Intake Manifold Thermal Reduction

Dr.Jeff said:
O.k., then I think you might see a significant difference in temps between that point (air filter lid) and the intake manifold in general, with the manifold being hotter. I don't know if between the throttle body and the runners there is as much difference, for a cross flow head (I think that's what you have). However with a counterflow head (X1/9) there will be a big difference in temp due to the runners being right over the exhaust manifold, as Huss siad. To me that is all the more reason to add the insulator spacers at the head rather than between the runners and plenum; try and reduce the runners' temp as much as possible by insulating them from the head AND by adding a heat shield between it and the exhaust. But as you noted, your plastic intake manifold may be a much better insulator and therefore the runners could be much hotter than the throttle body.
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20190307_163644.jpg

Maybe this will clarify things:
Added a pic of the intake manifold. It's one piece that includes the throttle body mount, a plenum about 8" below the tb, and the runners that wrap around the plenum and bolt directly to the head. All one piece.
Ignore the 72mm tb, that has been replaced with a 58mm.
 
Ok, here's some readings from our Pontiac G6/2.4L, basically the same setup as in the 600 except the Fiat is 2.2L. Engine idling, hood open. Outside air temp 48F

Coolant temp -- just under 225F on gauge.
Highest actual was 227F on water pipe on back of engine, but near exhaust.
Temp at water pump 174F.

Cylinder head near intake manifold 135F.
1" from head into runner 118F.
1" from head with wife briefly holding an unsteady 2500RPM went down to 116F.

Below tb at plenum about 8" into manifold 97F. (Stayed at 97F at 2500RPM.)
 
gene cooley said:
Maybe this will clarify things
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Ya, I was picturing something completely different. That's kind of a funky design, most likely due to packaging/space requirements I imagine.


gene cooley said:
Cylinder head near intake manifold 135F.
1" from head into runner 118F.
1" from head with wife briefly holding an unsteady 2500RPM went down to 116F.
Below tb at plenum about 8" into manifold 97F. (Stayed at 97F at 2500RPM.)
Click to expand...
So I see a couple things. 1) the temps at idle and at 2500rpm really are not significantly different, although it might be at full load/full throttle conditions. So lowering intake temps in general will benefit across the board. 2) the temp at 1" from the head is still quite high (relative to the head temp). So insulating the manifold at the junction between the head and the manifold should offer a significant decrease of intake temps. 3) the temp drop from the 1" reading and the "below the TB" reading is pretty significant (20*). Given your plastic manifold should have a similar insulating effect as the phenolic spacer, then I'd expect the spacer could offer a decent insulative benefit on the Fiat SOHC. It seems worth doing to me. Thanks for sharing the data. ;)
 
Jeff, even though I was careful in taking the readings there are so many variables involved here that I think at best you can only get a general idea of what they are telling you.
My feeling is that you are going to get better results if you can shield the intake manifold from the exhaust header. That's where your main heat source is.
 
Agree on both points. However I'm still going to insulate the intake manifold from head heat in addition to other forms of thermal management.
 
tonyism7 said:
What do you think is the best way to make one?
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I bought a section of the phenolic material and will cut them out by hand. It is fairly easy to work with; band saw, hole saws, sanding drums, etc. However if you can make a digital file with the shape you want, then you can have them laser cut. That would be much better and cleaner. Unfortunately I do not have the resources (read 'ability') to make such a file. But if someone else does I know of a couple places that can cut them for us. ;)
 
Dr.Jeff said:
I bought a section of the phenolic material and will cut them out by hand. It is fairly easy to work with; band saw, hole saws, sanding drums, etc. However if you can make a digital file with the shape you want, then you can have them laser cut. That would be much better and cleaner. Unfortunately I do not have the resources (read 'ability') to make such a file. But if someone else does I know of a couple places that can cut them for us. ;)
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If they do laser cutting there's a good chance that they can scan the flange on the manifold and do everything right there. Costs more but
it takes away the chance of having to redo anything ar your expense.
 
Oddly the two sources I have for cutting will not scan things. Nor will they create files, use certain types of files, or do file conversions. I wish they did because there have been several things I wanted made but could not due to the inability to generate an appropriate file. On the plus side, they have very reasonable cutting costs.
 
mkmini said:
What is notmal air temperature in the plennum on these SOHC with turbo compared to ambient?

Maybe @Bjorn Nilson and others that can see this data can share Your results?
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I don't have much experience yet. I've been driving hard on track just once with the new engine. It was 150m above sea level, 16 degrees C and wet.
I don't think there is a "normal" intake temperature, it is all about ambient air temperature and altitude, how hard you drive and size/type of IC. Under the circumstances above, my maximum intake temp climbed from 20 to 35 degrees C during hard accelerations.
I don't know what to expect from a charge cooler like mine, but to me it seems like it does the job.
Worth to mention is my cooling issue. The engine tends to go warm when pushing it hard for some time. I hope an aluminum radiator and dual fans will fix the problem.
 
It’s ~0C here now altitude could be ~20m max above sea level.
Intake temp is 35 to even 50C at city driving
I have intercooler from uno turbo, I guess that should enlarge sidescoop for it asap :D

and make a heat shield netween manifolds, Ut one didn’t fit with PuntoGT intake manifold
 
mkmini said:
Intake temp is 35 to even 50C at city driving
I have intercooler from uno turbo, I guess that should enlarge sidescoop for it asap :D
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How does it behave when cruising on the highway? And if driving hard at high speed?
I assume your city driving doesn't require much boost unless drag racing at red lights. So find out if this is an IC capacity issue or an air flow issue.
 
Same on highway ~38C.
I haven’t drive very hard yet, fine tune will happen in January.

Now it is limited to ~0.5bar boost, I was told that after fine tune when boost will be bigger then intake system’s airflow is going to help everything cool down, is it really like that, not sure.

Maybe I should also try to make a ducting from IC to radiator’s 1st fan, because on hard driving if coolant has to be cooled more, then it will suck air through the IC first.

*for those who are reading this and don’t understand, I have radiator in the trunk
*1st fan is on the left side
*and snorkel for intake manifold cooling 😂
EF12851E-7D01-444B-B654-E7CD4BA05D9B.jpeg
 
Increase of Intake air temp speed is a litlle slower than increase of coolant temperature.

For example if I had stopped after driving, then air temperature starts to increase from 35 to ~50C at idle.
 
Seems like a "belts and braces" approach to heat mitigation is needed. Perhaps ceramic coating the exhaust manifold inside and out in addition to the spacers and shields?
 
mkmini said:
Same on highway ~38C.
I haven’t drive very hard yet, fine tune will happen in January.

Now it is limited to ~0.5bar boost, I was told that after fine tune when boost will be bigger then intake system’s airflow is going to help everything cool down, is it really like that, not sure.

Maybe I should also try to make a ducting from IC to radiator’s 1st fan, because on hard driving if coolant has to be cooled more, then it will suck air through the IC first.

*for those who are reading this and don’t understand, I have radiator in the trunk
*1st fan is on the left side
*and snorkel for intake manifold cooling 😂
View attachment 39988
Click to expand...
Your main engine coolant rad is in the runk?

So what is up front where the rad would normally be?
 
mkmini said:
For example if I had stopped after driving, then air temperature starts to increase from 35 to ~50C at idle
Click to expand...
Probably because of accumulated heat in the turbo and no air flow thru the IC.
Your current boost 0.5 Bar is not much. Expect this problem to become even worse with more boost and summer ambient temperatures. Even the tiny stock IC should be able to handle such small boost. I think more air flow is needed.
 
mkmini said:
...on highway ~38C....Now it is limited to ~0.5bar boost, I was told that after fine tune when boost will be bigger then intake system’s airflow is going to help everything cool down, is it really like that, not sure.
Click to expand...

A clever guy called Boyle figured out a few things to do with gases, another guy called Charles was also quite clever and he did more research on the subject, together they figured out the "combined gas law"

The combined gas law relates "before and after" conditions of a gas:
P1V1 / T1 = P2V2 / T2

where P is pressure, V is volume and T is temperature.

and this tells us what will happen when you double the boost from 0.5 to 1 bar....

the volume doesn't change, so we can drop that from the equation and we get

P1 / T1 = P2 / T2

cross multiply to clear the fractions

P1 x T2 = P2 x T1


Divide to isolate the T2 (the number we want to work out is T2)


T2 = (P2 T1) / P1

T2 = (1.0 x 38) / 0.5
T2 = 76

(dividing by 1/2 is the same as mutiplying by two)

this tells us you will double the amount of energy that compressing the gas to 1 bar will absorb as heat... note this is ICT before your charge cooler, (which can only cool so many joules of energy per unit of air flow across it)... if you double the temp in things can go a bit crazy in the engine (sometimes)

It's hard to say what the ICT will be on the discharge side of the intercooler at 1 bar boost, as at the moment I only know the discharge temp and not the inlet temp at 0.5 bar, but there are calculators to work out the relative efficiency of your charge cooler if you can measure pressure and temp on both inlet / discharge.

SteveC
 
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