sound of the v12

Talk about the E-Type Series 3
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Barry
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#21 Re: sound of the v12

Post by Barry » Fri Sep 01, 2017 11:06 pm

Oh dear, some of you do talk bollocks! It is rather sad that some of you decide to denegrate the real expert engineers who know what they are doing from years of experience. I have been recently dealing with Roger Bywater, a development engineer at Jaguar who worked on the V12, KWE Engineering, experts on V12's and fuel injected cars in particular, New Forest Classics, Ecosse exhausts and finally Eagle who need no introduction at all. This post was about how to make your V12 sound better, believe it or not. Some guys came on talking about butchering a standard exhaust with ,agical claims. Lost on me how you could destroy a good exhaust system! However, Well done! I'm pleased for you, but that solution is not for me. I prefer to go to the experts and pay for a proper job, properly engineered. But to criticise these engineers of false claims or whatever is completely ridiculous! A little knowledge is a very dangerous thing, and it is probably best to conclude each to his own.

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MarekH
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#22 Re: sound of the v12

Post by MarekH » Sat Sep 02, 2017 7:24 am

Dear Barry,

Do tell us exactly what, to your mind, doesn't make sense, rather than a blanket statement aimed at everyone and no one.

I certainly wouldn't dismiss the happy amateurs who work on these cars - automotive engineering has moved on a long way in 45 years since Roger was a trainee and you'll find plenty of people now delving into the fluid dynamics of manifold and cylinder filling on our v12s, unravelling the assembly code in the 16CU or simply datalogging every known parameter of the car's ECUs out on the road to look and see what is going on inside these engines in real time.

What the gist of the thread covers is that altering just one component, e.g. the exhuast, may well have a knock on effect on overall performance, may be somewhat difficult to compensate for, or disentangle the consequences of the lack of balance that might be introduced. This is especially difficult for the end user of a carburettored car to do as there is little by way of recordable information as to what is actually going on.

kind regards
Marek

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AussieEtype
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#23 Re: sound of the v12

Post by AussieEtype » Sat Sep 02, 2017 8:53 am

Maybe an exhaust like this V12 XJS has is what we want - sounds like a V12 should :bigrin: If it works for a XJS will work on a E-Type.

Turn up the sound


Garry
1971 Series 3 E-type OTS
1976 Series 2 XJ 12 Coupe

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chrisfell
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#24 Re: sound of the v12

Post by chrisfell » Sat Sep 02, 2017 12:45 pm

"Oh dear, some of you do talk bollocks!"

Yup! Got a diploma in that and everything.

However, when others talk bollocks I do try, ever so hard, not to get all preachy and superior, 'cos I know I'm actually not as bright as others might think I am.
Chris '67 S1 2+2

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Barry
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#25 Re: sound of the v12

Post by Barry » Sat Sep 02, 2017 7:28 pm

Thanks Marek. Point taken!

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Woolfi
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#26 Re: sound of the v12

Post by Woolfi » Tue Sep 05, 2017 10:19 pm

Heloo Barry !
Who has written this ? A really expert or a fool like me ?
"Returning to the classic short branch tubular manifold it will now become more obvious why this arrangement CANNOT (!!!) work very well."

Regards Wolfgang Gatza

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Barry
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#27 Re: sound of the v12

Post by Barry » Wed Sep 06, 2017 6:44 am

So, tell me guys. Is there a tubular manifold for a V12 out there which will improve the performance; and torque in particular. The choice seems to be either ClassicFabs, Hayward and Scott, and a ridiculously expensive one from SC Parts. Surely they can't all be wrong!

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#28 Re: sound of the v12

Post by Woolfi » Thu Sep 07, 2017 1:44 pm

I don't know, if there is a tubular manifold, with short pipes fitting into the narrow engine campartment of the e-type V12, which gives more power.
Mr. Bywater says "No!" http://www.jagweb.com/aj6eng/tt_explained.php
Aj6 wants to sell tt-pipes. The other three companies want to sell tubular manifolds. Who is correct ?
The tubular manifolds of the EV12 racecar of Group 44 have been much longer.
Regards Wolfgang Gatza

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#29 Re: sound of the v12

Post by MarekH » Thu Sep 07, 2017 4:51 pm

What Mr Bywater said was that the original headers weren't that bad a design in principle because the three cylinders they each served fired 240' apart and didn't interfere with each other. His headers simply extend each group of three.

The reason to do that would be to consider the exhaust as a tuned item, where speed of exhaust gas = frequency x wavelength for the given tube diameter. If you remember your 'O' level physics, or do some research into transmission lines, then I suspect the wavelength/4 is the desired length of the headers for peak torque at a particular rpm.

I won't try too many calculations, because although the speed of sound in air is ~330m/s, the speed in a hotter gas will be higher and in a denser gas will be slower. At 330m/s, with a length of 1m to the join up on the AJ6 headers, that gives a frequency of ~80Hz, which is 4800cycles per minute. That's in the ball park for "rpm", but I suspect the real figure aimed for using real data will turn out to be nearer 2500-3000 rpm.

On Ducati twins, when they went to the underseat exhaust with the 916 in 1995, they deliberately made the two exhausts different diameters because the engine is mounted vertically and one cylinder has to have a longer exhaust than the other.

Changing the diameter of the tubing and the length of the header (along with the intake runner length) will proportionaely change where peak torque will occur and no doubt the AJ6 ECU is deliberately tuned to match this. Unless you want to do some r&d, I think it'll be hard to give any guidance on specific products.

kind regards
Marek

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#30 Re: sound of the v12

Post by Woolfi » Fri Sep 08, 2017 10:25 am

M. Bywater is writing:
"Returning to the classic short branch tubular manifold it will now become more obvious why this arrangement cannot work very well."
My english is a little bit poor. What does he mean with "this arragement" ? The tubular manifold or the original cast iron 3into1 manifold ?
Regards Wolfgang Gatza

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#31 Re: sound of the v12

Post by Ikebaddog » Fri Sep 08, 2017 10:47 am

MarekH wrote:What Mr Bywater said was that the original headers weren't that bad a design in principle because the three cylinders they each served fired 240' apart and didn't interfere with each other. His headers simply extend each group of three.

The reason to do that would be to consider the exhaust as a tuned item, where speed of exhaust gas = frequency x wavelength for the given tube diameter. If you remember your 'O' level physics, or do some research into transmission lines, then I suspect the wavelength/4 is the desired length of the headers for peak torque at a particular rpm.

I won't try too many calculations, because although the speed of sound in air is ~330m/s, the speed in a hotter gas will be higher and in a denser gas will be slower. At 330m/s, with a length of 1m to the join up on the AJ6 headers, that gives a frequency of ~80Hz, which is 4800cycles per minute. That's in the ball park for "rpm", but I suspect the real figure aimed for using real data will turn out to be nearer 2500-3000 rpm.

On Ducati twins, when they went to the underseat exhaust with the 916 in 1995, they deliberately made the two exhausts different diameters because the engine is mounted vertically and one cylinder has to have a longer exhaust than the other.

Changing the diameter of the tubing and the length of the header (along with the intake runner length) will proportionaely change where peak torque will occur and no doubt the AJ6 ECU is deliberately tuned to match this. Unless you want to do some r&d, I think it'll be hard to give any guidance on specific products.

kind regards
Marek
I've never noticed the different size pipes on my 996, nor did I on my old 916, very interesting, i now need to have a look :bigrin: :bigrin:
John
S3 2+2 1971
Aston V8 Vantage 2006
Caterham Supersprint 1.7 1989
Jeep Wrangler TJ

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#32 Re: sound of the v12

Post by MarekH » Fri Sep 08, 2017 12:42 pm

Woolfi wrote:M. Bywater is writing:
"Returning to the classic short branch tubular manifold it will now become more obvious why this arrangement cannot work very well."
He means "a manifold made up of short tubes cannot work very well" and looks to be referring to the D-type 2x 3into1 arrangement shown in the second picture on that page of his website.

What he is promoting is the extractor exhaust which helps to scavenge exhaust gasses from the cylinder, thus reducing pressure in the cylinder and thus allowing higher volumetric efficiency when the cylinder is refilled - which will cause leaner running conditions than standard, which thus means more fuel is needed than before. Essentially, more fuel and more air makes a biger bang and the extractor exhaust, so long as it is fed more fuel in the first place, does just that. The dimensions of the extractor exhaust are designed such that this happens in a useful band of rpm, rather than simply promoting top end power.

kind regards
Marek

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Barry
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#33 Re: sound of the v12

Post by Barry » Fri Sep 08, 2017 6:57 pm

My good friend Ian Stewart from Ecosse (well known maker of the top quality exhausts for E-types) said for the Road he would consider using the standard manifold as the design is quite good, but have the inside polished, and then ceramic coated inside and out. This working on the principal of getting the hot gases out quicker. Then maybe possibly have a bigger bore set of down pipes with crossovers. Certainly a lot cheaper, and Ian confirmed that unless you have longer pipes as per the racing set ups, then it is frankly a waste of money.

I could well go for that if Ian will do it for me. What is the view?

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#34 Re: sound of the v12

Post by Woolfi » Sun Sep 10, 2017 11:13 am

Unless Ian can't show you a dyno sheet, which is part of the buyers contract, he is a fairy-teller, like thousands of other tuning-part dealers.
If the bigger down-pipes are reducing back-pressure, you have to "reshape" the 4 carb needles. Otherwise the mixture is becomming leaner and the motor is loosing power.
I never have heard , that somebody is coating the cast manifolds inside, to allow gases to flow quicker.
The original 2into1 roundabout 12 inches long down-pipes have a step, where they merge from two into one. This step causes a dynamic reducing of the inside diameter of the outlet pipe. If you take one of these two-into-one down pipes and look from the one pipe to the inside, you can see this step very clear. I think it is a good idea to grind this step to zero, that the gases can flow better.
Also the two inlets of the back silencer of the EV12 have a diameter of only 40 mm. A friend of me hase cut the two pipes directly the the muffler and checked this. I don't know if it is possible to make the entrance at this point wider.
I have some pages from a vintage Jaguar-magazine about the first speed testing for the press of the EV12 in 1971 on the italian autostrada. in this article is written, that Jaguar took away the back muffleraund the two small air trumpets (inside diameter at the front of 32 mm) leading to the air filter boxes, that the motor was a little bit stronger, so that the new EV12 reaches a speed of 145 mph.
Regards Wolfgang Gatza
Last edited by Woolfi on Fri Sep 22, 2017 4:18 pm, edited 1 time in total.

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#35 Re: sound of the v12

Post by Woolfi » Sun Sep 10, 2017 11:18 am

"He means "a manifold made up of short tubes cannot work very well" and looks to be referring to the D-type 2x 3into1 arrangement shown in the second picture on that page of his website."

Also Mr. Bywater descibes the power gaine (nearly zero) of commonly sold tubular headers for the EV12.
I found this in the internet, written on the page of AJ6:

"Can you supply multi-branch exhaust manifolds for my Jaguar V12?
Well we could - but the trouble is that there isn't enough space to install pipes of the right dimensions to work properly. If the dimensions are wrong then the system can actually have a negative effect. There is virtually no overlap of exhaust pulses into the cast three-into-one manifolds of the V12 (and 6 cylinder engines) so replacing them with separate pipes doesn't reap much improvement for the cost and trouble involved. As the TT system keeps each group of three separate for a considerable distance it provides the most viable solution."

Regards Wolfgang Gatza

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#36 Re: sound of the v12

Post by Woolfi » Mon Sep 18, 2017 9:01 pm

The following I found on jag-lovers.org . 46 hp or 53 hp gain with tubular manifolds ? lol . . . The hp-gain of tubular manifolds in a normal jaguar V12 motor seems to be nearby zero !

In reply to a message from tobmag sent Wed 17 Nov 2010:
I.
Well goes to show you that a little bit of knowledge is a very
dangerous thing.. (in this case to your pocket book).
Where to begin..
And guys to keep this readable I'm going to greatly over simplify
stuff. That data is out there, just go looking for it..(or ask)
First those headers aren't headers.. They are tubular exhaust
manifolds.. Second the stock cast Iron manifolds are remarkably
great once you understand what they do. A V8 really needs headers
because of it's firing order. (pls. ask) The V12 because of
It's !! perfect firing order doesn't need headers as much. Think
of the V12 as Four 3 cylinder engines each firing 120 degrees from
the other.. in perfect order, unlike a V8.
OK the two things exhaust headers do is;
First reduce back pressure. Look at the V12 manifolds, there are
no pinched spaces and the curves are gradual enough (Look at
Formula 1 for the standard of how sharp a radius exhaust can flow
without losing horsepower..)
Second is time pulses to aid in extraction of spent gases and
assit on creating a vacum to pull fuel/air intake into the
cylinder.
The V12 is such a fuel hog that there is almost no overlap on the
intake/exhaust stroke. There is more horsepower if there is
overlap but fuel mileage, already poor would drop dramatically.
IF you are prepared for really poor mileage and a unmuffled
exhuast. PLus have the camshaft required to make use of the
potential gains then yes the potential exists for power gains..
The next issue would be fitting the proper length headers under
the hood..On my XK-E V12 tht required moving or eliminating an
awful lot of things plus cutting the body to allow the tubes out
the rocker panels.
On a XJ-S or XJ-12 the amount of work would be equally as tough!

The second
Now I had a set of real headers on my XK-E V12. They were equal
length and 31 inches to the collector. Equal length is hyper
critical if you want a header to do what headers are supposed to
do.. and the length will vary according to the camshaft used In
my case a serious full race camshaft. A street camshaft or milder
camshaft will need even longer ones to gain any benefit.. If you
need to run the exhaust through a muffler forget it! There is no
gain possible (on a V12, V8's are differant as I said a number of
times already)
AJ6 engineering has a good article about headers on it's web
site.. Written by Roger Bywater who is extremely knowledgable about
the subject. It's well worth your time to spend the 5 minutes it
takes to read.. If you want you can buy a book about making headers
that will give you the formula's used to confirm the required
length of primary tubing.
Please don't fall for claims..In all probability they aren't
lying rather simply not doing a back to back comparison.. Chances
are One car has more restrictive mufflers than the one with the
tubular manifolds.
MGuar
Wayzata Minnesota, United States
--Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]--

In reply to a message from tobmag sent Wed 17 Nov 2010:
II.
OOPs, even the price is wrong..
Now add the rest of the system.. Because if you bolt those
tubular manifolds up to the stock exhaust system there won't be any
gains..
To get the horsepower increases back pressure must be lowered.
You could also get it if they were equal length (exact) and tuned
to the camshaft.. those camshafts would have to increase the
overlap to show any gains. However increasing the overlap on the
already thirsty V12 will drop the fuel milagage dramatically.
ON the other hand.
Yes they are nice. Stainless steel will look nice untill heat
turns it yellow and purple but even that looks better than those
cast Iron things.. They also look racy as heck. Most people don't
know and the few of us who do know are tired of explaining things
over and over again..--
MGuar
Wayzata Minnesota, United States
--Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]--

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Barry
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#37 Re: sound of the v12

Post by Barry » Thu Sep 21, 2017 2:22 pm

Thanks Woolfi. That sums it up nicely, a big NO to a short branch manifold! I am going to fit one of Roger Bywater's Super Sports systems with a central box so the sound will be midway between the TT I already have fitted and the full on SS system. Anyway, that is what Roger suggested. A winter project, but will get dyno figures before and after, and post on the Forum. Although, bear in mind my car is a 6.0 with injection, and AJ6 Torque Plus kit.

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