Hi guys,

Interested in some thoughts. Having just gotten an XJ6 again I am interested to hear what ideas are out there as far as improving economy making it easier to drive the car as much as possible?

I had planned to do an LPG conversion on the original motor. This seems an easy way to improve economy, however I HATE the smell of LPG exhausts, I can't stand sitting behind a car running on gas in traffic, and I am concerned if this smell seeps into the car it may ruin the experience.

V8 Conversions - common, but I love the humm and torque of the 4.2 DOHC engine, the refinement and smoothness, an american V8 just doesn't seem right

What other things have been done?

What is the reliability and economy of a later Jag 6? Could a more modern Jag inline 6 and paired auto box be mated in relatively easily or would the electronics be too much work?

BA or so series Ford Falcon 6 (for the Aussies on here)? I know earlier Falcon 6s have been done, the last of the inline 6s from Ford was meant to be world class for smoothness, but without the DOHC would it just sound and feel like a taxi?

BMW DOHC 6 - I know nothing about these, no idea how good or bad or reliable they would be?

Any other ways to get more economy from the existing engine? Fuel injection from a later motor?

Any diesels that would be smooth and powerful enough not to destroy the drive of an XJ6?

Not saying I plan on doing any of these things to my S2 XJ6 Ivy, just wondering what has been done before, and what people have thought of doing.

 

Any Falcon straight six is going to sound way too much like a taxi, imagine pulling up in a Jag and the people across the street coming out for their cab?

It depends what kind of economy you are chasing, mine was sucking an average of 21L/100km when I got it. Now it is doing about 16-17l/100km around town and 11-12L/100 on strictly highway drives. That is better than my 2011 3.7L V6 Jeep can manage.

Lpg seems to have a lot less value to the end user these days. Back when I ran LPG it was 15c/litre and petrol was 65c/litre. Now LPG is pushing 70c/ litre and petrol is usually double that if not more. And remember you use about 30% more LPG by volume for the same miles........takes a long time to recover the cost of the conversion.

Be happy, don't worry. Just drive it and enjoy it, I find it cheaper to run than our new car so stopped thinking about fuel economy and sold the wife's Mazda 3 to top up the fuel account(lol). She doesn't think that is funny.

 

AJ6 engine from xj40. fairly straightforward swap, inline 6, still a jag.

 

Keep it well serviced and tuned, change the ignition to an electronic one (123 or petronix seem to be popular), convert to manual choke, manual gearbox (for the drive, the economy is a bonus).
Then count the amount of money that you're not losing in depreciation, compared to 95% of the cars on the road around you.
That's my plans anyway.

Maybe triple Webers and a free flowing exhaust manifold (purely for the economy you understand!) as I understand (maybe in my dreams) that they would be more efficient and therefore more economical (provided you can keep your foot off the loud pedal).
Not just because they look gorgeous and add a few extra horses.....honest.

Probably cheaper to add the fuel injection bits form a series 3 or later.

 

AJ6 or so was one of my ideas Wilfred if there was enough advances in their design to make it worthwhile, then I wondered what improvements had been made to that engine in the generations after.

The depreciation argument only works if you are comparing to late model cars, which is one reason I have never owned a late model car.

 

All of this will make a huge difference, especially if you change out the diff to a 2.88. Also lighten up the load by exchanging the stock radiator for an aluminum radiator, manual trans is lighter and change out the cast iron brake calipers for alumninum. Also install a set of aluminum wheels.
There is around 400Lbs. of weight that can be lost on my US Spec 1975 XJ6-Coupe.

 

Well, the AJ6 is a completely new engine. Not based on the xk engine or so. It's bulletproof, xj40 scrappers go cheap (in NL at least).

It definitely gets better mileage. I get to drive 10 kilometer on 1 liter of petrol
(In US terms: 23.5 miles to the gallon)

It also has a 4 speed transmission connected to it, resulting in lower revs at cruising.

AJ16 is basically the same engine, only improved on performance, not so much on fuel economy. After the aj6, Jaguar went v8. I have no data on the jag v8's or so. but seems more expensive as v8 scrappers go for more money.

All in all, aj6 is a good choice in my opinion. OR convert your xk to fuel injection. I don't really like carbs but that is just me.

 

Thanks for that, I wonder how the sump location, engine dimensions etc will play with the S2 enginebay. The XJ40s are nice and cheap here too, definitely worth considering.

 

Look at my thread: series 1 with aj6 engine.

Drives great, fits nice.

 

Link Below

https://www.jaguarforums.com/forum/x...engine-107712/

 

If you're doing an engine conversion purely for better fuel economy, you're not really thinking straight.

The cost of a conversion will run into the thousands, and to recoup those costs from using less fuel per kilometre is a long process.

To do a conversion for the sake of better drivability, more power, smoother operation, etc with an added bonus of better economy, makes a lot more sense.


As said, another option would be to remove weight.
a new alloy radiator, lightweight wheels and alloy calipers all will help.
doing an engine conversion will also save a ton of weight, esp going to an all alloy motor, and looking at the size of the stock air con equipment, and looking at modern sized stuff, there'd be a bit of weight saved converting it all to modern style.

But if you dont plan on spending much money, simple things like, different tyres and pressures can play a great part in rolling resistance.
Getting a wideband O2 sensor and tuning cruise to a lean mixture 15:1 or higher (my 350rwkw skyline runs 16:1 AFR at 110kph and can get 8litres per 100km, aftermarket ECU)

 

I worked out years ago about economy. LPG versus engines versus diesel etc.

The bottom line being what is going to be the proposed cost of doing it? Buy an engine plus conversion say around $1000+/-

That equates to needing to save $1000 worth of fuel to cover the expense. Gives you an idea of what you might save a year with the Ks you do in it. Often = I'll have sold it before I recover costs. If you intend keeping it for the rest of your life maybe.....$0.02 worth,

Ps Stoney was typing exactly at the same time,but posted before me with the same train of thought.

 

I spend time on the conversion, but that is just my hobby.

However, it didn't cost me money. I earned money. Scrapper was 500 euro. Hoewever, I sold parts for 900 euro. (Headlights, alloy wheels, electrical components, suspension parts, doors, mufflers, tail lights, interior trim etc etc etc. I specifically searched for a higher spec scrapper, as they have more wanted parts.

Then I had series 1 engine parts left, (steering pump, transmission, radiator etc). Sold it for 500 in total.
Finally, I had a heap of scrap metal which deliverd a final 100 euro.

So in total I earned 1000 euro. Of course, taking into account the time I spent on the conversion I didn't earn a lot per hour. But still, no money went into the conversion.

And I learned a hell of a lot doing it. Woulde definitely do it again.

 

Thanks for the link, a few questions for Wilfred:

• Do you think series 3 tanks and pumps would be suitable instead of the custom tank you have made?
• If your existing rack and pump are good would it be plausible to fit an S2 power steering pump to the motor, eliminating the need to do the rack swap?
• Could the original S2 radiator system be used with alternative hoses?

Some alternative thinking along these lines, obviously from what I am reading in your thread from others the smaller 3.6 motor has less wiring a gearbox which does not require as much work to get running, what does all the computer/electronics/etc actually do in this motor? Could it be run with a simple aftermarket injection and ignition system removing a lot of electronic bulk?

 

I have a series 3 tank now, with series 3 fuel fump. Works fine.

Steering rack: Mine was shot, needed a new one anyway. so choose the xj40 rack, as it saved money. But, I heard from another guy that the xj40 steering pump gives too high pressure for the original s2 rack. (actually, he had AJ16 engine, see pic below





The higher pressure caused the original S1 rack to leak. so If you keep original rack, also keep original pump. Than its fine.

getting it running with aftermarket ecu doesn't seem smart. Cost more, and the xj40 engine loom is very small and easy to comprehend. Especially with the 3.6, there is very few wires. Just the loom to the ECU, a feed and ground and basically that's it.

Radiator can be used. I choose xj40 rad cause it had bolt in connections for tranny and steering rack cooling and I used the xj40 fan pack. Was easier. It's just a matter of connecting hoses.

 

Ok cool, seeing the amount of wiring in your 4l gave me a scare, hence the aftermarket question.

 

LPG:


Interesting, but around here has lost it's allure along with diesel. The $ thing.


In 1955, I returned from army service. Wifey and I purchased a cracker box house.
Swamp coolers were the thing in El Paso, Texas at the time. House stubbed for one, but no roof top cooler.


Uncle, said, I have one you can have and the use of my winch truck to set it. Deal!!!
Well, the truck was a 40's era Chevvy that had once seen service pulling a semi trailer in his haulage business. Now, as a winch and pole truck. Much battered and fueled by propane. Fired up rather easily. Hung he cooer off it's line and ack roads to our new house. "No plates"!! Backed in to drive and started to use the winch. Oh, oh, killed the engine. No fire.


Unc came and with just a tad of movement it fired. He expertly lifted and set the cooler roof top. Done., Hook up up to me.


UNC was the ultimate DIY guy. worked til his 80's hauling big tractors with his big GIMMY diesels.


Carl

 

It is sounding more like my S2's motor needs at least a head rebuild, which I am guessing will set me back a fair bit?

Given this I have been looking around more at these economy options and came across a donor S3. It is running Gas Research (injection I believe) dedicated LPG. I have heard some more modern gas injection systems can provide similar fuel economy to petrol, this system doesn't look incredibly high tech, but still fancier than most being a dedicated system.

I am a little concerned by swapping it onto another car then getting certification for it, and also by running a dedicated gas system with no petrol backup. Interested to hear thoughts on such an idea.

 

I ran three vehicles with LPG, and glad I never had dedicated LPG. There are so many gaps in the supply chain around Australia for LPG you will at some point require that 400-500 km worth of petrol in the tank to get to your next LPG filling station.

Even from Brisbane to Glen Innes we had to either travel 90km further south to top up in Armidale or get back to Queensland (Warwick,200 km) on petrol. That was only a 800km round trip and we had supply trouble.

A lot of our trips were to way out of the way places and had over 1000km between LPG and 500km between petrol so we even needed the LPG to get between petrol stops without long range petrol tanks.

It all depends on how far you will be travelling. We do a lot of big mile trips and would need both full or carry enough petrol for a 700km range just to be safe. Not that the Jag would be the vehicle we would use to go outback,just making a point.

Duel fuel or long range tanks are the way to go in Australia.

 

Get a good S3 head and fit it to your engine. Bigger valves and if you can by a good one then you save the money on refurbing your head.