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How lean is too lean for idling?

 
Old 07-02-2015, 03:37 PM
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Default How lean is too lean for idling?

My '00 is idling at 16.0 to 16.8 AFR. Im currently all stock with MSPNP2. I set the base timing and have a good AFR table and Fuel VE table (I think). The car is idling fine, no sputters and no knocking but I'm very skeptical to drive it. I took it out for a quick spin and when i give it full throttle it drops down to 10.5-11.1 AFR according to my wideband gauge. I used VE analyze but it only made it leaner and it idled like crap.
Why is it not staying within my AFR Table??


Here's my AFR table


Here's my Fuel VE table
Attached Thumbnails How lean is too lean for idling?-afr%2520table%2520_zpsgtzpspyw.png   How lean is too lean for idling?-fuel%2520ve%2520table_zpsv83yiltg.png  
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Old 07-02-2015, 03:54 PM
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VEAL won't work for idle. Idle has to be done manually.

Before you start tuning, make sure you use the "Incorporate AFR into fuel table". If not, you'll have to redo your entire map.

The pro's of using Incorporate is that when you want to change something, you'll only have to change your AFR map, instead of the VE map. Will make your life easier when you get the MS dialed in.

Also, you want idle as lean as possible, but keep in mind that timing, and loads (power steering at full lock, A/C on) is going to affect idle.

So I have my idle roughly 14:1 but I live in TX so I need A/C. My A/C virtually on all the time, and I couldn't deal with it sputtering when A/C first kicks on.
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Old 07-02-2015, 03:57 PM
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Dont let VEAL tune idle. Lock the cells out. Manually add more fuel in the 700-1000rpm, 20-29kpa cells. I use to idle rich 14ish with MS2, idle control is far better in MS3 so now 14.7 is fine.
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Old 07-02-2015, 04:07 PM
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Have you verified that your wideband in tunerstudio is reading the same as the wideband gauge? I've always had to mess with mine to get it reading correctly, and if that's the problem your tune will never be right until you adjust it in tunerstudio.

I use megalogviewer instead of analyze live, but it always seems to want to pull fuel from those low kpa cells so I just tune those manually and set the software to ignore anything below ~30kpa. Not really a solution, but a nice bandaid at least.
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Old 07-02-2015, 04:39 PM
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Originally Posted by pdexta View Post
... it always seems to want to pull fuel from those low kpa cells so I just tune those manually and set the software to ignore anything below ~30kpa. Not really a solution, but a nice bandaid at least.
You are not the first person I'm aware of who does the same.

Originally Posted by armfish02
Why is it not staying within my AFR Table??
I just got done screwing with this so its fresh in my mind. Does it lean out when it gets hot? I'm not sure what firmware the MSPNP2 is using, but look for the "MAT Air Density Table" (pulls fuel based on higher IAT) and "MAT-Based Timing Retard" (pulls timing based on higher IAT) as these both caused my displayed ARFs to not jive with my AFR Targets. Its in the last couple pages of my build thread.
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Old 07-02-2015, 08:41 PM
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<p>I manually tune idle VE cells to the AFR that produces the most vacuum (lowest MAP kPa values).&nbsp; The exact AFR is unimportant to me, so long as it seems reasonable.&nbsp;</p><p>I'm assuming your car is a n/a 2000? based on your AFR targets.&nbsp; 11:1 is really rich.&nbsp;</p><p>&nbsp;</p><p>&nbsp;</p>
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Old 07-03-2015, 03:36 AM
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Originally Posted by pdexta View Post
Have you verified that your wideband in tunerstudio is reading the same as the wideband gauge?
tunerstudio reads 11.1 all the time. My gauge and controller are both grounded to the block by the CAS and im getting 12v from the power window switch. The output wire is going to the secondary o2 pin (because CA spec) EGO2 i believe. my gauge was reading the correct AFR's with the stock ECU and i was only getting the CEL for the heater circuit.
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Old 07-03-2015, 09:35 AM
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you connected the WBo2 to the rear o2 wire?
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Old 07-03-2015, 11:57 AM
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Originally Posted by Braineack View Post
you connected the WBo2 to the rear o2 wire?
Yes because my car is ca spec and the primary o2 sensor is right in the exhaust manifold and the secondary is after the cat. The exhaust system is totally different than the fed spec.

Here's a diagram
http://i155.photobucket.com/albums/s309/shoult/Misc/1999-2000-CASpecExhaust.jpg
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Old 07-07-2015, 07:18 AM
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Why would you actually want to read after the cat?

The whole point of the rear o2 is to determine if the cat burned up all the extra goodies in the exhaust after the combustion.

The whole point of a wideband is to determine exactly how much fuel you are burning.

If you put the wideband after the cat, a point where extra gas gets burned in the catalyst, how are you going to know exactly how much fuel you are combusting? (answers your thread title btw)

Furthermore, the MS doesn't even connect to rear o2 sensor, so it has no way of reading the wbo2 signal because that's not where it's looking for it...

it needs to connect to the front o2 input, or the optional wbo2 input on the extra connector.


(yes, I realize the rear o2 of the CA spec is in the same relative location as the front o2 of non-CA spec)
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Old 07-07-2015, 10:49 AM
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<p>If you care about the environment and have your CAT still try to keep your idle&nbsp;near 14.7 for best emissions. If it's not happy there then slightly richer until it is.&nbsp;</p><p>&nbsp;</p><p>Having your O2 sensor post CAT effctively dampens your signal and slows down the response time. But overall your reading will still be accurate. You just might not be able to EGO Correct the transients as quickly. (edit: this <span style="color:rgb(34, 34, 34)">presupposes&nbsp;</span>that its wired correctly)</p>
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Old 07-07-2015, 11:02 AM
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The post cat reading will ALWAYS be leaner due to the nature of converting hydrocarbons which changes the make-up of the exhaust from converting o2 into co2 and thus alters the oxygen reading. crazy enough, o2 sensors read o2--alter the o2 in the exhaust and you dun gone screwed up your afr reading.

it's not linear and the amount difference pre/post has no rule-of-thumb.

that being said, I always saw a good 1 AFR difference lean on post-cat readings.


It's odd you'd go with saying that it changes the response time (something probably unmeasurable) but does not change the afr reading (something measureable and backed by basic chemistry)...

Last edited by Braineack; 07-07-2015 at 11:15 AM.
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Old 07-07-2015, 11:15 AM
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Originally Posted by armfish02 View Post
Yes because my car is ca spec and the primary o2 sensor is right in the exhaust manifold and the secondary is after the cat. The exhaust system is totally different than the fed spec.
To clarify:

Did you merely hijack the rear O2 sensor wire, or did you actually install the wideband sensor itself into the rear O2 sensor hole?

If the latter, what's been said above is correct. You need to have the wideband O2 sensor installed upstream of all catalytic converters if you expect it to produce accurate readings. No exceptions. This is the whole reason that automakers put that second sensor there in the first place- it's supposed to read artificially lean; this verifies that the catalytic converter is actually working, as required per the OBD-II standard.

If you're concerned about heat given the close proximity of the forward sensor hole to the exhaust ports*, there are spacers / heatsinks which can be installed between the sensor and the manifold:
Amazon.com: Innovate Motorsports 3729 Heat-Sink Bung Extender HBX-1: Automotive Amazon.com: Innovate Motorsports 3729 Heat-Sink Bung Extender HBX-1: Automotive

You can also fabricate your own: Innovative performance O2 sensor heat sensitive in Hyundai Genesis Coupe - Torque News






* = I've always been curious about this. Does the exhaust stream really lose a meaningful amount of heat over the 12-18 inches or so between the header merge and the location in which we traditionally mount the sensor in single-cat cars? Has anyone ever actually documented this?
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Old 07-07-2015, 11:19 AM
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I feel like that copper "heat sink" is actually a "heat shield" more than anything else.
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Old 07-07-2015, 11:26 AM
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no, it's a sink. touch a sensor once it's warmed up, then the exhaust. which hurt less?

also I love when JP agrees with me in the morning...
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Old 07-07-2015, 11:45 AM
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<p>
Originally Posted by Braineack View Post
The post cat reading will ALWAYS be leaner due to the nature of converting hydrocarbons which changes the make-up of the exhaust from converting o2 into co2 and thus alters the oxygen reading. crazy enough, o2 sensors read o2--alter the o2 in the exhaust and you dun gone screwed up your afr reading. it's not linear and the amount difference pre/post has no rule-of-thumb. that being said, I always saw a good 1 AFR difference lean on post-cat readings. It's odd you'd go with saying that it changes the response time (something probably unmeasurable) but does not change the afr reading (something measureable and backed by basic chemistry)...
</p><p>&nbsp;</p><p>I'll post the page I read that from the Bosch Engine Managment book when I get home. Basicly the Cat converter is chemical balance between Reduction of NOx and Oxidation of HC and CO. There is no net Oxygen generation or reduction in the balance of the system. Your O2 sensor is an excess oxygen measuring device that does not change readings in the &quot;medium term&quot; for pre and post cat.&nbsp;</p><p>&nbsp;</p><p>There's a neat graph overlaying pre and post cat O2 reading on the same pipe with the pre cat O2 oscillating and a higher amplitude with the exact same mean value of the post cat O2 sensor which has small amplitude of oscillations. Hence the dampening effect.&nbsp;</p>
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Old 07-07-2015, 11:49 AM
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Oh, I'm sure it does both. I'm not gonna take that dare.

I have a fancy round brass one I've been using and will continue to use. I'm sure it works fine/
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Old 07-07-2015, 12:40 PM
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If you have a combustion that produces: CO2 + H2O + NO2 + 2CO + HC + O2 + N2

then you pass that through a cat, the Nitron rips from the oxygen and pairs with the nitro and the N + NO2 becomes: 2N + O2

so: CO2 + H2O + 2N + 2CO + HC + 2O2

then the oxygen combines with the carbon monoxide...

so: 5CO2 + H2O + 2N + HC


how will an O2 sensor produce the same voltage when the O2 from pre to post has now gone from 1 part to 0 parts even though there was no net O2 generation or reduction in the balance of the system?
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Old 07-07-2015, 12:45 PM
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Originally Posted by Braineack View Post
If you have a combustion that produces: CO2 + H2O + NO2 + 2CO + HC + O2 + N2

then you pass that through a cat, the Nitron rips from the oxygen and pairs with the nitro and the N + NO2 becomes: 2N + O2

so: CO2 + H2O + 2N + 2CO + HC + 2O2

then the oxygen combines with the carbon monoxide...

so: 5CO2 + H2O + 2N + HC
+ for science.



However, further reading: http://www.dtec.net.au/Lambda%20Test...0Converter.htm
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Old 07-07-2015, 12:56 PM
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<p>
Originally Posted by Braineack View Post
If you have a combustion that produces: CO2 + H2O + NO2 + 2CO + HC + O2 + N2 then you pass that through a cat, the Nitron rips from the oxygen and pairs with the nitro and the N + NO2 becomes: 2N + O2 so: CO2 + H2O + 2N + 2CO + HC + 2O2 then the oxygen combines with the carbon monoxide... so: 5CO2 + H2O + 2N + HC how will an O2 sensor produce the same voltage when the O2 from pre to post has now gone from 1 part to 0 parts even though there was no net O2 generation or reduction in the balance of the system?
</p><p>&nbsp;</p><p>The ratio of NO,&nbsp;NO2 &amp; NO3&nbsp;that gets reduced compared to the CO and HC that get oxidized?&nbsp;</p>
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