Well here's the car about a year ago. Only had exhaust and Growler intake.
http://www.youtube.com/watch?v=Y9RZZvBcoIU&feature=plcp
200kmh limiter (on private road, of course lol)
http://www.youtube.com/watch?v=OGm86mXWFgg&feature=plcp
low rev driving etc
http://www.youtube.com/watch?v=e1wuxmnJ ... ure=relmfu
Idle when exhaust was brand spankers.

Yeah on turbo diesels. 4x4s like low down torque, and it's been proven time and time again that too big will hurt low down torque.

Ahhh but I'm not after low down torque. If it were staying auto, than yes I would. But being that I'm going manual conversion, I don't need so much down low. Anything under 2000rpm I don't care about.

The negative effect will be negligible.

You will make more power with a twin 2.25" system. I don't see the point in going twin 2.5"?? just to say you have a twin 2.5"

Just for comparison of cross sectional areas.

Twin 2" is 4053mm^2
Twin 2.25" is 5130mm^2
Twin 2.5" is 6333mm^2
Single 3" is 4560mm^2
Single 2.5" is 3166mm^2

And I needed that why?

Sorry TheKrazyD but Im gonna jump in here again

I have to be clear that in all this where I'm advocating "the larger the better" - I'm talking about cat back. I think people underestimate how much (ie. how little) pipe quite effectively tunes the exhaust - so as long as there's nothing crazy done about huge pipework forward of the cat, whatever is done behind falls into the category of bigger is better as it's effectively fairly irrelevant to the engine itself - it's about getting rid of waste gas and making note.

Whats wrong with being able to say you have twin 2.5?? (tho for my money it's not about what other people know about - it's about my own satisfaction - and I suspect TheKrazyD is similar) - it's a free world and IMO if you decide to open up your system as absolutely much as it can be, then the comfort of knowing you've done that outweighs any concern about offending the sensibilities of thought police.

If in the eventual reality it sounds like a wet f@rt and struggles to keep up with a 2 year old Mazda 121 then that would be an indication to rethink things - armchair experts blurting that it's overkill I'm afraid is not...

My personal beef with exhaust places is exactly that I've only ever wanted to know if things CAN be done - not whether they SHOULD be done - the results will speak for that and when I embark on a path then that's with full acceptance that I'll wear the result!!

I'll make no bones that 3 inch off extractor collector and thru a 3 inch cat then into single 2.5 is fine, but I personally WOULDN'T go larger than 2.5 single behind that kind of forward configuration because at low revs there's gonna be too much weight of material too close to the ports for the engine to push (bit like having brake master cylinder the same size as the caliper pistons). I think that keeping it 2.5 off the extractor collector and thru a 2.5 cat - then into a monster system would make better power overall WITHOUT dumping bottom end - in fact even 2 1/4 in that critical forward section should be fine as long as the cat is good and there's no other mechanical obstructions - ie. press bends or s**t welding (after all there have been many big volume V8's in the states that have made huge power thru clean 2 1/4 systems). And anyone who thinks I've just contradicted myself doesn't understand at all what I've been trying to say all along - go back and read it again if you can be bothered.

My issue now is whether or not to put it on after the tune, so I can see the net results of a better flowing exhaust, or put it on prior so I won't have to go back a second time. I would like to see how much affect it will have, but then again the extra cost of a re-tune afterwards.

At the moment I have Pacemaker 4495's sitting in the garage. I've decided to go with a Venom 400 Series 3" - 100cpsi cat converter.

No reason for the sizes, just a comparo for interests sake.



If the headers were designed with a well functioning collector, the rest of the piping after that is fairly irrelevant, but all headers available to us are made to fit within certain boundaries.
ie: Must fit up to standard cat-back exhaust systems, must have provision for a cat, location of cat, etc.

JMM are the only ones I've seen that have ignored a boundary and moved the cat further back.

I've been researching header design a bit lately, and from the basics I reckon these engines should have much longer primaries and a good length more in the secondaries too. But there is so much more that I don't know.
I've had ideas of running duals off the headers with a x-pipe in the system, or dual from the headers to the diff (very long secondaries), then joined by a y-pipe to a single over the diff and out.

Limitations of cat placement, if at all, are a huge factor. To do the dual I've mentioned you would need two cats, and available space is minimal for that.

Do a search on headers and systems for Chev and BMW I6's and see the multitude of different types that are out there. The variety is huge compared to what we have for our small market.


But in a world where you can just strap on a turbo and wind up the boost, who would bother with fine tuning a Ford I6. I agree there is too much of "this is how it's done" in the exhaust industry no-one wants to step outside the square because no-one wants to pony up the money for something that is unproven.


I really hope your venture in to duals works out well, I'd love to hear some variety from these motors rather than the same old redback drone.

Those Pacemaker style extractors - with relatively long secondaries - IMO lend themselves perfectly to the rule of whatever goes on behind that can be as big as you want.

JMM are interesting in what they've done because they've put into practice the idea that the tuned part of the exhaust system ends where it hits the cat - ie. as long as your pulse length requirement is satisfied by the time the cat is reached then you're all apples - and they've determined that needs to be a tad longer than the factory location.

MAD sums up my sentiments exactly - well put!!

Last edited by Greenmachine on Wed Sep 19, 2012 4:31 pm, edited 1 time in total.

Here's another vid of my 3 inch setup - I ended up feeling "urgency of being filmed" so was a bit severe on the throttle - was stabbing it really violently - and forgot to just run it for little while at 2500 or so steady. Engine wasn't dead cold but wasn't properly warm either - it's a tad more responsive when it's warm. IRL it's deeper - much more like the second vid below tho not quite as pleasantly bubbly in note.

http://www.youtube.com/watch?v=bXj-77QovMk

With an Aerochamber I think it would sound much more like this (drool) :

http://www.youtube.com/watch?v=bd3vmf6LC_o&lr=1

Last edited by Greenmachine on Wed Sep 19, 2012 3:32 pm, edited 1 time in total.

Doesn't sound too bad there mate. Did you have a listen to mine up the top?

Yep - sorry, I should have commented - that's not too shabby either - from inside it's VERY similar to mine (per the clip driving thru streets) except that mine does this wierd thing where as the engine revs build the interior sound fades quite drastically and it shifts to a deep throaty exterior bellow that comes back thru the windows. In fact with the windows up it almost feels like a resonance - which I guess it is - but it's against the outside, not thru the car if that makes sense? - ie. it's greater if there are buildings or other traffic around.

- and yours has a decent decel burble - which is totally absent in mine.

- you know, looking at your clips again your idle clip is VERY similar to my IRL sound - maybe a tad higher piched - my clip is really crap at conveying how deep it really is - all that comes thru is the ripping note which yeah is VERY similar - standard thing I suppose for I6 with straight thru mufflers of whatever size... - I guess the primary purpose for my putting up that clip is to demonstrate that 3 inch doesn't necessarily automatically mean a loud fluffy moaning note.

Last edited by Greenmachine on Wed Sep 19, 2012 8:16 pm, edited 1 time in total.

Yeah, I'm only running one muffler at the rear. I did record this from a $900 HD Video Camera, so sound quality is great. (Handles recording at concerts with nil distortion from over modulation etc)

My only issue is that the cat was only a 300cpi ceramic lol hence why it's already collapsed after a year.