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Old 08-04-2009, 12:09 PM   #1
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EVO Intake discussion I had with a mechanic.

I just wanted to make an observation I had with another mechanic. I was talking about headers and he saw that I have mentioned I had an EVO intake. He was saying I should put the stock one back in as soon as possible to prevent further damage to the engine. When I asked why it was because of the vast amounts of hot air. This would make sense but the EVO came with a shroud to block it off from the engine bay and I went a set further and sealed all the gaps less a tiny drain hole for water.

Now I've been running with this in the car for a year and a half with no issues but that got me wondering if anyone here has real data on if these make a difference or really do more harm than good. My old box was damaged so that was the main reason I replaced it. A used factory box is cheap so I can always go back if they really aren't that good.

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Chris

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Old 08-04-2009, 12:21 PM   #2
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Well, the factory intake is, as you know, already a fully sealed cold air intake, and if you install the EVO kit, I'm not sure it fully blocks off all the air from the top, as the engine cover may not seal fully well against the rubber piping. Did you cover the top of the EVO, like this guy did?....

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Old 08-04-2009, 01:14 PM   #3
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I would really question the mechanic's opinion...harmful to the engine? Even if there were a small air leak, it is nothing compared to the air the 997 cup cars and RSRs pull in with thier setup.

The air would be warm, not hot anyway; even if it were pulling some in. I've had an Evo Hi-Flow on my car for the last four years, without issue.
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Old 08-04-2009, 02:05 PM   #4
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I think the mechanic is wrong, it may well be that the hot air negates any hp gains but I see no reason this modification would harm the engine.


PS I am however worried about jmatta making the 666 post in this thread.
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Old 08-04-2009, 02:06 PM   #5
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Your mechanic doesn't know what he is talking about. I don't think there is much, if anything that is gained by the EVO intake, but warm intake air doesn't damage the engine.
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Old 08-05-2009, 07:15 AM   #6
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I don't think there is much, if anything that is gained by the EVO intake

I tend to agree; a couple HP, if any?

But the sound is pure intoxication!

PS I am however worried about jmatta making the 666 post in this thread.

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Old 08-05-2009, 06:42 PM   #7
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I'd like to know where your mechanic came up with the notion that sucking in hot air was some how damaging your engine? Education is a wonderful thing.

The only thing the hot air is doing is cutting down on the power your engine is making. Hot air (O2) molecules are expanded and you get less of them in the cylinder on the intake stroke. That's why the trick is to draw in the coldest air possible, in which the same O2 molecules are closer together (dense). More O2 + more fuel = more power.

That's the reason nitrous oxide (N2O) is such a great (and cheap) power adder. It's molecule is made up of 1 nitrogen and 2 oxygen molecules. During the combustion process the N2O molecule is broken down and the O2 is released. That added O2 combined with extra fuel that's injected produces allot of power. It is hard on the engine though.

I also have an EVO intake installed on my car. A properly installed and properly maintained EVO system will not damage your car and will provide more airflow into the engine because it is not as restrictive as the stock intake.
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Old 08-05-2009, 07:22 PM   #8
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He isn't my normal guy I just happened to have a conversation about something else and it came up. My normal place does race Porsches and even they have one with a custom box on a 911.
Chris
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Old 08-06-2009, 08:22 AM   #9
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Quote:
Originally Posted by jmatta
I would really question the mechanic's opinion...harmful to the engine? Even if there were a small air leak, it is nothing compared to the air the 997 cup cars and RSRs pull in with thier setup. .....
I don't think the 997 intake, in that photo is drawing air from the engine compartment. I think the rubber boots probably connect to the outside world when the hood is closed. The hood probably has some ducting that fits into those rubber boots, otherwise they wouldn't have clamped the rubber boots on there.
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Old 08-06-2009, 09:28 AM   #10
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I don't support or deny what the mechanic said, but one thing I'd like to add is that increase in temp of the intake air will raise the threshold for engine detonation. Turbocharged engines normally have an intercooler set up to aid in cooling intake air to make more power which is related to reducing odds of detonation.

Most newer cars have knock sensors that automatically adjust engine management when the knock sensor is triggered that would prevent dammage.
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Old 08-06-2009, 09:34 AM   #11
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Get a scangauge tool. Plugs right into the obd2 port and you can watch all kinds of things, including air intake temps. I had a cone filter on and while driving I was getting 86deg fh. on a 80 degree day but while stopped I was getting high 120's. With my stock box back in on a 88 degree day I was getting 88-90 degree temps and while stopped I was only hitting 105 and that was stopped for a long time.
KISS Keep It Simple Stupid and stay stock with a drop in filter. There is plenty of noise if that is what you are after if you desnorkle.

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Old 08-06-2009, 03:30 PM   #12
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[QUOTE=turbo23dog]I don't support or deny what the mechanic said, but one thing I'd like to add is that increase in temp of the intake air will raise the threshold for engine detonation. Turbocharged engines normally have an intercooler set up to aid in cooling intake air to make more power which is related to reducing odds of detonation.

Most newer cars have knock sensors that automatically adjust engine management when the knock sensor is triggered that would prevent dammage.[/QUOTE


Detonation is caused by crap gas in high compression, turbo and supercharged engines. It has NOTHING to do with intake air temp. The intercooler in a turbocharged engine is NOT related to reducing the odds of detonation.
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Old 08-06-2009, 04:49 PM   #13
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Quote:
Originally Posted by Boxtaboy
Well, the factory intake is, as you know, already a fully sealed cold air intake, and if you install the EVO kit, I'm not sure it fully blocks off all the air from the top, as the engine cover may not seal fully well against the rubber piping. Did you cover the top of the EVO, like this guy did?....

Hey Rich, you pimpin out pics of my engine bay?! Sweet!
I would take what the mechanic said as a grain of salt as the EVO intake is a negligible gain in engine performance without headers, chip, high flow cats and exhaust. All itreally does is give tha car a real nice sound. I also found that the way the engine delivers the power has changed, no dyno charts to back this up, but its my seat o pants feeling.

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Old 08-06-2009, 05:00 PM   #14
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[QUOTE=Jaxonalden]
Quote:
Originally Posted by turbo23dog
I don't support or deny what the mechanic said, but one thing I'd like to add is that increase in temp of the intake air will raise the threshold for engine detonation. Turbocharged engines normally have an intercooler set up to aid in cooling intake air to make more power which is related to reducing odds of detonation.

Most newer cars have knock sensors that automatically adjust engine management when the knock sensor is triggered that would prevent dammage.[/QUOTE


Detonation is caused by crap gas in high compression, turbo and supercharged engines. It has NOTHING to do with intake air temp. The intercooler in a turbocharged engine is NOT related to reducing the odds of detonation.

Uh... anything which causes the A/F charge to ignite prematurely is detonation!

Too high a CR for the fuel used, too high a charge temperature (intake temp or fuel temp), too advanced a spark, too low an octane fuel for the CR, too little engine cooling, improper mechanical timing, the wrong heat range spark plug, carbon deposit hot spots in the cylinder, or the cumulative effect of any combination of the above.

And, it doesn't only affect force aspirated engines either (turbo, s/c), today's naturally aspirated engines are just as prone to it.

Modern engine management software will advance the spark to just shy of the detonation threshold to achieve maximum efficiency. As such, it doesn't take too much of an adverse condition to throw it beyond that threshold.

Once the knock sensor senses the increase in vibration, which it attributes to knock, it increases it's base signal to the ECU which then begins to retard the spark either to a pre-programmed level, or it will advance the spark until detonation is achieved and then retard it back slightly from that mark.

Because of this, naturally aspirated engines are more sensitive than ever to such things as the intake temperature.

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Old 08-06-2009, 06:30 PM   #15
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^^ Thanks...
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Old 08-06-2009, 08:25 PM   #16
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Quote:
Originally Posted by Lil bastard
Uh... anything which causes the A/F charge to ignite prematurely is detonation!

Too high a CR for the fuel used, too high a charge temperature (intake temp or fuel temp), too advanced a spark, too low an octane fuel for the CR, too little engine cooling, the wrong heat range spark plug, carbon deposit hot spots in the cylinder, or the cumulative effect of any combination of the above.

And, it doesn't only affect forced aspirated (turbo, s/c) engines either, today's naturally aspirated engines are just as prone to it.

Modern engine management software will advance the spark to just shy of the detonation threshold to achieve maximum efficiency. As such, it doesn't take too much of an adverse condition to throw it beyond that threshold.

Once the knock sensor senses the increase in vibration, which it attributes to knock, it increases it's base signal to the ECU which then begins to retard the spark either to a pre-programmed level, or it will advance the spark until detonation is achieved and then retard it back slightly from that mark.

Because of this, naturally aspirated engines are more sensitive than ever to such things as the intake temperature.

LB,
I agree with what you said except the intake air temp claim. For ambient air temp to affect the engine it would have to be pretty high, 150-200 degrees. In a naturally aspirated engine I think you will agree that the air temp in the manifold is pretty low, in some instances actually causing frost to form because of rapid expansion. I'd like to know where the temp is taken that Jaay is getting on the Scangauge tool.
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Old 08-06-2009, 08:59 PM   #17
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Quote:
Originally Posted by Jaxonalden
LB,
I agree with what you said except the intake air temp claim. For ambient air temp to affect the engine it would have to be pretty high, 150-200 degrees. In a naturally aspirated engine I think you will agree that the air temp in the manifold is pretty low, in some instances actually causing frost to form because of rapid expansion. I'd like to know where the temp is taken that Jaay is getting on the Scangauge tool.
Well, not really. Adiabatic heating is the result of compressing a gas - any gas, including air.

The basic numbers are that for every PSI in pressure increase, you increase the charge temp by 1F. Now I do not have absolute values for the Boxster, but several other mid-engined cars I owned ran engine bay temps of 130F - 150F.

Let's say that a Boxster is driving in 90F ambient temperatures. And, for ****************s and giggles, let's say the engine bay temp is 150F. Now, lets assume that for the short run through the airbox that the 90F intake air picks up an additional 8F of heat through engine bay heat migration (I have no idea what the actual value would be, but feel these are conservative - I suspect the actual value is higher, by maybe 10 - 15F, but for theory's sake, we need to use some value). Anyway, you would now have 98F air entering the cylinder.

The Boxster has an 11:1 CR, meaning that you are compressing the air 11 times it's normal volume, and increasing it's temperature 11F to 109F, or greater than 10%.

10% is a lot when you consider that the DME is so finely calibrated to react to dynamic conditions.

Even if the addition of 11F of heat is insufficient to actually cause, or contribute to detonation (and I'm not saying that it isn't), given the very definite parameters programmed into today's ECU's, it's entirely possible that this value alone could cause the DME to select different (read less efficient) maps to operate the timing advance, EFI duration and volume, etc.

When an ECU is forced to operate under less than ideal conditions (which is what it's optimally programmed to do), it responds by causing the engine to operate in a less than ideal state with respect to performance, emissions and/or range.

I too am not confirming or condemning the mechanic's statement(s), only pointing out that with today's modern engines, concerns about intake temps are more valid than ever and any device with the potential to increase them should be looked at very hard before blindly implementing them.

So far as any values returned by the scangauge, I suspect that they're derived from the intake temp sensor which is integral to the MAF.

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Old 08-07-2009, 08:13 AM   #18
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EVO is EVIL.... just look at that picture again and you can see it's a real monster.
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Old 08-07-2009, 08:38 AM   #19
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Hey Rich, you pimpin out pics of my engine bay?! Sweet!
I would take what the mechanic said as a grain of salt as the EVO intake is a negligible gain in engine performance without headers, chip, high flow cats and exhaust. All itreally does is give tha car a real nice sound. I also found that the way the engine delivers the power has changed, no dyno charts to back this up, but its my seat o pants feeling.

Steve
Ha, yeah, you're the first person I've seen who's rigged up a top cover for their EVO intake. Not that you could hear it over the GHL!

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