Acceptable Intake Air Temperature

[belize1334]

I've been casually searching for a long time now and I can't find any consensus on what an "acceptable" manifold temperature is. I realize that there's no simple answer since it all depends on fuel, timing, etc...; but there's got to be some common wisdom that says if you're IM temps are above/below X then you're in danger/good to go.

Now that SD is a reality maybe somebody can post a log?

 

[Muskrat]

Ideally, you'd be at ambient air temp, or even below. I don't think there is a set number that say's, "Whoa! You're too hot!". You just tune for what you have, and try to reduce your manifold temps as much as possible. Higher temps means less air/volume so less fuel can be added, less timing advance, you'll see detonation earlier, etc.

Now, there is a measure of common sense to this, if your seeing something really high maybe there's an issue with your compressor. But I feel it's a common sense thing, not really a set number. A screaming 16g is going to show higher IAT's than a GT35R at the same boost pressure, for example. Doesn't mean the 16g's IAT's are "bad" as long as they're tuned for properly.

 

[belize1334]

I understand the physics behind the search for cooler charge temps. What I'm looking for is a benchmark value. Just a number that I could throw out there as a "good" charge temperature against which real world values can be measured.

The motivation is that I'm considering switching from my knockoff of a spearco 2-230 core to a different knockoff of a 2-231 core. If you look here you can see that these cores have listed temperature reduction based on coolant temperature inlet temp and airflow. The 2-230 is a monster...more than enough. But it's also bulky and takes up a lot of room in my engine bay. The 2-231 on the other hand is smaller and appears to be about 81% efficient at 450 cfm. For this the ambient temperature is the coolant temperature (110*F is consistent with giving it a beating). Extrapolating to 16g like numbers, that'd put my intake temps at about 150*F.

What I'm interested in finding is whether 150*F is generally considered "good", "ok", or "too hot".

 

[Muskrat]

I doubt you're going to get much data, as I don't think many people who run a 16g have the capability to log IAT at the manifold, and those who do probably have a set up much different than yours and the comparison will be moot.

What are your IAT's right now? If the intercooler is the only thing you're changing, and you're going to have higher IAT's you'll lose power. Like I said you tune to what you have, not really the other way around. The goal is the lowest possible with what works with your set-up.

If fitment is more important to you than performance then make the change. Remember the tiny intercooler these came with?

You also need to consider on boost performance. A big intercooler will cool better, but increases turbo lag due to larger intake volume. It's a big balancing act. Choose what you think will be best, and go for it.

 

id also like to add an ongoing debate to think about...some people say that with an efficient intercooler you'll be right around ambient temp if not a little higher. others say that (which is indeed factual) that when you pressurize air it gets hot, thus the need for intercoolers.

the way I see it; when you run a side mount and run stock boost, the temp of the air charge going into the motor it's equivalent to running a little more boost with a larger intercooler.
there are other things to keeping in mind like engine compartment heat-soaking on the IC piping too.

just some things to think about.

 

[prove_it]

Isn't the average turbocharger outlet temperature around 100 for low boost and 300 for high boost? That would be pre intercooler temps also.

I would say that ambient temp to around 150 degrees would be the general range. Can't forget to take into account for heat soak off the radiator and other factors like sitting idle at stop lights, or hot lapping on the track.

I'll be converting to speed density soon, but won't be for another couple weeks. Once I do I can post my logs for ya.

 

[NateCrisman]

Datalog with air temp

this log is from a 11.1 @ 123 pass on 116 octane racegas. No nitrous or meth. Pretty much the same mods as in my members section list other than I was running full exhaust and a 3" intake pipe. Going to a 4" cold air intake helped the air temp at tb by a good chunk.

I'll see if I can dig up any info from runs when I had a 16g with the same fmIc core.

 

[steve]

Any idea the ambient temp that day? Only because I know someone will ask. /ubbthreads/images/graemlins/wink.gif

 

[belize1334]

^^ From the logs I'd guess it was in the mid 70s since that's what he was seeing at idle. I'm surprised that your temps don't seem to reflect boost. I wonder if perhaps there's some delay in the sensor? Even so, the fact that you never get over 120*F tells me that I should shoot for much lower than 150*F which means that the 2-231 won't do it and I'll just stick with the 2-230 that I have now.

 

[NateCrisman]

yeah, Timeslips say 71*F. The sensor doesn't have much lag time at all, it's a GM air temp sensor mounted in the upper ic pipe. It responds near instantly to temp change (like take the sensor out of the pipe, plug it in..it reads ambient. if you blow on it while watching datalogger, you see it jump up to 90* instantly (I breath hot i guess).

anyway....the data is exactly what I expect for an intercooler that acts more like a heat sink than a radiator.

 

[belize1334]

Well I guess that goes to show you that intercooler efficiency isn't really fixed. If the efficiency were always 80% (for example) then as your turbo outlet temps jump from 75* to 300* (spoolup), the IAT should jump from 75* to 116* basically instantly. What we're in fact seeing is that the intercooler is basically 100% efficient and then as it heats up it gradually drops to about 78%.

Anyway, assuming that the IAT is a true reflection of the charge temperature (which sounds reasonable given your experience monkeying with the sensor) then this is exactly the kind of data I was looking for. Of course we all know that the tune is important and one configuration will be different from another, but this gives me a benchmark value for what it means for intake temps to be "nice and cool".

 

[NateCrisman]

I was monkeying with the sensor one time when I had suspected the sensor of dying but it ended up being a wire was pulled out of the plug.

Yes intercooler efficiency is all over the place. It changes relative to vehicle speed. But most of what you see on a quick run down the dragstrip is heat soak. Intercoolers, IMHO for drag racing do more absorbtion of heat (acting as a heat sink) than they do as a radiator...where they are passing heat off to the ambient air flowing through the core. In first gear when the mass of the core is at ambient temp it can absorb a larger amount of heat from the post turbo air than it can at the top of fourth gear when the core's mass is likely up in the 100*F range.


My gut feeling is I could air-dam the front of the bumper completely...blocking all the airflow to the intercooler and so long as the car was cooled down between runs, I think we would see roughly the same air temp graph with the starting line temps a few degrees above ambient and going up 40-50*F during the run.

 

^^^ that's why I think FMIC's are better for continuous driving, where as in drag racing, a water to air IC will deff be lower than ambient air temp so long as the water is on ice.

I wonder what kind of temp difference there would be between the ambient air temp and IAT on a rainy day when the FMIC is being hit by rain mist.

 

[RedTwo]

One of the local tuning houses pulls the plug when you start heading towards 40-50* celcius, which is around 105* F.

 

[NateCrisman]

One thing I wanted to add to the conversation, is that I have logged air temp throughout my time racing dsm's and I have always seen the same overall graph...near ambient air temps on the starting line and a progressive gaining ait throughout the run. Iv logged my talon when it had a stock sidemount and a 14b for "stock appearing" class..and saw over 220*F at the trap running the turbo with as much boost as it would make.


Here is some general info I posted about on EvoM from 2005 when I swapped from the stock Evo8 OEM fmic core to the monster garret 24x12x4" core ($900 from Buschnuts). That garret core is INSANE efficient for an air/air, nearly unbelievably so.

http://forums.evolutionm.net/evo-engine-turbo-drivetrain/161755-br-race-fmic-track-test-results.html

 

[Dialcaliper]

The absolute limit is dictated either by:

A) Intake air hot enough to cause detonation unless timing is severely retarded. i.e. by increasing boost and flow, you actually lose power from pulling timing

or

B) The intake air is getting hot and turbo efficiency drops to the point that the *mass* of air entering the engine starts dropping even though pressure is increasing (pressure can be increased either by adding more air mass or increasing temperature. You want more of the first and less of the second).

There's really no set rule, but at high boost pressures, you are usually running into problems with A, not B unless you're running race gas/E85/Methanol. Intake temperatures in the 150 range aren't unbearable, but aren't ideal either.

The closest you can probably get is to use timing advance as an indicator - If you're using timing advance in the teens at mid-higher RPM, you're probably not making the best use of the air in the engine, and are running too hot. From there you can determine yourself what intake temperatures are reasonable, especially as you run the engine longer and start heat soaking.

Edit: Garret suggests that typical temperatures are around 100-130F for intercooled setups, and 175-300F for non-intercooled turbochargers.

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[H05TYL]

Quoting RedTwo:
One of the local tuning houses pulls the plug when you start heading towards 40-50* celcius, which is around 105* F.



Who?

 

[NateCrisman]

Quoting RedTwo:
One of the local tuning houses pulls the plug when you start heading towards 40-50* celcius, which is around 105* F.



That honestly sounds to me like this tuning shop must either put out cars that are way under potential (run at quite low boost levels) or every car has a wonderfull intercooling setup and only run in nice cool weather.

Would they not tune a stock evo8? Im pretty sure my basic modded Evo8 ran intake temps at the throttle body in the 160* range with the stock 16g turbo and fmic when the boost was set to 23psi. which most people would consider a very conservative street/pumpgas setup. I bet a completely stock Evo8 pegs 105*F with easy on the factory boost setting of barely 15psi /ubbthreads/images/graemlins/confused.gif