I don't have a dyno for a DC5. That can't be said for other cars with a similar setup
If you really are interested and not just arguing for the sake of it, read
http://racingbeat.com/intake.htm
extract:
Quote:
In addition to our usual round of dyno testing with each intake, we've added over the-road and static intake temperature tests. Intake temperature is perhaps the most important factor that aftermarket intakes can affect. Since every increase of 10 degrees in intake temperature costs almost one percent in power output, an intake that pulls in hot air can actually hurt power, while a properly designed cold-air intake can improve performance far more than the airflow potential would imply.
In conducting our intake temperature testing we've attempted to simulate normal driving with easily repeatable tests conducted at almost identical ambient temperatures. We plumbed a thermocouple into the throttle body for all measurements and conducted moving tests at sustained speeds (45 and 70 mph) in fourth gear. We then stopped and let the car idle, taking measurements after 30 and 60 seconds of idle time to simulate what might happen to intake temperatures in traffic.
In addition to simply presenting these temperatures for your intellectual enlightenment, we used the standard SAE correction factors for temperature and adjusted the dyno readings to represent the effects of intake temperature at 45 mph. Since we always conduct dyno tests with the hood open, this after-the fact correction is a more accurate representation of real-world power gains.
CAI:
http://racingbeat.com/jacksonintake.htm
http://racingbeat.com/images/jackson.jpg
SRI:
http://racingbeat.com/hksintake.htm
EXTRACT:
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As discussed, the obvious problem with this design is that it places the intake quite close the blazing hot exhaust header. As we've learned time after time from underhood intakes, the power-stagnating effects of engine heat can easily cancel any power gain made an otherwise efficient intake.
http://racingbeat.com/images/hks.jpg
RESULT:
Amounts to on the MIATA 2hp atw and 2 LB-ft of torque...JACK ALL. Not much of a difference after 60 seconds. The difference between ambient air temp here from idle at 30 seconds to 60 seconds was 4 degrees and 2% power.
If you can't see how performance will decrease further after the car being on for longer, don't bother trying to understand it.
Times your car is not on for more than 60 seconds:
- moving it from one end of the driveway
.....otherwise this will affect you in some way if you have a SRI right next to the headers, as above.
More information:
http://autospeed.com/cms/A_0360/printArticle.html
EXTRACTS:
Quote:
Intake Air Temps
How hot or cold the intake air is has a big impact on the way an engine performs. High intake air temps will results in decreased power (because there's less oxygen in each cubic foot of air) and also a higher chance of detonation occurring. So, why would the intake air be any hotter than the temp of the day, anyway?
First up, let's take the case of a naturally aspirated engine. Many engines have air intakes that are positioned under the bonnet. This means that lots of the air that is being drawn into the engine has already passed through the radiator - so it's bloody hot! How hot? - up to 60 or 70 degrees C. Of course, there will also be airflow into the engine bay from around the engine, and past openings like the headlights. But in many cases, on a warmer day the air being drawn into an underbonnet engine intake can still be as high in temp as 60 degrees! And since - as a rule of thumb - engine power drops by 1 per cent for every 4 degrees C that the intake air temp rises, this isn't good..... (Incidentally, that's why AutoSpeed doesn't have much of a liking for exposed underbonnet filters installed without heat shields....).
Quote:
In all cars, the lower the intake air temp, the better. In a naturally aspirated car with efficient cold air induction, when the car is moving the intake air temp should be less than 10 degrees C above the temp of the day. The best we've ever seen is 5 degrees above ambient, and many cars - even after cold air intake modification - still have an intake air temp about 15 degrees C higher than the day temp. In forced aspirated cars, the highest temp that you want to see - depending on how much boost you're running, of course - is about 30 degrees C above the day temp.
Quote:
Another common occurrence is heat soak. Drive a car on a hot day until it is up to operating temp and then park it. Hop back in after half an hour or so and it's not uncommon to see intake temps of 70 or 80 degrees C for the first minute, remaining elevated for some kilometres of driving. Forced induction cars with water/air intercooling systems will stay high in intake air temp for 10 or 15 minutes, as all that thermal mass of the water needs to be cooled.
Theres so much more information available. Haven't touched the car forums yet
summary
From various articles and studies inclusive but not exclusive to the above sources:
6-10 degrees increase = 1% drop in power.
People will and can legitimately argue that 1% = jack all.
Whilst this is somewhat true for street application, it is not true for race application. And keep in mind that 4 degrees in ambient temp. was a 30 second idle difference in the study above. How much the temp will go up after that I wasn't able to find a measure, but with common sense you can imagine that it would definately go higher if 4 degrees higher was in the 2nd 30 second period.
Also we on the DC5 normally aspirated 4 cyl 2.0L platform don't have big numbers to begin with, and a 10KW atw difference can cost you cams and an ecu ($5000+?) so it makes sense to care about small differences
the concept of heatsoak exists
First you need to understand and agree that:
- cool air ie lower intake tempreture is beneficial
- this is because in cool air any given volume of it is more dense and contains more oxygen than any given volume of warm air
- and the concept of engine combustion, if you cannot understand this you will not understand heatsoak
ENGINE COMBUSTION:
http://users.telenet.be/cleanteam/in...n/image997.gif
Quote:
1. Intake
* Combustible mixtures are emplaced in the combustion chamber
2. Compression
* The mixtures are placed under pressure
3. Power
* The mixture is burnt, almost invariably a deflagration, although a few systems involve detonation. The hot mixture is expanded, pressing on and moving parts of the engine and performing useful work.
4. Exhaust
* The cooled combustion products are exhausted into the atmosphere
This process is obviously how power is produced. This process is more efficient with more oxygen per volume of air, as in step 1 the mixture (AIR/FUEL) is injected into the combustion chamber and this ratio is a set A/F ratio controlled by the ECU...Whatever the air requirement of this is, it needs it, and the air intake will need to draw in that amount of oxygen to satisfy efficient combustion as set by the specific A/F.
Cold air will satisfy this requirement as it will need less volume of air to draw in any given amount of oxygen as cold air is more dense with oxygen compared to hot/warm air.
So..
Heatsoak: inefficiencies in combustion given by warm air as higher volumes of warm air are needed to draw certain amounts of oxygen. As tempretures get higher and higher more volume of air is needed, if the intake can not provide to scale the increases in requirement of air volume than power is lost.
This is less of a problem as a DD but still evident, and tempretures will increase with time and workload
SRI on a DC5 is more subject to hotter air than a CAI as a SRI is right next to the headers, where combustion products in step 3 of the above process have detonated and are ejected through the headers as exhaust fumes and exit the engine block. This is the hottest part of the engine bay so logic says the air around the header is also quite hot and subject to increases in tempreture as more exhaust fumes exit through the header as workloads and time increase.
Since tempretures around the header is known to be high and it can be shown that intake tempretures of a pod next to them reflect this, as well as the fact that warm air makes combustion inefficient which can lead to a loss of power.
Heatsoak exists for the DC5
here's your 'legit answer'
now of course. This will affect differing builds in differing ways and differing degrees. But there is no doubt it exists.
And if you can avoid it by simply choosing a different intake style, why not? especially when it is supplemented with better gains anyway
