What did you do to your NNBS GMT900 Tahoe/Yukon Today?

[Doubeleive]

I'm completely confused by these Temps sensors..

so today I checked the diagram, yep only intake air sensor wiring is in the maf. so I go pull up the scanner, start the truck and watch the intake temp and the ambient air temp. they are different by about 20deg.

unplug the maf, the intake air temp goes to its default of negative whatever, the ambient temp doesn't move, then I plug it back in and intake temp goes back to 120ish, all of a sudden the ambient temp goes to 14deg F and both cooling fan kick on max. like wtf? I didn't touch the sensor in the bumper.

so check codes and ambient air temp open code, very weird. havc still says 98deg. yesterday when I unplugged then air sensor in the bumper the hvac detailed to 58deg. I force update that by hitting the 2 buttons, it jumps to 100deg. scanner still reading 14, fans still on max.


so I pull out the tech 2, check everything, havc module still reading ambient Air raw same as havc display (ish 2deg off). go into ecm data and intake temp normal, ambient 14F. clear codes a few times, cycle power. still the same, so I take it for a drive thinking it needs to reset at a speed. take it up to 60mph and still 14, weird.

drive it back to the shop, pull in, turn the ac off and the cooling fans go off high speed, pick up the scanner. now the ambient Air temp is 17F.


i got nothing. parked it, went inside for a bit, checked it later and it's at 18deg F. fans not on, no codes for anything. my only guess is it will reset itself slowly over time. it's gotta be a fake temp like oil temp, somehow using maf temp and math to guess for something filtered.


not that any of this matters to anyone else haha, but if you want to compare the outside air temp to your intake air temp as it passes thru the maf, you'd have to force update the hvac display temp and look at the manifold air temp to see how well your cold air box is working. mines about 20deg different cruising, creeps up to more like 30deg at stopped in traffic.


and if you ever get a ambient Air temp sensor fault code, but the hvac temp is correct. I have no clue how to fix that haha. maybe an intermittent wire in your maf sensor plug.

the ambient air temp will update after 5 miles of driving, particularly if you are unplugging and messing with it, go drive it at least 5 miles and check again
if you suspect it is faulty, replace it they do get brittle and break easily from being exposed to the elements

 

[Doubeleive]

WHICH ONE HAS MORE AIR FLOW?

 

[Geotrash]

WHICH ONE HAS MORE AIR FLOW?
View attachment 431681View attachment 431682

The bottom one.

 

[Doubeleive]

got my most recent oil analysis back, I think the last one they handed me a sample from someone elses vehicle because they said it looked like a 6000 mile oil change and the viscosity was off.
hopefully this means my cam is probably ok

 

[Doubeleive]

The bottom one.

think so? just doesn't seem like it to me, too bad there isn't a way to test this theory easily. I can get a chrome mesh one without the gmc logo blocking some air

 

[Geotrash]

think so? just doesn't seem like it to me, too bad there isn't a way to test this theory easily. I can get a chrome mesh one without the gmc logo blocking some air

Just a hunch because round holes flow air better. But you could do it by counting the holes, measuring their area and making the calculations.

Round vs. Square Hole Stainless Steel Perforated Mesh: A Comparative Analysis - The Mesh Company

Dive into the detailed comparison between round & square hole stainless steel perforated mesh, exploring their applications & advantages.

themeshcompany.com

 

[tuckerrnr1]

Figure the surface area of one hole then multiply. Figure the area of the rectangles. And you thought you would never use geometry in real life. Geotrash beat me to it.

 

[Doubeleive]

Just a hunch because round holes flow air better. But you could do it by counting the holes, measuring their area and making the calculations.

Round vs. Square Hole Stainless Steel Perforated Mesh: A Comparative Analysis - The Mesh Company

Dive into the detailed comparison between round & square hole stainless steel perforated mesh, exploring their applications & advantages.

themeshcompany.com

yes that is comparing small squares, not big rectangles.
I suppose math would determine just as well but too lazy lol

 

[gooffeyguy]

think so? just doesn't seem like it to me, too bad there isn't a way to test this theory easily. I can get a chrome mesh one without the gmc logo blocking some air

Put a box fan behind each one and use your airflow/cfm meter on the other side

 

[Doubeleive]

Put a box fan behind each one and use your airflow/cfm meter on the other side

I would have to build a cardboard funnel behind it to get a accurate reading. i haven't bought one yet either just thinking,,,,,,,,

 

[gooffeyguy]

I would have to build a cardboard funnel behind it to get a accurate reading. i haven't bought one yet either just thinking,,,,,,,,

Why a cardboard funnel? You don't drive down the road with a cardboard funnel taped to the front of the truck do you?

Simulate driving down the highway.
Box fan set to same speed during both tests. Place grill like a foot away during each test and take reading like a foot behind the grill.

 

[89Suburban]

 

[j91z28d1]

the ambient air temp will update after 5 miles of driving, particularly if you are unplugging and messing with it, go drive it at least 5 miles and check again
if you suspect it is faulty, replace it they do get brittle and break easily from being exposed to the elements

that's the thing, I didn't touch the actual ambient Air temp sensor thats behind the grill. I only unplugged the maf plug and plugged it back in. then the ambient temp on the scanner crashed to 14F. which is a very odd. default. it is slowly coming back thou. it was up to 21deg by the time I got home from work, way more than 5 miles thou.

this is scanner/tech 2 ambient Air temp, not the actual ambient Air temp displayed on the hvac display. that one actually follows the behind the grill sensors. I tested tested that yesterday.

 

[j91z28d1]

got my most recent oil analysis back, I think the last one they handed me a sample from someone elses vehicle because they said it looked like a 6000 mile oil change and the viscosity was off.
hopefully this means my cam is probably ok
View attachment 431689

Blackstone sells a nice little hand pump that goes down the dip stick to get a sample. we have one at work, it might be worth while if you're not sure the guys at the shop are doing it right. it really show be taken while up to temp and from mid drain.

eaiser to just shut it off and pump out an ounce at home.

 

[j91z28d1]

WHICH ONE HAS MORE AIR FLOW?
View attachment 431681View attachment 431682

I think there's more than just the surface area of the holes involved in the match when air flow modeling is involved. something like the faster air flow, the more it can shroud itself.

something I read years about about a 2 valve head vs a 4 valve head. the 2 smaller valves have much more surface area for flow at lower speeds and lifts, but once the air speed gets up for high rpm, the center of the valves the air flow shrouds itself and one large valve can flow just as much air.

they had graphs and all to show it on a flow bench. not that I can say they were telling the truth or not. I have a 4 valve engine that shifts at 14k. but just what I read. I can imagine at high speeds, say 70mph the small hole grill flowing much less than the wider slats. at least in my head. especially if the slat angle is correct where the small hole grill lays back more, the slates form a air dam on the way up and over the hood.

 

[Grady_Wilson]

Blackstone sells a nice little hand pump that goes down the dip stick to get a sample. we have one at work, it might be worth while if you're not sure the guys at the shop are doing it right. it really show be taken while up to temp and from mid drain.

eaiser to just shut it off and pump out an ounce at home.

Or install a Fumoto valve and connect a short hose to the oil sample container and fill it, close the valve.
EZPZ

 

[Fless]

Why a cardboard funnel? You don't drive down the road with a cardboard funnel taped to the front of the truck do you?

Simulate driving down the highway.
Box fan set to same speed during both tests. Place grill like a foot away during each test and take reading like a foot behind the grill.

I think there's more than just the surface area of the holes involved in the match when air flow modeling is involved. something like the faster air flow, the more it can shroud itself.

something I read years about about a 2 valve head vs a 4 valve head. the 2 smaller valves have much more surface area for flow at lower speeds and lifts, but once the air speed gets up for high rpm, the center of the valves the air flow shrouds itself and one large valve can flow just as much air.

No math needed, except for a ruler (not your wife kind of ruler...). See @Geotrash's post. Apples-to-apples comparison. EZPZ

 

[89Suburban]

 

[j91z28d1]

Or install a Fumoto valve and connect a short hose to the oil sample container and fill it, close the valve.
EZPZ

I got the feeling he wasn't getting under the truck himself.

I honestly wouldn't trust a lube tech to know how to open the valve. they would just unscrew it

 

[Doubeleive]

Why a cardboard funnel? You don't drive down the road with a cardboard funnel taped to the front of the truck do you?

Simulate driving down the highway.
Box fan set to same speed during both tests. Place grill like a foot away during each test and take reading like a foot behind the grill.

because i may be placing the meter in a sweet spot with the open slats, a better test would involve a more controlled environment. If i build a funnel to about a 4" hole then I can get a reading for either one more accurately. I have plenty of cardboard and tape.
I personally think the slots will catch more air but that's just my brain seeing big open slots versus small holes