Exhaust design thread...

[Thom 6,651]

crossflows usually don't sound as good because the early engines have a shared exhaust port in the centre of the head it gives them that distinctive sound (I do know of a bloke who successfully recreated that sound on an xflow my joining the two centre pipes together for about 2.5" and then split the front 3 cylinders from the rear 3) it usually doesn't sound as good with a balance pipe (or x pipe)

[gerg 10,871]

Those manifolds were a bit goofy-looking and offered no performance benefit. They were designed like that purely for packaging. A crossy manifold is by no means a performance item either, but light years ahead in design.

 

That said, there is a mob in the states that makes a manifold they call "6=8"... http://www.cliffordperformance.net/Merchant2/merchant.mvc?Screen=PROD&Store_Code=CP&Product_Code=53-0186&Category_Code=F200

It's pretty much your standard 2-branch 6 into 2 headers but don't merge and instead are flanged for an exhaust on each. What makes them unique is the fact that they've swapped all the cylinders around so one "bank" gets 1,4,6 and the other gets 2,3,5. So the pulses in the exhaust would go L-R-R-L-R-L (if 1st bank was left pipe) which is very uneven, and sounds V8-like. This offers zero performance gain and they offer an x-pipe to go with it which increases performance apparently. Defeats the purpose because the x-pipe will kill the burble that the pipes are designed to create.

 

If you want pure performance headers, stick to 6-3-1s.

[ando76 4,354]

Well team I do not conform to any of the established beliefs or opinions till I have heard it for myself.  My woody, which runs twins sounds sweet, no doubt due to the shared centre port as high lighted. 

 

I will be sticking with my current extractors which started life as tuned length genie 6-2-1 however they now have very long secondaries as I have (and I'm not alone here) found bulk power and torque gains from having 250ci of internal volume in the secondaries before they meet a collector.

 

This twin system will have the same length secondaries (in internal volume as I have increased pipe size to 2.5") but instead of meeting a collector they will meet the x pipe.  I have drawn out the exhaust pulses and I know what I am trying to achieve and on paper it will work.  Remember that this is no 9:1 compression street motor - rather a highly stressed 12:1 roller cam methanol motor so the pulses are 1/3 stronger than a factory x-flow. 

 

If we all walked the same line, life would be very boring.  I appreciate your input and thoughts tho - but I'm doing this regardless as I can't see it hurting anything.  GT (my guru) once told me that he didn't care what I did with the exhaust once I had 250ci in the secondaries so I'm off on this journey

[revhead 1,392]

il post up piccic of the mufflers im using next week on my xe ,

 

for me im running headers ,into 2.1/4, dual straight through no centre  mufflers at all over the diff ,ive removed and ditched the petrol tank and am running my mufflers up the back under the rear of the car ,side by side drag car style with 4x outlets both mufflers stainless ,i want it deep not to loud ,to keep the cops off my back

[gerg 10,871]

If we all walked the same line, life would be very boring.  I appreciate your input and thoughts tho - but I'm doing this regardless as I can't see it hurting anything.  GT (my guru) once told me that he didn't care what I did with the exhaust once I had 250ci in the secondaries so I'm off on this journey

 

Mate nobody's knocking you for doing your own thing. I'm the same. It's folks like us on here that love to try different things and buck convention to discover new ideas.

 

I didn't realise you were talking about 2 different engines. Your woody wagon is pre-cross flow I gather, so its exhaust note would be a bit lumpy with the duallies.

 

A cross-flow might be a bit barky and slappy with separate pipes, but the x-pipe might cure a bit of that. Certainly it'll be nothing like a V8... I guess there's one way to find out if it all works.

[ando76 4,354]

yeah we will see, and hear how it goes. 

[Thom 6,651]

very interested in the result

[slydog 7,873]

There's merit in the design but I'm using a merge tapper collector (well 2 infact) where as your using the X pipe but finding the combo that suits each car will be the fun bit.Im going to have to lengthen my secondary's to suit my needs aswell but just wondering where thats gunna leave me under the car for a front loop,hence it's not made yet.

 

Plus there still a xflow and they will sound like shit anyway...only thing I don't like about em really

[ando76 4,354]

Depends on the pipe size of the secondaries.  My 2 1/4 secondaries finish up just past the gearbox extension housing on the single rail.  This gives me the 125cu in in each pipe. 

 

My twin setup should be a little shorter as I'm going to have a step up after an short initial run of 2 1/4.  As you know Rob I love my expansion chambers in high comp, high rev application. 

[ando76 4,354]

Gents - here is the reply that I got from Summit when I asked about using an X-Pipe on an I6 engine via their You tube x pipe vs H pipe video.

 

 

Summit Racing

 

2 days ago

 

Hi +tony anderson,

Yes, by all means you should try it. If you can, get a dyno number before and after the installation. Not only will this give you a new horsepower number, but it will also tell you if your power band has moved at all so you can change your gearing accordingly! Good Luck!!

[slydog 7,873]

So now your there AUS based research team...LOL

[ando76 4,354]

bahahahahaha - yeah sounds like I'm the only one stupid enough to give it a go.  Oh well - nothing ventured - nothing gained. 

[slydog 7,873]

My only concern here with a twin system on the ute is how bad it is going to sound.I mean it won't be a old thong slapper but I can't imagine it sounding too awesome either...The old single sounded pretty good as far as tractor engine go but I'm not convinced this set up will be so good...LOL

[gerg 10,871]

I think you're under-estimating the potential of your setup Sly.

 

It's not like you're strapping a fart-can to a Hyundai. It's a dedicated, well-flowing system that has no sharp bends, rapid change in size or any shearing to the flow of the gas.

 

The twin systems that you might not like are the separate L & R ones with 1-2-3 and 4-5-6 going to each. They do sound terrible. However yours with the x-pipe effectively joins the two "banks" so the sound will be 6 firing pulses from each pipe, not 3 as with the other setup.

 

Another factor is the camshaft and breathing potential of the engine. If you over-exhaust a stock engine, you get that horrible ear-piercing bark like you used to hear from Geminis. Yours however is not stock. The pipes will be accommodated easily by the flow potential of the cam and engine.

 

Just remember too, one of the most glorious-sounding inline sixes in history, the Jag 6, is a long-stroke engine... with twin pipes!

[ando76 4,354]

oh my god - I had forgotten about Jags and their beautiful noise and massive six cylinder. 

 

I agree - with the cam and comp of this engine and the breather potential on the other side of the head, Rob's thing is going to sound as sweet as. 

[XES 859]

You wont hear the exhaust over the awesone induction noise that will be coming from those webbers any way

[PRO250 1,506]

^^^^^^^what he said^^^^^^^

my exhaust was noisy as and the webbers are as clear as day over them

[slydog 7,873]

LOL yeah I'm sure it will be loud under load and @ RPM but I want it to sound OK too as we all know xflows are far from a nice sound and TBH I never heard a serious twin pipe x-flow?

[ando76 4,354]

No such animal exists that I know of. Not one with big cam and comp anyway. I'm hoping to have my x pipe system done and dusted by mid march. You will have yours in and running 11's by then.

[adrianphu123 73]

hey guys, just wanted your opinion on something i've been looking into. 

 

What about welding something like this onto the back of the collector

 

 

Its meant to go from 2.5" to 2.125" with a 12 degree taper. you'd cut it right as it starts to taper, discard the excess straight tube and weld that right to the back of the collector in order to speed up the flow and help it clear the collector?

(in actual fact, it goes from 2.5" to effectively 2" which might be too small and the taper is wrong (17 degrees) in that due to my measurement error.)

 

Then you can taper it back out to 2.5" using another transition like so

 

 

That piece is meant to go from 2.125" to 2.5" with a 7 degree taper. In actual fact, it goes from 2" to 2.5" with a 7 degree taper.

 

What do you guys think of the concept? Any measurement suggestions? The transitions havent been welded up properly, just in the thought experiment phase right now. I'm thinking 2" effective ID neck is too small, the secondarys on my headers are 2" so 2.25" effective ID neck might work better to ease the 2" secondary to the 2.5" exhaust. Its only a mild motor but i wanted to test the concept out.

 

thoughts? ideas? suggestions? is the concept fundamentally flawed?

[gerg 10,871]

So you're effectively making an expansion chamber. I think there are formulas for calculating them available online. They are rpm-specific and must be calculated using engine displacement and VE as well. Just looking at what you've got, I'm thinking you'll need a much longer section of 3" before tapering back down. I take it you're not running a cat.

[adrianphu123 73]

i dont think its an expansion chamber mate, were you thinking of a pressure wave termination box?

 

To clarify, my set of headers has a 2.5 inch outlet, im thinking of tapering it down imediately after the last collector down from 2.5" to 2.25" to help the gas clear the collector, and then slowly taper it back out from 2.25" to 2.5"

[gerg 10,871]

Ok my bad, somehow I thought you had some 3" in there too. How long is the 2-1/2" section on your headers after the merge? I'd personally cut it and neck it down with the more gentle of the tapers to 2-1/4" straight after the merge (to keep the velocity up) and a foot or two after that you can then flare it back out to 2-1/2" with the sharper taper to act as a reversion dam.

[slydog 7,873]

Did you read into where that style of pipe was best functional? A short exhaust that usually doesn't run pipes...Hence me moving away from the idea and running long secondary extractor pipes and a merge collector then a single 3.5 into twin 2.5.

 

I see merit in the basic design for speeding up airflow but the actual pipe size may be a restriction IMO and what the collector look like?

 

After talking to Sam @ Westend performance and his back to back dyno work on a few set's of collectors and the difference was a total of 4 or 6hp on a 500ish hp Chevy.He found and research supports a bigger pipe size or more total area boosts torque down low but longer pipes are needed.Modern V6 Commy use twin 2.5"standard so why wouldn't yours benefit from more pipe size?

 

Makes you wonder doesn't it...well it doe's me.

[adrianphu123 73]

I didnt think to check the current design of the collector

 

 

 

As you can see, not great by any stretch.

 

When extending the secondaries, is it a case of the longer the better or is there a general rule to it? and from a fabrication standpoint, i dont think pacemakers are a two piece flange. This might sound stupid, but how did you weld up each extensions right in the middle of the two pipes?