Thanks classic, I bow to your greater knowledge here.
Sorry to sound dim on this, so LPG has lower calorific values than petrol for a given volume. This I understood.
Apple for the teacher, help me here, I'm the sad anorak that would really like to grasp this, please, marks out of ten for the following...
1) Because we can't increase the capacity of the engine when running gas, for any given swept volume cycle of the engine, less energy is going in with LPG, so because we are forced into less energy going in, we must expect less energy out.
2) We could negate the effect of 1) by increasing the boost when running LPG by whatever proportion of energy we are short-measured. Hence if there's 5% less energy per stroke 'going in' running LPG, ideally we would up the boost by said 5% (solely on LPG, mind) and we're on a level with petrol. Because now, per cycle, we are putting the same energy in.
3) Does my point about some of the power loss is brought about due to the CR being fixed by petrol's lower CR requirement stand? In an ideal world you would up the CR when running LPG, only we can't?
4) You wrote
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The ECU retards the ignition on petrol with the boost.
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OK, so unless this can be changed, this is another power-killer for LPG, because it may have lower calorific value, but it does like more advance. Really we would advance the ignition a tad running LPG. Do systems allow you to do this?
5)
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Old mixer systems loose more but not major
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Not sure I see why. I can see that the metering will not be good, and we'll lose power becasue of this, but why would an old mixer system suffer more than proper kit in any other respect. Apart from better metering by reading the lambda etc, what is it that proper kit does that an old mixer doesn't?
6)
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You do not lose any power with LPG due to the CR as this is the same for both petrol and LPG.
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So you do (kind of) lose more power because of the lower CR, but because you can't do a thing about that, we live with it. Or conversely you don't lose more power because of the lower CR because the ECU you install tricks up the advance and boost to get round this issue in other ways. I'd assume by Boost increase and ignition advance?
7) Am I getting my higher octane and further advance requirements remixed-up?
a) LPG needs more advance because it has a slower flame-front? Hence is slower to ignite? Correct?
b) LPG has a higher octane but it is of no advantage in a BiFuel conversion set-up because this property is hobbled. The engine can't be changed back and forth to suit each fuel?
Which bits do I have right/wrong?
In short if I have hte above about right, for there to be little or no power losses running LPG, what does a top-end install do to achieve this? Aside from more advance, or a altered advance curve, do they up the boost on gas for example?