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UK_Sub
Moderator

United Kingdom
2166 Posts

Posted - 04 Jan 2018 :  09:36:13 Show Profile Reply with Quote
Why do you need the balance pipe?

My V8 didn't have a balance pipe, just a pipe down each side of the car and that sounded great.
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pchristy
V4 Guru

United Kingdom
1774 Posts

Posted - 04 Jan 2018 :  15:37:57 Show Profile Reply with Quote
I'm no expert on car exhausts, but from what I've read a balance pipe (or an "X" pipe) will slightly increase the power output on a V8. It allows each bank of cylinders access to the "other" pipe during down-time, increasing gas flow. Although on a V8 the gains are quite small, I recall reading somewhere (I thought it was on here) that not fitting a balance pipe to a V4 will cause a massive power loss.

Remember our V4s are a bit odd. Because of the offset crank pins, it actually behaves more like an in-line 4 in terms of firing and overlap of the cylinders, rather than as a true "V" engine.

A Google search turns up lots of interesting links about balance pipes, but little information on their ideal location! I've had a couple of Ford 351 ci V8s myself, but both used a "two-into-one" exhaust - a bit like Andy's - so the V8 burble was well muted....


--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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UK_Sub
Moderator

United Kingdom
2166 Posts

Posted - 04 Jan 2018 :  20:03:08 Show Profile Reply with Quote
Good to know, I always thought it was a shame that the V4 didn't sound like a small V8, so if you've cracked that - that's superb!
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TTruckie
V4 Fanatic

United Kingdom
291 Posts

Posted - 04 Jan 2018 :  21:54:02 Show Profile Reply with Quote
According to Jack Ashcraft's Fast V4 tuning book the tuned length for a Y-shape 2-1 'extractor' exhaust is 54'. This type of exhaust uses the offset pulses to assist each bank to get the gasses out faster and therefore gives more power. Apparently the Balance pipe is the next best design.

I think Woody's S&R Y-exhaust is this type.
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greg124
V4 Fan

United Kingdom
134 Posts

Posted - 29 Jul 2018 :  11:26:02 Show Profile Reply with Quote
A mate of mine who builds hot rods was in the pub on Friday night, and he was telling me that the next job on his current project is to fabricate his own stainless exhaust. He's got all the kit to do it. It looks like we might be fabricating one for a V4 soon as well, which is why I've revisited this thread.
I'll be fitting a Weber DCOD 28/36 on the correct manifold, but I can't decide whether go for a system like Peter's or Andy's. I'd like to optimise the system to suit the Weber, and retain the burble, but not be too intrusive when travelling at cruising speed.
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pchristy
V4 Guru

United Kingdom
1774 Posts

Posted - 06 Aug 2018 :  18:54:02 Show Profile Reply with Quote
If you want the "V" burble, you really need a twin system, which is also easier to fabricate, I suspect! The balance pipe on mine could probably use moving back a bit. Aside from the exhaust design considerations, its a bit close to the front cross member that makes a useful jacking point! Just be careful not to block access to the gearbox drain plug!

Mine could use some more silencing. With just the rear boxes, it has quite a bark to it! The problem is finding some that won't reduce the ground clearance too much. My rears sit in the same place as the original (standard) silencer - mirrored on the LHS, of course.


--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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greg124
V4 Fan

United Kingdom
134 Posts

Posted - 09 Aug 2018 :  09:32:35 Show Profile Reply with Quote
Thanks Peter,
The V burble is a must have. I don't know whether the magical 54" is also relevant with a twin system, in terms of the position of the balance pipe, but I've done a rough measurement and that would bring us to about 6" behind where the front wheel arch meets the sill, so that doesn't obstruct anything.
What size rear boxes are you using? I don't know what the size limit is under the rear wings, as I currently have both rear wings off the car for repairs to the shell.
Smaller diameter front boxes somewhere under the front seats should reduce the noise level, and oval ones would minimise the loss of ground clearance

Clive
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pchristy
V4 Guru

United Kingdom
1774 Posts

Posted - 16 Aug 2018 :  09:20:29 Show Profile Reply with Quote
To be honest, I'm not sure what size the boxes are. They were "off-the-shelf" items that matched the Jetex rear box pretty closely. They certainly fit neatly enough, but aren't that effective at silencing! Its quiet enough below 3000 rpm or on a light throttle, but floor it above 3000 and all hell breaks loose!


--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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pchristy
V4 Guru

United Kingdom
1774 Posts

Posted - 16 Aug 2018 :  16:06:57 Show Profile Reply with Quote
quote:
Originally posted by TTruckie
According to Jack Ashcraft's Fast V4 tuning book the tuned length for a Y-shape 2-1 'extractor' exhaust is 54'. This type of exhaust uses the offset pulses to assist each bank to get the gasses out faster and therefore gives more power. Apparently the Balance pipe is the next best design.

I think Woody's S&R Y-exhaust is this type.



Thinking about this logically, if the distance from the head to the "joining" of the two pipes should be 54", then 54" should surely represent the middle of the balance pipe. So the placement of the pipe should be 54" minus half the width between the pipes at that point.

Can anyone spot a flaw in this argument?


--
Pete
"Duct tape is like the Force: It has a light side and a dark side, and it binds the Universe together!"
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greg124
V4 Fan

United Kingdom
134 Posts

Posted - 19 Aug 2018 :  20:51:03 Show Profile Reply with Quote
Pete,

the tuned length is a function of several parameters: exhaust valve open duration, induction manifold length, valve overlap and the diameter and length of various parts of the exhaust system, and probably others that don't just come to mind. I haven't read Jack Ashcroft's book but I suspect that 54" was arrived at for a particular setup. So, if for example J.A. was quoting 54" for a "bunch of bananas" inlet manifold, this would yield a different figure to a single twin-choke Weber set-up
I can't think of a logical reason not to use the mid-point of the balance pipe; however, I suspect it may not be that simple

Clive
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melle
V4 Guru

United Kingdom
2603 Posts

Posted - 19 Aug 2018 :  20:58:07 Show Profile Visit melle's Homepage Reply with Quote
If not for a performance engine, will 1" more or less than 54" really matter?

www.saabv4.com
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greg124
V4 Fan

United Kingdom
134 Posts

Posted - 20 Aug 2018 :  00:37:13 Show Profile Reply with Quote
I can't imagine an inch or so making a noticable difference Melle. I am by no means a tuning expert, but I would like to optimise the output while keeping the engine internals standard (apart from hardened valve seats for unleaded). I'm quite prepared to read up on the theory, then do a bit of trial and error - that's half the fun...

Clive
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melle
V4 Guru

United Kingdom
2603 Posts

Posted - 20 Aug 2018 :  21:27:57 Show Profile Visit melle's Homepage Reply with Quote
I know, I'm the same, hence my question!

www.saabv4.com
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