Thanks for reply, i'm currently in process of taking decision about the best way to move on, fiddle with stock ECU or spare funds for megasquirt conversion.

 

For me it is the worst part in Jag, V12 by its nature is very revvy and lively engine, but not with this slow and heavy transmission.

 

It’s a little different here. Regular gas has 10% ethanol or 15% ethanol. E 85 is 85% ethanol* or you can pay extra and Get non-oxygenated fuel.
The more power you want the more ethanol you will use. Indianapolis 500 cars are all ethanol ( well 98% so the mechanics don’t drink it NASCAR is using 15% ethanol
Drag racing the advantage of alcohol moves you up a class
Sprint car Racing is all alcohol

 

I had good luck with a gallon of xylene and lucas fuel lube added to 94octane.

 

apples to bananas man. Gross horsepower to net DIN horsepower cars with a top speed of 110 MPH Lumpy crude truck motor in a relatively light chassis not conforming to safety or smog regulations. That 450 horsepower 454 cu in motor made only 235 horsepower SAE net
Compared to a sophisticated quiet emissions and safety compliant luxury cruiser. With a real top speed of 150. Horsepower 264 DIN net. Or 29 more horsepower than the 454. Add a Little because the slight difference in rating between SAE and DIN. Or multiply the Jaguar motor times 1.0139. To get SAE.

So would it sound better if Jaguar advertised the V12 at 500 horsepower rated? It’s the same motor and any way you slice it the Jaguar made more than the 454 once they were both rated the same. In Europe the V12 made another 35 horsepower on top of the 29 of the 454
Jaguar took great pains to make the engine smooth and quiet. The air filter has a snorkel that costs 28 horsepower to ensure the occupants don’t hear the rush of air coming in. They had 4 mufflers on the car to ensure no exhaust noise was heard. There is 210 pounds of sound deadening. And it has an all up weight of over 4600 pounds. On top of that to get better fuel mileage it has a 2:88-1 final drive ratio ( which also allows it to have a top speed of 150 mph )
Don’t compare the Jaguar to a Chevelle. Just too different. It’s fair to compare it with the Cadillac.

 

100 percent correct., I have both in my possession... a 6.0L with a close ratio 6 speed and a 4l80e Auto for direct comparison. If I drive them back to back I cant believe it's the same engine. The difference is stark.

 

If you keep the car locked in 1st it'll stay in the screaming high rev range and give you a taste of what a proper manual seems like. Force shift into 2nd at 5500rpm.

I did find a company that makes manually or computer tuned TCM controllers for modern transmissions meaning you use a knob to turn shift points etc on a box unit, out of curiosity which auto transmission would suite the Jag v12 the best? If cost and tuning are no longer a concern.

I'll try to find the link but they basically build for every application.

 

I had a 1975 XJS that I converted to a manual transmission from a wrecked series 3 XKE. The improvement in that car was astonishing that was a pre HE (7.8-1 compression ratio ) with a 3:54 final drive.
still astonishing!

 

MaG , i had a 1975 XJ12C , with factory 4 speed manual , 3.54 rear , it was a great car , BUT no way could match My XJS , with V12 and 700R4 trans , 3.73 rear LSD!!?


1975 XJ12C

4 speed manual

XJS V12 roadster, 700R4 , 3.73 gears!

 

pix say a thousand words,, talk sometimes is BS!

 

I’m sorry Your government doesn’t support making more power( Yes I understand that wasn’t the original intent but you look for the good in everything

As long as you keep your car original. E85, turbo charging, other serious power adders won’t mean anything. Plus the closer you keep it towards original the more value it will retain.
Modified cars, especially highly modified cars, wind up as parts donors or just scrap. Not just Jaguars but any car.
Obviously the exception is nice race cars with a National/international well reported and documented history. group 44 /TRW etc.

 

Lol..

Was it hard to put in the 700r4?

 

Ron what would you like pictures of?

 

All of which is lost on this guy. And apparently I'm not alone. The XJ-S is the cheapest V12 sports car you can buy, and I think the quiet and the auto trans are the reasons for that.

Where is that 210 pounds of sound deadening and how do I remove it? Also, I'm curious about the 4600 pounds part. My owner's manual says the curb weight was 4040 pounds when new. I'm thinking of taking some used engine oil to the dump just to get a free trip across the scales to find out what it really weighs.

PO got rid of the intake snorkels for me, along with two of the mufflers. It's still too quiet. I checked the idle with a meter and got 58 dBA from the driver's seat with the windows up. My Mercedes diesel with stock exhaust measured 59. My Triumph put out 76 measuring from where my head would be whilst riding.

I wasted $1900 on rebuilding the TH400 before I found out what a Getrag 265 kit from Simply Performance cost. I was unhappy with the rebuild and brought it back with specific instructions to make the WOT 1-2 shift happen at 6000 rpm. I even told the guy how to do it. You put lighter weights in the governor. He ended up pulling the stock governor and putting in a different one, instead of just changing weights. This got the WOT 1-2 up to 5200, and 5800 if you lock it in 1st. I have a governor calibration kit on my living room floor in the pile of parts that need to go on the Jaguar after I get the Mercedes back together and out of the garage. To me, asking what's the best auto trans is kind of like asking about the best disability to have. I supposed if you're dead set on an automatic, a 4L80E will work better than most. The wide ratio spacing and tall overdrive would allow you to use a much shorter rear end and keep the engine in the power band more of the time while keeping cruise rpm down.

 

I’m a racer So yes, being quiet doesn’t matter to me. I’ve never owned a Jaguar that isn’t a race car.
I race Jaguars because so few people recognize just how cheap they are and what great parts they are made from.
Most production cars in order to competitively race them you have to spend 10’s of thousands of dollars just to get parts that will take the stresses of racing. When I race a Jaguar it’s amazing how fast I can go for how long on how little money.

So I put the body shell on my rotisserie and got out the torch. Seam sealer, undercoating. and sound deadener all count towards the weight I removed.

page 7 of the Haynes manual lists
weights from 3947 ( 1972 V12 sedan EXCLUDING North America.). To 4656 for 1978 on North America XJS ( minus 106 pounds for manual transmission )
considering the publication date it won’t include the HE models or anything post 1980.

but My goal is to get the car under 3000 pounds and hopefully closer to 2700 pounds race ready with my fat butt sitting in it on the grid.

 

Have you looked into the reinforced fiberglass hoods and trunk lids? Theres a few hundred lb right there that can go away.

 

LOL. It depends I guess. My diesel truck with a fully computerized 5spd is (tuned by a professional) to function exactly like a manual with the Tow button/function repurposed as an electronic j-brake or sport mode depending on inputs (if your braking or hammering the pedal) in the end you'd hardly see a difference when comparing to a manual version of the same engine.

I can't see the logic in a manual V12 unless you like carpel tunnel syndrome in your left foot and blowing 15k on all the parts etc. My XJS is my daily driver I'd never make it in a?manual in Vancouver traffic haha, could simply find a transmission at a junk yard, pay the $1500 or whatever for the aftermarket controller and perhaps a trans rebuild or refresh.. $2000 or so if doing the bulk of it yourself.
What about this 6spd https://www.novak-adapt.com/knowledg...utomatic/6l80/ it is abit heavier but slightly shorter than the stock 3spd.

 

Me neither. The XJS isn't a sports car, its a Grand Tourer. A friend of mine has one of the fairly rare 1994 factory 5 speed manual cars, and I have the 6.0 V12. I drove them back to back, and to me the V12/auto combo is what the XJS is about - effortless wafting along at high speed with plenty of power to drive in a rapid, but very comfortable manner. To me, the manual spoils that, it takes away from the smoothness and effortless of driving. I have other cars with manual transmissions, but they don't do what the XJS does so well.

 

How wide is it? personally I'd be happy with the 3 speed if it had a lock-up torque converter. I looked into one 4-sp kit and it was £6k plus fitting, which even at UK costs, is probably more than I would spend on petrol for it in my lifetime.

 

I make my own. In order to get under that 3000 pound limit that’s where I go. Hood Doors trunk lid and fenders. (I don’t save that much weight on the fenders in carbon fiber over the steel but having spare parts sitting in the molds means in the event of an accident I’m not out of the race and starting from scratch.)

But I go a little further. If you shop for expired Prepeg Carbon fiber, I’ve often found it almost as cheap as fiberglass cloth. Since I don’t use a autoclave or vacuum bag. the final few ounces of using liquid resin doesn’t bother me. The limitations of getting expired prepeg to conform around corners and sharp curves can be dealt with if you gently and carefully pre heat the carbon fiber. On warm days I’ll set it out in the sun and then use a hair dryer in the really tight spots.
once everything is about ready I use a paint roller to liberally apply the resin. Then use a squeegee to remove the excess resin.
Using that technique I made a XKEV12 hood ( bonnet to the British) that weighed only 35 pounds.