Lean Tip in started - Can O2 clamps fail? - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-07-2012, 03:55 PM   #1
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Default Lean Tip in started - Can O2 clamps fail?

Hi guys and gals,

Recently my turbo'd set up has started running lean between gear changes, wideband goes off the scale and the car bogs down, come off the throttle and back on again an AFR's jump back down to 13 then back to 14/15.

Also on light throttle in a high gear AFR's are high in the 17 range.

Car is fine under boost (11.5) and on the motorway (14.7/15.4).

Here is the current spec;

-GReddy/Mitsubishi TD04h turbocharger
-GReddy cast manifold with relief cuts done & uprated mounting hardware
-Flyin' Miata stainless turbo heat shield
-Begi/GReddy seperated gasses 2.5" stainless steel downpipe
-2.5" stainless decat-pipe, with O2 bung for wideband O2 sensor
-2.5" "XS-Speed" stainless steel cat-back single exit exhaust
-Magnecor KV85 uprated ignition leads
-K&N cone air filter
-Racing Beat air filter adapter mount
-GReddy Emanage Blue ECU controller (complete with USB cable & software)
-O2 clamp (made by miataturbo.net member "olderguy")
-2 bar Weber MAP sensor
-AEM wideband 02 sensor & guage
-Intercooler & silicone/stainless pipework
-SARD R2D2 blow off valve
-320cc Supra "yellow top" injectors with resistor pack
-Flyin' Miata dual feed fuel rail with stainless lines
-Stainless oil feed line
-Oil return tapped into sump.
-Cam-cover breather filter

And the first vid of the car under boost;


Ignore the missis'. I've owned much faster cars yet she still makes funny noises.

And this is the day to day through the gears where it goes lean and can kangaroo sometimes if on part throttle etc.


Sorry they're not great quality.

The car was fine the first few months I owned it, i've checked all the wiring and nothing has come lose.

Could the MAP or O2 sensor be buggered?

Can i check it somehow?

Would like to get this sorted as it's messing up the driveability and also not good being lean.

Cheers.
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Old 11-09-2012, 01:04 PM   #2
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It looks like the lean condition occurs when air flow is low. Problem with maf signal?
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Old 11-09-2012, 05:52 PM   #3
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I'm not sure if MAF problem.

Im new to EMB and software, I just connected EMB to the laptop and took a screen shot of these cells;



This map hasn't changed since I got the car and it was running great when I got it about 4 months ago so im thinking it must be something mechanical rather than a problem with the map, it's fine on boost and cruising on motorway.

Sorry for being a noob, I am reading to, to find a solution.
Attached Images
File Type: jpg EMBMap.jpg (83.3 KB, 64 views)
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Old 11-10-2012, 04:28 AM   #4
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I guess a blow off valve leaking under high vacuum conditions could cause something like this.

That said, it should be possible to make an EMB log file and use map trace to see which cells are associated with the lean condition. (You could also post your gsc and lgd files so others can take a look.)
With cooler weather fine tuning of the map could be needed. Most of the EMB miata maps I have seen do not use airflow adjustment but rather map / additional injection. The -20 tps air flow figures look unusual. I am curious, how is fuel pressure regulated? what size are the injectors? what injector re-size is used in EMB?
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Old 11-10-2012, 07:07 AM   #5
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Ok I will try and get a log of the files.

I will also remove the BOV and blank it to see if it still runs lean.

Fuel pressure is regulated by the stock items.

Fitted with 320cc Supra "yellow top" injectors with resistor pack but in EMB settings injectors change is 220cc > 280cc with a correction factor of 0.786.
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