Idle tuning tips
#1
Idle tuning tips
First some details about my setup - its in an mx5 based kit car I'm building not actual mx5.
1.8bp engine
diy MS2 running diypnp turbo basemap (afr and spark) ran autotune VE at idle and moderate driving but no WOT yet.
No IAC valve
TD04 turbo on diy manifold with small intercooler
380cc yellow rx8 injectors
AEM wideband (setup as custom linear wideband)
Starts ok from cold and runs a little rough as expected with no IAC valve but after a minute or so it idles quite nicely. When it gets up to full temperature it splutters and missfires a lot (once per second) although still maintains a reasonable idle (900rpm +/-30). AFR of 13 although the needle fluctuates. If I give it some revs it continues to splutter under no load but when actually driven in gear it doesn't. It drives ok - leans out on sudden acceleration but I want to get idle sorted before I worry about that.
Anyway I've tried giving it more or less fuel around idle and advancing and retarding the spark and none seem to improve it which leads me to believe that it might be issue with setup or even hardware (coils dodgy when hot?).
Any suggestions?
Other thought was I have a v band on the downpipe upstream of the wideband sensor and perhaps these don't form a perfect seal leading to false readings? Here is a pic of the setup. Ignore the tiny air filter - that was just to keep the dust out while building and has been replaced with proper one Note that I haven't finished the exhaust beyond the downpipe.
1.8bp engine
diy MS2 running diypnp turbo basemap (afr and spark) ran autotune VE at idle and moderate driving but no WOT yet.
No IAC valve
TD04 turbo on diy manifold with small intercooler
380cc yellow rx8 injectors
AEM wideband (setup as custom linear wideband)
Starts ok from cold and runs a little rough as expected with no IAC valve but after a minute or so it idles quite nicely. When it gets up to full temperature it splutters and missfires a lot (once per second) although still maintains a reasonable idle (900rpm +/-30). AFR of 13 although the needle fluctuates. If I give it some revs it continues to splutter under no load but when actually driven in gear it doesn't. It drives ok - leans out on sudden acceleration but I want to get idle sorted before I worry about that.
Anyway I've tried giving it more or less fuel around idle and advancing and retarding the spark and none seem to improve it which leads me to believe that it might be issue with setup or even hardware (coils dodgy when hot?).
Any suggestions?
Other thought was I have a v band on the downpipe upstream of the wideband sensor and perhaps these don't form a perfect seal leading to false readings? Here is a pic of the setup. Ignore the tiny air filter - that was just to keep the dust out while building and has been replaced with proper one Note that I haven't finished the exhaust beyond the downpipe.
Last edited by luke2152; 07-27-2014 at 03:29 PM.
#2
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The location of your wideband sensor is less than ideal, and it will not give accurate readings especially at lower loads and idle. I would expect readings to be leaner than actual, really way leaner than actual at idle and light cruise.
If it clears up while driving, then I would doubt secondary ignition problems. However, I'd also clean up the high tension leads and install them in the combs to ensure they make no contact with the valve cover.
Lean spike when transitioning to throttle is AE and generally can not be tuned until after the fuel table is. Also bear in mind that there is a slight delay in wideband reading.
Past that, you will need to post a short datalog and a copy of your current tune for further assistance.
Nice car, you should show more pics.
If it clears up while driving, then I would doubt secondary ignition problems. However, I'd also clean up the high tension leads and install them in the combs to ensure they make no contact with the valve cover.
Lean spike when transitioning to throttle is AE and generally can not be tuned until after the fuel table is. Also bear in mind that there is a slight delay in wideband reading.
Past that, you will need to post a short datalog and a copy of your current tune for further assistance.
Nice car, you should show more pics.
#4
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You're not getting a true AFR reading, it'll be way out, so any minor changes to the fuel table you're doing won't really have any effect.
#6
Where it is, but with an exhaust behind it, the problem with your current setup is you'll get fresh air reversing into the exhaust. Closer to the turbine will mean its likely to cook. You can mitigate this with heatsinks.
You're not getting a true AFR reading, it'll be way out, so any minor changes to the fuel table you're doing won't really have any effect.
You're not getting a true AFR reading, it'll be way out, so any minor changes to the fuel table you're doing won't really have any effect.
#7
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Looks like a real nice car. I have found difficulty getting back into Miatas after driving Westies, Exocets, and Locosts.
Your fuel and spark tables go only to 100kPa. I hope you've been staying out of boost.
Your fuel and spark tables go only to 100kPa. I hope you've been staying out of boost.
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