The limit would seem to be the materials in the combustion chamber and the level of cooling that they get.
It's very difficult to tell without specialist equipment and expert knowledge.
I was tuning the Duratec (2.0 with Jenvey TBs and megasquirt) for some fuel economy in the 2500-3500rpm range. I can see 16.5:1 afr in the gauge
(almost the same in TunerStudio) and the engine seems to be happy. TPS was at 5% so very low load.
Is these dangerous for the engine?
Thanks!
My understanding of this is that Lean mixtures run hotter - hence it may be an issue. It just depends how hot is TOO hot
The limit would seem to be the materials in the combustion chamber and the level of cooling that they get.
It's very difficult to tell without specialist equipment and expert knowledge.
Yes I saw the engine was running at 85º instead of the 82º using a richer mixture.
This is one of those cases where you are genuinely playing with fire - I think you need to find out what the high vacuum air fuel ratios and the
timing is for the original motor. You then need to take an educated look at the what the impact of the modifications you have made on the cylinder
filling and evacuation is at those vacuum levels and then decide what will work.
I would certainly not go any leaner with mixture and any more advanced with timing than what the standard motor runs at when pulling a high vacuum.
I wish I could get the stock map for this engine!
I guess the engine won't see much load at 5% throttle (unless you have a really perverse style), plus, if pushed to the edge - perhaps the
antiknock sensors would get involved before anything went bad. A guess.
Hopefully where you are, there are octane levels available that allow exploring the fuelling/ignition. If you've only got access to 80's
octane (RON) perhaps unwise to push the limits. Some of our American friends have very poor fuel.
quote:
Originally posted by motorcycle_mayhem
I guess the engine won't see much load at 5% throttle (unless you have a really perverse style), plus, if pushed to the edge - perhaps the antiknock sensors would get involved before anything went bad. A guess.
Hopefully where you are, there are octane levels available that allow exploring the fuelling/ignition. If you've only got access to 80's octane (RON) perhaps unwise to push the limits. Some of our American friends have very poor fuel.
quote:
Originally posted by Nitrogeno25
Yes I saw the engine was running at 85º instead of the 82º using a richer mixture.
FWIW the hottest mixture is stoic (it has the highest energy output per unit fuel), if all other factors are correct for the mixture, either direction
takes you cooler, one through excess fuel and other causes and the other through excess air and a few other causes. You'll see hotter lean mixes
if you're not advancing the timing at the same time. But you're grouping a whole load of points into a general one - are we talking EGT,
cylinder wall temp, cylinder head temp etc etc. And are you changing the ignition timing to match the differing mixture? Are you talking about at a
fixed RPM and load, or does your RPM and load change with the adjusted mixture and timing?
You really need EGT and torque feedback to tune properly and try to run at extremes, otherwise stick to known safe AFRs.
[Edited on 15/4/13 by coyoteboy]