LPG tune/fuel mixtures in turbo application, any suggestions?
LPG tune/fuel mixtures in turbo application, any suggestions?
(OP)
ok i know its a bit broad but maybe some of you would have a opinion.
im running a turbocharged 6cyl engine on LPG, compression is at 8.2:1 and fuel mixtures are between 10.8 to 11.3 under full boost which is at 18-20 psi.
im in australia so the engine in question is a 250ci (4.1 ltr) pushrod 6cyl, with a cast piston and standard conrods. i used to run the same setup in a daily driver at 16psi(and 20psi at the track frequently) and a front mount air to air intercooler and never had any issues but now with the boost set at 20psi and a water to air intercooler i have bent a rod. timing is reasnobly safe and now detonation signs on sparkplug or cast piston but the big end bearing showns signs of slight detonation.
to cut a extremly long story short, do you guys think that the fact that LPG enters the engine in a reasnobly "hot" state compared to petrol that it would be causing high combustion chamber temps that would therefore lead to detonation? if timing is right and air fuel ratio is safe, where is my detonation coming from?
im running a turbocharged 6cyl engine on LPG, compression is at 8.2:1 and fuel mixtures are between 10.8 to 11.3 under full boost which is at 18-20 psi.
im in australia so the engine in question is a 250ci (4.1 ltr) pushrod 6cyl, with a cast piston and standard conrods. i used to run the same setup in a daily driver at 16psi(and 20psi at the track frequently) and a front mount air to air intercooler and never had any issues but now with the boost set at 20psi and a water to air intercooler i have bent a rod. timing is reasnobly safe and now detonation signs on sparkplug or cast piston but the big end bearing showns signs of slight detonation.
to cut a extremly long story short, do you guys think that the fact that LPG enters the engine in a reasnobly "hot" state compared to petrol that it would be causing high combustion chamber temps that would therefore lead to detonation? if timing is right and air fuel ratio is safe, where is my detonation coming from?
RE: LPG tune/fuel mixtures in turbo application, any suggestions?
RE: LPG tune/fuel mixtures in turbo application, any suggestions?
Franz
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RE: LPG tune/fuel mixtures in turbo application, any suggestions?
RE: LPG tune/fuel mixtures in turbo application, any suggestions?
Running an engine at this rich AF ratio deprives the engine of air by displacement.
Otherwise, your comments about lean running are right on. Given the choice, I would rather run lean burn than rich burn.
Franz
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RE: LPG tune/fuel mixtures in turbo application, any suggestions?
I'm skeptical that running richer than stoich moves you toward detonation (i.e. on a vapor fuel). What is the basis for your statements to that effect?
RE: LPG tune/fuel mixtures in turbo application, any suggestions?
RE: LPG tune/fuel mixtures in turbo application, any suggestions?
You may run straight antifreeze if your cooling system has the extra capacity. It doesn't boil and you won't get steam pockets.
RE: LPG tune/fuel mixtures in turbo application, any suggestions?
RE: LPG tune/fuel mixtures in turbo application, any suggestions?
I have spent more hours (days, weeks) in an engine dyno lab than I care to count, and one thing we watched more than anything else was the AF ratio in direct correlation to exhaust temp. When running an engine in rich mode on a vapor fuel, there is no evaporative fuel cooling (we have discussed this on this forum multiple times). Up to the point of rich misfire, which I feel this engine is dangerously close to, adding fuel will increase the combustion temps.
One thing to remember, that reducing ignition timing on a turbocharged engine may NOT reduce detonation since delayed ignition timing results in increased exhaust temps and increased turbo pressures, and this too can cause increased detonation. It is very easy to reduce detonation by quickly leaning the fuel mixture.
Many people will mistakenly richen the fuel mixture on a vaporfuel engine trying to reduce detonation and pre-ignition while the opposite is true. Remember, a vapor fuel behaves VERY differently under boost than a liquid fuel. Conventional theory with liquid fuels does NOT apply with vapor fuels. More than one engine has been lost on the dyno.
Franz
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: LPG tune/fuel mixtures in turbo application, any suggestions?
Can you explain the mechanism when already rich of stoich, how going richer increases combustion temps? Where is the additional energy release coming from?
RE: LPG tune/fuel mixtures in turbo application, any suggestions?