 1-7/8 American Racing LT Headers ( catted)

1MEAN18

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Pype's makes a set that are a 1 3/4" primary that then expands into a 1 7/8" tube primary. I have a set, catless. They are awesome! Supposed to help keep bottom end torque from dropping off down low...they work well on my set up running the corn and a JLT intake
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GregO

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Keep in mind I might stay NA. The answer I seem to get is if I am staying NA. 100% just do 1-3/4. It’s better overall through the powerband. But if I am going to boost the car obviously 1-7/8. My question has a second part. If I do 1-3/4 and get the itch down the line will that hinder the supercharger at all?
Simply stated;
(1) ROUSH Stage 3 = 710 SC H.P. w/OEM headers and cats while meeting 50 state EPA.
(2) Don't lose sleep over 1.75" vs.1.875" primary tube diameters. If OEM headers w/600 cpsi cats support ROUSH's 710 warranted HP then 1.75" primarys are fine.
(3) DO lose sleep over the quality and construction of After Market Cats. The typical High Flow 200 cpsi cats are substandard junk that fail at emission reduction, core substrate unwinding and melting at elevated EGT's.
(4) The best High Flow race cat that survives High heat / High HP and substrate loaded with quality precious metals that meet EPA requirements is "HJS" made in Germany. At 450.00 + each most choke at the price point and decide to poison the air.

The message; be very cautious as to what Cat you decide to hang off the headers regardless of primary tube diameter.
 
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Semp1

Semp1

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I went with American Racing Headers. If it wasn’t them it would’ve been Kooks. Kooks though nickels and dimes you on the elbow connection for Corsa so I went with ARH 1-7/8 as the choice. Not concerned about quality. Known to be high end and used by Ford on race applications like their Cobra Jet. That was never a concern with them as a brand. Now to decide to add the procharger. Hmmm. Baby steps.
 

LethalPerformance

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I’ve read that you should build for the future with headers. I guess If boost the car this will be important to me later on. I’ve also read that with the bigger diameter you lose low end torque. From the numbers I’ve seen these 2 seem the exact same on the dyno at the top end Matter of fact the 1-7/8 produced slightly overall better numbers NA in the hp dept which it’s supposed to and the exact same tq numbers at the top end. My question is how much tq am I losing if I stay NA and do 1-7/8 in the low end? Don’t want to buy the 1-3/4 and say I should’ve just bought the 1-7/8 down the line. Also don’t want to buy 1-7/8 and say I should’ve went with the smaller diameter because it’s better for my application. My upgrades are a custom dyno tune , Roush cold air, Corsa Xtreme catback w/active. Keep in mind I might stay NA. The answer I seem to get is if I am staying NA. 100% just do 1-3/4. It’s better overall through the powerband. But if I am going to boost the car obviously 1-7/8. My question has a second part. If I do 1-3/4 and get the itch down the line will that hinder the supercharger at all?
I'd definitely recommend doing the 1-7/8" headers. You won't see any loss in TQ whatsoever compared to running the 1-3/4" headers and you're going to give yourself room to grow into a FI setup later on down the line.

If you have any other questions shoot us a message or give us a call at 561-753-8105 and we'll be glad to assist you.

Thanks!
 
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Semp1

Semp1

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I'd definitely recommend doing the 1-7/8" headers. You won't see any loss in TQ whatsoever compared to running the 1-3/4" headers and you're going to give yourself room to grow into a FI setup later on down the line.

If you have any other questions shoot us a message or give us a call at 561-753-8105 and we'll be glad to assist you.

Thanks!
Yes thanks for the help. I ordered from you guys same way I ordered my Corsa setup back a few months ago. Looking forward to the power and sound increase.
 

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BmacIL

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Simply stated;
(1) ROUSH Stage 3 = 710 SC H.P. w/OEM headers and cats while meeting 50 state EPA.
(2) Don't lose sleep over 1.75" vs.1.875" primary tube diameters. If OEM headers w/600 cpsi cats support ROUSH's 710 warranted HP then 1.75" primarys are fine.
(3) DO lose sleep over the quality and construction of After Market Cats. The typical High Flow 200 cpsi cats are substandard junk that fail at emission reduction, core substrate unwinding and melting at elevated EGT's.
(4) The best High Flow race cat that survives High heat / High HP and substrate loaded with quality precious metals that meet EPA requirements is "HJS" made in Germany. At 450.00 + each most choke at the price point and decide to poison the air.

The message; be very cautious as to what Cat you decide to hang off the headers regardless of primary tube diameter.
Great points.

Green cats are going to be there, thus the price point.
 

DB83

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Well, I guess it depends on where you live but 1-2 owners have tried high flow cats here in the UK and failed spectacularly on emissions, and that is on the non-GPF equipped pre-2019 models. So, if you go for high flow cats or catless in most places in the world then you will need a friendly emissions shop.
Do you know anyone running the Kooks green cats? I'm looking to run those in the hope that i can pass emissions testing and not have to take them off every time i go for testing, which would really suck!!

I live in Spain, so we have pretty much the same emissions testing as the UK.
 

GregO

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I'm looking to run those in the hope that i can pass emissions testing and not have to take them off every time i go for testing, which would really suck!!
Reach out to Milltek in the UK and talk to them about their Milltek / HJS cats. I’d suggest you stick with components on your side of the big pond.
I’m not so sure GESI cats with get you to EU emission levels.
 

DB83

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I don't know.......the GESI units are 300 cpsi with precious metals, and the HJS are 200 cpsi and they don't specify anything about their construction. I also think the US EPA standard is just as strict as the european ones no?
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