Typical EGT for I.C.E.'s
Typical EGT for I.C.E.'s
(OP)
can anyone tell me what typical exhaust temperatures (at the header) would be for a 4-cylinder normally aspirated, gas-fired engine.
secondly, what about that same engine with a factory turbo installed? (e.g. mitsubishi eclipses 1990 - 1999 models, lancers,.. ) would there be a dramatic temp difference or would they be within the same range?
i'm asking because those temps influence/determine which header materials would be suitable. i tend to think there will be little temperature difference between the two engines esp as exhaust gas reaches the exhaust manifold/header pipe.
any thoughts?
secondly, what about that same engine with a factory turbo installed? (e.g. mitsubishi eclipses 1990 - 1999 models, lancers,.. ) would there be a dramatic temp difference or would they be within the same range?
i'm asking because those temps influence/determine which header materials would be suitable. i tend to think there will be little temperature difference between the two engines esp as exhaust gas reaches the exhaust manifold/header pipe.
any thoughts?





RE: Typical EGT for I.C.E.'s
You will need a substantially heavier gauge steel for the turbo exhaust manifold than is normally used on NA engines.
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RE: Typical EGT for I.C.E.'s
i thought the N/A engine & turbo would both have temps ~1000 to 1400°F. does that seem about right or way off?
i'm really looking for values here.
RE: Typical EGT for I.C.E.'s
The headers are cast iron.
Most aftermarket headers are constructed of 304ss (although I think it should at least 304l if not 321/347 -thats more of a personal opinion.)
I do know that one company makes an inconel up-pipe (headers -> turbine inlet) it adds about 200-300$ to the price.
Try some of the hobbiest fourms (IE: www.nasioc.com) for the motors you are interested in, this is a pretty well known piece of information needed for tuning aftermarket timing/fueling controls.
Nick
I love materials science!
RE: Typical EGT for I.C.E.'s
also i noticed the same about a lot of aftermarket headers. from what i read about the two material props, 321 would seem more suitable for header material because of its higher heat tolerance. i guess 304SS is cheaper than 321?
does any one else have knowledge of what the temp ranges could be for a non-turbo engine?
RE: Typical EGT for I.C.E.'s
A drawback to 304 is that when welded (heat sensitized) it is susceptible to intergranular corrosion if exposed to road salt.
And it doesn't take much salt or very lengthy exposure to cause a part failure.
304L seeks to minimize this effect by reducing the amount of carbon in the alloy, with some success.
321 doesn't have this drawback, nor do the much less expensive stabilized ferritic alloys such as 409 and 439.
All of these have much greater elevated-temperature strength yield strength than do any carbon steels.
RE: Typical EGT for I.C.E.'s
I do know that 409/439 (I dont know wich) forms a nice hard oxide scale at turbine output temps after ~18mths. (salt dirt soap exposure).
I am going to throw my opinion with Pat. Although I've never measured EGT on a NA motor. Rob might be right then.
RE: Typical EGT for I.C.E.'s
also does SI mean "straight, inline"? as opposed to "horizontally opposed" or a "vee" configuration.
if you live in an area where road salt is uncommon then that corrosion concern with 304SS becomes less of an issue right? does that then leave concern with thermal fatigue as nick eluded to?
RE: Typical EGT for I.C.E.'s
However, I would think that both NA and Turbo engines would be limited by detonation and piston meltdown when trying to get maximum power. In that case, both combustion chamber temperatures would be similar.
Even though the temps might be the same inside the chamber, I would also think that as the gas passes out the exhaust valve and expands into the port it will cool a bit. As an NA will not have as much pressure in the exhaust port, I would think the NA engine will allow the exhaust to expand more and therefore cool more.
Regards
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Typical EGT for I.C.E.'s
RE: Typical EGT for I.C.E.'s
I did nothing of the sort.
I stated the well known point that not only does welding sensitize 304; so will exposure to temps in the same region as exhaust temps.
This sensitization is the precipitation of chrome carbides, 304L is a low carbon grade and minimizes it to some extent as Rob states, 321/347 have Ti/V as alloying elements, the kinetics are such that the carbon prefers those over chrome, leaving the chrome to provide corrosion resistance.
Nick
I love materials science!
RE: Typical EGT for I.C.E.'s
I dont think that you are comparing apples with apples. The two engines you mention will not be the *same* in turbo/non turbo guise. There will be myriad changes, compression ratio, piston & valve material, valve timing etc etc
However I get your gist and a modern SI (spark Ignition) engine will generally have max exhaust temps of ~950degC.
For a given engine set up (NA or FI) one is const
1) Detonation
2) AFR
3) Exhaust Temps
To increase the torque at a given engine speed (and therefore power) the amount of air in the combustion chamber must be increased. However as with everything there is a compromise: -
As the airmass per stroke increases so does the tendency to detonate.
To stop this detonation the spark must be retarded.
As the spark is retarded the exh temps increase.
As the temps increase the AFR must be reduced.
This 'richening' can only continue until such time as rich misfire occurs - or no more torque is produced because of the extreme retarded spark.
At wide open throttle the modern Bosch Motronic EMS systems run closed loop exh temp control (with AFR being the control parameter). This allows best fuel economy and also means that different octane fuels can be used with their active knock system without fear of overtemp in the exhaust.
MS
RE: Typical EGT for I.C.E.'s
i appreciate your input. however don't let my simplification mislead you into thinking i presume the engines (esp. internals) are exactly the same. that was not the point. i fully understand there are substantial, as well even slight, differences between a NA & turbo engine.
my point was simply to use the same engine block for comparitive basis of EGT not to compare the engines in of themselves. i did not want to compare say 12-cylinder to a 3-cylinder or a 2-stroke versus 4-stroke, etc. i suggested a common "platform" such i did to minimize other variables.
e.g. i pointed out that the 1990's version of mitsubishi eclipses (& talons & lasers) did just that. they used the "same" 2.0 liter, 4 cylinder engine, but had different internals (& other accessories) for the NA versus the turbo. however, when you look at the engine block & they appear identical.
that being said, you indicated a max EGT of ~1700°F is typical. are you saying this applies to both NA & FI engines? would this be temp be at the exhaust header/manifold? & as i said before, i am not doubting anyone's veracity, but what is your source for that value?
thanks again.
RE: Typical EGT for I.C.E.'s
The temp I quote is the max exh port temp within the head and is the most recent that I have worked on in an SI application. However I would expect that some OEMs might be anywhere up to 50-100deg less than the 950degC I quoted.
MS
RE: Typical EGT for I.C.E.'s
kj