Dave Bailey
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| posted on 30/11/13 at 09:14 PM |
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Closed Loop Lambda...
Just gauging if I am going about this right way... I had the car set up on a rolling road but the tuner would not tune using my wide band lambda wired
into my DTA ECU... Anyway I got the car through IVA but the general running below 3000 - 3500 RPM is not good. Fuel consumption is high. I have
closed loop enabled and having run the car for about 100 miles I have created a fuel correction map. The map in places espacially low down is showing
a 30% reduction in fueling required.... I have refreshed the main map with this update but just wondered if I people run closed loop lambda
control.... I don't know yet if this refresh will help... Before this the car sputtered and would not idle very well... Sometimes stalling if
the idle falls too low... I don't think I have any air leaks.... It seems to run better if closed loop is not enabled but based on fuel
consuption it is running rich. Pops and bangs a bit on over run also...
Getting to a point where I bite the bullet and shell out on another tuning session...
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coyoteboy
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| posted on 30/11/13 at 10:34 PM |
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There's a few things coming into play. Is your wideband accurate? Many ECUs (no idea on DTA) let you set limits on the controller authority (how
much the fueling can be changed) and how fast it can be changed, also bounds for operation etc. With the likes of the megasquirt you can find if you
give it too much authority and not enough speed it'll oscillate all day, if you speed it up you end up with misfires due to the constant
lean/rich switching. You need to get the right mix. The tuner will rely on their calibrated sensor - was that correctly calibrated?!
I run 02 correction at all times with an AFR map of my choosing, anywhere about 1200 RPM and below 7.5psi of boost. I run about +/-5% authority and
allow 1% change every 5 cycles IIRC - this keeps my idle at +/- 0.2ish AFR unless something particularly large disturbs it. It also passed it's
MOT with flying colours with these settings, but the MOT regs for my car are not too tough (3.5% and 1200ppm IIRC).
My stock ECU ran closed loop and stoic up to 4000rpm and half throttle (even at 9psi of boost?!) which I found odd.
The times you want to be wary of using closed loop, such as high boost and high revs, and you want to make sure the sensor's default output is
lean - if it's rich and you lose the sensor for some reason (power spike, sensor glitch) your ECU will attempt to correct by leaning out, which
could be at WOT 6kRPM - not good.
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Dave Bailey
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| posted on 30/11/13 at 11:08 PM |
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Thanks for the response... I managed to pass IVA gas test no problem using closed loop with my sensor... I have an innovate I think it is an LC1...
I have closed loop turned off above 4000... I have a digital dash and can display lambda and when driving the Lambda is anywhere betweem .68 to high
.8 so running rich if I can believe my sensor remembering it was ok for IVA... Settings are shown below... it seems that max adjust is set at 30%
hence why I have seen thsi value in the correction map...
[img] [/img]
Dave B
[Edited on 30/11/13 by Dave Bailey]
[Edited on 30/11/13 by Dave Bailey]
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sebastiaan
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| posted on 1/12/13 at 08:18 PM |
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Sounds like it is indeed running really rich. I'd either get it mapped again or consider doing it yourself.
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Dave Bailey
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| posted on 3/12/13 at 07:33 PM |
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I am going to try to use the closed loop lambda correction map to lean out the mixture..
I will if this isn't going well when the weather gets better take a trip to Bailey Motorsport in Telford...
Dave B
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