why is my A/F ratio different from day to day?
 

as the title says....i've been noticing that my A/F ratio fluctuates from time to time. for example, a few nights ago i was doing some data logging and the A/F numbers were consistently under 13:1. the next day, however, i did more pulls and the numbers peaked above 13:1 for awhile which i do not like. the only difference between them was that the first time it was in 3rd gear and the second time it was in 2nd gear. does the ECU automatically richen it up a bit at higher speeds? i'm running an SMC+ for fueling. the temps were about the same even though one was day and one was night bc its winter so its cold all the time https://honda-tech.com/forums/images...s/emsmilep.gif here are some graphs to see what i'm talking about....please give me some input. i'd hate to tune it rich then have it end up in the 11:1 area.

first run:
http://www.we-todd-did-racing.com/we...ZmQzMXk1NDE%3D

second run:
http://www.we-todd-did-racing.com/we...ZmQzMXk1NDE%3D

because A/F ratio guages are inaccurate! and the ratio changes at different altitudes and temperatures,

Re: (rudebwoy)
 

different intake charge temps, heatsoak etc..

Re: (rudebwoy)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rudebwoy &raquo;</TD></TR><TR><TD CLASS="quote">because A/F ratio guages are inaccurate! and the ratio changes at different altitudes and temperatures, </TD></TR></TABLE>

since when? this is a wideband caliberated for my altitude (which doesnt change). and the EGT's should be roughly the same as well.

Re: (rudebwoy)
 

and the maps don't compensate too much for OUTSIDE temperature. The colder it is, the leaner the AF because there is more air per volume. Humidity too. The more humid, the RICHER it would read because the water in the air takes up space so there is LESS air per volume.
But all that is just general. Its more complicated when you put it all together.

Re: (rudebwoy)
 

He says he is datalogging so I'm assuming he tuned it with wideband https://honda-tech.com/forums/images...s/emsmilep.gif

Tuning during the day and night is going to be......well, is going to be 'day n night' difference. You may not notice the difference in temp cos its already so cold as you said but did you measure the difference in the temp during the day and during the night? It could have been considerably colder at night which could be the reason for the inconsistent afr, assuming that you tuned it in the same area and all other conditions are the same (ie, intake, engine bay temps etc...).

Re: (swlabhot)
 

i should probably mention that this is a supercharged setup, so if its -10 outside or 30 above, once the car is warmed up the intake temps are over 100 regardless. thats mainly why i'm not convinced its responsible for the inconsistencies because the IAT sensor sees the same in the end (its after the blower).

Re: (keebler65)
 

So your IAT is reading the true charge temp? The JRSC kits on some cars do not relocate the IAT sensor. They leave it before the supercharger, so it never reads to "real" intake temperature.

The IAT does directly affect the a/f ratio. This can easily be seen via the JR IAT enrichment relay. Once boost kicks in, the relay forces the IAT up to 5 volts...forcing the ECU to see the coldest temp possible. It's a cheap and dirty way to richen up the mixture. The problem is, the ECU sees the same temp regardless of what the air temp really is.

Are you still running the relay?

Sonny

Re: (Sonny)
 

thanks for the response sonny. my IAT is in the manifold, however i've never used the JR relay since i never used the FMU setup. it all seemed to ghetto for me https://honda-tech.com/forums/images...s/emsmilep.gif i figured i'd want the sensor in the manifold so that its seeing the air that the motor is seeing. am i correct in my thinking?

Re: (keebler65)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by keebler65 &raquo;</TD></TR><TR><TD CLASS="quote">thanks for the response sonny. my IAT is in the manifold, however i've never used the JR relay since i never used the FMU setup. it all seemed to ghetto for me https://honda-tech.com/forums/images...s/emsmilep.gif i figured i'd want the sensor in the manifold so that its seeing the air that the motor is seeing. am i correct in my thinking?</TD></TR></TABLE>

Yup...you got it. If you think it's inconsistent now, you should try it with that stupid relay! The ECU must see the true intake charge temp. If you make it see 0 degrees, it will dump in as much fuel as possible. That might be ok when it's really cold outside, but the engine will run pig rich when it's 100 deg outside.

The ECU has enrichment tables for the IAT input, but they are calibrated around the stock injectors. My guess is that when you switch to larger injectors, the calibration is no longer exactly right any more.

The fact that the IAT is all over the MAP makes JRSC cars in general a PITA to tune. Here are some pics that show you how fast the IAT changes with the JRSC. That kit really is incomplete without an intercooler...that's one of the key reasons that I sold mine.

http://www.muller.net/sonny/hondata/...s/day1run2.gif
http://www.muller.net/sonny/hondata/.../hotashell.gif

Sonny

Re: (rudebwoy)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rudebwoy &raquo;</TD></TR><TR><TD CLASS="quote">because A/F ratio guages are inaccurate! and the ratio changes at different altitudes and temperatures, </TD></TR></TABLE>

That kills me! He reads somewhere that gauges are inaccurate and offers some advice. I wish my A/F gauge gave me a readout like that! LOL

Re: (Sonny)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sonny &raquo;</TD></TR><TR><TD CLASS="quote">The ECU has enrichment tables for the IAT input, but they are calibrated around the stock injectors. My guess is that when you switch to larger injectors, the calibration is no longer exactly right any more.
</TD></TR></TABLE>

i like that as an explanation https://honda-tech.com/forums/images...s/emsmilep.gif maybe now i can sleep better at night. i plan to intercool down the road so i guess for now i'll have to put up with it.

thanks for the thinking https://honda-tech.com/forums/images/smilies/emthup.gif

Re: why is my A/F ratio different from day to day? (keebler65)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">does the ECU automatically richen it up a bit at higher speeds? i'm running an SMC+ for fueling.</TD></TR></TABLE>
Higher rpms, yes.

Re: why is my A/F ratio different from day to day? (sharkcohen)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sharkcohen &raquo;</TD></TR><TR><TD CLASS="quote">
Higher rpms, yes.</TD></TR></TABLE>

no i meant speed as in the ECU sees i'm in third gear from the VSS/motor RPM and richens it up more?

Re: why is my A/F ratio different from day to day? (keebler65)
 

No, the stock ecu doesn't know what gear you are in, but it calculates a percent load based on the various sensors, and reacts to that from a predetermined map. I don't know if the VSS signal is included, though.

Re: (keebler65)
 

I did not know was a wideband. my mistake! I don't know anything about widebands

Re: (RedTegLS)
 

not only because I read somewhere, I also notice 2 diferent readings from my apexi turbo timer and from my autometer A/F gauge, and I research and was told so by a lot of reliable sources, dont start flaming know it alls, experiences are what counts.<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RedTegLS &raquo;</TD></TR><TR><TD CLASS="quote">

That kills me! He reads somewhere that gauges are inaccurate and offers some advice. I wish my A/F gauge gave me a readout like that! LOL</TD></TR></TABLE>

as I said before I never used a wideband so I dont anything about it, forgive me if I'm not correct dont flame me, these forums are designed to help, not to showoff knowledge.

Re: why is my A/F ratio different from day to day? (keebler65)
 

keebler, what wideband are you using, just curious.

Re: why is my A/F ratio different from day to day? (keebler65)
 

Here's a good example of how IAT effects a/f ratio. Run 11 (blue line) was with the JR IAT relay disconnected. It was really hot that day (~100 deg). Since the IAT on the 2000 Civic Si is in the intake boot before the compressor, it never saw true charge temps (this is before I switched to an OBD1 IAT sensor that went in the manifold).

http://www.muller.net/sonny/dyno/scdyno2.jpg

As you can see, in run 11, the ECU saw the real outside temp...~100 deg. In the others, the ECU saw 0 deg....the temp that it is tricked into seeing by the IAT enrichment relay.

You make the call. https://honda-tech.com/forums/images/smilies/emwink.gif

Sonny

Re: why is my A/F ratio different from day to day? (sharkcohen)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sharkcohen &raquo;</TD></TR><TR><TD CLASS="quote">keebler, what wideband are you using, just curious.</TD></TR></TABLE>

techedge v1.5

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sonny &raquo;</TD></TR><TR><TD CLASS="quote">
As you can see, in run 11, the ECU saw the real outside temp...~100 deg. In the others, the ECU saw 0 deg....the temp that it is tricked into seeing by the IAT enrichment relay.

You make the call. https://honda-tech.com/forums/images/smilies/emwink.gif

Sonny
</TD></TR></TABLE>

damn thats quite a difference. thanks again for all of your help https://honda-tech.com/forums/images/smilies/emthup.gif

Re: (Sonny)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Sonny &raquo;</TD></TR><TR><TD CLASS="quote">

The ECU has enrichment tables for the IAT input, but they are calibrated around the stock injectors. My guess is that when you switch to larger injectors, the calibration is no longer exactly right any more.

Sonny</TD></TR></TABLE>

Thats more than a guess, its absoutley correct! https://honda-tech.com/forums/images/smilies/emthup.gif I've been saying this over and over for as long as I've been registerd here and very few get it, and the ones that don't just flame me. Just try it, tune a car on a 100 degree day and try to run that tune year round with a wideband installed. If you are still running that tune with larger than stock injectors in the beautiful single digit tune we are now experiencing in the northeast at the moment, you will be running dangerously lean. The bigger the injectors, the worse the problem is. My friend with a turbo CRX had to add 10% more fuel from this summer, to keep simillar a/f ratios.

Re: (danl)
 

this makes sense too, especially for the JRSC's temps because they are higher than honda would have ever planned on. so if they are using lookup tables in the ecu i'm sure they dont go to 150+ deg https://honda-tech.com/forums/images...s/emsmilep.gif i wish there was a simple fix for this though...like somehow alter the signal depending on the temp range.

Re: (rudebwoy)
 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rudebwoy &raquo;</TD></TR><TR><TD CLASS="quote">not only because I read somewhere, I also notice 2 diferent readings from my apexi turbo timer and from my autometer A/F gauge, and I research and was told so by a lot of reliable sources, dont start flaming know it alls, experiences are what counts.</TD></TR></TABLE>

what readings do you get from your turbo timer compared to yur a/f guage....im confused on that one......

Re: (TravSi)
 

sometimes the guage is reading rich, while the timer is reading 20 volts, or so on they never reads the same, and the are hooked up correctly, except the timer is hooked to ecu o2 signal, and the guage is hooked to the o2 sensor white wire.<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TravSi &raquo;</TD></TR><TR><TD CLASS="quote">

what readings do you get from your turbo timer compared to yur a/f guage....im confused on that one......</TD></TR></TABLE>