Lean Burn engine
#1
Lean Burn engine
Hi there, got a stupid question...
anyone ever tried to tune the engine below 2.5k to 3k rpm like a lean burn engine:
this means afr above 20:1 to max 28:1
it's only possible under low rpm, cause such lean mixture would burn quiet slowly --> at high rpm the mixture would still burn when the exhaust valve opens...
therefore high ignition advance would also be a must...
furthermore knock sensors...
and a wideband lambda which is possible to detect levels above 20:1
anyone tried so far?
what I am aiming for is:
better fuel economy for low revs
thx for your thoughts
anyone ever tried to tune the engine below 2.5k to 3k rpm like a lean burn engine:
this means afr above 20:1 to max 28:1
it's only possible under low rpm, cause such lean mixture would burn quiet slowly --> at high rpm the mixture would still burn when the exhaust valve opens...
therefore high ignition advance would also be a must...
furthermore knock sensors...
and a wideband lambda which is possible to detect levels above 20:1
anyone tried so far?
what I am aiming for is:
better fuel economy for low revs
thx for your thoughts
#5
i have a stock engine, but turbo charged (95 ROZ)
of course i know that igniting the leaner mixture is not a simple task, i already have a better ignition system
the loss of power is cause the ignition has to be extremly advanced, otherwise the peak pressure is reached beyond the optimal point (10-20 degree after tdc)
probably a cylinderpressure sensor would be useful...
but i want to know if any1 tried so far?
thx for your thoughts ;-)
of course i know that igniting the leaner mixture is not a simple task, i already have a better ignition system
the loss of power is cause the ignition has to be extremly advanced, otherwise the peak pressure is reached beyond the optimal point (10-20 degree after tdc)
probably a cylinderpressure sensor would be useful...
but i want to know if any1 tried so far?
thx for your thoughts ;-)
#8
There was a P-40 pilot in WW2 that figured out how to set his **** to lean burn, then he went and taught all the other P-40 pilots about it. They noticably extended the range of the P-40. The concept is proven, but it's prone to making mistakes. The ignition is advanced significantly to start the burn early, and the burn completes shortly after TDC, effectively providing more power for the down stroke than the resistance of compression on the up-stroke. The problem can be the transition from lean-burn to stoich burn (where you have to bridge the detonation range of the AFR) - WW2 planes that were just cruising pretty much set the RPM and stuck to it.
IIRC, I thought the prius was set as a lean-burn engine. The EPA doesn't like them though.
IIRC, I thought the prius was set as a lean-burn engine. The EPA doesn't like them though.
#12
This topic was featured in hot rod i think?
Yeah it was:
http://www.hotrod.com/techarticles/e...ine/index.html
Also:
http://www.legendarycollectorcars.co...clusive-video/
There is more to it than better mpg; Smokey Yunick actually made power with his setup.
Yeah it was:
http://www.hotrod.com/techarticles/e...ine/index.html
Also:
http://www.legendarycollectorcars.co...clusive-video/
There is more to it than better mpg; Smokey Yunick actually made power with his setup.
Last edited by danotakulus; 03-28-2011 at 10:06 PM. Reason: grammar
#14
This topic was featured in hot rod i think?
Yeah it was:
http://www.hotrod.com/techarticles/e...ine/index.html
Also:
http://www.legendarycollectorcars.co...clusive-video/
There is more to it than better mpg; Smokey Yunick actually made power with his setup.
Yeah it was:
http://www.hotrod.com/techarticles/e...ine/index.html
Also:
http://www.legendarycollectorcars.co...clusive-video/
There is more to it than better mpg; Smokey Yunick actually made power with his setup.
#16
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One time I drove on the highway following Saint_foo here up to a dyno day. in the rain going +80mph my fuel map needed work and I was hitting over 17:1 before it would need more fuel. Got pretty good mpg IIRC.
I typically highway cruise at 16.5:1.
I typically highway cruise at 16.5:1.
#17
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I read about the honda "lean burn" at one point. It wasn't as extreme as Smokey's IIRC, just sorta using vtec in an economy mode and leaning it out bigtime like we try to do with our standalones, but with honda's better tech. cylinder head and cam timing. Worked great on those old civics but then the EPA didn't like the emissions and killed that idea. Back when I was ignorant of emissions and had my link ecu I went thru the NJ inspection with a very lean 17ish AFR, thinking it'd pass no problem as I wasn't using much fuel. WRONG. I forget what goes sky high when you go lean but something was off the chart.
#18
Can't seem to find the full article any more though.
#19
I can't remember exactly where it was, but it was nothing special. I suspect the cylinder head design was more important - the Civic CX could go even leaner.
If Smokey's hot air engine wasn't a hoax - which I'm not ruling out either - there were a lot of details about that motor that Smokey kept hidden from the media. My own guess is that the engine was a homogenous charge compression ignition engine. That would fit a lot of the published details - that the engine ran extremely lean, and that the air was heated to almost the point of autoignition - as well as some educated guesses - such as that the engine appears to have been a total bitch to tune, given how several companies he'd licensed the technology to couldn't get a production version working.