Purist question re: "Bundle of Snakes"

[Keith Hardy]

I am a bit bemused by the use of this expression applied to any exhaust scenario that features a "crossover" system.

As far as I recall, the term was first (and correctly) used to describe the exhaust configuration of the Ford Indy DOHC motor as it exited the centre valley, and could TRULY be worthy of the description, which is very different in appearance to the regular exhaust crossover design on a conventionally fueled and exhausted V8.

Or, am I being trivial, anal and nit picking? And if you want to call your exhaust a "nest of vipers" why shouldn't you?

Eh?

[Mark Worthington]

I vote for trivial and nitpicking.

[Big-Foot]

Originally Posted by Mark Worthington

I vote for trivial and nitpicking.

X2

[Russ Noble]

Yeah, I think the correct terminology is "a can of worms"

Cheers

[Jac Mac]

Having built these and most other types of systems over the years I can tell you that 'A Bundle of Snakes' or a 'Nest of Vipers' is very mild terminology to describe them by!

Jac Mac

[Keith Hardy]

Good, thanks. More now please....anal is good it seems...

(easy)

[John Lowe]

Good, thanks. More now please....anal is good it seems

My mom said I should'nt try that whatever it means

[Doc Watson]

"The firing order of all production V8s, regardless of make, has one cylinder in each bank that will fire within 90 degrees of crankshaft rotation of another cylinder in the same bank. This occurs twice during completion of the entire firing order. These two cylinders will be exhausting almost simultaneously into the same exhaust manifold system.

Full-length four-tube headers help separate these pulses until the collector is reached. If this is a full race car running "open exhaust", you will notice the collector dumps into a short open pipe at least 2.5 times the size of the header pipes, or the header pipes dump direct without a collector. This is done to avoid the conflict of pressure caused by the timing of the 2 counter firing cylinders, which will create back pressure and degrade torque, horsepower and general performance, especially at higher RPM.

On a full exhaust system, after the header tubes dump into the collectors, the two close firing cylinders are fighting each other for space in the collector and exhaust pipe. The result is reflected pressure waves traveling back up the exhaust system, backpressure, lost power and poor economy.

At the same time two cylinders exhaust in one bank, there is no activity in the opposite bank.

The traditional H-pipe equalizer allows some of the excess pressure to bleed over to the 'quiet side' of the exhaust system, resulting in some low and mid-range torque improvements. At high RPMs, however, in traditional exhaust systems, the gases cannot bleed across the H-pipe fast enough to help power significantly. Performance systems with the H pipe design, attempt to over come this by using a shorter cross over pipe which is also slightly larger in diameter as the main exhaust, then would be used in a standard exhaust.

To overcome the power loss of "over loading" the H pipe design, Exhaust manufacturers came up with the X pipe design, which features a tangentially Siamese crossover junction to synchronize exhaust pulses. The X-pipe concept is to split the flow in the crossover junction, so the pressures on both banks will be equal and pulse-free after the crossover, regardless of the rpm. Volumetric efficiency and power are therefore improved at all engine speeds. The negative aspect to the X pipe design is, because of the crisscrossing of the flow stream, harmonic pulsations will develop on some systems at certain RPMs, which will be perceived as a buzzing or humming sound."

Taken from...

Cross Over Exhaust Pipe Explained...

The GT40 system isnt a H or X system, it takes the exhaust from the 2 cylinders and puts one through each of the the 2 collators eliminating the increased pressure which occurs when both are joined in the same collator.

I think.... I also seem to remember that the crossover also makes the effective length of the exhaust the correct length, anybody know anything about this?

Andy

[Jac Mac]

Originally Posted by Doc Watson

I think.... I also seem to remember that the crossover also makes the effective length of the exhaust the correct length, anybody know anything about this?

Andy

That would have been the case with the rev limits of the 289 thru 427 the cars ran in their original form ,ie flat tappet & Non-Roller rocker setups. With the upper rev range & limits being used today the calculated length is shorter than it is possible to acheive on the crossover system, however there is an old school of thought here that a bit of extra length never really hurt anybody & helps build a bit more low to mid-range torque which at the end of the day is more useful to most 'really good' drivers .

Jac Mac

[Straight 8 Racing]

Whilst I, like most of us I expect, want to maximise power and torque, one of my primary requirements is to minimise noise from the system, could someone just confirm that the "cross over" system is the best way of acheiving this ?

Thanks

Iain

[Jac Mac]

8 into 1.

Jac Mac

[Brett James-McCall]

Originally Posted by Doc Watson

I think.... I also seem to remember that the crossover also makes the effective length of the exhaust the correct length, anybody know anything about this?

Andy,
Do you remeber Adam C's work on pipe length found here: Primary pipe length formula

Brett

[Malcolm]

Originally Posted by Iain Pretty

Whilst I, like most of us I expect, want to maximise power and torque, one of my primary requirements is to minimise noise from the system, could someone just confirm that the "cross over" system is the best way of acheiving this ?

Thanks

Iain

I have run both non cross over and cross over systems on my car. There definately is a difference in noise output but is one quieter than the other? I think smoother is a more useful word here as the riffling of the gases was possible on the cross over and not in the non cross over system. Maybe that did make it a little quieter? Both systems passed the Goodwood static noise test. And both systems need repacking every so often especially if you go to high RPM regularly if you want to keep meeting the circuit noise regulations.

[Keith Hardy]

This is very evocative stuff, as half the battle is in the "noise". However, my question was as to the correct terminology as applied to crossover systems in general rather than their technical attribues.

I suppose my question should have read:

"Why do owners of mid-engined cars consistently and erroneously (in my view) refer to their crossover exhaust systems as a "bundle of snakes exhaust" when this terminology was applied to the appearance of the DOHC exhaust configuration of the Ford Indy engines - a very different configuration from a crossover exhaust in a conventionally exhausted V8" ?

Just a debate, is all folks.....

[David Morton]

finger trouble...

[David Morton]

Hi Keith,
IMHO, firstly the exhaust headers/ primary's on a gt40 and any lookalike cars could never be described as a 'bundle of snakes' and the orderly manner in the way they are frequently designed is a very clever skill. (visualize some of the really good ones that Tony Law made). Secondly, any V8 with twin silencers/mufflers with 2 left and two right side cylinders into each silencer sounds (SOUNDS: A VERY SUBJECTIVE TERM) so much better than any other configuration. In fact it's almost a sexual thing.
Almost........

Mine looked like this before it was taken apart (again)

[Bob Childress]

Here is a picture of a Ford DOHC Indy engine in car GT40/103. It is easy to understand why later GT40s with conventional V8s continued to have the crossover headers called a barrel of snakes. I think that description is part of the lore of GT40s including other “special words” like twin nostrils and Gurney Bubble.