Throttle body coolant line sender discussion
 

The weather has been particularly cool in the late evenings here on the central coast of Ca. lately. We normally have pretty mild weather year round. Lately, late evening temps have dropped into the upper 30's on a regular basis.

I have my coolant temp sender in my throttle body coolant line. Lately, when driving at night on the freeway, my coolant temps are staying at about 170. I'm not boosting the car, just cruising home on fairly flat roads for about 15 miles. I believe that my temp gauge is working properly because it gives me the readings I expect during warm up, and around town. I'm thinking that the cold air temps are keeping the TB pretty cold, and that the cool TB may be dropping the temp of the coolant before it reaches my sender.

I don't have a way to measure intake temps. I'm wondering what intake temps would generally be when cruising down the freeway on a 35 degree night, with no boost (or heat soak), and coolant temps of 180. If intake temps are close to ambient, would they cool the TB enough to effect my sender?

Helpful comments appreciated :)

Thanks, Adam

I also have the sender "T" into the coolant line at the throttle ,one thing i can say is that it seems to be roughly 10 degrees lower than what the power FC says (which is the thermostat housing)

To add mate, when im crusing on the motorway im getting tempratures about 72 degrees which is about 162F roughly same as yours (i have M2 large intercooler and noticed that when lifting the bonnet after motorway cruising the throttle body is remarkably cool so i wouldnt be supprised if this was responsible for the difference in temprature between throttle body and thermostat housing)

The PFC uses the temp sensor mounted in the block, not in the t-stat housing.

Hey Adam, how are things? AITs on my car in that type of weather just cruising are typically in the high teens C.

i have been using TB temp location for a while now and i have the same results. On cold days just cruising my temps dont get over 170 ish. I would asssume that it is because the sender cools a little bit....

Im curious to know why as well?

Yesterday in NJ it was 20deg. My TB sensor moved between 180-220. Same as it does in the summer.

Same thing here in San Diego.

My car rarely ever runs below 85C even in cold NY winters when I lived there. A few days ago, I was cruising down a long hill (Torrey Pines) w/o throttle input at all and was surprised to see my coolant at 82C and AITs in low 20C iirc.

Ambient was something around 50F. Brrr that was cold. :D

Hi. Things are going reasonably well. Can't complain too much. So, do you think AIT's are about 20 degrees (F) above ambient under those conditions?

The question is: How does it act on a cool night, when on a long cruise, and no boost?

I have never seen it go below or above these temps since I installed the gauge last summer.

When I first installed the TB sensor, I tested it against my upper radiator hose sender. The tests were done at idle. I got almost identical readings at several different temperatures. I didn't do a test with the car in motion. I have not removed the radiator hose sender, or the wiring to it. Perhaps I should do a test to see what differences there are during driving conditions.

I have the sensor mounted in the TB hose (of course!) and I also have the HKS fan controller that reads temps from the ECU's water temp sensor which is on the back of the water pump housing right by the fan thermoswitch. BTW, this is also where the PFC reads its temps from.

My temps dead-on agree with each other, but I had some air in the system after the intercooler install and would sometimes read lower on the gauge due to the air.

Besides that, they've dead-on agreed with each other. Sometimes when warming up the temp gauge reads higher, as it's seeing the hottest water in the engine first. That sender might also react a bit faster as well. Once up to temp, they agree within one or two degrees.

Dale

Dale,

Do you get any cold evenings in Pensacola to test this?

Rynberg as dale said the temprature sensor is mounted with the fan switch in the water pump/thermo housing (i was racking my brains then thinking i dont remember the temprature sensor been in the block). ive noticed my throttle coolant line gauge is always 10 degrees short of my power FC from cold until they reach about 170F then they seem to be within 2 degrees of each other.

The PFC reading reacts much more slowly than the t-stat sensor location. And you're saying the TB line reacts even slower than that? This is yet more evidence that the t-stat location reacts faster than the TB location...further cementing my opinion that the t-stat housing is the best place for the sensor. :)