Intake Air Temp reading 6°F too high. Is this a problem?

SouthArk370Z

Thanks for the input.

Question the 1st: How bad is that? Will it cause any damage?

Q2: Can I do the recal or is that a CONSULT job?

Q3: Can I swap MAFs and see if the other sensor reads any closer? Or is the miscalibration in the ECU?

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synolimit

No danger. Since temp only works with timing, if you pull say 3 degrees of timing at 100 degree temp, you'll just pull the 3 degrees sooner. So at 94 degrees temp you'll just be down on power vs someone else.

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SouthArk370Z

Thanks. Not the best of situations but at least it won't do any harm. I've still got more power than I know what to so with and don't care if someone else's car is faster than mine.

I've looked through the '09 FSM but can't find what is considered "in spec". How many degrees off does it have to be before Nissan considers it a problem? Since the reading is fairly close, I'm assuming the resistance check described in the FSM will show good.

I think I'll call my local dealer first and see if they will re-cal under warranty. If they balk on that, I'll try swapping the MAFs (I've searched the FSM and can't see where that would cause any problems).

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synolimit

Well the drops in timing/power are pretty far apart and low to start. Here's my last WRX. If the 370 is anything close, everyone starts to lose power at 86 degrees. FYI a full degree on the WRX can be 10hp or a little more since its turbo'd. So the NA car won't make as much or even close. Then a big hit at 104 degrees. Then you're good till 122* or for you 116*.

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SouthArk370Z

Living in South Arkansas, where the Summer temps regularly reach 90 and 100 is not uncommon, that doesn't sound too good. But not a big deal for me and my DD. Thanks for the info.

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SouthArk370Z

I called my local Nissan dealer and was told that they would have to do an inspection/troubleshooting/&c and couldn't give me any kind of estimate of how much it might cost or if it would be covered by warranty. Went round and round with the rep. I asked "If we assume that the ECU is out of calibration by 6F, is that covered under warranty?". Got the same we'll-have-to-troubleshoot-it answer.

I swapped the MAFs and IAT is still 6F high.

I called the dealer back and talked with a different rep. Instead of going through the long explanation of what was wrong, I asked how much to recal IAT and is it warranty. This time I was told that re-cal was one hour labor (~$100 after taxes) and it should (but no guarantee) be covered under warranty.

I have an appointment for recal tomorrow morning. Even if I get stuck paying for it, it's worth $100 to me just to have the damn thing read right. Not so much for any performance benefit but just because I like my instrumentation to be right.

This should be a good time to get them to adjust the insolation sensor for turning on the headlights - been wanting to do that for several years now but didn't feel like paying $100 to do it.

Anything else I should have them tweak while they have it hooked up to CONSULT? It should take no more than 5 minutes each for the IAT and insolation - I'll still have 50 minutes that I'll have paid for.

Thanks for the help and support, people! I'm not sure which I like better, my Z or this site.

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IDZRVIT

What is an insolation sensor?

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SouthArk370Z

"Insolation is a measure of solar radiation energy received on a given surface area and recorded during a given time." - Insolation - Wikipedia

It's the sensor on the top of the dash, near the bottom of the windshield, that cranks the A/C up when you drive into a sunny spot and turns the headlights on when it gets dark (if you have the lights set to Auto). My headlights don't come on until it gets pretty dark and I'd like them to come on sooner.

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IDZRVIT

Thank you.

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SouthArk370Z

Got back from the dealer a little while ago. Complete waste of time. They looked at for about 45 minutes and finally decided there was nothing they could do about it - CONSULT doesn't have access to that data. Why the hell couldn't they tell me that over the phone? I snuck into the shop area and talked to the mechanic - he was working on the ambient temp until I explained to him that I wanted the IAT re-calibrated. Good thing they didn't want to charge me for doing nothing or I'd be asking for bail money right now.

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chops

if temp in the duct, and ambient temp were both 63...then you have nothing wrong. or am i missing something?

SouthArk370Z

"Duct temp" was measured by a digital thermometer with a remote probe. The IAT was reading 6 degrees higher than the probe in the duct. The fact that duct and ambient temps were the same was just an indicator that the engine was cooled down.

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juld0zer

after extensive insulation and thermal management experiments, the lowest i can get the IAT down to is 4*c while cruising - using the ambient sensor as the reference, which i know is slow and inaccurate at best.

While at most red lights, delta is usually around 10-13*c above but quickly recovers with vehicle movement.

This is with a Stillen G3 intake, wrapped in exhaust wrap, then wrapped in building sarking foil material, sarking foil over the power steering reservoir, and a sheet of sarking foil underneath the RHS/USDM passenger side intake pipe. The sheet underneath the pipe made a dramatic difference to stationary IAT temps, including situations such as short visits to the supermarket.
MAF cables are wrapped in exhaust wrap and sarking foil 4 inches up from the sensor flange.
I've also got huge ram air scoops which curve around the K&N filters so getting fresh, cool air is no issue.

FYI bank 1 = RHS/USDM passenger side.
Swapping maf sensors wont make a difference/cause any harm.
ECU only reads IAT from bank 1's sensor. I am unsure if the ecu will chuck a fit if you disconnect the IAT sensor (eg, cut the wires or de-pin them) from bank 2.

Since the IAT sensor is a thermistor, it's not 100% accurate by nature. Hence why the fsm for a lot of cars will show a table with two curves and a shaded area - ie the tolerance range.

You cannot calibrate a thermister, but you can program some compensation in some ecu's. Not sure if ours supports it - might be a question for uprev/ecutek. The principal is the same for using a non-OEM IAT sensor with a different resistance curve.

Our cars came with a lot of thermal management issues. Heatsoak is a major problem and really robs your enjoyment of the car. This problem is not helped by the narrow diameter of our intake pipes (and even the Stillen ones). Why? Because the IAT sensor is too close to the pipe wall, which radiates heat and affects IAT readings. If the pipes were of larger diameter, then the thermistor would be isolated further from the pipe walls and suffer less from radiant heat interference.

What's worse is there is a blazing hot metal coolant pipe running right underneath our intake manifolds. Not the black plastic thing, the metal toblerone manifold between it and the head! So no matter how well insulated your intake is, the air is going to get heated up right before it goes into the cylinder! I know the air velocity will keep the heat transfer to a minimum but every bit counts... and this heating is post-IAT so the ecu can't compensate for it.

So the 6*f high reading you get may not be much of an issue in reality, if we could measure the air temp right before the valves accurately you might be surprised.

juld0zer

another source of intake air heat is the CCV system - CCV vapours are not cooled in a stock set up..

which i guess could be done with a remote catch can setup with super long hosing and a can which is cooled by fresh air. but condensation of oil vapours can create a lot of muck.

1slow370

the only way to recalibrate engine sensors like this is through an ecu reflash, consult is a repair tool and as such is not designed to things like this, a factory calibration for the factory sensors is flashed into the ecu and the repair procedures are if there is a problem replace it. unfortunately non of the aftermarket reflash tools have cracked the ecu's architecture far enough that they can locate and perform recalibration for sensors and instead just leave that entire block of code the way it is from nissan. not just the iat sensors even things like changing from an oil pressure switch to an oil pressure sensor are not possible with the current software.as it is the only way the engine knows if it has low but not nonexistant oil pressure is if the cam timing gets affected from the solenoids not having enough pressure to accurately work. Current software only allows for the overwriting of the MAF flow correction table, so you have two sensors you can recalibrate (but not the iat because it is a seperate sensor even though it is part of the maf).

Also per the fsm the ecu only uses IAT sensor bank one for all of its calculations bank 2 sensor has a dtc but is completely ignored. also looking at the sensor graph it is much less sensitive as temperature rises. At lower temps around 30F a 1kohm difference is about 10 degrees but at 140F 0.1kohms is almost 40degrees. the tolerance of the ecu's settings combined with the inaccuracy of the factory iat sensor makes you wonder how they expected to get any kind of an accurate reading at all so if it's only 6 degrees off you should be happy lol

Edit:also dealerships charge 100 dollars to just think about working on your car. Fontana wanted to charge me $118 to take 5 minutes and do the NATS reset on my car after I swapped the ecu. The procedure is literally key car to on, put fob in slot, connect consult3, click repair, click immu, click nats innitialization, click start, wait, switch keys, click continue, wait, shut car off and restart. <-$118 F****N dollars

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