LPG S2
- Thread starter tref
- Start date
vitesse
Active member
My son & I went to a Rally course day in mid Wales run I think by Pete Ellis on his site up a mountain.All the cars were running on LPG including MK2 Escorts(for the rally driving tuition),a rear wheel drive Escort and a Escort Cosworth All went like "stink" but without stink,all were said to be extra reliable & cooler running(given the duty) & far more economical(given the duty).His other business was LPG conversions mainly commercial but also "thirsty" cars and his continued permission to operate a rally school was influenced by the "cleaner" LPG in that beautiful valley.
I had a look at RS... hugely expensive for a display, but then I expected that... Then I strated trawling the net, and discovered that it would seem that an awful lot of Digital Multi Meters have an input for a K-type thermocouple, range of -40 to +1000 C.
There appears to be a selection on the Maplin website between £15 and £30. Obviously I'll need a thermocouple or two as well, but any experiences of using a DMM for temperature measurement?
I really just want to take some "before" measurements to make sure "after" isn't significantly higher!
I must also do some more scientific performance measurement with my little G-Tech thing as well.
Regards,
Tref.
sawood12
New member
I was under the impression that LPG is not more economical that petrol in terms of MPG, but due to its cost is far cheaper to run. In anycase I can't see why any car cannot be successfully converted. It's just a question of correct fuelling.
The only other thing i'd want to understand is that our cars have KLR's that run our cars upto knock in real time. I believe that most other cars - even new cars, don't do this. The knock sensor basically is a vibration detection device that is looking for the tell tale vibration signature of knock in amongst the mish mash of other vibration signatures coming from the valve train and other moving parts of the enigne. My question is - does LPG have the same vibration signature as petrol when it starts knocking? If not then you can risk running the car in the knock condition.
The only other thing i'd want to understand is that our cars have KLR's that run our cars upto knock in real time. I believe that most other cars - even new cars, don't do this. The knock sensor basically is a vibration detection device that is looking for the tell tale vibration signature of knock in amongst the mish mash of other vibration signatures coming from the valve train and other moving parts of the enigne. My question is - does LPG have the same vibration signature as petrol when it starts knocking? If not then you can risk running the car in the knock condition.
pauljmcnulty
Active member
LPG is slightly worse for mileage, but half the cost, so works out significantly cheaper over high mileage.
As I understand......[&:]
Scott,
Interesting question - not one that I had considered.
Why would the knock signature on LPG be any different to the knock signature on petrol? They are running at a very similar temperature, in the same engine, running at the same speed. I would have thought that the knock signature would be identical.
I would have thought that the knock signature would be far more dependant on the engine type than on the fuel type.
BUT this is all written from a position of complete ignorance. (Did I tell you that I failed a Mech Eng degree once?)
Oli.
Interesting question - not one that I had considered.
Why would the knock signature on LPG be any different to the knock signature on petrol? They are running at a very similar temperature, in the same engine, running at the same speed. I would have thought that the knock signature would be identical.
I would have thought that the knock signature would be far more dependant on the engine type than on the fuel type.
BUT this is all written from a position of complete ignorance. (Did I tell you that I failed a Mech Eng degree once?)
Oli.
sawood12
New member
Havn't got a clue Oli, i'm just brainstorming here. Maybe when LPG pre-ignites it does so at a different frequency/speed thereby producing a different vibration signature? Just trying to think of potential problems. I'd imagine the vast majority of the common vehicles that LPG converstions are conducted on, such as Range Rovers, might not have knock computers therefore do the established installers appreciate the interaction of a knock computer?
Scott,
It's a good question - carry on brainstorming! (Are you an engineer? Looking at thinking such as yours, I am realising why I failed!) I simply don't know enough to shed any light on it, but it's a very good question. I guess that the different (higher) octane rating of the LPG over the petrol may change the knock signature - but given that it is a significantly higher octane, it may well be that it simply cannot be made to knock within the ignition timing envelope such as can be set by the S2 ECU.
Not sure about the RR's not having knock sensors. I don't think that they are *that* primative! OK, the early ones may be, but the later ones probably are not, and I think that LPG is a popular conversion for a wide range of them age-wise. .
The next question is whether the knock sensor is wired into the new ECU ... it is wired into the existing one, but is there the facility to wire it into the new one? Is the new one a stand-alone system or a piggy-back on the existing one? Is the new system specific to the 944S2 that Tref has, or a generic one-size-fits-all affair?
Is the Pope Catholic? Will the Olympic stadium be built on-time? Will Brown win the next General Election? Is the Porsche Cayman S better than the Lotus Europa? Is there life on other planets?
I dunno! I'm off to ask my cat. (Dammit, she woke me up at about 2.00am this morning with a dead spider - she owes me some answers!)
Oli.
P.S. I may or may not have had half-a-bottle of good Argentine red before writing this.
It's a good question - carry on brainstorming! (Are you an engineer? Looking at thinking such as yours, I am realising why I failed!) I simply don't know enough to shed any light on it, but it's a very good question. I guess that the different (higher) octane rating of the LPG over the petrol may change the knock signature - but given that it is a significantly higher octane, it may well be that it simply cannot be made to knock within the ignition timing envelope such as can be set by the S2 ECU.
Not sure about the RR's not having knock sensors. I don't think that they are *that* primative! OK, the early ones may be, but the later ones probably are not, and I think that LPG is a popular conversion for a wide range of them age-wise. .
The next question is whether the knock sensor is wired into the new ECU ... it is wired into the existing one, but is there the facility to wire it into the new one? Is the new one a stand-alone system or a piggy-back on the existing one? Is the new system specific to the 944S2 that Tref has, or a generic one-size-fits-all affair?
Is the Pope Catholic? Will the Olympic stadium be built on-time? Will Brown win the next General Election? Is the Porsche Cayman S better than the Lotus Europa? Is there life on other planets?
I dunno! I'm off to ask my cat. (Dammit, she woke me up at about 2.00am this morning with a dead spider - she owes me some answers!)
Oli.
P.S. I may or may not have had half-a-bottle of good Argentine red before writing this.
xenon
New member
Admittedly the 944 was ahead of its time in having knock sensor microphones, mainly to enable Porsche to market the same engine worldwide, with vasty differing petrol qualities in countries in which it was sold thereby reducing costs. However, this was twenty years ago. All manufacturers compete on the global stage nowadays and with increased emission targets I would say that all modern engines have knock control in the DME. The BMW S54 engine has a microphone for each individual cylinder.
Hi Tref,
A friend of mine (auto electrician and former land rover / range rover mechanic) has done a few succesfull conversions, was chatting to him today, he said that valve wise any car that can use unleaded should be fine on LPG, but the key is to run a little richer to keep the temps down. His brothers range rover with a TVR power engine runs gas - a conversion he did - apparently you get no carbon build up within the head at all. He offered his exhaust gas analyser and we may be able to get him interested further, he is mainly into audis but I am trying to convert him
Will catch up once I have had some days back in the UK.
Good luck,
Tony
A friend of mine (auto electrician and former land rover / range rover mechanic) has done a few succesfull conversions, was chatting to him today, he said that valve wise any car that can use unleaded should be fine on LPG, but the key is to run a little richer to keep the temps down. His brothers range rover with a TVR power engine runs gas - a conversion he did - apparently you get no carbon build up within the head at all. He offered his exhaust gas analyser and we may be able to get him interested further, he is mainly into audis but I am trying to convert him
Will catch up once I have had some days back in the UK.Good luck,
Tony
Thanks Tony,
Jon Mitchell said exactly the same thing about teh lack of carbon... which I reckon has to be good for the oil too... but I am surmising... which may go some-way to explaining 300k miles on the other 944 that has been converted.
Certainly any assistnace and feedback of other experiences are all useful...
As to Knock sensors, where are they? I don't recall ever finding any on the earlier 944s, but then, the engine loom usually stays with the engine when the latter is removed from the car, so it could be that I have never noticed them.
Regards,
Tref.
Jon Mitchell said exactly the same thing about teh lack of carbon... which I reckon has to be good for the oil too... but I am surmising... which may go some-way to explaining 300k miles on the other 944 that has been converted.
Certainly any assistnace and feedback of other experiences are all useful...
As to Knock sensors, where are they? I don't recall ever finding any on the earlier 944s, but then, the engine loom usually stays with the engine when the latter is removed from the car, so it could be that I have never noticed them.
Regards,
Tref.
On the carbon front - apparently when oil is drained from an LPG engine, it is as clear and golden as when it is new, rather than being black like oil from a petrol-fuelled engine. However it is still used engine oil, and will have lost a number of it's lubrication properties, and should therefore be changed. (i.e. Oil condition is not just a function of appearance.)
Oli.
Oli.
I agree that the oil will still be "worn", but assuming it carbon that is making it black, wonder about the abraisive properties, and I understand that in idle engines, it combines with condensation to form some nasty acid that eats away at bearings...(unsubstantiated)
But then I am looking for all the positives I can get at the moment!
I spoke to the person that had the problem with the tappets today, and it does indeed sound like valve seat regression - that is on a Mitsubishi something or other, but hasn't suffered any more problems since the initial installation two years ago.
But then I am looking for all the positives I can get at the moment!
I spoke to the person that had the problem with the tappets today, and it does indeed sound like valve seat regression - that is on a Mitsubishi something or other, but hasn't suffered any more problems since the initial installation two years ago.
sawood12
New member
Didn't realise LPG was higher octane than petrol. On the basis our cars are only capable of +/- 6 degrees of advance/retard then I guess you are probably unlikely to get into a knock situation then so maybe it isn't an issue.
However part of the point is that I don't believe that the vast majority of modern cars have knock sensors, even to this day. it was the system that alot of German maunufacturers adopted, probaby because of the autobahn where long periods of high speed running can bring on knock. It is certainly the case that the vast majority of aftermarket stand alone EMS and aftermarket ECU chip systems don't have knock protection and rely on good accurate and cautions mapping to avoid knock altogether.
However part of the point is that I don't believe that the vast majority of modern cars have knock sensors, even to this day. it was the system that alot of German maunufacturers adopted, probaby because of the autobahn where long periods of high speed running can bring on knock. It is certainly the case that the vast majority of aftermarket stand alone EMS and aftermarket ECU chip systems don't have knock protection and rely on good accurate and cautions mapping to avoid knock altogether.
Scott,
The irony of the much (much) higher octane rating of LPG (I think it's about 106, from memory) is that if you were to build a LPG-only engine, you could put in a massive compression ratio with serious advance, and get a really good slug of power out of it. And good economy as well. On cheap fuel ... yum!
Most people however start with a petrol-designed engine, and produce a hybrid that is more tuned towards petrol than LPG, hence never really realise the full potential of the LPG.
Oli.
The irony of the much (much) higher octane rating of LPG (I think it's about 106, from memory) is that if you were to build a LPG-only engine, you could put in a massive compression ratio with serious advance, and get a really good slug of power out of it. And good economy as well. On cheap fuel ... yum!
Most people however start with a petrol-designed engine, and produce a hybrid that is more tuned towards petrol than LPG, hence never really realise the full potential of the LPG.
Oli.
vitesse
Active member
I thought that all cars running electronic fuel & ignition mapping were fitted with knock sensors to enable optimisation of ignition advance with fuel enrichment for performance & emission control.Both my Honda V6 engined Rovers and 4 cylinder Turbo Vitesse Rover had them;the engine control diagrams showed them.That was over 10 yrs ago.
That's my understanding as well. It means that the ignition advance can be aggressive as possible, given the other variables (temperature, fuel quality, ambient pressure, RH etc etc etc). It is one of the feedback sensors into the ECU of a lot of modern cars, I think ... and allows the ignition advance software to work pretty much as
10 Advance ignition as far as possible.
20 If it pinks, back off the ignition until it stops pinking.
30 Goto 10.
(But I could be wrong!)
Oli.
sawood12
New member
You can also control advance/retard via manifold pressure but this is obviously not a closed loop control system like knock sensors.
Read a pretty snazzy article on the next generation of engines that are being developed and should be hitting the streets in about 5 to 10 yrs time. They are Diesel/petrol engine hybrids that offer the advantages of both systems. They basically have variable compression ratio either controlled by eccentric big end bearings on the crank (the mercedes route), or by trapping some of the exhaust gas in the cylinder to increase compression (the GM route or shortcut). They use petrol, so none of that horrible Diesel stuff, and operate as a diesel engine at partial throttle conditions and when you are pressing on and at WOT switch over to spark ignition cycle. The really tricky bit that is real crux of the reasearch and development is how to control the enigne when it is in transition between the two cycles. They reckon you'll get better than diesel economy with all the benefits of the better perfomance of a petrol engine. Sounds pretty good and best of all it spells the end of that horrible, smelly, filthy diesel stuff.
Read a pretty snazzy article on the next generation of engines that are being developed and should be hitting the streets in about 5 to 10 yrs time. They are Diesel/petrol engine hybrids that offer the advantages of both systems. They basically have variable compression ratio either controlled by eccentric big end bearings on the crank (the mercedes route), or by trapping some of the exhaust gas in the cylinder to increase compression (the GM route or shortcut). They use petrol, so none of that horrible Diesel stuff, and operate as a diesel engine at partial throttle conditions and when you are pressing on and at WOT switch over to spark ignition cycle. The really tricky bit that is real crux of the reasearch and development is how to control the enigne when it is in transition between the two cycles. They reckon you'll get better than diesel economy with all the benefits of the better perfomance of a petrol engine. Sounds pretty good and best of all it spells the end of that horrible, smelly, filthy diesel stuff.
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