MPG benefit from vacuum advance.
Discussion
My Chim has never been economical (18-20) but it's never a big concern as it does 5k a year max.
I've just found out that the vacuum advance on the dizzy isn't working so that can't be helping (it still only gets 18-20 when cruising on the motorway at 75/80mph).
What kind of MPG increase could I expect from fitting a new vacuum advance?
Thanks.
I've just found out that the vacuum advance on the dizzy isn't working so that can't be helping (it still only gets 18-20 when cruising on the motorway at 75/80mph).
What kind of MPG increase could I expect from fitting a new vacuum advance?
Thanks.
Depends on how heavy your shoes are, seriously around town mine probably does 20mpg
On a run it can muster about 26 mpg. It's a re built engine 5000 miles ago.
I once got about 28 mpg on the M6 but was driving at about 60 mph!
Other than the engine it's completely standard, disi, air intake pipe, etc.
the chip has been changed also. Dunno if that helps!
On a run it can muster about 26 mpg. It's a re built engine 5000 miles ago.
I once got about 28 mpg on the M6 but was driving at about 60 mph!
Other than the engine it's completely standard, disi, air intake pipe, etc.
the chip has been changed also. Dunno if that helps!
When working correctly the vac advance unit will add up to 10 degrees of ignition advance, but only when you have a high depression in the inlet manifold.
That means when the pumping forces of the engine are high but the throttle is almost closed.
The only time you get this high inlet manifold depression is when you're cruising at speed, so this is where you'll see the economy benefit.
Due mostly to their light weight these cars can easily achieve 27-28 mpg at a steady cruising speed of 80mph, this is extremely impressive given the inefficient (in modern terms) nature of the Rover V8.
Drive the car through town, drive it vigorously and you're MPG will immediately fall to the high teens/very low 20's.
The only real way to make a meaningful improvement in economy is to buy cheaper fuel, and the cheapest fuel out there that the Rover V8 runs happily on is LPG.
I pay £3.14 a gallon for LPG which my car consumes at 22mpg, in cost terms this is exactly the same as your petrol powered Chimaera doing 40mpg.
That's an economy difference you really notice!
That means when the pumping forces of the engine are high but the throttle is almost closed.
The only time you get this high inlet manifold depression is when you're cruising at speed, so this is where you'll see the economy benefit.
Due mostly to their light weight these cars can easily achieve 27-28 mpg at a steady cruising speed of 80mph, this is extremely impressive given the inefficient (in modern terms) nature of the Rover V8.
Drive the car through town, drive it vigorously and you're MPG will immediately fall to the high teens/very low 20's.
The only real way to make a meaningful improvement in economy is to buy cheaper fuel, and the cheapest fuel out there that the Rover V8 runs happily on is LPG.
I pay £3.14 a gallon for LPG which my car consumes at 22mpg, in cost terms this is exactly the same as your petrol powered Chimaera doing 40mpg.
That's an economy difference you really notice!
I picked up my new Chim last and managed 27 mpg bringing it home the 150 miles of motorway!
Of course I took it easy as i didnt know the car and my son was sittin next to me !!
Anyway, after taking family members for a spin, the main driving has been showing co- pilots what it can do, i have managed to get it down to 12 mpg
She is cheaper than propping up a bar and more fun
Of course I took it easy as i didnt know the car and my son was sittin next to me !!
Anyway, after taking family members for a spin, the main driving has been showing co- pilots what it can do, i have managed to get it down to 12 mpg
She is cheaper than propping up a bar and more fun
markd67 said:
I picked up my new Chim last and managed 27 mpg bringing it home the 150 miles of motorway!
Of course I took it easy as i didnt know the car and my son was sittin next to me !!
Anyway, after taking family members for a spin, the main driving has been showing co- pilots what it can do, i have managed to get it down to 12 mpg
She is cheaper than propping up a bar and more fun
More like it Of course I took it easy as i didnt know the car and my son was sittin next to me !!
Anyway, after taking family members for a spin, the main driving has been showing co- pilots what it can do, i have managed to get it down to 12 mpg
She is cheaper than propping up a bar and more fun
I dont think people are getting it.
The objective here is not to ignore the performance attributes of the car, clearly this is primary element of any TVR's personality & character.
No, the objective is to achieve the best possible performance using least chemical energy, and extracting the best performance from the least chemical energy can simply be defined as efficiency.
No one should should be intimated into feeling embarrassed about improving the efficiency of their TVR, indeed to me improving efficiency represents the most exciting development challenge of them all.
In fact improving power & improving economy are the same thing, either way the objective is to improve the efficiency from a given displacement.
For me the big challenge is to get more out for less in, as such it's very much in line with the direction F1 is taking now, if you study the new F1 technology you'll appreciate how exciting & innovative it is.
The age old objective of making big power from an internal combustion engine was achieved years ago, the exciting technological challenge now is to make the same power figures using less & less fuel.
Of course if you're looking to improve the efficiency of in internal combustion engine the old Rover V8 is a completely inappropriate platform to work with.
The old Rover V8 is an efficiency joke, the truth is there are so many limitations in it's archaic design that it'll never be developed to make reasonable power using less fuel, which is why the only real way to make it more economical is to feed it on fuel that costs less.
So my plan is to supercharge 'Ol Gasbag' for 350hp while retaining it's 40mpg cost equivalent fuel economy, it'll be as fast as Daz or Peter's cars but as cheap to run as my wife's Nissan Micra.
Having my cake & eating it, that's what floats my boat
The objective here is not to ignore the performance attributes of the car, clearly this is primary element of any TVR's personality & character.
No, the objective is to achieve the best possible performance using least chemical energy, and extracting the best performance from the least chemical energy can simply be defined as efficiency.
No one should should be intimated into feeling embarrassed about improving the efficiency of their TVR, indeed to me improving efficiency represents the most exciting development challenge of them all.
In fact improving power & improving economy are the same thing, either way the objective is to improve the efficiency from a given displacement.
For me the big challenge is to get more out for less in, as such it's very much in line with the direction F1 is taking now, if you study the new F1 technology you'll appreciate how exciting & innovative it is.
The age old objective of making big power from an internal combustion engine was achieved years ago, the exciting technological challenge now is to make the same power figures using less & less fuel.
Of course if you're looking to improve the efficiency of in internal combustion engine the old Rover V8 is a completely inappropriate platform to work with.
The old Rover V8 is an efficiency joke, the truth is there are so many limitations in it's archaic design that it'll never be developed to make reasonable power using less fuel, which is why the only real way to make it more economical is to feed it on fuel that costs less.
So my plan is to supercharge 'Ol Gasbag' for 350hp while retaining it's 40mpg cost equivalent fuel economy, it'll be as fast as Daz or Peter's cars but as cheap to run as my wife's Nissan Micra.
Having my cake & eating it, that's what floats my boat
Edited by ChimpOnGas on Thursday 29th May 08:29
rigga said:
Everyone's turning into clones of Daz and worried about mpg ....its gone to the dogs this place 
I'm not worried about the MPG as I said in the origin post that I expect to keep the 18-20 that I'm currently getting. Just trying to work out if it's worth spending the £60 to get a new advance or not bother. I think the only benefit the advance gives is MPG on a cruise and I don't do too much of that.
A900ss said:
rigga said:
Everyone's turning into clones of Daz and worried about mpg ....its gone to the dogs this place
I'm not worried about the MPG as I said in the origin post that I expect to keep the 18-20 that I'm currently getting. Just trying to work out if it's worth spending the £60 to get a new advance or not bother. I think the only benefit the advance gives is MPG on a cruise and I don't do too much of that.
A900ss said:
What kind of MPG increase could I expect from fitting a new vacuum advance?
Thanks.
Thanks.
A900ss said:
I'm not worried about the MPG as I said in the origin post that I expect to keep the 18-20 that I'm currently getting.
Just trying to work out if it's worth spending the £60 to get a new advance or not bother. I think the only benefit the advance gives is MPG on a cruise and I don't do too much of that.
The answer to your question is roughly a 2-3 mpg improvement at cruise.Just trying to work out if it's worth spending the £60 to get a new advance or not bother. I think the only benefit the advance gives is MPG on a cruise and I don't do too much of that.
Under all other driving conditions the vac advance does fek all, and neither would you want it to.
Having converted a Jag XJ8 to LPG a few years ago I find it hard to disagree with Chimpongas!
I went from an average consumption of about 24/8 mpg ( petrol) to about 40/8 mpg on gas!
I calculated that in one year alone I basically halved the fuel running costs.
Going way into the future chimp might be onto something.
I love your re developement work Chimp on gas, soon as you have those power figures I'll be getting mine done!
The speed of change regarding the use of petrol is allarming. One day it might be the only alternative we have.
Don't knock it, it works very well.
On track I can get mine down to about 7 mpg !??!?!
I went from an average consumption of about 24/8 mpg ( petrol) to about 40/8 mpg on gas!
I calculated that in one year alone I basically halved the fuel running costs.
Going way into the future chimp might be onto something.
I love your re developement work Chimp on gas, soon as you have those power figures I'll be getting mine done!
The speed of change regarding the use of petrol is allarming. One day it might be the only alternative we have.
Don't knock it, it works very well.
On track I can get mine down to about 7 mpg !??!?!
ChimpOnGas said:
I dont think people are getting it.
The objective here is not to ignore the performance attributes of the car, clearly this is primary element of any TVR's personality & character.
No, the objective is to achieve the best possible performance using least chemical energy, and extracting the best performance from the least chemical energy can simply be defined as efficiency.
No one should should be intimated into feeling embarrassed about improving the efficiency of their TVR, indeed to me improving efficiency represents the most exciting development challenge of them all.
In fact improving power & improving economy are the same thing, either way the objective is to improve the efficiency from a given displacement.
For me the big challenge is to get more out for less in, as such it's very much in line with the direction F1 is taking now, if you study the new F1 technology you'll appreciate how exciting & innovative it is.
The age old objective of making big power from an internal combustion engine was achieved years ago, the exciting technological challenge now is to make the same power figures using less & less fuel.
Of course if you're looking to improve the efficiency of in internal combustion engine the old Rover V8 is a completely inappropriate platform to work with.
The old Rover V8 is an efficiency joke, the truth is there are so many limitations in it's archaic design that it'll never be developed to make reasonable power using less fuel, which is why the only real way to make it more economical is to feed it on fuel that costs less.
So my plan is to supercharge 'Ol Gasbag' for 350hp while retaining it's 40mpg cost equivalent fuel economy, it'll be as fast as Daz or Peter's cars but as cheap to run as my wife's Nissan Micra.
Having my cake & eating it, that's what floats my boat
Your fuel economy with the Turbo will go down even on normal driving ! Every tweak on the throttle pushes more fuel and air in .. The objective here is not to ignore the performance attributes of the car, clearly this is primary element of any TVR's personality & character.
No, the objective is to achieve the best possible performance using least chemical energy, and extracting the best performance from the least chemical energy can simply be defined as efficiency.
No one should should be intimated into feeling embarrassed about improving the efficiency of their TVR, indeed to me improving efficiency represents the most exciting development challenge of them all.
In fact improving power & improving economy are the same thing, either way the objective is to improve the efficiency from a given displacement.
For me the big challenge is to get more out for less in, as such it's very much in line with the direction F1 is taking now, if you study the new F1 technology you'll appreciate how exciting & innovative it is.
The age old objective of making big power from an internal combustion engine was achieved years ago, the exciting technological challenge now is to make the same power figures using less & less fuel.
Of course if you're looking to improve the efficiency of in internal combustion engine the old Rover V8 is a completely inappropriate platform to work with.
The old Rover V8 is an efficiency joke, the truth is there are so many limitations in it's archaic design that it'll never be developed to make reasonable power using less fuel, which is why the only real way to make it more economical is to feed it on fuel that costs less.
So my plan is to supercharge 'Ol Gasbag' for 350hp while retaining it's 40mpg cost equivalent fuel economy, it'll be as fast as Daz or Peter's cars but as cheap to run as my wife's Nissan Micra.
Having my cake & eating it, that's what floats my boat
Edited by ChimpOnGas on Thursday 29th May 08:29
The vacuum advance can add 10 to 12' to the centrifugal advance, so its a significant amount extra to improve when the peak of the explosion takes place. You could simply say that not having it will make the timing 10-12' far out. Typically you should see 10-15 % mpg improvement with it running as it should.
blitzracing said:
The vacuum advance can add 10 to 12' to the centrifugal advance, so its a significant amount extra to improve when the peak of the explosion takes place. You could simply say that not having it will make the timing 10-12' far out. Typically you should see 10-15 % mpg improvement with it running as it should.
Is that not the same as my answer?ChimpOnGas said:
The answer to your question is roughly a 2-3 mpg improvement at cruise.
Under all other driving conditions the vac advance does fek all, and neither would you want it to.
Also, use "Peak cylinder pressure" and "burn" to replace..Under all other driving conditions the vac advance does fek all, and neither would you want it to.
blitzracing said:
so its a significant amount extra to improve when the peak of the explosion takes place.
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