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Old 10-01-2002, 04:39 PM   #1
n2xlr8n
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Default UTEC "Rich" indication in A/F

Hey guys, I was reading the thread mentioning this subject, and figured rather than hijack......
Can I use the "rich" indication to tune? So far, I've crept up on everything (boost~16 psi max, 24 deg @ 7000, less than "1" in every fuel column past load point) and it STILL shows rich all the way. My injectors are showing better than 90%, so rails and injectors will be my next step before I dial in additional boost (or even run it hard). If I'm that rich, will pulling fuel out of the map help the injector duty cycle enough to get out the low 90% range? I'll log some tonight and bring them to work for your viewing pleasure. Thanks for the input! BTW, my mods are:

Turbo Specialties 16G @ 20 psi
TXS STG 4
Samcos / K&N
Godspeed uppipe
Walbro GS344
Perrin rails / STi injectors
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Edit: updated mods for current data
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Last edited by n2xlr8n; 04-15-2003 at 03:07 PM.
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Old 10-01-2002, 04:50 PM   #2
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Absolutely...

Just remember... RICH will still show up at 11.172:1

It's typically understood that 10.5:1 is decently safe. 11:1 would not be bad... if you can tune so you are RIGHT on that border of 11.172:1 your making pretty damn good power, but you'll be running pretty hot in the EGT's... as a result, you will have less room for failure.

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Old 10-01-2002, 05:16 PM   #3
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Quote:
Originally posted by RiftsWRX
Just remember... RICH will still show up at 11.172:1

It's typically understood that 10.5:1 is decently safe. 11:1 would not be bad... if you can tune so you are RIGHT on that border of 11.172:1 your making pretty damn good power, but you'll be running pretty hot in the EGT's... as a result, you will have less room for failure.[/url]
RiftsWRX, would I be safe to assume that whenever the UTEC says "RICH," a DeltaDash would report an A/F Sensor #1 value of .76 (i.e. Lambda=0.76)? Would I also be safe in assuming that the UTEC and the DeltaDash obtain their estimates of A/F ratio using, essentially, the same technique?

Last edited by Jon [in CT]; 10-01-2002 at 05:22 PM.
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Old 10-01-2002, 05:18 PM   #4
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Thumbs up

Thanks, Jorge. So if I understood you right, 11.173:1 will NOT show up as "rich", but you'd better be spot on tune to run there, correct?
Thanks for the help!
IMO, the UTEC is BY FAR the best $999 I have ever spent on a car, bar none. The car is totally different to drive; it should have come this way from the factory!
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Old 10-01-2002, 05:24 PM   #5
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Thumbs up Good question

Quote:
Originally posted by Jon [in CT]
RiftsWRX, would I be safe to assume that whenever the UTEC says "RICH," a DeltaDash would report an A/F Sensor #1 value of .76 (i.e. Lambda=0.76)? Would I also be safe in assuming that the UTEC and the DeltaDash obtain their estimates of A/F ratio in essentially the same manner?
I'd also like to know the correlation between the mv output of the factory WB and Stoich. Can you guys give the long/short of it? Thanks!
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Old 10-01-2002, 05:35 PM   #6
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Quote:
Originally posted by Jon [in CT]
RiftsWRX, would I be safe to assume that whenever the UTEC says "RICH," a DeltaDash would report an A/F Sensor #1 value of .76 (i.e. Lambda=0.76)? Would I also be safe in assuming that the UTEC and the DeltaDash obtain their estimates of A/F ratio using, essentially, the same technique?
I don't really know how the DD does it. But in essense the milivolt readings from the sensor are used to calculate that on the UTEC.

and yes.... FWIW, basically .76 was used as the same ceiling (from what I've logged and seen)

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Old 10-01-2002, 06:56 PM   #7
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Quote:
Originally posted by RiftsWRX


I don't really know how the DD does it. But in essense the milivolt readings from the sensor are used to calculate that on the UTEC.

and yes.... FWIW, basically .76 was used as the same ceiling (from what I've logged and seen)

Jorge (RiftsWRX)
www.ProjectWRX.com
The DeltaDash uses pins 4, 5 and 6 of the Data Link Connector to poll the stock ECU for A/F Sensor #1 lambda numbers. Although the WRX's front A/F sensor's signal wires pass through the UTEC, I believe the UTEC can do nothing with them but, instead, polls the stock ECU for A/F Sensor #1 lambda numbers (just like the DeltaDash) by using those same three wires from the Data Link Connector (which also pass through the UTEC). I also believe the UTEC uses this "polling-the-stock-ECU" technique to acquire values for intake air, exhaust, and coolant temperatures.

I appologize for assuming that you were aware of the UTEC's inner details and that you'd been instructed not to reveal certain "features" of the UTEC.
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Old 10-01-2002, 07:09 PM   #8
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Default Good info, but...

What I was asking was the correlation (or scale) between the mv output of the factory WBO2 and 14.7? doyuoknow doyouknow doyouknow? Thanks!
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Old 10-01-2002, 07:32 PM   #9
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so jorge, how do you know if you're stinky rich (i.e, 9:1) or even lower? Would you tune to 11.2 and then back off a bit to get back into the "rich" range. Its seems like a real crapshoot. it seems its easy to prevent going too lean with the utec but what about going too rich??

jc
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Old 10-01-2002, 07:46 PM   #10
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Default Not to butt in or anything, butt..

Quote:
Originally posted by thejean
so jorge, how do you know if you're stinky rich (i.e, 9:1) or even lower? Would you tune to 11.2 and then back off a bit to get back into the "rich" range. Its seems like a real crapshoot. it seems its easy to prevent going too lean with the utec but what about going too rich??

jc
From what I've gleaned from tuning / listening, it's safer to run more timing / boost "rich" than it is advantageous to go leaner than 12.0 with less boost / timing. I'm saving my tune showing "rich", watching the EGT and knock, and lettin' 'er eat. (when I get my fuel system where I need it, that is.)
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Old 10-01-2002, 07:46 PM   #11
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Default Re: Good info, but...

Quote:
Originally posted by n2xlr8n
What I was asking was the correlation (or scale) between the mv output of the factory WBO2 and 14.7? doyuoknow doyouknow doyouknow? Thanks!
The WRX's front A/F sensor doesn't work like most 0-1V oxygen sensors. The factory ECU supplies positive voltage TO the sensor down both wires (+ and -). The factory ECU then measures the resulting current flow through the sensor. The current flow is the sensor's "signal," not voltage.

The relationship between current and lambda looks like this:


I don't believe that the UTEC can measure this current without either disturbing it or changing the circuit's resistance (which the stock ECU also needs) and, therefore, without interfering with the stock ECU's closed-loop A/F control ability. This is why I believe the UTEC must poll the stock ECU (using the DeltaDash/Select Monitor interface) in order to obtain A/F values. I hold a similar view for all of the WRX's resistance-based temperature sensors (IAT, EGT, Coolant).
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Old 10-01-2002, 08:07 PM   #12
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Default Re: Not to butt in or anything, butt..

Quote:
Originally posted by n2xlr8n


From what I've gleaned from tuning / listening, it's safer to run more timing / boost "rich" than it is advantageous to go leaner than 12.0 with less boost / timing. I'm saving my tune showing "rich", watching the EGT and knock, and lettin' 'er eat. (when I get my fuel system where I need it, that is.)
agreed. but what i'm wondering is how you know exactly how rich you are. for istance, being too rich can almost be as bad as being too lean. your car will not run well and unburnt fuel in the exhaust can lead to high egt's as well (or so i've read).

jc
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Old 10-01-2002, 08:48 PM   #13
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Default Re: Re: Not to butt in or anything, butt..

Quote:
Originally posted by thejean


agreed. but what i'm wondering is how you know exactly how rich you are. for istance, being too rich can almost be as bad as being too lean. your car will not run well and unburnt fuel in the exhaust can lead to high egt's as well (or so i've read).

jc
Exactly how rich I am is what I'm trying to get from Jon or Jorge (by interpolating the mv value of the WBO2 as seen by the UTEC)....I don't think I'm anywhere near the "unburnt fuel in the exhaust" stage or "high EGTs", simply because my EGTs are still around 1400F at max boost, and there is no evidence of detonation (which can also occur when too rich). Your concerned is well aimed, though...... Keep up the dialogue, JC, you are one of the most diligent hungry-for-facts person on this forum.
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Old 10-01-2002, 10:35 PM   #14
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Correct me if im wrong.
But you guys are using the stock o2 sensor as a tuning tool here?
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Old 10-01-2002, 11:05 PM   #15
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Default Re: Re: Re: Not to butt in or anything, butt..

Quote:
Originally posted by n2xlr8n

Exactly how rich I am is what I'm trying to get from Jon or Jorge (by interpolating the mv value of the WBO2 as seen by the UTEC)....I don't think I'm anywhere near the "unburnt fuel in the exhaust" stage or "high EGTs", simply because my EGTs are still around 1400F at max boost, and there is no evidence of detonation (which can also occur when too rich). Your concerned is well aimed, though...... Keep up the dialogue, JC, you are one of the most diligent hungry-for-facts person on this forum.
thanks, its nice to be appreciated! anyway, based on Jon's graph, it appears that the breakpoint in the curve is about 12:1 and you would go very rich, very quick beyond -13mA. direct interpolation will not work. extrapolation will however. but, basically, if you keep the amperage greater than -15mA, you'll be above 10:1 which is fine. so, tune for "rich" with a front 02 sensor amperage greater than -15mA? Is this what I'm reading out of all this?

the chart quickly shows why the stock lamda value goes srewy at A/F's less than 11.2:1. the stock ecu algorithm likley has an equation to describe the relationship Jon showed at more than 12:1. now, if you extrapolate that curve to left according to the same trend that is exhibited above 12:1, you can see how the equation would not report accurate A/F's.

TXS, i hope your listening to this next statement... I believe that you don't need an upgrade for the UTEC. Mathematically, we could estimate the curve that the stock ECU would follow and looking at the actual curve that Jon posted we could figure out an equation to describe the correction factor when A/F's are less than 11.2:1. Then, just program this into the UTEC and there you go, you can now measure A/F's down to at least 10:1 and maybe even lower. Yuo could even go lower than that but granted, it would be a little more "blind" as we don't have a curve for that area. plus, the current would become close to the -15mA limit. Can anyone comment if this truly is a limit or just a function of the presentation of the graph? Jon?

jc
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Old 10-01-2002, 11:17 PM   #16
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I'm not really sure I agree about unburnt fuel in the exhaust raising EGT's. I've had my car running so rich lately you could light the exhaust fumes, and my EGT's are still below 1450F in the uppipe at WOT. Either that, or yet another (this would make 3 of 3) of my Dakota Digital gauges is reading incorrectly.
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Old 10-02-2002, 12:19 AM   #17
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Quote:
Originally posted by SFastWRX
I'm not really sure I agree about unburnt fuel in the exhaust raising EGT's. I've had my car running so rich lately you could light the exhaust fumes, and my EGT's are still below 1450F in the uppipe at WOT. Either that, or yet another (this would make 3 of 3) of my Dakota Digital gauges is reading incorrectly.
do you have a catless up-pipe? the precat seems to aggravate this somewhat. now, i haven't personally experienced but i read some theories on it. is it correct? i'll be honest, i don't know. but, it does make sense to a certain degree. i think AZScoobie brought it up once in a very early EGT thread. if you want more info, i can try to find the thread for you. otherwise, we should try to stay on topic... We don't want to get accused of hijacking now do we?

JC
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Old 04-15-2003, 12:00 PM   #18
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long time bump... because the A/F statement thejean made is still pending in my mind... and still worthy of discussion.

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Old 04-15-2003, 03:03 PM   #19
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Default Re: Re: Re: Re: Not to butt in or anything, butt..

Quote:
Originally posted by thejean



TXS, i hope your listening to this next statement... I believe that you don't need an upgrade for the UTEC. Mathematically, we could estimate the curve that the stock ECU would follow and looking at the actual curve that Jon posted we could figure out an equation to describe the correction factor when A/F's are less than 11.2:1. Then, just program this into the UTEC and there you go, you can now measure A/F's down to at least 10:1 and maybe even lower. Yuo could even go lower than that but granted, it would be a little more "blind" as we don't have a curve for that area. plus, the current would become close to the -15mA limit. Can anyone comment if this truly is a limit or just a function of the presentation of the graph? Jon?

jc
You mean that one?

Me too; I was under the impression that we weren't able to use the stock front O2 because of it's limitations, but if someone (Pete) were to extrapolate the curve and add the data to the UTEC's firmware, that would be handy.
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Old 04-15-2003, 05:07 PM   #20
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The stock WB02 was never intended to be used when in a pressurized environment. It's likely not very accurate in such an environment. Much testing should be done, comparing to a reference WB02, before deciding that the values it reports are useful for tuning.
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Old 04-15-2003, 05:24 PM   #21
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Quote:
Originally posted by D_REX
The stock WB02 was never intended to be used when in a pressurized environment.
/Southern slang on/ Do what? /sso/

How would a WBO2 work in a vacuum? Or at ambient pressure?
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Old 04-15-2003, 05:50 PM   #22
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Default Re: Re: Good info, but...

Quote:
Originally posted by Jon [in CT]

I don't believe that the UTEC can measure this current without either disturbing it or changing the circuit's resistance (which the stock ECU also needs) and, therefore, without interfering with the stock ECU's closed-loop A/F control ability. This is why I believe the UTEC must poll the stock ECU (using the DeltaDash/Select Monitor interface) in order to obtain A/F values. I hold a similar view for all of the WRX's resistance-based temperature sensors (IAT, EGT, Coolant).
Hmm, that seems to make sense. Can anyone confirm/deny this theory?
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Old 04-15-2003, 06:11 PM   #23
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Quote:
Originally posted by n2xlr8n


/Southern slang on/ Do what? /sso/

How would a WBO2 work in a vacuum? Or at ambient pressure?
Your exhaust manifold is pressurized when the turbo is pressurizing the intake manifold. This doesn't happen in closed loop, where the ECU is monitoring the WB02.
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Old 04-16-2003, 11:12 PM   #24
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You know from tuning a few WRX's I can tell you that rich doesn't actually mean anything concrete. It's simply not accurate enough. I have seen it read rich when the fuel is at 11.8:1 or higher (as measured with the MOTEC AF meter) before so I wouldn't trust it at all. Best to use a wideband O2 if possible.
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Old 04-17-2003, 01:56 PM   #25
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Quote:
Originally posted by god
You know from tuning a few WRX's I can tell you that rich doesn't actually mean anything concrete. It's simply not accurate enough. I have seen it read rich when the fuel is at 11.8:1 or higher (as measured with the MOTEC AF meter) before so I wouldn't trust it at all. Best to use a wideband O2 if possible.
Ditto. I think on clayton's car, it read up to 13:1 A/F from the Dyno. He had tuned it the week before to the 'rich' range with the Utec.

Tom
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