S3 V12 weber six pack carburettor set-up--any views?

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JIM BAUMANN
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#1 S3 V12 weber six pack carburettor set-up--any views?

Post by JIM BAUMANN » Mon Oct 08, 2012 7:23 pm

Good evening all - recently joined, have V12 E. Love the car, smooth, sweet, et al. However I have perhaps been spoilt a bit as I also have an MGB GT with a 4.6l V8, lashings of torque - small car = big engine. E-type low down appears to be able to not match the torque or accelerative performance of the MG, granted the B is very exciting and noisy twin straight thru with 4 x wadding boxes which fight a losing battle over 3500 rpm). Ergo maybe its deceptive but I thought the E-type should be quicker (than it feels) or feeling more effortless low down I hoped. The 4 x Strombergs have just been set-up this week by SC Jaguar @ Netley Hamble Southampton and the car is MUCH nicer and smoother now just not "grunty" from 0-40/50 - above that it's lovely!! does anyone have views/experience and do's/nots on this set-up?

http://www.webcon.co.uk/Downloads/PJA601-Feb07.pdf
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MGB GT V8 4.6 1972
Renault Caravelle 1967
Peugeot 504 cabriolet 1973
Jaguar E-type V12 1973
Panhard PL 17 1960

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#2

Post by Heuer » Mon Oct 08, 2012 7:36 pm

Jim

Suggest you just post in one place rather than double post. If it is wrong we can easily move it :D
David Jones
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#3

Post by PeterCrespin » Tue Oct 09, 2012 1:22 am

If you want low down grunt don't go for Webers. There isn't room for the required inlet tract length with that setup.

If you want to overcome the tyre grip more easily than you can at the moment, switch to a lower transmission ratio. Either a lower-geared diff or a manual box if it's automatic. This multipliers the torque to the back wheels by whatever ratio change. You can also convert to a 4-speed auto but really the V12 E is not a dragster.

I got the advertised 6.3s to 60 out of my auto, so it's not exactly sluggish. What is you 0-60 time? You need to get past how it 'feels' (which is deceptive with the V12) and put some numbers to those feelings, if only to quantify any changes. The Webers would probably only feel fast because the car would bog down at low revs and then perhaps come alive at higher revs, giving an impression of speed. But feeling a shove in the back is no help if you've already bogged down and lost ground to begin with.
1E75339 UberLynx D-Type; 1R27190 70 FHC; 1E78478; 79 S2 XJ12L; 97 XJ6L

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#4

Post by JIM BAUMANN » Tue Oct 09, 2012 6:53 am

Thank you for your response and thoughts Petercrespin! This is exactly what I wanted concrete thought! I should have mentioned that myV12 'E' is manual. I probably would not want to lower the axle ratio as such - the engine seems plenty 'busy' as it is... :lol: So with the 6 x twin Weber set-up at what point is there an advantage gained and what is the sum total of that? I can understand that to feed fuel at the required rate to 6 throats from nil requires revs. anyone have this set-up in their car? Interested to hear more.
MGB GT V8 4.6 1972
Renault Caravelle 1967
Peugeot 504 cabriolet 1973
Jaguar E-type V12 1973
Panhard PL 17 1960

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#5

Post by ene703 » Sun Oct 14, 2012 11:32 am

Jim, What do you mean by "the engine seems plenty 'busy' as is"? I remember when I started my S3 the first time I thought the engine was idling too fast... checked the tach, no, idling perfectly as the book said... still, seemed too fast. Checked exhaust... yep, lot of cycles... Then I realised why.. It's a V12 it has 1/3 more cyliners than the V8 I was used to driving. Could that be what you mean by "the engine seems plenty 'busy' as is". The V12 has massive amounts of low end grunt and as Peter said 0-60 in 6.3 with an auto is not shabby. My S3 w/slush box did the JCNA slalom course in 1st. :D
1S70526 71 V12 2+2

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#6

Post by JIM BAUMANN » Sun Oct 14, 2012 5:01 pm

Indeed--you are of course right--there are a lot of bits of metal whizzing up and down--that what t I meant as the engine being "plenty busy" !--so many moving parts! You are all of course right a datum line of actual figures would be useful to establish to build on from. The engine does appear to be in fione fettle with excelent oil pressure. The 4 x Strombergs have all been balanced and are running in harmony. I was simply interested in getting some first hand opinions/experiences on the possible gains in performance that the additional quantity of fuel air mix that appears to be possible to ram into the engine that 6 x twin choke carbs should( might) give! Anyone out there actually have this carb set installed and what other alterations and/or modifications were required or carried out? ie ignition/camshafts etc etc...?

Regards and thank you for thoughts

I was inspired down this track by this video


Jim Baumann
MGB GT V8 4.6 1972
Renault Caravelle 1967
Peugeot 504 cabriolet 1973
Jaguar E-type V12 1973
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#7

Post by MarekH » Sun Oct 14, 2012 5:34 pm

Dear Jim,

The common wisdom is that it doesn't really fit under the bonnet. It really wants a few more inches which simply aren't there unless you make the bonnet bulge higher. This means that the kit is "made to fit" and the trumpet length is shorter than would be were you to have a blank sheet of paper to start with. The other common bit of wisdom is that it'll be under 10mpg - the figure I heard bandied about is 8mpg. The last bit of anecdotal, possibly old wives tale quality, but worrying bit of evidence is that of spitting back petrol into the engine bay if poorly tuned. If you really want performance, consider a manual gearbox or fuel injecting your car. There are plenty of options here and with fuel injection you get 20mpg economy thrown in. Also, beware of the "spot the benchmark" problem, in that no-one who has shelled out a couple of grand on hardware is going to admit that they are wearing the Emperor's new clothes. I have nothing against the idea, but the flipside is that, other than "eye candy", I can't see any advantages.

kind regards
Marek

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#8

Post by Heuer » Sun Oct 14, 2012 5:40 pm

Some further reading from our Knowledge Base:

Weber Set up Guide 1: http://dl.dropbox.com/u/8496016/Weber%2045DCOE.pdf
Weber Set up Guide 2: http://dl.dropbox.com/u/8496016/Weber%20Wisdom.pdf

Seems like a lot of work for little all round gain.
David Jones
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#9

Post by PeterCrespin » Mon Oct 15, 2012 2:42 pm

That is a good guide but you CAN get reasonable gains using Webers on a six as part of a package and if properly set up.

The issue with the V12 is that you can't really get the gains under an E-type bonnet, or even an XJ-S or XJ bonnet is very tight. Jaguars are sleek cars and the long, low, look means no spare room above the engine which you need if going from side draught to down draft carbs. Period.

Moreover, the physics of air flow on the V12 are that if the objective is low-down grunt, then fitting Webers is the opposite of what is required. The IDF installation considerably shortens the inlet tract and constricts airflow through the front trumpets. If you were building a race motor with wild cams etc and didn't mind moving the torque up the rev range then yes, ultimately by re-engineering the bonnet mounts an inch or so, or dropping the engine a few extra millimetres, you could get better airflow at WOT but that's the opposite of what is being sought.

There is an installation option where DCOE Webers can be fitted to long manifolds curling over the camboxes and although I've never spoken to anyone who has done that, I'd expect good low-down torque from such a set-up until the lack or air cleaner room and breathing hot air took its toll. And getting the car set up, using twelve of every jet, emulsion tube etc. every time will get eye-wateringly expensive for an uncertain gain.

I think Jim is being fooled by the deceptive turbine nature of the V12 power curve. I would be surprised if a stock luxurious manual V12 E is left for dead by an MGB V8, no matter how unrefined and hairy-chested. He should get someone he trusts to race him in his own car and report back. The tyres will be easily overwhelmed on both cars, so it will come down more to technique and rubber size than engine power I bet. And if the MGB gets away up to 30 mph thanks to lower inertia or gearing, try a rolling top gear acceleration at 100 and see what happens.
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#10

Post by Woolfi » Wed Oct 17, 2012 10:49 am

That's the reason,why 6 Weber are not working well on a EV12. The length of the runners is much to short. The motor will loose power in the midrange and will have some more torque over 5500rpm. If the motor is loosing midrange power, somebody will "feel", that the motor has much more power in the higher revs. This is a misfeeling.
On the left side of the graph is torque, and mm is the length of the complete distance from mouth of the carb to the inlet valve written in mm.
The graph is for a 6-cylinder inline motor. A Jag EV12 with 6 Weber is breathing like two 6-cylinder inline motors.
A Ev12 motor with 4 carbs is like 4 3-cylinder motors. There is a big difference in low down power of a 3-cylinder and a 6-cylinder motor.

Regards Wolfgang Gatza

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#11

Post by MarekH » Wed Oct 17, 2012 1:36 pm

Dear Wolfgang,

That's a very interesting graph. I have made a rough and ready measurement for the length of the standard v12 inlet tracts as:-

carburettored v12 : 35-38 cms
fuel injected v12 : 33-43 cms

kind regards
Marek

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#12

Post by Woolfi » Wed Oct 17, 2012 2:42 pm

Another interessting graph. It shows the typical torque curve of a motor, if he has 2 or 4 or 6 cylinders. The EV12 motor with carbs is acting like 4 connected 3-cylinder motors. The torque is higher than with the other two types of motor-construction and the maximum torque is in the low rev-range.
I have a EV12 with a 6,0 liter motor from a 1993 limousin and the original stromberg carbs. My friend has a very expensive EV12 with the same 6,0 l motor , but fuel injection. When we compared the cars accelerating from 2000 rpm in 4 gear, my stromberg-car was accelerating quicker than the injection car. The programming of the injection was done on a rolling road from a very experienced specialist in Germany, his name is Bilas. Bilas has done hundrets of coversions from original injection to programmed injection for sport cars in the last 20 years.
Therefore I am thinking, that a conversion to injection is nearly worthless.
Regards Wolfgang Gatza

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#13

Post by MarekH » Wed Oct 17, 2012 4:41 pm

Don't be fooled Wolfgang. You aren't quite comparing like with like:- according to your graph, the peak torque and torque variation on these two motors will be totally different because of the inlet tract length and also bear in mind that the carburettored engine is absolutely pumping gallons of petrol into the cylinders and by comparison, the injected engine isn't. According to your second graph, the same test done at 3750 to 5000 rpm would expect to reverse the result. If fuel injection were such a step backwards, we'd all be converting our regular cars back to carburettors. The injected engine will easily manage 20mpg, a figure which will never be seen by its carburettored ancestor.

kind regards
Marek

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#14

Post by Woolfi » Wed Oct 17, 2012 5:45 pm

written new.
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#15

Post by MarekH » Wed Oct 17, 2012 6:08 pm

Dear Wolfgang,

A few people have converted their v12s to fuel injection using Megasquirt. Take a look at the photo albums on the jag-lovers.org website by Philip Lochner "jagwit" and myself "MarekH".

It look to be a slightly more popular conversion than the Weber conversion. The advantage of the self build approach is that you are forced to learn and understand what you are doing, rather than spend money with a third party and regret it later.

My fuel injection conversion was about GBP2500, but I have the original engine, complete with all ancillaries as a spare should I ever buy another etype. I'd suggest that your friend has been as we say "taken to the cleaners".

Much of this deserves to be in a "fuel injection conversion" thread rather than a "Weber conversion" thread, unless Jim is happy to widen his search for more low down torque. Your graphs may help persuade him that he his heading in exactly the opposite direction than he wanted to go.

kind regards
Marek

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#16

Post by Woolfi » Wed Oct 17, 2012 6:16 pm

"Don't be fooled Wolfgang. You aren't quite comparing like with like:- according to your graph, the peak torque and torque variation on these two motors will be totally different because of the inlet tract length and also bear in mind that the carburettored engine is absolutely pumping gallons of petrol into the cylinders and by comparison, the injected engine isn't."
Marek you speak about gas comsumption of theses two type of cars. Have you done a real test in the reality or are you believing ? I think you have not tested.
"If fuel injection were such a step backwards, we'd all be converting our regular cars back to carburettors. The injected engine will easily manage 20mpg, a figure which will never be seen by its carburettored ancestor."
All what you say seems correct and is common known. But lets leave the area of theory and enter the reality.
1. The gas consumption of my car at a speed between 70 und 80 mph is roundabout 22 mpg. I think the gas consumtion in real life traffic of the EFI-car would be lower, but I also think the difference would not be so high. I have never checked the gas consumption of my friends car, when I am driving this car like mine.
Until now, we have only done this acceleration test between 2000 and 4000 rpm (4000 rpm in forth gear with a 2,88er diff is roundabout 125 mph on a german Autobahn. My car has a 2,88 diff and his car has a 3,07 diff. Therefore the difference in real torque must have been bigger, because of the difference in acceleration.
"According to your second graph, the same test done at 3750 to 5000 rpm would expect to reverse the result."
I also would expect this. At which rev range are you using this cars ? Low end torque is important for every day drving. My motor has a lot of this. Therefore I am happy with my 4 x 3 cylinder motor. When we have done the test, my friend had only time for half an hour. We have only done two times this test from 2000 to 4000 rpm and not also in third gear up from 3750 rpm to lets say 5800 rpm.
Another friend is doing also this conversion to a 6,0 L motor and a programmable injection. I am waiting since two years, that we can repeat this test. But still he is working on his car. (Still in 9/2014 he is working on the motor)
"If fuel injection were such a step backwards, we'd all be converting our regular cars back to carburettors. The injected engine will easily manage 20mpg, a figure which will never be seen by its carburettored ancestor."
Shure a car with injection would be a better car, than a car with carbs, IF you can buy a ready made car from a big producer. My plan was also, to converse to injection. I have not done, because I wouldn't like to spend big money.
But let's again check reality. My friend ordered the full "programm" from AJ6 including a reprogrammed electronic box. He spend 3000 Euro for the tuning parts and the changing of the programm by Mr. Bywater. In the beginning the car was driving bad and was a sheep and not a tiger. The man who has done the conversion, has done minimum 20 of theses conversions in his life. He has done the first conversion of a EV12 to injection at 1980. He is the most experienced specialist for EV12 in germany. Not a normal car-mechanic. He has studied motor-construction on a university, therefore intelligent and very well understanding, what he is doing.
My friend had some emails with Mr. Bywater and was becomming very angry, that nothing went better with his motor. At the end he brought the car to Bilas, spending another 7000 Euro for a other injection. It took some month, to debug and to make the car running well. At the end of this we have done the test and my friends face became longer and longer, when my car "slipped away".
I still thinking, that the effort for this conversion is MUCH to big, if you check the results. When I have done my conversion to this motor, it took also two month , to make the car running without problems. But the effort for a conversion to injection is much higher and much more expensive.
I don't want to tell, that my car and his "producer" are top. I just want to give serious information about this EFI-conversion, like I have seen in reality.
I will also inform about the comparison with the second EFI car, which will be driving next spring.
Some years ago I have done the same acceleration test with a EV12 coupe with a conversion to XJ12 Series II EFI. The result was similar. I had big problems to undertstand why this has happened , until I found this graph (typical torque curve of a 3, 4 od 6cylinder car) in a tuning book.
OPEL offered a 6-cylindeer "Senator" with 3,0 L Motor in the nineties with a so called "dual-ram injection system". Below 4000 rpm the motor acted like two 3-cylinder motors, about that a "door" opened in the system, that all 6 cylinders sucked from one box. This system had a higher torque in the low revs like the normal one.
If you would compare your megasquirted car with a goog running carb car, maybe you wuld have the same results.
Mr. Peters, who has done a lot of these EFI-conversions drove my car and was impressed by the punch of the motor in the low and midrange. He is planning to make the next car with a 6-cylinder motor and 4 SU HD8, because he often had problems with the injection.
He hadn't tried this before, because Mr. Bywater told him, that the HE-Motors are not working well with carbs. My experiendce is different, but I am still hungry for more information about this. Leraning never stops and is part of the fun with these old cars.
Marek, if one day you have been passed by a red "flash", maybe it was me. But at the next gas station, you will pass me again.
How have you adjusted your mixture ? Lamda = 1 or lean at part throttle ? Me motor is running with roundabout Lambda 1,1 at part throttle.
Regards Wolfgang Gatza
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#17

Post by jagwit » Thu Oct 18, 2012 7:07 am

Hi all

This is my first post on this forum.

I have a '71 XKE OTS which I converted to EFI using Megasquirt-2 and standard HE EFI hardware. The engine has also been converted to HE spec using 11.5:1 pistons and HE heads. Our local Jaguar Club had an event in Nov last year called "V12 Economy run". This was done over about 240km with mainly open road driving. I could not find the ability to add pics on this forum so I copied the info from my excel spreadsheet, so it wont appear as it should but I think you should be able to make sense of it.

Model Engine HE Pre-HE Mods worth noting that could affect economy Ltrs L/100Km Km/L Mpg US Mpg UK
XJS Cab 5.3 X None 26.92 10.12 9.88 23.2 27.9
XJS-C 5.3 X None 27.06 10.17 9.83 23.1 27.7
E-type 5.3 X 11.5:1 HE, EFI, EDIS-6 Megasquirt ECU 30.78 11.57 8.64 20.3 24.4
DD6 5.3 X 82degC thermostats 31.32 11.77 8.49 20.0 24.0
DD6 5.3 X AJ6 Super Enhanced ECU 32.57 12.24 8.17 19.2 23.0
XJS 5.3 X EDIS-6, Megasquirt ECU, 5sp manual 29.82 11.21 8.92 21.0 25.2
E-type 5.3 X Upgraded ignition - no vacuum advance 34.35 12.91 7.74 18.2 21.8
Best Regards
Philip
71 E-type V12 Coupe,
80 XJS (EFI by Megasquirt & EDIS-6 + 5sp manual overdrive)
73 Jensen Interceptor
74 Interceptor (EFI by Megasquirt + overdrive 4sp auto)

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#18

Post by Woolfi » Thu Oct 18, 2012 7:45 am

My car is a E-type 6,0 HE-Motor from a '93 limousine, 4 Stromberg carbs, correct working vacuum advance with the CORRECT (!) port for the vacuum in the carb, 2,88 diff plus 0,81 5-Gear Getrag manual.
I would expect for my car for such a test:
11,5 - 12,5 liters per 100 km,
8 - 8,7 kilometer per liter,
23 miles per UK gallon.
If I understand the previous information correct the car with the lowest gas consumption was a stock HE XJS, using less gas than the EV12 with EFI. Is this correct ?
Does your EV12 with EFI have a correct working vacuum advance ? In my car the ignition at steady speed up to 100 mph is up to 16 degree earlier because of the ignition advance. This is worth maybe 1 Liter/100 km lower gas consumption. Important is , thatyou have the correct point, where to pick up the vacuum. This point is called "tappered edge". It is a drilling ending roundabout 2 - 3 mm before the butterfly in the Stromberg carb. If you use vaccum from the inlet runners, the "shape" of the vacuum curve is totally wrong. You have 26 degrees of advance at 700 rpm, because of full vacuum at idle.
If somebody is interessted , I can show prictures of my drilling position for the correct vacuum port.
Years ago I have red an scientific work from a technical university about a compere of two cars (Mercedes 239, mod 123, from the eighties) with EFI and with one Stromberg-Zenith carb. The diference in gas -consumption at steady speed was very small. In the city the differece was a little bit higher.
In todays cars this differece would be higher. But the difference between a good carb and a simple old styled EFI seems to be low. If both cars are running at steady speed with lets say lambda 1,1, why should there be a difference ?
Regards Wolfgang Gatza
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#19

Post by MarekH » Thu Oct 18, 2012 8:40 am

Dear Wolfgang,

The Megasquirt ECU has fully programmable igntion and fuelling, so there won't be anything to drill and tap and no diaphragms to heat up, crack and cause vacuum leaks later down the line. You simply dial in the advance table (or multiple tables for different grade petrol or autogas) with a laptop. Philip's comparative table is very useful as it gives actual data, not assumed data. The cars all travelled together (same speed) on the same route on the same day with the same grade petrol. The relevant direct comparisons are E vs E and XJS vs XJS and saloon vs saloon. It suggests the HE heads and programmable ignition/fuelling is worth ~12% (21.8>24.4) mpg. It's a shame there was no Weber car for comparison.

kind regards
Marek

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#20

Post by Woolfi » Thu Oct 18, 2012 9:23 am

Hello Marek !
Do you know how much ignition advance does your motor has at lets say 60 miles per hour in 4th gear ? Mine has roundabout 30 +/- 3 degree.
Regards Wolfgang

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