Full throttle switch, Wide Open Throttle switch, electric one
 

Do all cars have electric one? I don't see one on my 89 Marelli car but maybe I took it off when dissembling the engine and forgot to reinstall?

I do have the vacuum operated switch. If i have this vacuum operated one, do I need an electric one? Looking at wiring diagram the electric look redundant.

Not 100%, but I recall that some markets did not get that mechanical micro switch.

Then the Marelli cars were different again.

That is 100% correct Grant. The UK and Europe spec cars (Oz too?) only had the vac switch, while for some reason US spec cars mainly seem to have had both.


Andy: As long as you have the vac switch and it is working, it does not matter whether you have the capstan microswitch or not: the microswitch is in effect a redundant system. Both switch the same electrical feed, thereby ensuring full enrichment at WOT to prevent any danger of lean burn causing detonation in the combustion chamber.
Greg

My 89 Marelli has the full throttle capstan switch, but it looks like its for transmission kickdown not enrichment.

What vacuum level is supposed to switch the vacuum version? I understand they are adjustable. I'm down shifting too easily. I can easily set the micro switch but I don't have info on the vac switch.

The change down is not affected by the full throttle enrichment switch. It is controlled by the modulator in the gearbox. If your car is changing down too much, you can buy an adjustable modulator to alter the change point. Getting at the modulator and changing it is quite easy from under the car.
Greg

We got both on the HE, probably coz we Aussies are "special".

I will need to go rummaging through the scribbles in the library for those numbers. Tomorrow is raining, so if I get time, I will do that search and report back.

This is the adjustable valve. Not many cars have it for some bizzare reason. The earlier style unit is fixed, and I have NO numbers on that one.


Attachment 135698

Interestingly, S-58 suggests that while the two systems are redundant, at speed there may not be sufficient vacuum to activate the vac switch when WOT is demanded. The micro switch always activates.

Where the micro switch should activate is stated as "around 80%" and yet the adjustment instructions say to open throttle to open stop and set it to just activate. I suppose both could be correct as the throttle turntable has a ramp that rises under the switch. Since the ramp plateaus before the stop is reached it may actually activate at around 80% when set to be on at the stop.

Thanks Grant!

I would like to check and possibly adjust the vac switch but I don't know what I was going on about my shift points. Completely unrelated.

Off topic a bit, but those wanting a more aggressive transmission kickdown can use the throttle switch to activate the kickdown circuit. I've done so, works perhaps a bit too aggressive for some. Best to use a relay.

The Jaguar kickdown arrangement requires 100+% throttle before activating.

Cheers
DD

Jigjag, the vac switch needs zero vac to activate, it is the lack of manifold vac that WOT causes that makes the switch give full enrichment.
Greg

To increase the shift point use the B&M turbo400 governor kit part number 20248. It includes weights, springs, pins and gasket. I used the kit and like the results. I brought my shift points to approx 4700 rpm. You can go higher or lower

Right you are Greg. I should have copy pasted the info. It's the potential for a WOT and a vacuum level too high for switch activation that it was warning about.

i will test mine and see what vac level trips it. I assume your "zero vac to activate it" is a generality and that its actually some vac level above 0.


EDIT: 1 in. hg opens the switch.

Ok, found what I wanted, and the gauge I used, an OLD (like me) VDO Vac gauge in KPA, soooooo, you will need to be smarter than me, and convert to whatever rocks your world.

I drove around for days with this thing taped to the wiper arm, and wrote as I drove.

My engine had the following:

Cruising the suburbs, @ about 60KPH showed -60kpa, +/- a small amount.

Mild acceleration, as in increasing to 80KPH in traffic, showed -40kpa +/- a tad more, depending on the right foot.

Stoplight take off to keep with said traffic, showed about -25KPA, and NO +/-, too busy watching where I was going.

FAST take off, down to near zero.

Highway cruising @ 120KPH, just over the speed limit, ON cruise control, showed a steady -45 to -50kpa.

My switch was not closing those contacts until under -20kpa, oops.

Dug out the black goo, and adjusted to close at -30kpa. I played with different settings over a few months and heaps of various driving styles, and settled for that number.

The micro on the capstan is ramp operated, part of the casting of said capstan, and operates that switch at ABOUT 70% WOT from memory.

My vac switch did way more work than the micro, and I set it to suit MY driving needs. My Right leg is toast, with more metal than the Titanic, and full throttle for me is near impossible, hence why I did what I did.

I also deleted the kickdown crap, installed a compact modulator, and took the time to adjust it to change down when and where I wanted it. Worked a treat for me.

Every engine is different, so a one setting suits all, is a so-so approach.

Thank you for digging that up Grant!

I'm thinking of ordering an adjustable modulator. I'm shifting into second gear way too soon. I want to cheeply improve the tranny while saving up for a manual conversion.

Modulator and governor changes sound similar in effect. How do the two changes compare and or interact?

EDIT: All that info. http://www.jag-lovers.org/books/xj-s/20-Drivemods.html

Unit Translation:
-20 kpa = -6 in hg
-30 kpa = -8.8 in hg
-45 to 50 kpa = -13.3 to -14.8 in hg

What roll does the blue & white vacuum/electric switch play in a manual conversion car , if any ?
Larry

It is the same as in the auto. The system ensures that there is extra fuel at WOT thus preventing piston burn and detonation which might otherwise result from the mixture being too lean at wide throttle settings
Greg

I thought that's what the capstan micro switch does, supply extra fuel at WOT. Above you told Andy if the blue & white vacuum is working the micro switch is not needed.
Larry

That is correct Larry. The two systems duplicate each other. Some markets, eg the UK, only had the one system - the vac switch. You do only need one, but two gives a measure of redundancy if one system fails I suppose. Both types of switch switch the same loom circuit.
Greg