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Old 08-09-2006, 08:55 AM   #21
TSi+WRX
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^ Or datalogging. The Intake Air Temperature (IAT) would do.

I've actually "hung" a temperature sensor in this area as well as datalogged IATs. Typically, IATs are within 5 to 10 degrees of ambient - with the IAT being on the hotter end.

Our stock airbox is *AWESOME* at insulating the intake air, as well as allowing for incoming ambient air to be properly ducted to help lower IAT as fast as possible.

I have yet to play with this area on my LGT. I just haven't had the time. So far, I've only fab'ed a home-made full heat-shield for my Perrin Short Ram, out of laboratory/autoclave-grade thermoplastics and quite a bit of Thermo-Tec insulating tape (the thick kind).

However, on my old DSMs, I always similar crafted "cold air ducting" to what brother Effin cited.

And while I truly do not know (nor think) it much affected power (it was *not* butt-dyno-able), I can say with certainty that it does contribute tremendoulsy to lowering IAT and "intake area" temperatures as soon as any decent forward motion is had by the vehicle.

Think of it as our stock intake "snorkel," only drawing air from an even cooler location - and, depending on how large of an opening you've got, perhaps a even larger "funnel."

-----

So.....this is a question that's bothered me for a while.....

It's known that our ECU factors in IAT - the temperature at the MAF - into its magic-brain equation of how much timing it will allow us to run. This, of course, translates directly to how much "power" we have on-tap.

Now, then, my question is this:

Do we also have a sensor which reports the actual CHARGE TEMPERATURE (temperature after the heated intake charge passes through the intercooler, and is seen at the throttle-body junction) ?

I have yet to find this parameter in any free datalogging software.....

If not, and if how the ECU "judges" timing is only noted for IAT, then wouldn't it indeed be to our advantage to try to truly get IAT as low as possible?

And if there's no charge-temp. sensor, then how in the name of heck does a "better" intercooler help to make our car perform better? It's been proven that a "better" intercooler does contribute significantly to both peak power as well as the powerband itself, but how is this reconciled with the IAT *as referenced above*?

Questions posed for all.

Any and all advice/speculation/opinions are welcome.
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Old 08-09-2006, 09:12 AM   #22
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I don't believe we do have a sensor for intake charge temps, I think all readings/adjustments are made soley by the MAF.

Cooler air just means more air, and I don't think the ECU compensates timing for this. It usually is concerned about the A/F ration and fuel grade..

More to add later, I'm hungry, need lunch..
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Old 08-09-2006, 09:59 AM   #23
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Go feed your brain, then hurry back!
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Old 08-09-2006, 10:59 AM   #24
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Quote:
Originally Posted by TSi+WRX
Go feed your brain, then hurry back!
OK, back. Did some more thinking/researching, and I think I figured that the MAF is the only sensor it needs in it's current setup. The MAF on our cars measure air MASS. With a cooler intake charge and the same MAF readings you still get the same amount of air in the cylinders. Even if the charge is cooler, air going past the MAF = air going into the cylinder. Even though pressure, density, and temperature changed, mass stays the same. If we chill the intercooler, and the air gets more dense, and the engine uses more mass than is passing through the MAF, then a vacuum is created, more air flows through the MAF, and the system balances in milliseconds. While our cars do not have an intake air tempurature sensor after the turbo like some other cars (ours is built into the MAF), it can calculate the manifold air temperature basied off the MAF and MAP, combined with engine volume and rpm. This lets it judge the quality of the incoming air and, in combination with a bunch of other factors, and pick proper ignition timing from the map. So if your intercooler is heatsoaked from siting in traffic, the ECU will immediately pull timing because your intake charge is hot - it has a spot on the timing map for that hot intake charge. This is to keep detonation from occuring. This is also why the stock ecu can also handle a turbo and intercooler upgrade, on stock bost control and fuel - all you are doing is blowing cooler air.
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Old 08-09-2006, 01:45 PM   #25
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so then if we duct cooler air in (forced), wouldn't there be a positive effect especially when the car is stuck in traffic and there's no ram air effect?
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Old 08-09-2006, 01:53 PM   #26
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Quote:
Originally Posted by Effin Ponderous
so then if we duct cooler air in (forced), wouldn't there be a positive effect especially when the car is stuck in traffic and there's no ram air effect?
I'd have to say no. The turbo will stuck in that air and spit it out HOT. You'd be better off having that fan blowing on the intercooler. Maybe you could do a water spray system on yout TMIC?
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Old 08-10-2006, 04:07 AM   #27
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^ Exactly - if you're truly stuck in traffic or sitting at that infamous 4-minute traffic light right by where I live, you're SOL. Your TMIC will heat-soak, and then it's hotter air all the way. You'll literally be able to feel the car pull timing.

But if you're speaking of anything outside of heat-soak, then yes, it might help a little. Exactly how much you gain, though, especially without a tune to specifically take that into account, is more than likely negligible.


-----

RE: IAT vs. Charge Temp.

DM - That's very thoughtful, bro, and I'm inclined to agree with your reasoning. Thanks for putting it out there, as well as for your deductive effort. I just couldn't quite wrap my mind around it ( although, in a "moment of clarity" while feeding baby Anna her mid-night feed at around 3AM this morning, I *almost* reasoned it all the way through ) !

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Old 08-10-2006, 05:45 AM   #28
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Ok...back to the drawing board.
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Old 08-10-2006, 07:30 AM   #29
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Here's what Christian at Cobb had to say about this:

Quote:

Originally Posted by TSi+WRX
^ I've been wondering about this....
It's cited (both on this thread and many times elsewhere) that our ECU bases some of its timing "judgement" based on IATs, correct?
Do we also have a sensor within the vehicle for the actual charge-temp, and does the ECU compensate accordingly?

No, the vehicle does not have a charge temp. sensor, just an IAT at the MAF sensor.


Originally Posted by TSi+WRX
Or is the ECU basing things off the IAT as a good method of inherent fail-safe?


The engineers whom establish the ECU calibrations figure out the mechanical efficiencies of the chosen intercooler and establish their calibrations based on their research and findings.


Originally Posted by TSi+WRX
And if the ECU sees only IAT, but not charge-temp, how, then, does an aftermarket TMIC - or *any* intercooler, for that matter, help contribute to better performance?


A good intercooler is able to bring down the charge temperature to close to 30-50 degrees above ambient temperatures if it has been matched well and the turbo is still running within its efficiency range. You can usually see (datalog, use external sensors, etc.) how a vehicle reacts through dyno and road testing.

Take care,
Christian.
Christian's replies are in bold and highlighted blue to ease readability. I did not change his text nor wording.

Basically, like DM speculated, it's the computer doing its magic via an algorithm, and our only temperature sensor is at the MAF.
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Old 08-10-2006, 10:03 AM   #30
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Quote:
Originally Posted by TSi+WRX
Here's what Christian at Cobb had to say about this:



Christian's replies are in bold and highlighted blue to ease readability. I did not change his text nor wording.

Basically, like DM speculated, it's the computer doing its magic via an algorithm, and our only temperature sensor is at the MAF.
I knew it.
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Old 08-10-2006, 10:53 AM   #31
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OK guys, beat me over the head for this one, but:
If the ECU takes air temp at the MAF, and you could somehow lower the temp 30 or so degrees at the MAF, what would the ECU change based on lower intake temps? Does it raise or lower AF mixtures based on the density of the incoming air? If so, wouldn't this have to change something pretty significant? Maybe my density is too high here?
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Old 08-11-2006, 03:55 AM   #32
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^ No, no, your density is definitely just fine, bruddah!

From my perspective, yes, cooling the intake-area temps as much as possible should help plenty, but we've still got to keep in mind that even if you're cooling the IAT to-ambient via various ducting/fans (useful, say, if you're sitting at that year-long traffic light), your heat-soaked intercooler is not going to be properly cooling that first bolus of charged air, and that the vehicle itself, from pre-programmed algorithms which would likely signal a "hey, I've been idling for, like, the past 5 minutes" kind of a situation, would still pull timing accordingly.

If you're on the road doing 35+ MPH, or if you're running that fan because you're in some city-traffic, then yes, you'll probably do some good - at least that's my base belief. As long as there's airflow to cool both the intake air temperature (which, in this case, will be helped by the home-brew setup) and the intercooler is not heat-soaked, you're probably seeing some benefit from that kind of setup.

And yet again, the question of how much would this help rises up....

Honestly, I don't know. I'd imagine that if it's something that actually can be tuned for, its returns might be substantial enough that it can be butt-dyno-able (but considering the types of situations under which such a gadget would return "gains," would you really want it to be tuned for such? or would you rather keep it as a simple "fail-safe" kind of device, adding to your tune's inherent safety factor? my preference would be the latter). But from my past experience, I know that just "grafting on" such devices pretty much nets no discernable gain in the "butt dyno" department, although the air-temperature benefits *are* clearly visible on a truly quantitative basis.
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Old 08-11-2006, 07:00 AM   #33
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OK, I think I'm getting it now (and again, sorry for the redundance). What you are saying is that it's not so much the hotter air that gives the bad performance, it's the computer thinking there is hot air (and making adjustments) that does it. If that's the case, there's not a helck of alot that can be done without reprograming.

Ah Crap, then wait a minute...why would throwing a bag of ice on the IC make any difference in performance?
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Old 08-11-2006, 10:53 AM   #34
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Quote:
Originally Posted by Effin Ponderous
Ah Crap, then wait a minute...why would throwing a bag of ice on the IC make any difference in performance?
Yes. In fact, I usually throw slabs on dried ice on my IC when I'm at the strip (which is very rarely).
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Old 08-11-2006, 12:14 PM   #35
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^ Good question, brother Effin - and quite frankly, I don't know.

This is something I need to ask, and surprisingly ( or rather, not so, as I haven't really been able to make proper change at the grocery store since Anna was born ), totally forgot about.

Indeed, like brother DM said, it's quite true in the real-world that "icing your IC" will produce excellent results - both on the strip as well as on the dyno. Reducing charge-temp really does work.

And as brother DM speculated before:

Quote:
Originally Posted by Drift Monkey
If we chill the intercooler, and the air gets more dense, and the engine uses more mass than is passing through the MAF, then a vacuum is created, more air flows through the MAF, and the system balances in milliseconds. While our cars do not have an intake air tempurature sensor after the turbo like some other cars (ours is built into the MAF), it can calculate the manifold air temperature basied off the MAF and MAP, combined with engine volume and rpm. This lets it judge the quality of the incoming air and, in combination with a bunch of other factors, and pick proper ignition timing from the map.
Which, to-follow, while he later cited the example of heat-soak, it would thus also reason that the "natural balance" struck by the cooler air now resident within the TMIC/post-charge would give the MAF new data - and thus give us slightly more power when the IC is "cooled."

This is often why you'll see such IC "icing" at the strip (be it bags of ice, slabs/pieces of dry-ice, or even using a dry-ice/alcohol "slurry" in their air-to-water intercoolers) - or people who use either a water-sprayer or CO2 (or even nitrous) sprayer on their ICs right before/at-the-start-of a run.
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Old 08-11-2006, 02:57 PM   #36
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I think it's time to get the hoses and start some testing. Supplying cool air to the air box will be the easiest thing to start with.
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Old 08-11-2006, 08:51 PM   #37
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Quote:
Originally Posted by Effin Ponderous
I think it's time to get the hoses and start some testing. Supplying cool air to the air box will be the easiest thing to start with.
I think I'm going to tackle the ghetto intake mod on my car...saw that thread over on NASIOC, and it's got me thinking
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Old 08-12-2006, 04:17 AM   #38
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Quote:
Originally Posted by NALegacy
I think I'm going to tackle the ghetto intake mod on my car...saw that thread over on NASIOC, and it's got me thinking
What is that?
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Old 03-18-2007, 07:13 PM   #39
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for discussion sake, wondering if it's better to seal the hole after removing the silencer? cos i sealed mine, thinking that it is actually used to resonate the sound and not to introduce air. with the car moving at speeds, the pressure difference in the air coming in from the hole and the air duct mught cause a vaccum effect.

my $0.02 worth.

please comment and advise.
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Old 03-19-2007, 04:34 AM   #40
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Haven't noticed that at all a year or so later.

But on another note...I put in my K&N filter over the weekend. While I don't notice anything on the butt dyno, I can actually hear my stock BOV now!

Woohoo, rice-a-rony!
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