Quick google seems to be just under 1.5"That being said, any idea what the exhaust port size is on the stock heads?
Header primary needs to be bigger than the port to some degree. The valve is the first restriction, next the runner and port, next the header flange, and primary. If the primary isn't big enough it adds another restriction. Any time you can limit the restriction at any of of those points it keeps from compounding restrictions. The exhaust coming out of the head is still quite hot trying to expand, and high volume so the primary is still bigger than the port somewhat to keep from adding to the piling up restrictions. And it's all dependent on air volume. IE sforced induction pumps more volume. But the general concensus is 1 3/4 again is fine up to the 1,000+ range.So the 1 7/8" and now the 2" offerings are pointless above the 1 3/4" size? I guess before, I wasn't really considering that the Green cats that Kooks told me were good to 900hp were creating that much of a restriction, but after seeing so many posts where people have had them fold up/break apart, they are coming off.
Don't have data for an S550, but I have good numbers for 4.6 Terminators w 2.3 Whipples. Bro in law and I both had em. Identical setup, identical tunes from JDM. I had factory cats and Magnaflow 2.5" catbacks. He had Kook's headers, cats taken out and some seriously loud 3 inch header back exhaust. Me 610 to the wheels. He did 615. Draw your own conclusions.Good evening everyone,
I was wondering what all of your thoughts were on power loss (if any) from the 2.5" bottleneck on the OEM connection point on aftermarket exhaust systems? I have Kooks headers with green cats, a Magnaflow Foose edition Cat back, but it still has the factory sized bottleneck connection. I am running a P1x Procharger at 13 PSI max, and e85 with Lund tune. I guess my question is, would it be beneficial to me to either change the catback for a full 3" design or have an exhaust shop make it 3" all the way through? How much power am I giving up with the bottleneck in place at this power level if any?
Has anyone done before and after dynos or have any other data (1/4 times) or just opinions on the subject? If the consensus is 5 HP gain, then not worth the trouble. If the consensus is 20+ HP, then obviously it is worth addressing. I'm not chasing quarter mile times or lap records. I do however like things to be as efficient as possible and give me all of what I paid for/put into it.
Apologies if this has been answered before, I couldn't really find any solid info on the subject