Hi guys,
I am trying to find out how hot the intake manifold normally is... The tubes below it are made of plastic, so I am thinking it does not get that hot up there...

Has anyone actually measured the temp of the upper intake manifold? On mine it is the red part that the throttlebody plugs into and says FIERO on the top of it..

thanks!
STan

I've never measured mine but it should be ambient temperature plus radiant heat from the engine

It gets pretty warm. Keep in mind there are HOT exhaust gases being fed through from the EGR valve.

quote Originally posted by Patrick: It gets pretty warm. Keep in mind there are HOT exhaust gases being fed through from the EGR valve.

Not necessarily. The EGR is only open under light load at cruise speeds. The amount of exhaust gas being recirculated is also not enough to cause significant heat increase, as significant heat increase to the intake charge air would cause detonation. Since the 2.8 has no knock sensors or knock retard capability, you would certainly know if that was happening.

Most of the heat you feel when touching the top of the intake, is external heat soak from general engine bay heat.

quote Originally posted by dobey: Not necessarily. The EGR is only open under light load at cruise speeds.

I never said it was continuous under any/all conditions.

My upper intake plenum feels much warmer to me than the "general engine bay heat"... but no, I've never measured it.

quote Originally posted by Patrick: I never said it was continuous under any/all conditions. My upper intake plenum feels much warmer to me than the "general engine bay heat"... but no, I've never measured it.

You didn't straight out say it, no, but your statement did imply it, especially by adding the colored and capitalized emphasis on the word hot.

There's a reason I said heat soak there. When you open the decklid, the hot air trapped in the bay will escape very quickly, but the heat that is soaked into the metal components will escape much more slowly. If you leave decklid closed, and just let the car sit and warm up to operating temperature from idling, the upper plenum will feel about the same temperature as if you were to cruise on the highway at 60 MPH for an hour, and then pulled into a rest stop and felt the upper plenum.

I merely wanted to clarify that the EGR is almost certainly unrelated to any concerns about how hot the upper plenum on a 2.8 feels, unless the EGR system is not functioning properly; but then you'd also notice worse problems than slightly elevated temperature of an aluminum intake plenum when felt by touch.

quote Originally posted by dobey: You didn't straight out say it, no, but your statement did imply it, especially by adding the colored and capitalized emphasis on the word hot.

The "colored and capitalized emphasis on the word hot" was in reference to the temperature of the exhaust gases entering the upper intake plenum, nothing more. You've just got to touch the EGR tube after the car has been driven for awhile to know that the exhaust gases passing through this tube to the intake are HOT.

When I look at the EGR tube, I notice the hole into the intake manifold is actually quite tiny... When I researched why so little, what I read was to limit two things: a big vacuum leak if the stretchy tube breaks (as we all know it often does or is); and to limit the "forced injection" of exhaust gas by the exhaust looking for the least resistive path (easier to get sucked in a vacuum than resistance from exhaust components)... I am painting my manifold is the purpose of my question in the first place... I do not know if I actually need like "super-fire-hot" paint or if regular car paint is OK. The paint I am looking at says good to 200F... I would think that temp would burn your hand if you touch it...

Could someone put a thermometer on theirs to get some kind of vague idea what goes on there?

quote Originally posted by mrstan: When I look at the EGR tube, I notice the hole into the intake manifold is actually quite tiny... When I researched why so little, what I read was to limit two things: a big vacuum leak if the stretchy tube breaks (as we all know it often does or is); and to limit the "forced injection" of exhaust gas by the exhaust looking for the least resistive path (easier to get sucked in a vacuum than resistance from exhaust components)... I am painting my manifold is the purpose of my question in the first place... I do not know if I actually need like "super-fire-hot" paint or if regular car paint is OK. The paint I am looking at says good to 200F... I would think that temp would burn your hand if you touch it... Could someone put a thermometer on theirs to get some kind of vague idea what goes on there?

I would use 500F engine/caliper paint. The engine is designed to operate around 210-215F coolant temperature, and the exhaust manifolds will be around 700F, so it would be possible for 200F paint to get baked/broiled and flake earlier on.