Noddle Posted February 13, 2011 Share Posted February 13, 2011 Hi, I'm after some information about how lean I can run my engine before I do any damage, a little back ground, I have to travel about 300k (190 mile) once a fortnight, and since fuel is getting expensive (AU$1.95 a liter, about US$1.98), I want to try and save some money by leaning it out a little, I'm running Megasquirt, so I have full control over spark and fuel, On today trip, cruising at 110kmh (about 70 mph) sitting on about 3200 RPM, with a AFR of 16.2ish, with a EGT at 784C (1443F - EGT probe is open tipped and installed at the mouth of the turbo manifold exit flange, before the turbo), engine temp was normal, To me, the engine was running smoothly, a little lean misfiring, from coming onto throttle after rolling down a decline, but other than that, it ran great. I have also leaned it out similar as to what's about for 60,80,100 kmp/h (40,50,62 mp/h) AFR drop back to 14.7 - 11ish when I load the engine up, so I still have plenty of power for those over take moves. is this to lean ?, at what temperature will I melt something ? Nigel Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 13, 2011 Share Posted February 13, 2011 Nope, depending on loading and use of EGR, you can go as far as 22:1. Typically 18:1 is a generally accepted as a benchmark. Old lean-burn carburetted Chryslers were at that level, and as lean as 22:1. If you have EGR, it allows you to introduce it, lower combustion chamber temperatures and run a bit more advance. But it's an Emissions Thing, so take it off... Quote Link to comment Share on other sites More sharing options...
Snailed Posted February 13, 2011 Share Posted February 13, 2011 It really depends on the engine, but you have the right idea. As long as it's running smooth and temps are fine it's safe. I wouldn't bother making lean holes where you cruise on the highway. Lean out all the areas that are in deep vacuum and above say 1800 rpm. You want to keep the low stuff a little rich so it's smooth in parking lots. Same with timing, you might want to retard it compared to the very lean areas to keep it smooth. Just keep on top of the TPS enrichment because it's very easy to be in a lean area and get on it and knock the motor for lack of fuel. Quote Link to comment Share on other sites More sharing options...
Noddle Posted February 13, 2011 Author Share Posted February 13, 2011 But it's an Emissions Thing, so take it off... It's very relaxed here, there is no emissions testing. I'll do some more loggin and try to lean it a little more, but on my 3 trips so far, I have gone from 19 mile per gallon to 24, and my last trip 27, so I'm pretty happy. Nigel Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 14, 2011 Share Posted February 14, 2011 it was more of a comment regarding blanket removal of 'emissions parts'---the reason for EGR was to lower CC temps dropping NOx. Same thing happens where you retard ign timing. keeping egr, you can run more spark advance. with the diesels out there having "egr coolers" itvirtually eliminates the 'bad' side effects of injecting HOT EGR into the intake manifold. Really, flat tops got most the bad rap for the heat of the egr. Eliminate the heat, and keep the benefits. it's a thought, it won't be the easiest route, but you should see some gains. Quote Link to comment Share on other sites More sharing options...
Noddle Posted February 14, 2011 Author Share Posted February 14, 2011 it was more of a comment regarding blanket removal of 'emissions parts'---the reason for EGR was to lower CC temps dropping NOx. Same thing happens where you retard ign timing. keeping egr, you can run more spark advance. with the diesels out there having "egr coolers" itvirtually eliminates the 'bad' side effects of injecting HOT EGR into the intake manifold. Really, flat tops got most the bad rap for the heat of the egr. Eliminate the heat, and keep the benefits. it's a thought, it won't be the easiest route, but you should see some gains. I had to do a search on EGR, but once I saw a picture I knew what you was talking about, I have the non-egr manifold. I think I will just play with what I have, and see how it goes, I'll lean it out a little more on cruise, and keep a eye on the egt and thank you for the input, Tony, Snailed. Nigel Quote Link to comment Share on other sites More sharing options...
Leon Posted February 14, 2011 Share Posted February 14, 2011 it was more of a comment regarding blanket removal of 'emissions parts'---the reason for EGR was to lower CC temps dropping NOx. Same thing happens where you retard ign timing. keeping egr, you can run more spark advance. Injecting EGR into the combustion chamber will dilute the mixture and increase burn time. Saying that you can run more advance is a bit misleading, because it leads people to infer that they will then gain power. You have to run more advance with EGR than without in order to keep max cylinder pressure vs. crank angle the same. Quote Link to comment Share on other sites More sharing options...
rayaapp2 Posted February 14, 2011 Share Posted February 14, 2011 Injecting EGR into the combustion chamber will dilute the mixture and increase burn time. Saying that you can run more advance is a bit misleading, because it leads people to infer that they will then gain power. You have to run more advance with EGR than without in order to keep max cylinder pressure vs. crank angle the same. Specifically the EGR dilutes the mixture with hot inert gas. Absolutely To add to this: When speaking of EGR we are not speaking of a performance device or a performance robbing device. This is a device that is in function when the operator is not putting full demand on the engine. During events like cruise when the engine is only using a fraction of its output it can be advantageous to lean the mixture out to get better fuel economy. Leaning the mixture out at this point leads to higher combustion chamber temperatures and the formation of NOx in the least and can have other serious physical effects in and around the combustion chamber. This is where EGR is advantageous for all the reasons listed above. There is a reason why EGR was introduced during the gas crunch times... Quote Link to comment Share on other sites More sharing options...
Tony D Posted February 17, 2011 Share Posted February 17, 2011 Check some of the old Chrysler technical documentation on EGR injection rates on their lean-burn engines... Ford had tip-in stumble issues with their EGR, but Chrysler was pumping it in like crazy! Quote Link to comment Share on other sites More sharing options...
Leon Posted February 17, 2011 Share Posted February 17, 2011 Allowable %EGR and how lean you can run an engine depends a lot on combustion chamber design. The more efficient the combustion chamber (faster burning), the more EGR an engine will take before it becomes detrimental to performance (tip in hesitation, misfire, etc.). Quote Link to comment Share on other sites More sharing options...
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