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Old 11-18-2008, 05:12 AM   #1
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Default I'm RICH! and paying for it. (failed testing)

I failed on hydrocarbons - the trace shows a dump at each gear shift. And sure enough I'm super rich when I lift the pedal. So I installed a linear TPS and have thrown huge decel at it, but I can't make it go away. For example...

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Log and MSQ attached. btw, my zeitronix wideband AFR is custom linear 2xO2+9.6 if you're looking at the log.

Any idea why this happens?
Attached Files
File Type: zip datalog200811171840v104atps1.zip (135.3 KB, 36 views)
File Type: zip msq200811171839v104atps1.zip (5.4 KB, 31 views)
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Old 11-18-2008, 06:09 AM   #2
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My first guess would be you need to turn on Overrun fuel cut.

More Settings > Over Run Fuel Cut. Watching the duty cycle of my injectors it goes to 0 after the exhaust tone changes and you start to decel. It cuts off fuel injection when you're not accelerating, which solved that problem for me.

I have mine set to the following:

RPM: 1000
KPa Lower than: 20
TPS Lower than: 25
Coolant greater than: 60
after (sec): 0

Not saying those are perfect, or would work for you.. DIY has instructions on setting that.

Quote:
3) Overrun Fuel Cut (cuts off the injectors when you are decelerating, saves fuel, stops the rich pop, pop, pop sounds)

* Start the car and let it warm up.
* Note the idle MAP reading.
* Rev the car up to maybe 4000-5000rpm and then let off the throttle. Watch the MAP reading while the engine is decelerating. Repeat this a couple times.
* Note the lowest kpa reading you get on the MAP sensor when doing this. Add 3 to this number and remember this number for use in a moment. This is 'decel kpa +3'
* Open the 'More Settings' Menu and choose 'Over Run Settings'.
* Plug the number you just calculated (decel kpa +3) into the 'and KPa lower than (KPa)' field.
* Now use the same number you calculated for the previous exercise (4 points above closed throttle TPS ADC), and plug it into the 'and TPS lower than (Raw ADC)' field.
* Click 'BURN TO ECU' and then click 'CLOSE'.
Worth a shot.
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Old 11-18-2008, 01:33 PM   #3
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thanks for the suggestion - I think you're right! I'll give that a try on the way to work.

I did have overrun on for the test, but it was only MAP based so I had a 1 sec delay in there for driveability. The TPS changes EVERYthing.
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Old 11-18-2008, 01:42 PM   #4
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certainly doesn't change anything while testing at a constant 15mph and 25mph....
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Old 11-18-2008, 01:50 PM   #5
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True - and I wish that was all I had to contend with. We have a 4 minute driving simulation - with speeds up to 50mph. On the plus side, they don't care what you do under the hood as long as you pass.
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Old 11-18-2008, 02:32 PM   #6
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most of us dont run a delay at all on our decel fuel cut man might try that as well
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Old 11-18-2008, 03:27 PM   #7
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sigh. no joy with overrun fuel cut on 0 delay. The AFR still dives before the overrun can kick in. See attached log at 650 sec. Even the smallest drops in MAP cause a major rich "valley" in the log e.g. at 439 sec.

I think something's broken. Could it be a vacuum leak? MAP sensor slowness? It's a Mapdaddy 4bar.
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File Type: zip datalog200811181030.zip (136.3 KB, 25 views)
File Type: zip msq200811181013v104_tpsoverrun.zip (5.4 KB, 27 views)
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Old 11-20-2008, 01:03 AM   #8
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vacuum leak would lead ot overall richness. Dunno about the parameters of a 4 bar like the map daddy i know my standard map sensor works fine. As soon as i drop pedal i get 19-20-1 afr's I wish i could be of more help.
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Old 11-20-2008, 01:07 AM   #9
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I have the rich event when I lift for a split second, I just assumed it to be normal before overrun cuts the fuel. Hell, look at your Gammae corrections during the events, it's cutting fuel like crazy


If your simulated driving conditions test averages the results, then these anomalies should hardly contribute to the overall results.
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Old 11-20-2008, 01:11 AM   #10
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I have a slightly different approach for this and for me, it's working GREAT. I turned off the decel **** so it doesn't cut fuel on me. Then I just drive and let MLV tune the cells way down low at 20kPa in my ve table so that when I let off, it runs whatever AFR I have in set in my AFR table. Butter smooth now.
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Old 11-20-2008, 02:07 AM   #11
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yeah, brain - that's exactly what I thought. on average. but it goes rich each time I come off the accelerator or shift gears and the gonzo test driver is jerking on and off the gas constantly. my bov sounds like a steam train.

i was just looking at this. my tps and MAP signal line up perfectly, so there's no delay in the MAP or PW. from the spike on the left, it looks like there's a 0.3-0.4 sec delay in the AFR signal. that puts the problem squarely in the decel part of the curve, not the idle.

I'm using the stock FPR (and fuel pump) - could it be dropping pressure? or holding the pressure high for a little too long when the MAP is droppng?

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Old 11-20-2008, 02:12 AM   #12
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Quote:
Originally Posted by patsmx5 View Post
I have a slightly different approach for this and for me, it's working GREAT. I turned off the decel **** so it doesn't cut fuel on me. Then I just drive and let MLV tune the cells way down low at 20kPa in my ve table so that when I let off, it runs whatever AFR I have in set in my AFR table. Butter smooth now.
You realize that factory ECUs have Overrun fuel cut? Whlie it might not be significant, its also a waste of fuel letting the injectors supply the motor with fuel while its decelerating..
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Old 11-20-2008, 02:18 AM   #13
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Go into megatune. Open your msq. At the top, click 'basic settings' then click 'acceleration wizard'. Then, where it says "decel fuel amount %" enter zero there instead of 60. Done.
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Old 11-20-2008, 02:19 AM   #14
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Quote:
Originally Posted by elesjuan View Post
You realize that factory ECUs have Overrun fuel cut? Whlie it might not be significant, its also a waste of fuel letting the injectors supply the motor with fuel while its decelerating..
I know. I don't concern myself with mileage or the environment. I like it smooth and responsive.
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Old 11-20-2008, 02:38 AM   #15
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I'm going through your MSQ and asking myself some questions about settings.

Are you sure your required fuel is correct? I figured 1849cc, 440cc, 14.7afr and it comes out to 7.0 when you had 6.1. I'm not 100% sure my 14.7 figure is correct, however. Thats what I've been using. (ninja edit; didn't notice you've got a 1.6, so disregard your required fuel from my suggestions. Yours is correct.)

Another thing I found is your TPSDot numbers:



My TPSDot Numbers:



What I would try is go in and add the ms values in the right column next to each value, change your TPSdot Threshold V/S to 1.0 (rounds to 0.977), adjust your decel fuel amount to 100, check and make sure your overrun fuel cut is still set and try again. I'm suggesting these settings because thats whats given me success so its worth a shot, but may not be 100% accurate. Since you're actually using a TPS you need the ms values in there I believe, and straight out of the megamanual:

Quote:
The first thing to set is your TPSdot threshold (V/s). This setting determines the rate at which acceleration enrichment begins. If you set it too high, no accel enrichments will be applied, and the engine may respond poorly, backfiring or coughing under sudden throttle movements. If you set it too low, however, you may have inadvertent enrichment triggered by noise on the TPS signal. In general, use a setting between 1.00 and 2.00 (MegaTune may round these number slightly) - start with 1.00 unless you have a reason to do otherwise (it will be rounded to 0.977, which is fine). Check you datalogs to see if the accel enrichment is being triggered when you don't want it to be (like at idle). This will show up as very large jumps in the pulse width for no apparent reason (though later versions of MSLVV will show the Accel indicator).
I can't guarantee these will fix it, but I'm doing my best to help ya out. Hope this works!!
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Old 11-20-2008, 02:49 AM   #16
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I've tried the MLV approach in a big way too. OK, in a stupidly obsessive way. I'm on my 104th iteration. It gives me funny results that make me think I have a problem. I mean, the car has a problem.

I get a table like this. Lean tip-in causes the high values on the low RPM high kPa area. Fueling DECREASES to the right. Sort of like fuel pressure is building. Then as I lift the throttle and head down in MAP i get this need for lean.

What do we call this, anyway? We've got lean tip-in and ... rich bog-off?

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Old 11-20-2008, 03:19 AM   #17
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thanks for the suggestion elesjuan. I think those numbers in the right column will only add fuel - or do they work the other way too? ie. subtract fuel if v/s is negative? i ran a test on this and think it only adds.

you're right on the same track as me on that megamanual quote - the reason i have all those 0's in there is to make sure I don't suffer from inadvertent enrichment. even if I trigger accel enrich, no extra fuel would be added. working on getting rid of the rich. but I'm willing to give your settings a shot - will scale them by our req_fuel ratios.

any votes at all for the FPR? i have an extra that came with the turbo, but it's rising rate so I'd be back to the drawing board with tuning.
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Old 11-20-2008, 03:36 AM   #18
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Quote:
Originally Posted by patsmx5 View Post
I like it smooth and responsive.
uh, me too.

anyway, I'll give 0 a shot as well. like braineack said though, it's cutting fuel like crazy.
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