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Discussion Starter · #1 ·
I had a dyno done without the o2 sensor in my 92 gsr. naturally the check engine light came on.

Without the sensor in place the ECU switches over to open loop mode correct? Would this cause a misread in the final numbers due to improper readings of the A/F ratio? Or would the numbers I recieved still be accurate?
 

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your primary O2 sensor is offline at past 3/4 throttle in open loop running off the ignition and fuel maps but there is a transition between closed and open loop, where closed loop effects in OBD1 can affect open loop performance.

that's why the hondata guys tell their customers to deactivate closed loop while fuel tuning to avoid this spillover effect.

Tuning Implications

It is best to disable closed loop operation while tuning. Otherwise what commonly occurs is that the ECU will alter the mixture using the long term adjustment while the car is idling between dyno runs, which means that the mixture is not repeatable between dyno runs.

If changes are made to the engine which alter the amount of fuel that is delivered (bigger injectors, increased fuel pressure or altering the air temperature sensor voltage) the ECU will compensate the best it can using the long term adjustment. Under high load when the ECU stops running in closed loop the long term adjustment is still used so increasing fuel delivery via these means in not recommended unless the ECU is recalibrated or closed loop disabled.

At part load it is best if the ECU is tuned so that the mixture is close to stoichiometric. This reduces the amount of time the ECU will take to use the short term adjustment to alter the mixture to get the oxygen sensor voltage to swing past 0.6V, and keeps the long term adjustment from the zero position.
 

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Discussion Starter · #5 ·
So the numbers i'm getting are accurate then. That is good to know. The other thing I had a question about now that I couldn't find is the stock A/F ratio. Been on g2ic and here and pgfmi searches turn up nothing. Isn't 13.7 scary lean?
 

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I wouldn't rely on narrowband numbers.

they're pretty slow reacting and imprecise.

if you're tuning off the AF ratios invest in a separate wideband and add a second bung in the collector or just before the cat.

use your narrowband for ECU closed loop or you can use an adapter to use the wideband in closed loop.

didn't you read this article???

13.7 isn't scary lean.
what was your engine , oil or coolant temps doing at that time?
 

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Discussion Starter · #7 ·
I read it just now. So when the shop removed my narrowband and inserted it's wideband o2 sensor the readings I have are accurate as this was just a WOT dyno for a baseline no tuning involved.

I'm heading to the shop now to have a secondary bung added because I plan on tuning the car soon. I'm going to check to see if there are other ways of tuning other than A/F ratio. Is there an article I can read that will pertain to that?
 

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not here.

but there's plenty of AF/EGT or AF/engine temp combination tuning methods that you can find on the various stanalones website forum boards like aem ems or pgmfi.org or hondata's.

you don't rely on just AF if you can.

and you look at the effect on the tq curve shape as you change the fueling.

you should use AF and temp as compasses as to whether you continue in 1 direction of fueling or stop rather than targeting a specific AF ratio number.

The tq curve will tell you if you're going in the right direction , the compasses will tell you if you're getting into the danger zone to kaboom.
 

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Nemui on Feb/11/06 said:
I read it just now. So when the shop removed my narrowband and inserted it's wideband o2 sensor the readings I have are accurate as this was just a WOT dyno for a baseline no tuning involved.

I'm heading to the shop now to have a secondary bung added because I plan on tuning the car soon. I'm going to check to see if there are other ways of tuning other than A/F ratio. Is there an article I can read that will pertain to that?
Here you go
http://www.importbuilders.com/tuningacar.htm


BTW 13.7:1 is running more rich not lean.
 

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WildoutWhiteGSR on Feb/11/06 said:
BTW 13.7:1 is running more rich not lean.




compared to stoich...

however, for the working range and safety margins that we use at WOT and at higher rpms, it's considered , relatively speaking, to be on the lean end of the range of tuning Trennell.

for example, you won't see too many FI motors near the redline going leaner than in the 12's AF wise where as NA , including 12:1 CR motors can run a little leaner in reference to that 12 AF range in those higher rpms at WOT. It's a relative scale and depends on what you're reference AF is.

in closed loop 14.7 is your reference point but in open loop that's not the case...so when we say leaner or richer it's relative to something and it's not always the ideal 14.7.
 

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most people advise on the net to aim for 13.0-13.5 AF in the WOT runs.

we're a little different. we say, aim for the best tq, and use the AF together with temp to see if you're getting too close to detonating.

in some i/h/c/e packages, the "general rule" of blindly aiming for 13.0:1 AF doesn't get you the best performance and you still have lots of margin for safety or wiggle room.

it's how close you want to dance on the edge and add a little bit more safety margin.

if it's a high CR motor or FI, you won't play with fire and risk running on the leaner ranges (i.e. > 13.5:1) especially at the top rpms.

you tend to be in the richer end of the range closer to 12-12.5 AF.
 

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I am sorry for the misinformation Lucien. It completely slipped my mind that the stock ECU switches to open loop at 75% throttle.

Since everything is fine, can we boost it now?
 

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Discussion Starter · #20 ·
I lied. I just realized I dyno'd with the bottom half of the stock air box removed and not the 2.5" shorty. Everything else is properly listed. Does that hump indicate that somethign is quirky?

This car has yet to be tuned.
 
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