Nitroturtle

I'm looking for some advice on how to proceed with upgrading the exhaust on my '06. I don't do any racing and it's not my DD, just a fun weekend car.

My current plan is to eventually go with a 70mm HFC and Greddy SE exhaust. But since I just purchased the car, I have other priorities to deal with first, so I'm going to wait until next winter for a full exhaust upgrade.

For now, I plan on picking up Flashpro and getting a tune, with the goal of lowering VTEC. Based on what I've read in this thread, that means I need to ditch the stock cat. I have to deal with annual visual inspections, so a test pipe isn't really an option. In that thread, it also sounds like a 70mm HFC won't pair well with my stock exhaust.

So I'm looking at the following options:

1. Ebay 60mm test pipe and have a HFC welded in
2. 63mm Berk HFC
3. 70mm Berk HFC

If I go with something other than 70mm, I'll likely sell it next year and purchase a 70mm when I get the cat-back exhaust. I haven't had any luck finding a drop in HFC that matches the stock exhaust size. Going with 63mm seems pointless as it'll still have the increase/decrease issue with piping sizes, and I'd still be replacing it later.

My gut is telling me option #1 is probably my best bet, but I'm not quite sure which HFC to have added (or if there's a drop in option I've missed). It's also a little more cost and effort, as I'll need to visit an exhaust shop to have it welded and then end up selling it later to get the 70mm. Is it worth the difference versus just going straight to the 70mm?

Just looking for some input from those with more experience. Thanks!

Chuck S

A lot of of research has been done over the years on this and to summarize what I got out of it is keeping harmonic pulses out of the exhaust will yield the best performance. Going from a 57mm diameter header to a 70mm exhaust system drops the gas velocity dramatically and does not improve performance. May hurt it. "Test pipes" (wink, nudge) are irresponsible.

After study and some trial and error and determining who here is probably an expert (cough -- Gernby) here's my 2006 DBW setup starting at the beginning of air flow:

• K&N FIPK intake.
• Stock header. There's enough evidence here to convince me that a fancy header adds insignificant, if any power.
• Berk 63.5mm high flow cat. Drops right in between the header and exhaust without major gas flow disruptions. I had heatshield tabs welded to it to put the shields back on.
• Tanabe Medalion Touring dual exhaust. The exhaust is basically 60mm from the engine to the tail pipes.

First aftermarket exhaust I tried was the horrible Invidia Q300 that required earplugs and droned at cruising rpms. Lasted less than a month. My wife and neighbors hated it. Guys at the high school loved it though.

With a Gernby FlashPro road tune I posted 221bhp on a conservative Mustang dyno. With the VTEC now at 3600rpm the mid range power is impressive. This is the best money spent to date on the car.

-- Chuck

Nitroturtle

Thanks for the input, Chuck. I've seen your posts and I was actually contemplating going with the same setup. That's part of the reason I'd like to wait until next year to purchase an exhaust, as I'd like a chance to hear some at meets next summer before making my final decision.

My issue until then, is what to do as an intermediate step that will allow me to lower VTEC by only swapping out the stock cat.

Chuck S

With the Hondata FlashPro you can set the VTEC engagement point to anywhere you want. Just type numbers in the box on the screen. But to avoid engine damage that requires many other adjustments I could possibly learn to do but why reinvent the wheel with Gernby has done it extensively and can tune your car by email data exchanges. I do NOT have any pre-tuning dyno numbers to compare but Mustang dynos can read 10% or lower than some others. But the peak power number is vanity unless you drive at that rpm all the time. It's the area under the curve that counts and the Gernby tune makes a large area improvement.

A buddy with a fast 2002 (AP1) has driven my car before and after and refers to the "after" as a Beast. Rpm climb so fast in the lower gears I installed a red-line alarm to prevent bumping the rev-limiter constantly. Down shifts, certainly two gear downshifts, are rarely necessary since VTEC is normally just under my right foot.

Gernby can tune your car in OEM stock condition for more performance. Contact him regarding this and a re-tune after you make your modifications. He may have a different price structure for re-tuning.

There's a million different combinations to intake and exhaust for these cars.

The Tanabe Medalion Touring exhaust note is very pleasing to me. It's loud on startup in my garage but calms down after the engine warms up. Idling thru OSU football foot traffic in Columbus last fall got lots of "nice car" and thumbs-up.

I swapped out my exhaust two Springs ago. I squirted PB-Blaster on all the bolts and nuts several times over the winter. The top nut on the rear of the cat is tough to get to but I ignored it and pulled the system "header back." Start at the rear, not the front. We did my buddy's the same way and were unable to remove the OEM cat from the exhaust with power tools after is was on his lawn.



This is the Invidia Q300 installation but the Medalion Touring is very similar. The high flow cat is hiding under the heat shields. A rogue chunk of concrete was in the road and struck the cat heat shield cracking the tab welds so there's no cover on it now.





-- Chuck

Nitroturtle

Chuck, thanks again for the input. Definitely some good data points to consider when planning my end-game setup.

With that said, right now I'm specifically looking for the best option to:

• replace stock cat with HFC
• lower VTEC (Gernby will be tuning)

Keeping in mind that in a year I'll most likely be adding a 70mm exhaust.

What is my best option, using stock cat-back, for a HFC replacement that will have minimal resonance issues and allow a tune with a lower (<4k) VTEC engagement.

While I definitely plan on doing a full exhaust, I just want to know what setup would be best to run for next summer to allow me to get at some of that power under the curve by lowering my VTEC.

Right now, it seems that having a custom HFC insert made that matches my stock piping size would be the best performance. What I'm unsure about, is how much difference there would be just going with a 63mm or 70mm berk HFC, since those options better serve my long-term goals.