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Old 11-09-2006, 01:24 AM   #1
akira02rex
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Default What do you think of running this lean?

Today I logged my AFRs to check up on my tuning to see if it's consistent since MAF calibration/injector scaling is a bitch.
To my surprise my engine is running at 11.9 to 12:1 at 6k rpms lol.
I was running 11.4:1 at peak torque though so that was good.
This was on 22psi! eek! My timing was pulled way back by the ECU to 6deg at peak torque area and 19deg at 6k rpm. I heard a slight pinging when I did the pull.

The funny thing is, I just went on a long cruise beating the car badly through back roads. It's a good thing I turned the boost down to 20psi and only floored it probably less than 5 times or else this engine would probably be toasted now!

Has anyone tried running 12:1 with a lot less timing and less boost with good results?
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Old 11-09-2006, 09:20 AM   #2
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How do your EGTs look? I've run in the 12's at peak torque, but usually hit 11.5:1 or so at redline.

I've had good luck picking a target EGT (around 1600) and then removing fuel until I reach it. While removing fuel, you will have to remove timing which will cause EGTs to climb up, which will require more fuel and more timing.

At 22psi on 93 octane, I think I was runing around 11-12 degrees of timing at peak torque. Now, with water/meth injection, I've cranked the boost to around 27psi at peak torque and run 13-14 degrees. I'd much rather run more boost than more timing to make power. AFRs are not 12.5:1 across the board. EGTs don't get above 1550. I think it's still a touch rich......

Mike
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Old 11-09-2006, 02:12 PM   #3
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mike do you have a trap im just curious
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Old 11-09-2006, 05:44 PM   #4
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i trapped 103 on a 110 degree day. that was on par with stg2 stis. the biggest problem i was having was the POS ebay intercooler heatsoaking. i since then added a shroud which dropped outlet temps considerably. haven't been back to the track since (4th gear synchro is done and so is my clutch)

that was before the water/meth and header too. at that point i think i was seeing 4.64 mafV peak. now, i am seeing 4.7.

hopefully, i'll have a new tranny for next season and we can see what it will do.

also, to put things in perspective, my friend was trapping low 100's all day. i drove his car and managed mid 90's. i'm not a very good drag racer.

as an aside, i think the best tuning advice i was ever given was 'do what makes the car happy.' if you have a motor with good VE you don't need a lot of fuel or timing to make power. there is also more than one way to make power- when you can cool down the charge coming out of the turbo, you don't improve the efficiency of the turbo, but you do improve the efficiency of the whole system and that's what matters. my view is to run the turbo for all it's worth (assuming you can consistently cool the charge) and then make power using fueling and lastly, timing.

hth
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Old 11-10-2006, 02:23 AM   #5
Spec C Wannabe
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Quote:
Originally Posted by crazymikie View Post
How do your EGTs look? I've run in the 12's at peak torque, but usually hit 11.5:1 or so at redline.

I've had good luck picking a target EGT (around 1600) and then removing fuel until I reach it. While removing fuel, you will have to remove timing which will cause EGTs to climb up, which will require more fuel and more timing.

At 22psi on 93 octane, I think I was runing around 11-12 degrees of timing at peak torque. Now, with water/meth injection, I've cranked the boost to around 27psi at peak torque and run 13-14 degrees. I'd much rather run more boost than more timing to make power. AFRs are not 12.5:1 across the board. EGTs don't get above 1550. I think it's still a touch rich......

Mike

Is Timing you mentioned above the total timing (ie; Base timing + Igniton Correction) or Just Igniton Correction?
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Old 11-10-2006, 10:20 AM   #6
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Quote:
Originally Posted by crazymikie View Post
my view is to run the turbo for all it's worth (assuming you can consistently cool the charge) and then make power using fueling and lastly, timing.
fwiw, that's my method as well. i guess i'm crazy too?
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Old 11-12-2006, 10:10 AM   #7
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And you are probably on E10 gas so figure that you are even 1/2 point more lean then what you think.

t
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Old 11-12-2006, 01:15 PM   #8
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Because my wideband is lying right?
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Old 11-12-2006, 03:30 PM   #9
JMK508
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These AFR's are with no ALKY.......seems a little high huh....
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Old 11-12-2006, 05:57 PM   #10
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Quote:
Originally Posted by akira02rex View Post
Because my wideband is lying right?
If you are asking that question then you obviously have no idea what I am talking about and you don't understand the relationship of which I speak. E10 gas has a different lambda calibration on the wideband than regular gas. Read up. Research. For example, those who try to shoot for 11:1 AFRs need to actually shoot for about 10.6:1 AFRs on E10 unless you reset the wideband for E10. Cobb has a good worksheet for this ...

Check out the worksheet, the E85 tab. They have a listing for E10 on there too.
http://www.cobbforums.com/forums/showthread.php?t=31091
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Old 11-12-2006, 08:18 PM   #11
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A wideband O2 sensor can measure Ethanol you idiot..or any fuel for the matter.
Ethanol just needs to be run richer because it's "stoichiometric burn" is a LOT richer than gasoline. It's called an O2 sensor because it measures OXYGEN, NOT FUEL! ARE YOU ****ING RETARDED? "then you obviously have no idea what I am talking about" anything else you want to add?
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Old 11-12-2006, 10:44 PM   #12
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WOE!! Sits back with popcorn..
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Old 11-12-2006, 10:50 PM   #13
akira02rex
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More info taken from another site if you don't beleive me: "The oxygen sensor is a measuring probe for determining the oxygen content of the exhaust gas. Since the amount of oxygen in the exhaust gas indicates precisely how complete the combustion of the air-fuel mixture in the cylinders is, it is also the best starting point for controlling the. air-fuel ratio."
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Old 11-12-2006, 10:51 PM   #14
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Oh, and a wiki for you as well :
http://en.wikipedia.org/wiki/Oxygen_sensor
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Old 11-12-2006, 10:53 PM   #15
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Damnit...My FUEL SENSOR went bad guys..I was running too much Ethanol.. ugh!



hahaha...
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Old 11-13-2006, 01:14 AM   #16
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Regarding the general abuse over the oxygen sensor -- all F/A sensors I've ever worked with do, in fact, measure excess oxygen content. As such, they measure the completeness of combustion and output a signal proportional to equivalence ratio (lambda or phi, depending onm who gets to be on top). I'll also note that there is a significant temperature and pressure effect on the reading due to oxygen diffusion rates, but that's a different story.

Anyhow, for any fuel, the sensor will show the "correct" lambda, but most monitoring software that converts this info into A/F ratio makes an assumption about the fuel used. For example, if you're spot on stoich, you have lambda of 1.00 (lets pretend this is 2.0V output on the sensor). If you're running normal street fuel, that means stoich is ~14.7:1 so in this case 2.0V = 1.00 lambda = 14.7:1.

If instead you're running pure ethanol with a stoich F/A of 9.0:1, the same 2.0V output would still equal a lambda of 1.00, but this would in fact occur at 9.0:1 AFR. However, most ECU monitor programs would still display this as 14.7:1 since they assume petrol....Bottom line, lambda is a more reliable (and accurate) measure.

On a different front, there are disticint differences in the cooling capacity of ethanol versus petrol such that a lambda of 0.80 may keep your EGT's nice and happy on one fuel, but may melt stuff on the other (I forget which one has better cooling capacity, but I think it was petrol due to the higher heat ov vaporization ?)


Meanwhile, back to the OP questions -- as crazymike asserts, if your EGT's and turbine inlet temps are happy, you're safe at those AFR's. The balance of boost pressure, timing, and fueling for best power is not straight-forward though. You may be able to benefit with richer fueling and more spark (knock limit moving) but at 12:1 you should have a decent fuel economy/power tradeoff....
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Old 11-13-2006, 09:02 AM   #17
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Duh - of course it measures oxygen. I never said it measured fuel. Classic NASIOC retard'etry. So quick to jump and you have no idea. Dude, I've been tuning and working on cars for a long time. Everything you said is nothing new to me. Stop being a classic NASIOC retard.

Again, you need to recalibrate the O2 sensor for the fuel you are using. Simple as that. Different fuels contain different levels of oxygen. Duh. Lambda is different for different fuels. Simple as that. How is that so hard for you to understand?

Join the E85 thread you retard.

http://forums.nasioc.com/forums/showpost.php?p=14320135
http://forums.nasioc.com/forums/show...&postcount=487

t

Last edited by WolfPlayer; 11-13-2006 at 09:09 AM.
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Old 11-13-2006, 10:10 AM   #18
ride5000
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Quote:
Originally Posted by WolfPlayer View Post
Again, you need to recalibrate the O2 sensor for the fuel you are using.
why is that?

Quote:
Different fuels contain different levels of oxygen. Duh. Lambda is different for different fuels.
i disagree. lambda is lambda. lambda = 1 = stoich is always true--by definition. therefore, since our widebands convert lambda to a DISPLAYED afr, no matter what fuel you're using, if you read 14.7:1 on the wideband you're running stoich--it doesn't matter what's being squirted in the cylinders. as you said, it's as simple as that.

i've already mentioned this in another thread, but i've used concentrations of around 25% methanol right in my gas tank (ie M25). my displayed afr went about a point and a half leaner, from mid 11s to high 12s. however, my injected fuel to air ratio stayed the same, despite the difference in the gauge. i could tell this because IDCs didn't change for a given rpm/load. i made run after run with this mix in the tank. egts were not out of control. the car tolerated MORE advance despite the "too lean" afrs. the only reason it read lean is because some of the large HC molecules of gasoline were displaced by methanol molecules which not only contained less HC but also contained O. more O in the tailpipe means a higher read lambda which means a higher displayed afr... but the injected liquid fuel to air ratio did not change.

it is my contention that what we're really targeting is a particular liquid to air ratio, not a particular oxygen concentration in the tail pipe. liquid gasoline may be replaced by alcohol and/or water and the combustion stabilizing cooling and/or knock buffering effects are still realized, despite a shift in leftover oxygen.

i am curious as to why you state "you are probably on E10 gas so figure that you are even 1/2 point more lean then what you think." lean with respect to what? a liquid to air ratio? a leftover oxygen ratio?

you also state "those who try to shoot for 11:1 AFRs need to actually shoot for about 10.6:1 AFRs on E10 unless you reset the wideband for E10." this statement in isolation means nothing. when someone shoots for an 11:1 indicated afr, what are they actually targeting? the tools we have only indicate leftover o2, therefore targeting a particular AFR means we are targeting a particular leftover o2 level.

it should be obvious that i don't care very much at all about how much leftover o2 there is in the tailpipe. i care about cooling the charge, cooling the cylinder, cramming o2 and HCs into the chamber, and buffering the combustion process enough so that it can be lit off in a controlled manner.

comments?
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Old 11-13-2006, 10:16 AM   #19
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Hehe I was a bit tipsy when I wrote all of that up there!!
Sorry I got all over your ass about it.
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