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Old 03-31-2009, 09:31 PM   #1
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Default IAT affecting AFR more than CLT?

Hey guys, me again

So i've been trying to tune my car lately, and i'm moving along fairly well, however i've noticed that when it's cold, everything is significantly leaner.

I'm somewhat familiar with the warmup enrichments, but those are based on the CLT not IAT.

I may be wrong here, but to me it feels like even if the car is warm but the temp is still cold outside, then my AFRs are like half or 1 point higher..

Also, i see the car's in "WARMUP" until it hits 160, but then if i'm driving around and the CLT drops back down to 150 or 145, then the warmup enrichment doesn't come back.

Is this normal? Should i be looking for IAT enrichment somewhere??

-Tomaj
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Old 03-31-2009, 09:33 PM   #2
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clt-based air density corrections table.
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Old 03-31-2009, 09:45 PM   #3
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Quote:
Originally Posted by ctxspy View Post
Hey guys, me again

So i've been trying to tune my car lately, and i'm moving along fairly well, however i've noticed that when it's cold, everything is significantly leaner.

I'm somewhat familiar with the warmup enrichments, but those are based on the CLT not IAT.

I may be wrong here, but to me it feels like even if the car is warm but the temp is still cold outside, then my AFRs are like half or 1 point higher..

Also, i see the car's in "WARMUP" until it hits 160, but then if i'm driving around and the CLT drops back down to 150 or 145, then the warmup enrichment doesn't come back.

Is this normal? Should i be looking for IAT enrichment somewhere??

-Tomaj
IAT - You temperature sensor calibrations are off.

CLT - Your CLT should never drop down below 160 while the car is running once you are over 160. Seriously the thing should run 195+ since the factory thermostat is 195.

A. your thermostat is stuck open
B. your temp sensor calibrations are off


Where did you get your firmware from? I suggest searching for EasyTherm.
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Old 03-31-2009, 10:09 PM   #4
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IAT - You temperature sensor calibrations are off.
We gotta get mine fixed first .... one of these nice spring days.
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Old 03-31-2009, 10:17 PM   #5
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i got my firmware from scott pre-installed, he said it's hires 10g.

Hey Scott -- did you load a firmware on there that's expecting the GM IAT signal already?

-Tomaj
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Old 03-31-2009, 11:31 PM   #6
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I read this thread:
MX-5 Miata Forum - 160 degree thermostat?

It looks like a fairly popular mod a while back was to add 160degree thermostats to the miata... Are they marked as such? How could i tell what i have?

-Tomaj
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Old 04-01-2009, 12:43 AM   #7
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At the point where you could tell if there are markings you might as well just change it anyway.
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Old 04-01-2009, 12:51 AM   #8
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At the point where you could tell if there are markings you might as well just change it anyway.
yeah.. i checked the the m.net garage article, looks pretty easy.. not too expensive too online but i'll stop in at a local parts store 1st to see if they have it.

So assuming i change out to a 195* thermostat, that won't really change my other issue, which is that the car seems (to me at least) to run leaner when air is colder vs when it's warmer..

IOW the car could be hanging out at a toasty 195 CLT, but if it's 90 degrees out, then my tune made at 50 degrees will be worthless no?

Feel free to tell me i'm wrong and i'm imagining things. I mean is htis something everyone sees and knows about, or am i just wrong??
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Old 04-01-2009, 02:08 AM   #9
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Originally Posted by ctxspy View Post
if it's 90 degrees out, then my tune made at 50 degrees will be worthless no?
Not worthless, but you may have to adjust your engine start-up settings (cranking pulse widths, ASE, etc.) .... life gets more interesting when you have to tune the settings for cold winter weather.

You also need to understand that MS will never be a "set it and forget it" system. You'll continuously be driving along, minding your own business, when you happen to hit a cell in the VE table that you hadn't hit before. So do not over-react when you see a minor decrease or increase in AFR. It's not a big deal as long as your tune is in the ballpark. You'll need to re-tune (or at least tweak) with every changing season and every performance modification. In theory, once your car's mods are complete (if there is such a thing) for a full 12-month cycle, then your tuning will be done too. Unless the next summer is hotter than the previous one, or the next winter is colder ....
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Old 04-01-2009, 10:47 AM   #10
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Quote:
Originally Posted by ctxspy View Post
yeah.. i checked the the m.net garage article, looks pretty easy.. not too expensive too online but i'll stop in at a local parts store 1st to see if they have it.

So assuming i change out to a 195* thermostat, that won't really change my other issue, which is that the car seems (to me at least) to run leaner when air is colder vs when it's warmer..

IOW the car could be hanging out at a toasty 195 CLT, but if it's 90 degrees out, then my tune made at 50 degrees will be worthless no?

Feel free to tell me i'm wrong and i'm imagining things. I mean is htis something everyone sees and knows about, or am i just wrong??
I find it very unlikely that your actual CLT is under 160F while driving unless its down in the teens and you have an oversized radiator. Drive the thing down here and we can go over it, comparing it to how my MS reads your temps.

If your calibrations are correct you shouldn't have this issue. As air temp changes the MS adjusts fuel because air density changes, ie amount of oxygen. If your calibrations are correct you should maintain the same AFR regardless of IAT. If they are off you will experience exactly what you are seeing.

Here is what MS (or any ecu) does:

MS applies X fuel according to your RPM and MAP from your VE table and varies it according to IAT. As IAT increases fuel decreases because the engine is getting less dense air(less O2). As IAT decreases fuel increases because the engine is getting more O2. When functioning properly this maintains AFR.

Are you running standalone or parallel? Send me your car folder.
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Old 04-01-2009, 11:23 AM   #11
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Quote:
Originally Posted by paul View Post
I find it very unlikely that your actual CLT is under 160F while driving unless its down in the teens and you have an oversized radiator.
Even then you won't likely see it. I have a 52mm Koyo and started tuning my car when it was 0*F last month. Even then it would run at thermostat (192*F) temps. Never lower. Surprisingly, it gets up to full temp in one mile of driving 40 mph even at 0*F with that rad. I was worried about that initally.
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Old 04-01-2009, 11:50 AM   #12
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I should have been clearer, I meant EVEN IF he has a 160 t-stat like he posted previously.
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Old 04-01-2009, 11:52 AM   #13
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do you clt and ait temps looks correct and match in the morning?
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Old 04-01-2009, 08:03 PM   #14
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I just checked outside, car wasn't driven all day.

Megatune says 36/37 for both CLT and AIT, various weather sites say 44 degrees.

Paul, i think i have your e-mail address i'll send the car folder & msq.

-Tomaj
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Old 04-05-2009, 12:08 PM   #15
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I had a few minutes today so i took off the cross over tube (not the right name, i'm sure). I decided to install the IAT sensor on the RIGHT side of the car, if you're looking at the engine bay from the front back.

In this position, it's nearer the turbo than the intake manifold, BUT i did it this way because my coolant hose is actually touching the crossover tube on the other side, maybe one or two inches away from where i'd have to put the bung, so i figured this may reduce heatsoak issues.

I drilled the hole with ever-increasing sized drill bits until i got to my largest At first i was thinking that maybe i could thread the sensor directly into the pipe but decided against that for two reasons.. 1 the metal is thin, probably wouldn't be wise Also, my largest drill bit wasn't near large enough.

I went to autozone, bought some "jb stick".. i mixed up bit and mounted the bung supplied in the kit and pushed the JB all around, made it look all nice like. It seems to be hardening up, i'll probably shoot the whole ting with some hi-temp black to make it match the rest of the pipe.

So now the next question.. Are there any tricks to wiring this up? As per Paul it seems that my Megasquirt is already waiting for the GM IAT signal which is causing my screwy temp readings, so do i just wire it in? do i have to somehow disable the stock temp sensor? Once this is done - can i just remove the flapper?

-Tomaj
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Old 04-05-2009, 07:15 PM   #16
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Just cut the wire in the parallel harness(between the db37 connector and the big yellow one) and connect the sensor to the correct side. Other lead from sensor goes to ground.

I think you have to jump something so the fuel pump runs if you remove the AFM. Sorry, not a one six guy.
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Old 04-06-2009, 12:19 AM   #17
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Hey Paul,

I've already jumped the FP. For the non "MSPNP" (not sure if this is the only criteria) you need to do that as a part of the install..

I will give it a shot on the next nice day..

FWIW my JB-WELD didn't hold... i waited around 3 hours before trying to screw in the iat so i could drive the car even w/o it wired up... the whole weld / bung just came off in my hands once i applied some decent pressure.

I tried again using less material, scored up the metal a little more, and made a little jb-weld circle and pressed the bung directly onto that , maybe that will help..

-Tomaj
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Old 04-06-2009, 10:18 AM   #18
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FWIW I have installed 7 IAT sensors by just tapping the aluminum/steel IC piping and have had no problems with one leaking or coming loose. Of course I used the correct tap, 3/8 NPT.
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Old 04-09-2009, 08:11 PM   #19
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Hey, i followed your advice and tapped it (thanks for the tool SamL01). I threaded the sucker in, ran the wire thru the firewall.. I'm about to do the wiring into the MS harness... i'm still not sure how to do it, and i left my netbook at work so i can't see whether i did it right.
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Old 04-09-2009, 09:06 PM   #20
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OK update... I was trying to find a FAQ on wiring the IAT and i remembered Scott (braineack) sent me a word document with some instructions.

I ended up doing it hte way he indicated, which was to simply remove the harnessfrom the MAF and stick the two wires into the 1st and 6th holes on the female side.

Is that OK?? I drove the car, it started right up and everything seemed to work ok..

-Tomaj
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