Hot intake manifold

[manic]

I took my tdi for a quick spin today, was just long enough to get up to temp (90C) lifted the bonnet and it was HOT in there, fair enough warm day and all. Inter-cooler was warm, intake manifold was blazing hot.

Does it seem silly to have an enlarged inter-cooler deliver air through a hot intake manifold? Would it make any difference to performance if the intake manifold was somehow kept cool?

[Blknight.aus]

hows the airflow from the fan?

dont foget that the intake manifold is ontop of the exhaust and turbocharger directly attached to about the hottest part of the head, all of its aluminium and would take probably about 3 nanoseconds longer than the crank shaft takes to stop to begin to heat up to some reasonable temps.

[manic]

I've got a thermostat controlled electric fan, the coolant didn't get hot enough to trigger it on that run. I suppose a belt driven fan would keep the engine bay cooler but I was thinking a wrapped exhaust manifold and side exit vent on the manifold side of the wing for better airflow.

Coolant temps and egt's are good so perhaps no need.... I'm wondering how much a hot intake manifold adds to intake temperatures - negligible?

[Blknight.aus]

let me get this straight......

you had your engine up to temp, with no air flow from the fan and you're wondering why a chunk of aluminum bolted onto the side of and above the hottest parts of the engine was hot?

I'll ask that anther way

Are you Trying to warp the head?

[manic]

let me get this straight......

you had your engine up to temp, with no air flow from the fan and you're wondering why a chunk of aluminum bolted onto the side of and above the hottest parts of the engine was hot?

I'll ask that anther way

Are you Trying to warp the head?

I didn't think so much about about the surface temperature of the engine when I put in the electric fan - considering it is a water cooled engine. I assumed EGT, coolant temperature and level were good enough indicators and that so long as they are healthy the head is safe. So your saying that even with those temperatures sitting pretty I can warp the head?

I'm not wondering why it is hot. I am curious as to how much heat a hot intake manifold adds to the air after the intercooler... I suppose I could do some tests with a temp gauge and thermostat in the intake manifold. I would be interested to see how much an enlarged intercooler drops intake temps over standard then see if there is much difference with a wrapped intake/exhaust manifold.

But now you have gone and raised the possibility of a 'Warped Head' I don't really care about the intake temperature any more. Would it be worth getting some sort of surface temp sender on the cylinder head!?

[Blknight.aus]

yes, if your thermo fan is not coming on at the temperature at which the thermostat begins to open you are begging to put yourself into overheat and warp head territory.

my thermo fan comes on at 60 degrees on the thermostat housing and I have a warning light that comes on if the thermostat temperature goes about 95 that doesnt switch off till it goes below 85 (it was ment to be 90+80)

[manic]

Top hose and top section of radiator was hot, bottom hose was cool - I think the thermostat had only just opened up when I got to home so no harm done.

My thermo fan has two switchable settings: on at 88 degrees C and off at 83 and the other on at 92 and off at 87. It also has an override for wading, the fan switch may have been in the overide position. :eek: I'll do a couple of tests make sure its all working as it should before the next run.

Now I'm thinking cylinder head temperature sensor hooked up to the thermo fan so that it is switched on by both coolant and CH temp whenever needed.

Do you know of a good CH temp sensor and what CH surface temps are too high?

[Blknight.aus]

I just run the coolant sensor, the head temperature will vary depending on where on the head you measure it.

its hotter on the manifolds side cooler on the injectors side, cooler up the front hotter down the rear.

the head bolts that run down closer to the pots are hotter than the ones out nearer the outisde of the block and the bolts that run near the exhaust ports are hotter than the ones near the inlet ports.


Thermo fans dont shift a lot of air compared to an engine fan, the killer is that if you let the heat build up get ahead of the amount of cooling they can provide to the radiator the heat build up goes up rapidly and you pick up a lot more heat in the engine bay. Part of that is because the air coming out of the radiator is now hotter, and because the engine is running hotter its throwing more heat into the engine bay which isnt going anywhere because theres not enough air flow to get rid of it, because the heats not getting out of the engine bay as well the heat load thats normally lost out of the engine via the block now has to go out of the radiator.

Its not usually a problem if you're swinging around at highwayish speeds at low throttle settings but start working around town lots of 2/3 running speeding up and slowing down or working it off road and then things tend to get warmer faster.

its typically about this time that someone will turn the AC on because its getting hot.

[Sitec]

Don't scare the guy! If you've fitted a dustbin of an intercooler, have noticed that you have heaps more go then its working! Intercoolers are great at cooling pressurised air from the turbo which is bloody hot, and bringing it back down to reasonably cool. Don't think that it'll cool it to 10 deg or so... It can only ever cool to the ambient temp outside the vehicle. If the temp gauge is reading normal, the coolant is all still in the radiator and has been for ages, there's a good chance it's all fine! Having done a decent run, the heat from the top of the rocker cover might make it just touchable.... The inlet manifold will be the same. (Unless its a foggy 8 deg evening in the North of England... You do notice the power increase due to dense moist oxygen rich air). Panic not, cooled air from the intercooler at 50deg is far more useful and dense than hot, recently compressed 110 deg air straight out of the turbo!