Knocking In 2Nd Gear

[zorro]

I own a subaru forester and got it converted to gas. When I change to 2nd gear the engine start knocking. This problem is not there when i run on petrol. can any expert help ?

[VVTi]

Why on earth would anyone do that to a Subaru?

I am not sure, but the Boxer engine needs high octane fuel... LPG is not exactly higjh Octane if I am not mistake. Someone who knows more about the Subarus might know more.

[jdnet]

  On 12/21/2010 at 1:32 PM, VVTi said:

Why on earth would anyone do that to a Subaru?

I am not sure, but the Boxer engine needs high octane fuel... LPG is not exactly higjh Octane if I am not mistake. Someone who knows more about the Subarus might know more.

You might be mistaken there. AFAIK the octane rating of LPG is far higher than petrol. This itself maybe the cause of the problem.

[jdnet]

Just putting this out there, though i'm not familiar with LPG much; could a low gas pressure be causing your problem? If you have set the output pressure too low and you are not getting enough gas into the cylinder the engine may knock. Once again, not familiar with LPG but seems like a plausible diagnosis.

[VVTi]

Ok, but why only on 2nd gear then?

[VVTi]

  On 12/21/2010 at 2:38 PM, jdnet said:

You might be mistaken there. AFAIK the octane rating of LPG is far higher than petrol. This itself maybe the cause of the problem.

You are correct, Propane has a RON of 110. So like you said, this could be the reason in itself.

I think the main fault lies in the fact that these engines may not be suitable for LP conversions.

[shanX]

  On 12/21/2010 at 1:32 PM, VVTi said:

Why on earth would anyone do that to a Subaru?

Same question here

[MAS]

I dont know if this could be done to this engine but you need to manually advance the ignition for the 110 octane.

[Sumiya]

  On 12/21/2010 at 5:33 PM, MAS said:

I dont know if this could be done to this engine but you need to manually advance the ignition for the 110 octane.

Advancing Ignition timing result more knocking , so this will become worse then,

could be a octane ratio issue but how come it can happen only on 2nd gear , not possible

i am confused

thanks

regards

sumith

[Sifaan]

  On 12/21/2010 at 5:33 PM, MAS said:

I dont know if this could be done to this engine but you need to manually advance the ignition for the 110 octane.

just a thought... could it be that the timing was advanced too much during the conversion, hence causing knocking?

and is the knocking happening only when changing to 2nd gear (i.e. goes away when accelerating), or right throughout in 2nd gear (and goes away in 3rd)?

[MAS]

My old car was converted to gas 8 years ago. Then the ignition timing was advanced manually by the mechanic. But it is difficult to have an optimum duel fuel system beacuse it is tuned to gas and not for petrol. So now it runs only on gas. I have even removed the petrol tank to save some weight but it was not that heavy so I might fix it back

Zorro, you better take it back to the installer.