Stock airbox cover removal on a IX

[Evil_Rs]

^^ I was reading similar and i fully agree with him. Opening the top for longer periods of time(road racing) you will be getting heatsoak from the motor ALOT more than the cold air most would "Think" they are getting into while the top is off. I would love to see testing myself.

As i designed/build a ram/cold air induction for a friends civic and tested it on dyno and others and noticed differences in the temps/power made but trying the same setup without the pipe and just the top off it didnt show anything but the heat not getting released but getting sucked back thru.

IMO, fab a pipe to get air into a sealed box through part of bumper

[JohnBradley]

Originally Posted by cij911

You don't want to start pulling in hot engine bay air into your intake over 'cold / fresh' air from the outside.

As for John / John mod's I really cannot explain how or why they are seeing good results unless it was for short (e.g. 1/4 mile run) bursts.

My log showed significant temperature drop with the splashguard or rainguard or whatever you would like to call it out. Though I have no direct observational airflow data, I am thinking the the air is being pushed through the radiator/intercooler and either going under the car as it hits the engine or going straight up and out the vent. The airbox is closer to the ACD solenoid and headlight where its getting its own supply of air. Again I dont have proof that this happening other than the fact the air temps are 20*+ cooler with the guard out as measured by the engines air temp sensor.

I wont speak for John, but my measurements were both short WOT blasts (such as 1/4 mile passes) and steady state cruising on the interstate. Both showed lower temps than other configurations. I didnt measure the temps with the lid intact so I cant say how that might affects things. I believe John did some testing with the barometer sensor to see if there were gains, but I cant remember his results right off.

John

[whoang40]

I don't think this has any huge hp gains. Your'e going to just compress the air and get it hot by the engine heated up from the hotside of the turbo. The difference is after the intercooler, cooling the point entering the intake manifold. This is really a pointless thread, remember the formula PV=nRT from chemistry? More you compress the air, higher the pressure, then temperature.

[Evil_Rs]

Originally Posted by whoang40

I don't think this has any huge hp gains. Your'e going to just compress the air and get it hot by the engine heated up from the hotside of the turbo. The difference is after the intercooler, cooling the point entering the intake manifold. This is really a pointless thread, remember the formula PV=nRT from chemistry? More you compress the air, higher the pressure, then temperature.

This is all true, but if you can get the air that is going thru the filter cooler, then their logic would actually seem plausible. "The cooler outside air offers a more dense mixture of oxygen and a more powerful explosion when combined with fuel. It's this promise of increased horsepower."

[94AWDcoupe]

I am thinking that maybe the change seen at the barometric pressure is the key issue here. Barometric pressure is the weight of the air. This reading is important to the ecu and the a/f and timing maps are changed accordingly. The way the meter reads baro is directly changed when the shape of the box is changed. This in realty should not happen if the baro meter was doing its job. The barometric pressure of the air has not changed. But the ecu thinks it has. So for some the changes that the ecu makes is good for others the changes are bad. Depending on the tune, the mods, and the and whole host of factors.

For those confused. If you have a barometric pressure sensor on the windshield it would read the same whether or not the air filter box had a lid or not. As it should. Now drive from 100ft elevation to 1000ft elevation and now the meter on the windsheild will show less air pressure. as it should. The baro meter in the mass should read the same as the one on the windshield.

In the case where baro was changed from 10kPa to 5kPa. Is this good? 10kPa means the air has more density which is good. Yet this tuner thought 5kPa was better. If air is heavier that means more will be packed into the engine. Thats the whole point of the cold air intake is to injest cooler denser air. The ecu seeing a change from 10kPa to 5kPa is huge. I bet timing maps could easily be changed by 3-4 degrees. Which could make for a performance + or - depending on the cars state of tune.

[jcsbanks]

Since the baro sensor is measuring pressure after the airbox/filter/snorkel, the pressure it records drops as the airflow increases. My 10kPa vs 5kPa is the pressure drop I am recording at high revs on full boost compared with a reading when the car is idle. So the pressure I record might be 91kPa on the stock setup and 95 or 96kPa on the modified setup. The means the compressor inlet density (if the temperature is equal) is about 5% higher with the modified airbox. This means the turbo can run at a lower speed to produce the same airflow. This reduces charge temp, exhaust gas temp, exhaust manifold pressure, all good things. However, if you end up swapping your pressure improvement for a large increase in temperature you haven't won, which is why this needs testing on individual setups. On a summer day with these changes my air temp measured at the MAF sensor is not noticeably higher when the car is moving. This is in my cool climate with small cuts in the coldest side of the airbox. As I say, a compromise.

[cij911]

Originally Posted by JohnBradley

My log showed significant temperature drop with the splashguard or rainguard or whatever you would like to call it out. Though I have no direct observational airflow data, I am thinking the the air is being pushed through the radiator/intercooler and either going under the car as it hits the engine or going straight up and out the vent. The airbox is closer to the ACD solenoid and headlight where its getting its own supply of air. Again I dont have proof that this happening other than the fact the air temps are 20*+ cooler with the guard out as measured by the engines air temp sensor.

I wont speak for John, but my measurements were both short WOT blasts (such as 1/4 mile passes) and steady state cruising on the interstate. Both showed lower temps than other configurations. I didnt measure the temps with the lid intact so I cant say how that might affects things. I believe John did some testing with the barometer sensor to see if there were gains, but I cant remember his results right off.

John

John -- Very interesting... The airflow should come from the front through the radiators and then up through the hood (generally you don't want air that has passed through radiators to be used as your intake air). This has been a common design in racing for many years -- we would let wheel-well air out via louvers at the top of the fender to help with aerodynamics (reduce lift).... There was debate about the louvers helping a venturi effect, but I doubt they are needed as the air is going from a high pressure location to a low pressure location. What I am very interested in is how removing the louvers improved airflow and lowered engine bay temperatures. This seems to make sense to me, but I wonder why the engineers designed the louvers?? Also, when driving more than ~40 mph rain water should really not be able to enter through the opening (ever driven a convertible in the rain with the top down?).

I would still recommend adding a 3" pipe to bring air directly in from the outside and either shoot right into the box or aimed right at the opening.

Shameless -- You have started a very interested thread and I apologize for being such a D*** -- sorry. I have always seen bad results with these sorts of mods on other cars, but apparently I need to do some testing on the EVO.

[cij911]

Originally Posted by jcsbanks

Since the baro sensor is measuring pressure after the airbox/filter/snorkel, the pressure it records drops as the airflow increases. My 10kPa vs 5kPa is the pressure drop I am recording at high revs on full boost compared with a reading when the car is idle. So the pressure I record might be 91kPa on the stock setup and 95 or 96kPa on the modified setup. The means the compressor inlet density (if the temperature is equal) is about 5% higher with the modified airbox. This means the turbo can run at a lower speed to produce the same airflow. This reduces charge temp, exhaust gas temp, exhaust manifold pressure, all good things. However, if you end up swapping your pressure improvement for a large increase in temperature you haven't won, which is why this needs testing on individual setups. On a summer day with these changes my air temp measured at the MAF sensor is not noticeably higher when the car is moving. This is in my cool climate with small cuts in the coldest side of the airbox. As I say, a compromise.

JCS -- I believe your test is showing that on your car you benefited from more airflow. If you were able to fab a simple 3" inlet pipe (intake in the bumper) and shoot directly into the cut outs you have made I would bet you'd see an improvement. Furthermore, if you were to box the entire filter with both intakes shotting in (just cold air), you should see the best results (IMHO).

Time permitting, this will be my next mod on my car.

[jcsbanks]

I was all for believing that the standard airbox was fine on the stock turbo until I attached a gauge to the turbo inlet pipe and saw the pressure drop of about 1.5 PSI. When Evoscan then came out I could replicate the same readings with the baro sensor. It isn't really measuring baro, it is measuring pressure at the MAF sensor to trim the MAF readings. It would only be measuring baro if it wasn't in a restrictive environment in the inlet. It would be nice to get another snorkel into the other side of the airbox, but I don't see easy places to pick it up from.

I did get an APS induction kit, but the filter gets dirty and some cars have waterlogged their MAF sensors in heavy puddles and been stranded (although thankfully not hydrolocked) waiting a few hours for it to dry out. Additionally, it made the MAF misread low, made silly noises, and the filter was potentially not that far away from the radiator warm air - there was an unblocked area that I didn't want to block as I thought it would reduce cooling air to cooling fins on the transmission case.

[cij911]

OK I did a bunch more reading and looking at the car....Buschur's intake was tested to be better than the factory stock box by a few HP, but many have added cold intake tubes to yield even better results. JCS -- take a 2 - 3" flexible plastic tube (neoprene or other) and run it from the front left brake / IC cutout up to your cutout. That should give you fresh cool air and keep your stock box setup...

There are others doing this with the stock snorkel and Buschur setup .

[recompile]

Originally Posted by cij911

Shameless -- You have started a very interested thread and I apologize for being such a D*** -- sorry. I have always seen bad results with these sorts of mods on other cars, but apparently I need to do some testing on the EVO.

No worries, I understand everyone's disgust with performing mods that have no benefit (or can potentially cause harm)... and it's great that people care enough to desuade people from wasting their time/money/effort on lost causes.

Based on the feedback in the thread, it seems like something that is worth trying. I'm looking for a 2nd stock airbox so I can modify it to my heart's content.

I like your idea of funneling from the front IC duct to a cutout in the airbox, what kind of tubing do you think will work best?

Anyway, thanks again to all.

[ak47po]

Mitsubishi probably spent quite a bit of time,money and development designing the airbox for the Evo.I think they know alot more about the benifits of their design than any of us.If you must chop away at your airbox,it's your car but i think it's a waste of time and effort.If you want more airflow go with a aftermarket intake that has some thought put into the design and functionality.Just my thoughts about the idea.

[willsevo]

I dont have a dyno sheet for verifaction, but I have the K&N intake (open element) with heat sheild on a untuned IX and the turbo kicks in 300-400 rpm quicker and has a little more perk to its step. I have heard numrous people say its bad to put a intake on with out a tune. I have seen no down side to the intake, no water problems, no idle problems.

[TogueMonster]

I just bought a Blitz Induction Cover. I'll tell you this about running an open element filter. 1 Don't use it in the rain/carwash. 2 You'll run hotter intake temps and possibly have higher chance of getting knock because of it. If you use an intake like an INJEN or HKS RS you should be fine running it without a tune on a IX, different story on an VIII for some people. Stock airbox is pretty effecient though, spend your money elsewhere and you'll see greater gains. Exhaust, Downpipe, test pipe, lower intercooler pipe, boost controller would be better place to start.

[willsevo]

Originally Posted by TogueMonster

I just bought a Blitz Induction Cover. I'll tell you this about running an open element filter. 1 Don't use it in the rain/carwash. 2 You'll run hotter intake temps and possibly have higher chance of getting knock because of it. If you use an intake like an INJEN or HKS RS you should be fine running it without a tune on a IX, different story on an VIII for some people. Stock airbox is pretty effecient though, spend your money elsewhere and you'll see greater gains. Exhaust, Downpipe, test pipe, lower intercooler pipe, boost controller would be better place to start.

I have had a open element filter for about 6 months, leaving in D.C. raining at least 2-3 times a week, driving 11-14 miles in it, wash the car once a week, never had a problem with it.