TheV's

iTrader: (2)

Hi !, Newb here, just getting to grips with some tuning now. Today I noticed my MAT temps are ranging from 185F to 250F on an 80 deg day here in MI....I have a GM Open element IAT with the following calibration settings....

bias resistor setting of 2490 Ohms.

Temperature F Resistance In Ohms
48 7000
87 1930
146 560

I have attached a log of my run to work which didn't get quite as hot, but still pretty high, any thoughts as to why I've got such crazy high temps - I'm not even boosted....

Thanks for any suggestions and help !

Ben

iTrader: (33)

If you have a hot side air intake, the readings are probably accurate.

Onyxyth

iTrader: (2)

What is your intake like and where is the IAT located?

TheV's

iTrader: (2)

Sorry about the crappy picture....IAT near the throttle body, intake on the hot side...

Chiburbian

iTrader: (1)

Are you in a position where you can leave the hood open all night? (garage?)

If so, check your MATs before you start the car in the morning. If it is within a few degrees of what the weather channel says it is then it's probably accurate.

I have never seen MAT that high but then I went from stock airbox to intercooled turbo.

TheV's

iTrader: (2)

Good idea, i'll try that tonight...

Erat

iTrader: (5)

FWIW. My MAT's are always 5-10F higher than ambient before i coldstart my car. No matter if it's 30f out or 90f out.

Chiburbian

iTrader: (1)

well, that's in my realm of "reasonable." If it is more than 15 degrees off or more then I would be concerned.

Ben

iTrader: (33)

So you're pulling air from right next to the header, and you've removed the heatshield?
It's hot under the hood. You need to work on a cold air intake. The sensor is likely fine.

TheV's

iTrader: (2)

OK, so I left the hood open all night, ambient air temps were around 65F this am, before cranking I checked the MAT - 151F ! - sooo looks like my sensor is bad....The good news is that on my drive into work the MAT only got to 180F, so not too bad a heat rise on this cooler AM. Agree some form of Cold air intake would be a good idea, but based on this my sensor is bad....Can I re calibrate it (Was thinking hair drier and a meat thermometer !) or not worth it ?

pdexta

iTrader: (17)

I've had my intake temps read crazy when it was just a bad connection to the sensor. Disconnect/reconnect the plug on the sensor and see if it makes a difference, if not do the same where it connects to the maf harness. If it's still giving you problems a new sensor is $20: GM Open Element IAT Sensor with Connector DIYAutoTune.com

I've run several logs with a similar intake setup (except with the heat shield on) and temps were hanging around 140-150. That's definitely not an ideal setup, especially with the heatshield off.

Chiburbian

iTrader: (1)

Have your MATs ever been good? It's possible you put the wrong bias resistor in place?

TheV's

iTrader: (2)

Thankyou for the opportunity to reveal my noobness ! ;o)

- Is the bias resistor a part of the sensor, part of the MS3x circuit or a resistor I should have soldered into the harness ?

Chiburbian

iTrader: (1)

It is a resistor that would have been soldered onto the megasquirt board. I believe R7 and R4 are the resistors for coolant and air temperature. Which one is which I am not sure.

Are you sharing your sensors with the stock ecu or running full standalone?

TheV's

iTrader: (2)

Wow, thanks !

Thanks for the post - I'm full standalone

So last night a bought a new sensor, clipped it in, no difference - same high temps. Then I got out my wife's trusty meat thermometer (it's a good one with electric probe, don't tell her) and the hairdryer - and started tweaking some of the resistances in the hope I could set something near to 80F and something around 230ish. after a few tweaks things started to go weird - the gauge stuck on 70F no matter what resistance values were entered. I unplugged the sensor and it jumped between 0 and 70, a few seconds on each - whoa - what the heck is going on !? Then I plugged the sensor back in and temps went to a few degrees above ambient.....go figure. After a brief drive I saw temps rising and falling in expected ranges and it appears to be reading something near sane temps. So for now it appears to be working, but I'll keep a close eye on it and if you asked me what I did I'm not sure I could tell you the route cause or remedy....eeek

Chiburbian

iTrader: (1)

While it's nice to have everything working, sometimes the unknown "fixes" are the worst because you don't know how to fix it in the future. Perhaps it is a bad wire somewhere?

TheV's

iTrader: (2)

Yes...I know...I may run new wires just in case....

Thanks for your help anyway !

deezums

iTrader: (3)

Maybe I'm just dumb, but I couldn't ever get a good connection using the crimps that came with the DIYautotune connector.

I have a disease that makes me own 12 S10's and Blazers, so I just stole and soldered in a GM pigtail. Any 98-04 S10 pigtail should fit.

noname4me

That is some disease... I inherited a decent S10 Blazer from my Uncle. Spent quite a chuck of change fixing the AC, front suspension, etc... I still hated the Damn thing and traded it in when buying a GTI. I probably lost $1500+ trading it in and was still happy to see it go!

Anyways, back to vehicles that don't suck... (sorry, no offense meant!)