Air filters, is cold air really that important?

[Lozzaroo]

Recently bought an Integra Type R DC2 and have ordered an HKS mushroom type air filter. This won't fit in the airbox so will not be shielded from engine heat. What I want to know is, is this very important? It will be sitting about the air intake pipe so will be getting some external air blown onto it, but it sitting reasonably near the engine block.

I know that turbo charged cars benefit from colder air intake, but is it really that important for non turbo cars? Or are they just happy with air, generally?

Cheers!

[z4chris99]

colder air is denser is it not???

I might have made that up

[StottyZr]

Even more so important for non-turbo cars, as any turbo car with power will have an intercooler to cool the air.

Edit:
Just found a calculator:

http://wahiduddin.net/calc/calc_hp_dp.htm

Average air pressure at sea level is 1013mbars. This is 29.92inches HG.
At sea level, with dew point 2.

If we set the intake temp to 20deg and then to 30deg the difference is 2.1% in power.

So if you get 10deg heat soak you'll loose 2.1% as a rough guide.

Sounds quite accurate to me.

Edited by StottyZr on Wednesday 19th September 11:47

Edit: Also, air temp will affect different cars massively. For example, some will take full advantage of the denser air, others won't have a clue.

Edited by StottyZr on Wednesday 19th September 11:48

[McSam]

I'm not so sure about applying an exact percentage like that, but yes, it is very important. You needn't keep the filter in the airbox, that would lose some of its airflow benefit anyway, but you should apply some sort of heat shielding "box" around it or something.

A little like this one:



That way, you aren't having your lovely cold inlet air warmed up by the radiator and the engine. You'd be surprised just how hot it gets under there, and also how much difference it makes. I'm not sure you would feel it on all cars, but it's worthwhile.

And yes, more important for naturally aspirated engines than turbocharged ones, as a turbo engine is capable of getting whatever air mass it likes through and will heat it up massively during compression anyway.

[Captain Muppet]

z4chris99 said:

colder air is denser is it not???

I might have made that up

You might have googled it. Then you'd actually know something.

Yes it is.

[MrFrodo]

Yep, it's important. It increases the density of the air, so you can get more fuel into the cylinder and it also reduces the chance of knock (which probably means you'll be able to get a bit more power out of an engine fitted with a knock sensor).

[GroundEffect]

It makes a huge difference.

If you have an inefficient charge-cooler (a broken fan can really affect this) you can literally not have enough torque to pull away in first gear.

And it's not just the density, it's also the thermodynamic efficiency.

[Studio117]

Open cone air filters are like snake oil.

Ok the induction sound will be nice but inlet temps will increase considerably. You will get heatsoak in traffic.

The only viable replacement is a inclosed filter system. Like gruppe m or itg maxogen for example.

Also be careful you don't end up running lean with the extra air your putting into your engine.

[Lozzaroo]

Ok, thanks for all the replies, very helpful. Maybe I'll just stick with stock, I don't know if I can be bothered to make up a heat shield.

[C.A.R.]

It doesn't make as bigger difference as people are making out - certainly not performance-wise. It can affect MPG though, so colder air is definitely better.

Most MX5 CAI kits position the filter immediately above the exhaust manifold which is a major ballache, so I modified mine and fitted a ventilated headlight lid, the MPG went up, the noise went up. Maybe the performance did, I don't know and never will for sure.



On my Celica I noticed heat-soak with the induction cone so I refitted half of the airbox to deflect some of the heat away from it -

[HustleRussell]

Wouldn't be at all surprized if the engine performed better with the standard airbox than with the aftermarket one.

[g3org3y]

Very important ime. At speed, things aren't so bad with the constant flow of air coming in (although this also depends on the grill design) but once you slow down the heat soak effect can be significant.

McSam said:

I'm not so sure about applying an exact percentage like that, but yes, it is very important. You needn't keep the filter in the airbox, that would lose some of its airflow benefit anyway, but you should apply some sort of heat shielding "box" around it or something.

A little like this one:

^Agree with this. DaveF induction kit?

I remember those days, I ended up going for a GruppeM rep:


Sounded good. Not sure that was much benefit above the placebo effect tbh!

[Aphex]

Theres a few good tests available to read on jap forums about this. Especially the mushroom filters, few car dynoed back to back, all of which made more power with a standard air box and filter that had been smoothed for decent airflow.

Mushroom filters are to be avoided was the conclusion.

[Captain Muppet]

Studio117 said:

Also be careful you don't end up running lean with the extra air your putting into your engine.

Yeah, you'll need to rejet your carb.

[McSam]

g3org3y said:

^Agree with this. DaveF induction kit?

I remember those days, I ended up going for a GruppeM rep:


Sounded good. Not sure that was much benefit above the placebo effect tbh!

That is indeed a Dave F, that was the best example of a "homemade-ish" heat shield I could think of I'm doing my research at the moment, as I've got an E46 328i now! If you still have that Gruppe M I'd bite your hand off, it looks excellent. Similarly, any decent contacts for good replicas, or a Dave F, would be much appreciated. Seems it's getting harder to find such things.

[GroundEffect]

currybum said:

GroundEffect said:

It makes a huge difference.

If you have an inefficient charge-cooler (a broken fan can really affect this) you can literally not have enough torque to pull away in first gear.

And it's not just the density, it's also the thermodynamic efficiency.

I imagine a borked charge cooler in his normally aspirated engine would raise a few questions. :roll:

Was just an example

[danjama]

Lozzaroo said:

Ok, thanks for all the replies, very helpful. Maybe I'll just stick with stock, I don't know if I can be bothered to make up a heat shield.

That's the spirit!

[Mastodon2]

The biggest problem, I was told, with putting aftermarket filters on Type Rs is that the lower intake pressure at low rpms, bye bye throttle response, which is one of the major draws of a Type R over the turbocharged competition.

[z4chris99]

I have this shield from gruppeM

[900T-R]

McSam said:

And yes, more important for naturally aspirated engines than turbocharged ones, as a turbo engine is capable of getting whatever air mass it likes through and will heat it up massively during compression anyway.

Not really, unless your intercooler system is capable of over-cooling the charge (i.e. get it down to below ambient air temp). In all cases, the intake air temperature at the filter will always reflect in the charge air temperature you'll be getting, so assuming the former proviso is not being met the cooler the intake air at the filter end the better - just as with normally aspirated engines.

My old Saab 900T was a barsteward to set up properlyh, until the guys that handled the engine set up sawed a hole in the inner wheelwell and put the filter inbetween inner wheelwell and front wing, out of the engine bay. After they did this, they 'won' 25 bhp or so...