Thermostatic Vacuum Valve and Retard Unit

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Adamski
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#1 Thermostatic Vacuum Valve and Retard Unit

Post by Adamski » Tue Jan 10, 2017 10:51 am

My car is a UK spec manual. I bought it when it was 5 years old. It is fitted with the valve at the rear of the RH inlet manifold bank. I seem to remember that when I purchased it there were some pipes connected to it but not all. I presume some were removed or never fitted,little brass pipes carburettor run off valve connections,(unlikely). One of the functions of the valve is to supply vacuum to the RETARD unit on the distributer and once warm I presume stop supplying vacuum once warm.
I have been having hot running issues and diagnosed(by fitting an inline vacuum gauge) that the valve was not functioning and permanently supplying vacuum. Having researched this site and many others the retard unit makes the car run hotter primarily for emission reasons and apart from the diaphram in itself being highly fickle (I have replaced 2 over the years) it is not essential to normal running conditions.
I have spoken to another V12 owner and he tells me his car is not fitted with the valve although the parts manual clearly show one fitted to all models. This valve is no longer available.
I also understand that some models did not have the valve and had vacuum permanently connected from the LH rear carburettor connection, but this may have been the saloon, I don't know if this is true though.

So my question is do all S3's have the valve, and were they all connected when they left the factory for UK market? Is It realistic to have the retard unit permanently connected without the thermostatic valve in the circuit and risking high burn temperatures at tick over/traffic jams all the time?
Adam
S3 V12 E Type FHC Manual 1972-owned since 1978

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jagwit
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#2 Re: Thermostatic Vacuum Valve and Retard Unit

Post by jagwit » Tue Jan 10, 2017 3:57 pm

Have a read of this: viewtopic.php?f=6&t=9665

In short: I suggest you replace with the vacuum retard diaphragm with a vacuum advance unit. This will make your V12 feel more lively and should improve economy (or lack thereof) by at least 20%
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#3 Re: Thermostatic Vacuum Valve and Retard Unit

Post by MarekH » Tue Jan 10, 2017 6:28 pm

If you look in the Parts Manual then it will show you how it was connected or not and which models and for which markets this would have related to.

The Repair and Operations Manual ("ROM") also tells you under what vacuum the retard was applied. The ROM also tells you the static advance to apply.

If you decide to run more advance at partial throttle then you may want to consider changing the static advance setting.

I would have thought that overheating is more related to not having a cooling system in good repair as the etype v12 is not known for overheating. The later HE cars ran 88'c thermostats - i.e. they are permanently 6'c closer to overheating than your car ought to be.

kind regards
Marek - also a "ski"

kind regards
Marek

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#4 Re: Thermostatic Vacuum Valve and Retard Unit

Post by Adamski » Tue Jan 10, 2017 9:53 pm

To fit an advance unit I would need to drill the carburettor and make a tapping as the source needs to be local to the butterfly, not something I wish to do at present. The only advance on the S3 V12 E Type is through the centrifugal weights inside the distributor.
The RETARD unit was fitted to the V12 E Type to artificially make the car nun hot, due to emissions control. The thermostatic valve would shut the vacuum off once warmed up ,if working correctly. The vacuum source is from below the LHR carburettor and only has enough vacuum to operate the retard unit at tick over. This is probably how they passed start up emission tests.
My car is no longer overheating because I've addressed the cooling system,but it's very hot under the bonnet and the car is bogging maybe fuel vaporisation?.
What I need to know is are all V12 E Types fitted with their retard unit connected through the thermostatic valve, That's what the parts book shows but what it actual out there, can some of you owners check please.
Adam
S3 V12 E Type FHC Manual 1972-owned since 1978

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#5 Re: Thermostatic Vacuum Valve and Retard Unit

Post by Bob. » Tue Jan 10, 2017 11:04 pm

"So my question is do all S3's have the valve"

From engine no 7S8444 the Thermostatic Vacuum Switch was deleted from all non exhaust emission (E type S3 V12) engines.
(Source - Jaguar Service Information V1 No11 Item 113 March 1973)

The note does not define what happened to the pipework from the LHR carb to the vacuum retard unit but it is shown on the pages of the parts manual devoted to the pipework from the vacuum switch and those pages are headed - 7S 8444 on - Not Required.
Bob
'71 S3

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#6 Re: Thermostatic Vacuum Valve and Retard Unit

Post by jagwit » Wed Jan 11, 2017 6:00 am

Adamski wrote:To fit an advance unit I would need to drill the carburettor and make a tapping as the source needs to be local to the butterfly, not something I wish to do at present. The only advance on the S3 V12 E Type is through the centrifugal weights inside the distributor.

The RETARD unit was fitted to the V12 E Type to artificially make the car nun hot, due to emissions control.
Glad to see you have done your homework!!

Firstly, you won't NEED to drill the carb. That is only required if you want ported vacuum. My car's vacuum advance is permanently connected to manifold pressure and it works fine. Ported vacuum is when you do not want any advance when the throttle is closed (engine idle) - and why would you want that???
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#7 Re: Thermostatic Vacuum Valve and Retard Unit

Post by Adamski » Wed Jan 11, 2017 5:53 pm

My engine number is 7S 5099SB,1972 model.
I'm now beginning to think that most people have either junked the retard connection and plugged the carb or bypassed the thermostatic valve and run vacuum direct. If this is the case surely the car is running artificially hot at tick over in all conditions. Surely this must be detrimental to the engine? What do you guys have out there??
Are there users out there with retard permanently connected?, disconnected? (If advance unit is installed where is it purchased from or is it from another model?)
Regarding vacuum advance I was not aware this works from a normal vacuum take off. I enclose a mail I received from manufacturers of an advance unit and now am totally confused. Homework is an understatement and my understanding is that it is beneficial to have the advance just before the centrifugal weights kick in at pull off. After you pull off there possibly isn't enough vacuum in the manifold to operate the vacuum advance and that's why they want it ported. These people below and reading other stuff on the web just made me think that's the way it will only work. Paul Clarkson has also written a lot on this including here and his website. So now I'm confused.
Case histories please.

British Vacuum Unit <britishvacuumunit@isp.com>
Hi Adam
I find many Jaguar part suppliers do not sell the correct distributor vacuum units.
Many sell these cheap Chinese units. We manufacture all the correct original distributor vacuum retard and advance units 1940s on.
Installing the advance unit to the V12’s is something I have been doing here in the USA.
I usually set the static timing @ 12 degrees BTDC, distributor advance to start around 1100 RPMs with 22 degrees @ 2400 rpm and a total of 30 to 32 degrees @ 3600 RPMs.
I install one of our OE type 54405202 5 15 12 Jag V12 advance units with the adjustable limiter that is actually set to 5 12 8.
Static timing of 12 degrees helps cooling at low RPMs and no mechanical advance below 1100 rpms makes setting the carbs easier and faster with a nice smooth idle. Limiting the distributor advance to 9 degrees/18 engine degrees plus the 12 degrees static gives a total of 30 degrees at the crank.
Vacuum advance also needs to be connected to ported vacuum. Ported vacuum is above the throttle disc on one of the carbs. If you have SU carbs you may have ported vacuum. In the UK, you may have ported vacuum on some of the Zenith carbs. Need to check.
If you have the correct ported vacuum on one of your carbs and the distributor has a good advance curve you will need to install the vacuum unit and connect it to ported vacuum.
One last thing before the distributor is installed, you need to move the distributor drive gear over CC one tooth.
Going from a retard unit to a advance unit will change timing. Moving the drive gear CC one tooth will the extra room to advance the dist body to set the timing.
It can be a pain but it makes the jag V12 run like you added 2 more cylinders with better cooling, more power and better mileage.
Make sure you have the correct ported vacuum.
I attached instructions for the Triumph TR6. It gives you a idea what needs to be done on the Jaguar V12 moving the drive gear and ported vacuum.
Also attached a article on distributors and how they advance what vacuum advance does. It also can apply to the Jaguar V12.
Note the Jaguar advance pulls and advance limited to 9 degrees. The attached TR6 info is just to give a idea what needs to be done.
Hope this helped, Rob
Adam
S3 V12 E Type FHC Manual 1972-owned since 1978

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#8 Re: Thermostatic Vacuum Valve and Retard Unit

Post by jagwit » Wed Jan 11, 2017 7:46 pm

Adam, Rob says the following:
"Vacuum advance also needs to be connected to ported vacuum."

Again this word "need" features, but the REASON it is "needed" is not presented. Again I am of the opinion that ported vacuum is NOT NEEDED. It may be "desired" (at the expense of ????), but then for specific reasons and emissions is normally right there at the top of the list.

But don't believe me, just do the following exercise:
1) Disconnect the vacuum diaphragm altogether. Now ONLY centrifugal advance is active but since the rpms does not change MUCH even this aspect does not influence our experiment MUCH;
2) Set the spark timing at idle for 0 deg BTDC and note the rpms, but don't change anything else
3) now set timing for 10 deg and note the rpms;
4) now simply play around with the dissy until you find the point where the engine is running at the highest rpms and then determine the advance timing you have now.

I predict that at 0, the rpms will be lowish, a bit more at 10 and even more when you advance the timing even more as per step 4. I also predict that the timing for max rpms at idle might be in the region of 15 to 20 degrees.

Now I have a few questions:
1) WHY are we told to set the timing to 10 or 12 degrees as per the book when clearly the engine is happier with more timing at idle? (and everywhere else???)
2) WHY does the engine idle higher when you advance timing well beyond 10 degrees?
3) if we set timing at idle to 10 or 12 degs, WHY should we not let vacuum advance the timing to a point where the engine is even happier using PERMANENT manifold pressure (vacuum) instead of ported manifold pressure (vacuum)??

(Please also note that vacuum based timing acts COMPLETELY independently from centrifugal based timing - I trust you understand WHY...)

PS: Please just clarify this statement as I genuinely do not understand it : "After you pull off there possibly isn't enough vacuum in the manifold to operate the vacuum advance and that's why they want it ported."
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#9 Re: Thermostatic Vacuum Valve and Retard Unit

Post by Adamski » Wed Jan 11, 2017 8:44 pm

The reason why I made that statement was that I fitted a vacuum gauge by means of a tee piece into the vacuum supply to the retard diaphragm. Timing was set according to the book. I also had a strobe pointed at the timing marks. Car ticks over and vacuum is high, blip the throttle and vacuum is low. Ticking over with retard unit connected and strobe shows 4deg BTDC, blip the throttle and timing advances towards 12deg BTDC and then over virtually off the scale at 2500rpm by means of the centrifugal weights. But my deduction is that as soon as you open the throttle the low vacuum is insufficient to power the diaphragm. So I'm thinking why would it have enough vacuum to power an advance unit at pull off. This could only be verified on your vehicle by disconnecting the unit and checking the strobe readings with and without. Doing this whilst driving would obviously not be practical.
So if it cuts out the retard unit why would it still power an advance unit OR is it down to the spring inside the advance unit needs less vacuum?? Now that's got me wondering.???

I still also need feedback what others have done with their connections to retard unit direct connection, through thermostatic valve or disconnected.
Adam
S3 V12 E Type FHC Manual 1972-owned since 1978

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#10 Re: Thermostatic Vacuum Valve and Retard Unit

Post by MarekH » Thu Jan 12, 2017 9:12 am

Dear Adam,

Where you get your vacuum from very much affects how much of it there is to power the distribuor capsule.

What you need to do is use your gauge to measure 1/ manifold vacuum at various throttle openings; 2/ ported vacuum at the place where the later ZS carbs had their EGR connected at various throttle openings and finally 3/ vacuum from the LH rear carburettor which is where the oem retard unit was connected at various throttle openings.

You will get different results for all three at different throttle openings. That then translate to an advance or retard profile for a particular capsule, which will have its own vacuum usage profile layered onto whether vacuum was available in the first place.

The static and centrifugal timing are independent of this but additions you need to consider.

In essence what you ought to see for manifold vacuum is minimum advance at WOT, maximum advance at closed throttle whilst going downhill and proportional everywhere in between; for ported vacuum you should see a signal at partial throttle opening and for the LH rear takeoff you should see a signal mostly at idle only.

The thermostatic valve is probably a bit a red herring. Once the engine temperature exceeds the thermostat termperature, the radiator and fans should be able to keep the engine temperature cycling at or around the minimum thermostat temperature. If they can't do that, you'd overheat eventually anyway.

kind regards
Marek

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#11 Re: Thermostatic Vacuum Valve and Retard Unit

Post by Whitact » Thu Jan 12, 2017 11:46 am

Hi Adam,
You may have seen it already but the pages on this link (http://www.pclarkson.plus.com/Ignition1.html) gives a very practical account of moving from vacuum retard to advance.
Closer to home my FHC is a 1972 UK car running on SU's with the SNGB ignition system. The thermoswitch was not connected when I bought the car and I discovered very recently that the garage that fitted the ignition system had plugged the vacuum line so the car has been running with mechanical advance only.
My OTS is a very late UK car fitted with Strombergs and all the air injection and other emissions kit. It also has the SNGB ignition but with the retard module connected via the thermoswitch as original.
The OTS starts well, warms up quickly and did 22mpg over 3,300 miles on the RBCD last September.
The FHC is very reluctant to start from cold, needs the choke for a long time and returned just 17mpg over an 1,800 mile trip at New Year. (The throttle pedal is also very heavy due to the springs that are on the SUs).
Both cars have ETF five speeds (0.63 fifth gear and 3.07 diffs, about 35mph/1000rpm) and run with Iridium plugs.
So I have bought one of the vacuum advance units from British Vacuum (who provided great service). My plan is to get the Distributor Doctor to rebuild and re-curve a spare dizzy and fit the vacuum advance unit to the FHC. One of the SUs has a ported vacuum take off point so I will connect via that. I understand that using ported vacuum helps to provide a stable idle speed.
If it all works well I will probably try the modified distributor on the OTS and see what difference it makes.
Longer term I have a full Plus Torque kit from AJ6 so plan to fit EFi to the FHC but am still mulling whether to use the modified Jag ECU or to go with MS or similar.
Cheers
Adrian Turner
S3 OTS & FHC
S1 FHC
XK140 FHC

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#12 Re: Thermostatic Vacuum Valve and Retard Unit

Post by 42south » Sun Jan 15, 2017 9:08 am

Hi Guys
I have a 71 S3 with strombergs. I used the british vacuum unit timing and distributor curve advice, also the recommended vacuum advance module.
I got Rob to recurve my distributor to his spec. He also drilled the carb for ported vacuum at a very reasonable cost. He has made a jig to get the hole in the correct place.
I am very happy indeed with the performance of my car. No pinking or detonation under load, I haven't checked the fuel consumption yet as the engine is still running in.
Cheers
Mark Brown
1971 S3 Etype
Son: when I grow up, I want to be a pilot
Dad: You’ll have to choose.

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#13 Thermostatic Vacuum Valve and Retard Unit

Post by Adamski » Sun Feb 19, 2017 8:08 pm

I have now completely bypassed the valve and run vacuum direct to the retard unit from LHR carburettor. I purchased it recently from Jag Shop and although it works it now leaks slightly. This I have verified with my trusty big plastic syringe and it doesn't hold vacuum. I will at some point remove it and pressurise it in a glass of water. This will immediately show the leak if so.
I'm finally seeing the end of the tunnel and have posted on the Stromberg rebuild topic which has left me spending weeks trying to fix a misfire when hot that was actually introduced by the specialist that rebuilt my carburettors, so annoying.
When I do my eventual extensive road trials I will consider the advance unit from British Vacuum Units which seems to be a good option. It has been stated on this site that it doesn't necessarily need ported vacuum to function?
Adam
S3 V12 E Type FHC Manual 1972-owned since 1978

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#14 Re: Thermostatic Vacuum Valve and Retard Unit

Post by jagwit » Mon Feb 20, 2017 7:40 am

Adamski wrote:It has been stated on this site that it doesn't necessarily need ported vacuum to function?
This is my story (possibly not mine alone) and I stick to it.

Not having ported vacuum means you will have full vacuum being applied on overrun (no problem), light throttle(no problem) and at idle. This means you will have full vacuum advance being applied at idle.

If you set timing and idle speed "as per the book" (without vacuum being applied to the vacuum advance diaphragm), having full advance being applied at idle, may result in idle speed being higher than specified in the book. I don't let this bother me because:
1) alternator charges better;
2) more coolant flow;
3) higher oil pressure.
But if idle speed is really too high then, one can of course adjust idle speed lower.

Please remember that with the vacuum advance unit, timing must be set (at idle) with vacuum DISCONNECTED from the advance diaphragm.

In those rare cases where timing gets set on a dyno at higher rpm (say 3000rpm) at full throttle, the vacuum should actually remain connected, just in case there is still some vacuum advance being applied even though the throttles are wide open.
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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#15 Re: Thermostatic Vacuum Valve and Retard Unit

Post by Adamski » Mon Feb 20, 2017 9:50 pm

I have now completely taken the valve out of the system. In addition due to rubbish leaking retard units out there I have excluded and plugged the pipe and unit. I may do vacuum advance later but road trials are optimistic.
Adam
S3 V12 E Type FHC Manual 1972-owned since 1978

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#16 Re: Thermostatic Vacuum Valve and Retard Unit

Post by 42south » Wed Feb 22, 2017 1:13 am

Sorry I'm late to the party on this issue.
In answer to some of your queries. I ran my car with the vacuum retard disconnected for a number of years, no issues were observed. My car is a naked V12 with no emissions pipework, no valve fitted.
As part of the rebuild I did exactly as British vacuum recommends, and the car runs great. In particular no pinking under load or heavy acceleration.
My car is on ported vacuum from the top of the left rear carb.
I've just returned from a road trip with fellow enthusiasts and made 18 mpg British, on a fresh rebuild.
IMG_0084.JPG
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Regards from Downunder
Mark Brown
1971 S3 Etype
Son: when I grow up, I want to be a pilot
Dad: You’ll have to choose.

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#17 Re: Thermostatic Vacuum Valve and Retard Unit

Post by Woolfi » Thu Feb 23, 2017 3:11 pm

I have bought my EV12 in 2001. The owner has mounted a advance capsule und connected to the drilling at the LHR carb below. I fiddled 2 years with problems, spoke to some garage idiots, which understand nothing, red some books and started thinking and investigation about ignition.
1. Every gas motor is running best, if the motor has a advance of roundabout some (3 - 12 degree before tdc) degrees at idle, a lot of degrees before tdc at part throttle and less degree before tdc at full throttle.
2. The motor delievers more horsepower at part throttle / or needs less gas for the same amount of delievred power, if the time of ignition is lets say at 3500 rpm and 20% cylinder filling (part throttle), earlier than of the same rpm and full throttle, because a lower cylinder filling has a lower pressure nearby TDC and is burning slower. Power is max, if the point of highest pressure of the exploding gases is roundabout 6 - 10 degree after TDC. If a small filling is burning longer, it must be ignited earlier.
How can a simple (analoge) ignition system realise this demanded "curves" ?
4. For the V12 and the XK-motor roundbaout 10 degree at idle are good for a stable idle. Therefore set static ignition on 10 degree before tdc.
4. For the maximum early ignition without pinking and detonation at full throttle the advance curve is "formed" by the advance system with the wights. The higher the revs, the more early the ignition. If the burning-time of a full load is the same, the ignition-timie must be more early at high revs, that the point of highestprssure in the cylinder is allways roundabout 6 - 10 degrees after TDC.
5. If the timing shall be earlier at part throttle, "pre-time" has to be "added" by a separate system, depending on the load. The amount of load you can measure by the amount of vacuum /pressure below normal pressure between the "air-door" in the carb and the valves of the motor.
6. The amount of added pre-ignition shall be low at idle. Therefore you need a construction which gives no vaccum to the advance capsule at idle. If the capsule is connected to a port 2 - 4 mm BEFORE the butterfly, the vacuum at iddle is low. The capsule need a minimum vacuum to start to work. Therefore zero added-pretime at idel. Works well.
7. If the butterfly of the carb is wide open, the amount if vacuum at this port is again low. No added advance timing at wot. The piont of ignition is maaged by the advance system of the wights. Works well.
8. At part throttle, the 1 mm thick "end" of the butterfly in the car is nearby the port, the cleft between the butterfly and the wall of the cabr is small, the gas speed is high and therefore the vacuum is high. With low load, slow burning of the mixture in the combustion chamber, a lot of pre-ignition is needed. The vacuum advance-system generates max vacuum, the capsule generates max advance. The motor works well.
I have done this at my car. I had to drill this port into my carb. After some fiddling with the drilling ending at the wrong positon , closing the drilling and drilling again, the motor runs very well.
The result of the added vacuum-advance system is, that the motor takes less gas at 90 of its running time. Maybe 5 % less gas consumption. I have not exactly measure before and after.
The original retard-system of the EV12 was just to run hoztter / less colder in the minutes after starting, that the gas-poisons (HC and CO) in the burnt gases are lower. The motor runs hotter and therefore becomes hotter more quick. If the cilinder load is ignited later, the gases are staying hotter when leaving the cylinder. The energy is not transformed into working power. The energy remains as heat in the gas.
If you (Adam) have parts of the retard system. Disconnect it ! Don't fiddle with it. It is not worth to spend time or money.
If you have understood all, drill this hole into the LHR carb and connect a rubber hose to the advance-capsule.
I have done this all. The cars runs very well. Because of the information from the internet and my books I am shure, that the "stuff", what I have written her, is 95% correct.
I have mounted to my advance capsule a hand-pressure for vacuum. I drove 70 mph in steady state and gave vacuum to the capsule by hand. Then I opened a valve at the hand-pressure, that the vacuum dissapeared suddenly. I felt very clear a slightly beaking of the car and a speed which was 2 - 3 km lower. This shows me, that the power of a certain amount of gas-air mixture burned earlier at small part throttle is producing a little bit more power / torque than burned roundabout 16 (depedning of the type of capsule) degree later with out the vacuum-advance system. The diffence in gas consumption is not big. But in 16 years with 5 - 6000 miles every year it is becomming a nice amount, worth the money and work I have spent to mount the correct vacuum-advance system. :wink:
http://georgiajag.com/Documents/Vacuum% ... Retard.htm
Excuse my simple english.
Regards Wolfgang Gatza
Last edited by Woolfi on Thu Feb 23, 2017 3:59 pm, edited 1 time in total.

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#18 Re: Thermostatic Vacuum Valve and Retard Unit

Post by Woolfi » Thu Feb 23, 2017 3:53 pm

"Longer term I have a full Plus Torque kit from AJ6 so plan to fit EFi to the FHC but am still mulling whether to use the modified Jag ECU or to go with MS or similar. Cheers"
I offer a bet: the torque of a well working EV12 motor woth 4 Strombies has between roundabout 2000 and 3800 rpm a higher torque, than the some motor with a injection. The suction-system is different. The injected motor works as two 1 into 6 sytems. The carbed motor works as four 1 into 3 systems. A three-cylinder motor has a higher max-torque than the same motor with 6 cylinders. The 3-cylinder motor is succing every 240 degrees. In a 6-cylinder motor sometimes two cylinders are succing at the same time from the same "air-box". If I am correct thi is called "parasitic drag".
Opel ha s done a motor in the 80ties, which worked below 4000 rpm as two 3-cylinder motors and over 4000 rpm as a normal 6-cylinder motor. The area below the throttle-curve was higher with this construction.
I have done a test with my 5,3 and later with my 6,0 L car against one 5,3 and one 6,0 L e-type , both with injection. Both cars have accelarated less qick, when we pressed the pedal at 2000 rpm in fourth gear. Allthough my car has a 2,88 and the two other had a 3,07, my carbed car was accelarating much quicker between roundabout 2000 and 4000 rpm. Both owners have shown long faces after this tests.
Maybe both injected motors have not worked well, because the injection or ignition was not working well. Because of only two test in 12 years, this is not a hard fact. I still try to make this test again with another car (must have same displacement like my car).
As long as nobody has shown me that his injected EV12 is quicker, I remain sceptic. I think the big amount of money and time is an investment with a very low interest.
I can understand also , if a owner of an injected EV12 has a different opinion. But before I agree, I would like to see, that the injected cars is quicker , also in the middle of the rev-range. At higher revs the injected car should have a higher torque.
Regards Wolfgang Gatza

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jagwit
Posts: 507
Joined: Thu Oct 18, 2012 6:52 am
Location: Pretoria
South Africa

#19 Re: Thermostatic Vacuum Valve and Retard Unit

Post by jagwit » Thu Feb 23, 2017 5:49 pm

Woolfi wrote:As long as nobody has shown me that his injected EV12 is quicker, I remain sceptic. I think the big amount of money and time is an investment with a very low interest.
This will indeed be VERY difficult to show, so you have good reason to be skeptical.

This is just for interest: I had a fuel injected 71 V12 OTS which was as fast as my friend's '01 supercharged 4.2 XKR. This E had a 5.3 V12 engine, but with 11:1 HE pistons, standard cam, standard HE heads, standard air intake systems, std HE injectors including the HE air filters and air filter housings. Engine management (fuel and spark) was from Megasquirt-2. So we can not compare this car to a "normal E-type V12". But it was as quick as the supercharged 4.2 XKR. The car is still use by the present owner.

I also agree with the second sentence in the quote. Here is my main point of this post: I am of the opinion that rather than to convert to EFI, one should rather spend that money on either a manual or auto transmission with a deep overdrive to get a more relaxed drive on the open road and better fuel consumption. I've been through this lesson with my two Jensen Interceptors. I EFI'ed the 74, then upgraded the A727 transmission to a 4L60e. Whilst the EFI upgrade is interesting, I can now admit that the transmission upgrade has done much more for the car than the EFI upgrade. My 73 is still running with the A727 and the OEM Carter Thermoquad carb. In a drag race between the two cars, the carb'ed car wins convincingly - but its engine has been upgraded to high compression and probably a better cam whereas the 74 still has low compression pistons and original cam.

My E (auto) has a 3.31 diff and desperately needs a deep overdrive 4th for the open road. But the engine is as sweet, smooth and strong as it should be. All that is not standard is that it has a Lumenition ignition system and vacuum advance. Starts perfectly hot and cold. I'm hoping to find a 2.88 diff to install in this car.

PS: We must be careful not to divert the subject of this thread.
Best Regards
Philip
Jag: 72 E-type V12, 80 XJS (Megasquirt + 5sp manual O/D)
Jensen: 74 Interceptor (EFI by Megasquirt + O/D 4sp auto)
Chev: 59 Apache std, 70 C10 (350V8, 700R4)

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Woolfi
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Joined: Thu Jan 28, 2010 5:57 pm
Location: Germany
Germany

#20 Re: Thermostatic Vacuum Valve and Retard Unit

Post by Woolfi » Thu Feb 23, 2017 11:02 pm

I have a 2,88 and a 5-gear Getrag with 0,81 in fifth. At 90 mph the motor revs with 2700 rpm. The car runs smooth, unexicited and gas saving (19 - 21 mpg when crusing with the V12 6,0 L motor. Like jagwit says: long gearing is much more "feelable" than an injection.
I made with the EV12 6,0L a drag race from 30 mph up to 100 mph against a eight year old Maserati Quattroporte which has 395 hp DIN. The accelaration of both cars has been exactly equal. Also with four Strombies the car is quick.
When driving in the first gear at idle with 600 rpm and pressing the pedal immediately, the wheels spin immediately. But the first gear of the getrag is "shorter" than the first of the original Jag-box.
When I bought the car in 2001 I planed to switch to injection. After two street tests, I stoped this plan.
Now I am happy , that I have not done this.
Regards Wolfgang Gatza

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