Gas conversion mpg 4.2 engine
#1
01-11-2017, 04:55 AM
Join Date: Jan 2017
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
#2
01-12-2017, 04:13 AM
Veteran Member
Havent done a Jag but have over 500,000kms on gas (LPG) powered cars. Just a few comments.
- Gas burns hotter than fuel, so the car has to deal with more heat. XJ cooling systems are not their strong point. If you go this way make sure your cooling system is in good order.
- Best fuel economy I ever got was about 10-15% worse than fuel/petrol (direct multi point injection LPG). Normally this settles back to about 20% after 5000kms or so. Power is also slightly less, not much but noticeable under load.
- Your car is at the end of the leaded fuel era. Valve seats are an issue with this fuel as it burns dry and hot, and impacts valve seats that expect leaded fuel. Your systems in the UK may include valve seat lubrication, or you may have to look at getting hardened seats put in.
- Is it really worth it? Dont know any of your pricing numbers for petrol/gas/conversion in the UK (last time I was there petrol was pretty obscene, worse now by the sound of it). Over here LPG is roughly 50% of petrol and you need to be doing considerable annual mileage to make it cost effective over a few years(30k PA or more). Nearly every courier vehicle and taxi in Oz is on gas as they are doing 75k + per year (much more for taxis) and it pays off very quickly.
- Gas burns hotter than fuel, so the car has to deal with more heat. XJ cooling systems are not their strong point. If you go this way make sure your cooling system is in good order.
- Best fuel economy I ever got was about 10-15% worse than fuel/petrol (direct multi point injection LPG). Normally this settles back to about 20% after 5000kms or so. Power is also slightly less, not much but noticeable under load.
- Your car is at the end of the leaded fuel era. Valve seats are an issue with this fuel as it burns dry and hot, and impacts valve seats that expect leaded fuel. Your systems in the UK may include valve seat lubrication, or you may have to look at getting hardened seats put in.
- Is it really worth it? Dont know any of your pricing numbers for petrol/gas/conversion in the UK (last time I was there petrol was pretty obscene, worse now by the sound of it). Over here LPG is roughly 50% of petrol and you need to be doing considerable annual mileage to make it cost effective over a few years(30k PA or more). Nearly every courier vehicle and taxi in Oz is on gas as they are doing 75k + per year (much more for taxis) and it pays off very quickly.
Last edited by yarpos; 01-12-2017 at 04:24 AM.
#3
01-12-2017, 04:25 AM
Join Date: Jan 2014
Location: Delaneys Creek,Qld. Australia
Posts: 28,379
Received 6,317 Likes
on
4,367 Posts
Hello Karmad, welcome to the forum. When you get a moment please post an intro in the new member area.
https://www.jaguarforums.com/forum/n...-intro-must-5/
I had it in the 90's when I was doing 60k km a year but LPG was 15c a litre and petrol was in the mid 60c range. Now LPG is around the 70c mark and petrol around $1.28.
Since then LPG has quadruped in price while petrol doubled, it would have to be a strong argument to pay for the conversion these days.
The XK engine is not that heavy on fuel, I get better mileage from it than I do in a late model 3.7L V6 Jeep.
I know about throwing money in the tank every time I drive, but if I was into fuel economy I would drive my daughters Honda Jazz everywhere.
https://www.jaguarforums.com/forum/n...-intro-must-5/
I had it in the 90's when I was doing 60k km a year but LPG was 15c a litre and petrol was in the mid 60c range. Now LPG is around the 70c mark and petrol around $1.28.
Since then LPG has quadruped in price while petrol doubled, it would have to be a strong argument to pay for the conversion these days.
The XK engine is not that heavy on fuel, I get better mileage from it than I do in a late model 3.7L V6 Jeep.
I know about throwing money in the tank every time I drive, but if I was into fuel economy I would drive my daughters Honda Jazz everywhere.
Last edited by o1xjr; 01-12-2017 at 04:30 AM.
#4
01-12-2017, 08:19 AM
Veteran Member
Join Date: Jul 2012
Location: Walnut Creek, California
Posts: 6,796
Received 2,399 Likes
on
1,880 Posts
A couple of thoughts.
1. As I recall, perhaps incorrectly, LPG does not have the same BTU capacity that petrol does. Does that translate in to burning cooler, rather than hotter. Or since performance is less, just the result of more pedal ?
2. As previously stated, a computation of a pay back period is essential.
3. Availability of places to recharge.
4. As the head on the OHC 6 or heads on the V12 are alloy, seat inserts are already there. Sintered iron or a harder steel? I'm not sure.
5. Is adding a means to lube the upper cylinders needed? Even unleaded petrol has a small amount of lubricity. Gas has none.
6. Starts in inclement weather should be far easier.
7. In about 1955, I borrowed Unc's much abused old Chev 6 winch truck. On LPG. fired up easily, ran well. Working the winch a challenge!!!
8. I get it. I do like my old Jeep. 4.0 straight 6. Gas mileage, I don't look. But, I takes energy to propel a box !!!! Hatch strut change task has become a project.
Carl
1. As I recall, perhaps incorrectly, LPG does not have the same BTU capacity that petrol does. Does that translate in to burning cooler, rather than hotter. Or since performance is less, just the result of more pedal ?
2. As previously stated, a computation of a pay back period is essential.
3. Availability of places to recharge.
4. As the head on the OHC 6 or heads on the V12 are alloy, seat inserts are already there. Sintered iron or a harder steel? I'm not sure.
5. Is adding a means to lube the upper cylinders needed? Even unleaded petrol has a small amount of lubricity. Gas has none.
6. Starts in inclement weather should be far easier.
7. In about 1955, I borrowed Unc's much abused old Chev 6 winch truck. On LPG. fired up easily, ran well. Working the winch a challenge!!!
8. I get it. I do like my old Jeep. 4.0 straight 6. Gas mileage, I don't look. But, I takes energy to propel a box !!!! Hatch strut change task has become a project.
Carl
#5
01-13-2017, 05:34 AM
Veteran Member
Hi Carl
The temperature thing is more about the nature of the fuel being a gas already vs fuel which has to vaporise and provides cooling in the process. LPG engines tend to run slightly hotter cylinder head temps. Generally no big deal but worth noting for older engines with cooling systems that need some love.
Starting on LPG seems a mixed bag , some cars have no issues and others are flakey. I think a lot of the issues were with the old carby set ups (and probably lack of maintenance as usual) Modern LPG injection systems start on fuel/petrol and then as soon as there is any engine temp registering switch over to LPG which is pretty seamless. I run my truck on fuel for an hour or so each month just to make sure the fuel side of the system is still happy and injectors get a bit of exercise.
The temperature thing is more about the nature of the fuel being a gas already vs fuel which has to vaporise and provides cooling in the process. LPG engines tend to run slightly hotter cylinder head temps. Generally no big deal but worth noting for older engines with cooling systems that need some love.
Starting on LPG seems a mixed bag , some cars have no issues and others are flakey. I think a lot of the issues were with the old carby set ups (and probably lack of maintenance as usual) Modern LPG injection systems start on fuel/petrol and then as soon as there is any engine temp registering switch over to LPG which is pretty seamless. I run my truck on fuel for an hour or so each month just to make sure the fuel side of the system is still happy and injectors get a bit of exercise.