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Old 01-01-2010, 06:09 PM   #1
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Default runs rich in cold weather

Simply put the colder it gets the richer my tune becomes. What should I adjust? I had a nice solid map tuned in, running 13.0/1 at WOT with temps at or around the 50's (F) and now that we ae hovering around freezing the leanest it gets is 12 and thats only for a split second. Really its more like 11.5. Any Ideas?

92 mx5, MS1 3.0, standalone. close to stock N/A setup.
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Old 01-01-2010, 06:18 PM   #2
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11.5 -12 is where it should be when its in boost anyways....what you complaining about?

**Edit, never mind, I just noticed you said you were na. My bad!
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Old 01-01-2010, 06:20 PM   #3
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N/A= naturally aspirated. Turbo is still under my desk. I am rich all over right now. Clouds of exhaust on startup.
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Old 01-01-2010, 06:34 PM   #4
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are you getting out of warmup mode? do you have some sort of AIT corrections table setup?
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Old 01-01-2010, 06:41 PM   #5
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in megatune, swap one of your controls to "gammae" that will tell you your overall fuel correction percentage.

Compare your current values to logs of when it was running well at hiher temps. If there's a significant discrepancy then you probably have an IAT correction problem, where its adding too much fuel for the given temperature.

To correct for this, you can go to a menu called something like "IAT Related Correction" (not sure..) you can set various temps, then also set the adjustment percentage to try to correct back a little... that's the "HACK" way of doing it, but may work.

The issue also may be that your thermfactor is a little wacky, and not matched up to your sensor. I have no experience fixing this...

-Tomaj
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Old 01-02-2010, 07:48 PM   #6
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Just FYI, i took my car out today (19 degrees F) it was idling around 10.5 AFR.

FWIW i have my IAT corrections completely disabled for a while so I can do some empirical testing to calculate how 'off' the airdenfactor is when adjusting for fuel.

-Tomaj
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Old 01-02-2010, 09:03 PM   #7
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OK so i did some excel magic with another table of temps vs air density and compared it to the data in the airdenfactor file...

Everything seemed to match up 100%, so I'll have to say it's not that which is causing this issue.

I guess all that's left is the themfactor(? smart people chime in here). I didn't think it was this because my temps always looked OK to me on megatune.. Is it possible that the temps look OK in megatune but somehow megasquirt is interpreting them differently?

Joe Perez -- you know a lot about this stuff, any tips?
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Old 01-02-2010, 09:49 PM   #8
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I have a similar but opposite sort of problem... Took a log of my cold start up and from what I can tell my A/F starts out fairly rich but leans out a lot before the motor is warmed up anthen it richens up again once warms.

I would think that it could be fixed with the warm up wizard but I'm having a lot of trouble with it.

I'm wondering what else affects how it fuels at idle after start up ( ? )
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Old 01-02-2010, 10:02 PM   #9
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If you have the correct therm ini file, but don't have the correct firmware burned, I believe it will look right and the MS will interpret it wrong. You can try reflashing with a known correct easytherm firmware and burn your MSQ, or you can wait for someone else to chime in. I'm pretty sure MT/TS read the raw value and use a table to convert to degrees. The firmware also has this table which I believe is separate from the MT/TS ini table.
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Old 01-02-2010, 10:10 PM   #10
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TrickerZ, that sounds like a good plan... i'll probably do it some day but til now i've been scared to re-flash..

from what i've read i'll have to disconnect the ignitors and set some jumper on the MS? that's the annoying part b/c it's mounted in w/the regular ECU so it's a little annoying to get to..

---

Here's a question regarding the temps though -- How does the MS transmit the temp via serial port? Is it an "adc" value from 0 to 255? I'm trying to understand the mechanics of it because if it is simply a 0 to 255 value, then the MS in order for the MS to convert it and have it appear correct, it *should* actually be correct, because it's an encoded value not a raw reading from the sensor.. does that make sense?

-Tomaj
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Old 01-02-2010, 10:29 PM   #11
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Do you have the extra firmware? If so, you don't need to put the jumper on. You do need to disconnect the coils/igniter.

I believe the ADC is an 8 bit register on the Motorola chips. It works just like memory, so you access it by pulling from that register. Basically it converts 0-5V to a number from 0-255 and I believe that is what is sent across the serial line. The MS and MT/TS then convert that with the tables. So a raw ADC value of 128 would be 2.5V no matter what and the MS converts that 128 to say 60 degrees depending on the table. If you look at the thermfactor.inc you'll see what I mean
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Old 01-02-2010, 11:25 PM   #12
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i do have the "extra" firmware, so that's a bit of good news.

I think i also now understand your explanation of how the sensor input works...

To paraphrase, what you're saying is:

The sensor is reporting a given resistance which is immediately stored as a byte value between 0 and 255... the Megasquirt then references that stored value in two distinct instances. First, when doing its internal calculations for fueling etc, and second when sending it over the serial port.

If that's the case then I can totally see how megatune and the MS could be interpreting the results in two different ways.

Thanks!
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Old 01-03-2010, 01:26 PM   #13
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So it looks like the disscussion has evolved to another problem here (not that I mind the thread jack at all, so dont take that the wrong way) but I have switched AIT correction off. That is to say I have set it to "normal correction" and things have calmed down a bit. Did a couple of logs and it is coming back in line, but what have I changed? I dont really understand fully what the AIT correction does. ANyone want to point me in the direction of a decent explanation? megamanual makes no mention of it (none that I have found at least) and of course there is no instructions at all for tunerstudio.

To answer your question Brain, yes it is getting out of warmup just fine. All the temp readings in TS look reasonable. I am running the MSPNP software package and firmware. 029Q I "think". AIT sensor is mounted in the stock plastic pipe just before the T-body.

So what the hell does this correction adjust? I was ubnder the impression that the whole reason it has a AIT sensor is to correct for the O2 level in different temperature ambient air. Why would we need to adjust this scale? and why does it list "coolant" or AIT based correction. How the hell are we to correct the values for O2 in the air relating to the AIT sensor readings if we are using the same sensor to make the corrections?!
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Old 01-03-2010, 01:42 PM   #14
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I think all these settings tables and features are there to compensate for air density and fuel vaporization which are in turn dependent on temperature.
It has been mentioned that if the wrong firm ware is installed as when the AFM is removed and the GM IAT is used the Air temp correction will be off.

Right now it too freaking cold in the garage for me to try anything so my end of the discussion will be strictly as an arm chair warrior or purely academic.
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Old 01-03-2010, 02:18 PM   #15
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Yeah its effing freezing here too mate, I must be out of my bloody mind as I just spent the day polishing the car. Anyway I am using the "AFM removed" software from diyautotune, but I am ashamed to say I have never really looked into the temp values and related software adjustments. I tried easytherm way back when I first got the MS installed and couldn't make it work. Then I found the MSPNP software was free and the rest is history.

Having said that the temp values displayed in Tunerstudio seam to be about right when the engine is cold and the running values (warmed up) make sense as well so I trust the values from diyautotune are about right. Makes sense as they also sold me the AIT
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Old 01-03-2010, 06:49 PM   #16
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Blaize, you may be correct but as TrickerZ said, the temps may show up correctly in your tuning software but actually be misinterpreted within the MS itself.
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Old 01-03-2010, 07:19 PM   #17
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I had the same problem years ago, easytherm made life worth living again.
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Old 01-03-2010, 07:36 PM   #18
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yeah ctxspy, rereading the whole thread i see what you are getting at. I suppose it is time I got friendly with easytherm.

On that subject, where do I find the ini file? I remember it being pretty easy with MT to switch over to the settings menu and have a look at it all. anyone know where it is in TS?
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Old 01-04-2010, 12:11 AM   #19
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I'm not sure about the TS config as I haven't messed with it at all, but I'll answer your questions about the corrections.

Basically, the AIT correction is adjusted to compensate for heat soak. That is why it is disabled at higher RPM when a lot more air is flowing and heat soak is almost nil. If you happen to have the AIT in a plastic pipe, you could probably disable that entirely, but most people see a lot of heat soak at idle or in traffic with metal pipes.

My understanding is that the coolant related is the same thing, except you are adjusting the density based on the temperature of the coolant. So when you're sitting in traffic and the coolant temps start to rise, it doesn't necessarily mean the density is changing and you want to account for that so the car doesn't run too lean or rich. The reason coolant based sucks for our cars is that warmup is only 160* and our cars are actually warm at ~200* so it is trying to correct before the car is fully warmed up. You can probably modify the table enough for it to work, but AIT is a better value to use.
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Old 01-04-2010, 10:11 AM   #20
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Quote:
Originally Posted by TrickerZ View Post
I'm not sure about the TS config as I haven't messed with it at all, but I'll answer your questions about the corrections.

Basically, the AIT correction is adjusted to compensate for heat soak. That is why it is disabled at higher RPM when a lot more air is flowing and heat soak is almost nil. If you happen to have the AIT in a plastic pipe, you could probably disable that entirely, but most people see a lot of heat soak at idle or in traffic with metal pipes.

My understanding is that the coolant related is the same thing, except you are adjusting the density based on the temperature of the coolant. So when you're sitting in traffic and the coolant temps start to rise, it doesn't necessarily mean the density is changing and you want to account for that so the car doesn't run too lean or rich. The reason coolant based sucks for our cars is that warmup is only 160* and our cars are actually warm at ~200* so it is trying to correct before the car is fully warmed up. You can probably modify the table enough for it to work, but AIT is a better value to use.

Are we talking about the After Start Enrichement Settings ? Where do you adjust the coolant temp vs fuel relationship aside from the Cold Start Wizard thing in Megatune ?

Thanks
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