That's what I thought when it popped up.

:rotflmao:

IMO keep the heads and cam do exhaust. Fuel for E85 if possible then pulley.

That sure seems to be the consensus so far, and certainly doable without any top end changes. I am sold on upsizing the exhaust--my Dyantech's have 1-3/4" primaries, which I think would be fine but not thrilled with the 2.5" collectors--really feel 3" would be optimal but it is what it is. I currently have the catted y-pipe but could switch to the Dynatech 6.0L non-catted mid-pipes (which does not have a connected y-pipe), add an x-pipe, Borla mufflers and tailpipes. Basically what I said above but getting rid of the cats. Alternatively, there is a very fine set of lightly used Kooks 1-7/8 LTs that might be had, and then a 3" out the back...no more worries of 2.5" collectors and pipes being a restriction. I need to get my engine builder to nix the 2.5" option for me. What's that old adage...measure twice, cut once? Why can't I ever remember that when I start my hotrod projects!

Here's another thought I had on-the-fly.... As I mentioned, I have a Volant CAI with the Volant snorkel, feeding through the stock MAF to the Magnuson air tube and a NW 90mm TB...again, the Radix j-tube is untouched. I was thinking about swapping in a Banks Duramax Ram Air box, modifying the Banks 4" intake tube (heat with a PVC pipe heater blanket and bend to shape) for proper alignment with the Radix j-tube and putting a getting a 100mm MAF in between. Could get the j-tube ported and modified for a 102mm TB as well. Doing the math in my head, that's probably around $1400-1500 with the TB & MAF purchase...sounds great except the $$$, I think that one won't be getting past the mental drawing board.

https://cimg7.ibsrv.net/gimg/www.per...29fd141b38.jpg

Are you DBC or DBW throttlebody?

A couple problems.

First your ECL is 115
Second, your VE is 100, not 1. Also, at 10 psi I would have said 165 (10 psi is about 65% of atmospheric pressure on top of an atmosphere... confusing. whatever... just do it.)

The diameter I get is 1.92" with a length of about 40".

You nailed it on the first two points...ECL is 115, thanks for catching that. I went back and extrapolated from ICL & LSA, and 115 is correct. And another good catch on the VE field entry...the calculator clears all fields when run so I refilled them in again to make a screen shot with data...I missed that it had automatically placed the decimal, however I did enter a VE of 100% for calculating. I get your math on the VE...but I'm not informed enough to know if it is correct. When I was trying to determine approximate VE on my engine I found THIS PAGE which provides a formula (Equation 7) that when followed indicates an approximate of 107.7%. I used the values of 553 hp and 5800 rpm from my last dyno values for this calculation, although in after thought I realize that my entry value represents the rwhp and the calculation is likely looking for bhp to eliminate the parasitic loss variables. I will run it again using rwhp plus 18% drivetrain loss, just for grins. But in any event, I reran with the 115 ECL value and and calculated VE and it increased quite a bit...much more like what I'd expect to see. Even with the RWHP value it strongly indicates that a 3" collector would be beneficial as it sits today, with no other improvements...who said learning can't be fun?!

Fortunately Santa knows that I've been good this year, and he's working on a very nice set! :D

https://cimg9.ibsrv.net/gimg/www.per...6d597576cd.jpg
https://cimg6.ibsrv.net/gimg/www.per...e830ab3edf.jpg

I really appreciate you guys' input...the exercise is educational and body checks assumptions that I tend to leap to when left to my own devises. After I get the 4L80e in, I think it would be very interesting to do a new baseline dyno then upgrade the exhaust and tune it on the dyno to see what was changed (gains/losses) in the HP & TQ curves. So, unless WWIII breaks out, that is the plan...exhaust with no other changes.

I guess the 3" collectors requirement precludes the 2.5" duals out the back. You guys mentioned both dual 3" and single 4"...is there a technical/efficiency advantage, or does it boil down to space and cost?

Another variable you need to add back to your HP is blower drive loss.

558 HP plus divided by .8, and then add another 80 from the blower (just a guess). You are moving the air needed to make closer to 750-775 crank HP.

I'll get a quote for each and go from there. I know a few good 3" mufflers but I've read and watched so many threads and videos of 4" that they are all running together in my head...somewhere I watched a vid of someone running a 4" Corsa Duramax muffler on their turbo gas rig, and as I recall it sounded a bit "hollow" if that description makes sense. I didn't really care for the sound much but, for me, a bigger concern than tone is drone...won't have it. Any experience with a good 4" muffler?

Dude, you've got some good info...I'm going to doing more searching, I bet there is a calculator out there that allows for "boosted" application data input.