cold air intake

[Ryann]

A CAI will make your car louder, that's all.

[PumpItUp]

good, i'll have something to listen to
(no stereo)

[bmwman91]

I am a firm believer in the stock air filter setup.  The weird little trumpets & stuff are there on purpose.  There is far more to an intake than just making it a straight, unobstructed tube.  Intake resonance has a large effect on volumetric efficiency, and the resonator tubes are there to help even out the power band.  These are not racecars; they need to be useful in stop & go traffic, not just at redline.

Most CAI setups people run are actually sucking in a lot of hot air from the engine.  Your heat shield needs to mate firmly to the fender, hood & and anything else adjacent to it.  If you look at the tube coming from the airbox that fits into the shield behind the headlights, it is exactly this.  You aren't going to improve on it.

The intake tube is not a restriction.  It has more cross-sectional area than the AFM's flow passage.  Even the AFM is NOT restrictive, contrary to popular belief.  I have been working with MAF conversions for years now, and I will tell you right now that the AFM on the M42 is not a restriction, much less anything in front of it.  The real choke-point is the cylinder head; enlarge the ports & stick in larger valves.  That is where air flow chokes up.

Save your money & time for something else.  Intakes are pointless on an internally stock, street-driven M42.  Trust me.  I wasted my time & money on CAI BS when I was younger & it was just that...a waste.

[1991 E30 M42]

bmwman91 made some good points but when you increase displacement and compression, add cams, and port/polish the head, increased airflow and colder air can make a difference. here is the intake I made for my built engine http://m42club.com/forums/showthread.php?t=7590&highlight=real+cold+air+intake

[bmwman91]

when you increase displacement and compression, add cams, and port/polish the head, increased airflow and colder air can make a difference. here is the intake I made for my built engine http://m42club.com/forums/showthread.php?t=7590&highlight=real+cold+air+intake

Certainly, if you are doing things other than bolt-ons then it might be advantageous to change the intake up a bit.  I still disagree that one will pull any colder air than you do with the stock pipe & shield, but it's not really a big deal either way.  Once you are going at least 15mph, the stock inlet should have absolutely no problems finding cold air.  I want to see some dyno plots with a new paper filter in a 100% stock intake versus a cleanly built CAI setup.

Anyway, your point is correct that doing real mods to the motor could necessitate a CAI setup.  On an internally stock M42 motor though, I have just never seen any proof that changing the airbox does anything positive.

It's a hard pill to swallow for a lot of BMW owners that there is almost nothing easy to improve upon in the design (except the software, they deliberately gave the M42 a super weak tune) when American & Japanese compacts have all sorts of crap that can bolt on & make a difference.  Part of all that extra money people pay for a BMW goes into the R&D involved with developing & implementing performance upgrades so we don't have to.

[PumpItUp]

he does bring up a good point. people seem to think just because they bought their car used for the same price as a honda civic, it has the same level of engineering. on the other hand, i have a hard time believing the box and it's 2 inch tube is some masterwork of air flow planning. it has the proportions it does to house the paper filter, which is the same size as most other cars. they make them big so you don't have to swap filters every few thousand miles.

i don't like choking the engine of air with a sport intake, the low-end torque on this thing is bad enough. but noise is something you don't just brush aside. if we wanted a fast car, we wouldn't drive an e30. we drive an e30 because its fun, and does the simple things well. noise is a fundamental aspect of driving enjoyment. why else would people buy ferrari's.  and the m42 doesn't sound particularly awesome, even for a 4 cylinder. but at 4000+rpm with the intake noise, it can at least impersonate a nice sounding 4 cylinder like the 4ag (from the mk1 mr2 or gts corolla) :cool: i've read that if you get an m42 going above 6800 rpm it starts to hum like a bmw. too bad i never got it up that high (no chip)

has anyone done the mod i want to do? cut out some plastic next to the headlight to make a real grill, so the tube is pointed towards some fresh air rather than just the backside of the headlights. it's the conservative alternative to taking out your left high-beam. seems harmless to me, doesn't cost any money and might help some..

[bmwman91]

(Preface:  I know I come off as having a very strong opinion about this, and maybe express it in a slightly abrasive way.  My apologies if I do.  This just happens to be a topic that is beaten to death & there is virtually NO empirical, measurable evidence demonstrating any benefits to performance on the M42 from it.  I have been driving & tweaking an M42 for close to 10 years now & I have tried all the little "easy" stuff.  It doesn't do anything on an internally stock motor.)

If you are after a particular noise or sound, then by all means do what you like with the intake.  Different strokes for different folks, I suppose.  I liked the noise the open element filter made maybe 6 or 7 years ago, but that was high school & college.  Now it just sort of annoys me lol.  I am getting old.

It was some magazine somewhere that wrote a review about the 318iS & said something to the effect of it sounding like a "real" BMW when you rev it high enough.  That's silly IMO.  I think that by "real" BMW they mean an inline 6.  There is nothing you can do to it to make it sound like that.  I think that it sounds pretty neat for a four, and it is sort of distinctive (as long as you leave fart-can mufflers off of it).  The M42 has a unique noise to it & that is nice.

1991 E30 M42 seems to have one of the more low-key setups as far as pulling outside air from somewhere other than the headlights.

Nobody here thinks they will be getting the "ram air" effect, do they?  Dear god I don't want to have to blow up on another rant!

[Warsteiner]

I think that everyone should run out and buy the Vortec Cyclone to increase HP and fuel mileage.... eh bmwman91? LOL  Sorry couldn't resist.

To add a little, yes the restriction is in the head but more so on the ports than the size of the valves themselves.  Just like on the S14 you can get a Stage II port job to run just as well as a Stage III with bigger valves. Reason being the efficiency of the ports themselves due to shape and size of the port.  If you port too much then you lose your bottom end unless it's a race motor, where you don't care because you're always up in the higher rpm's anyway.

Testing has been done on S14's and S50/S52's for the street and yes the stock airbox is the best thing that you can leave alone for HP and Torque, AND the stock paper filter. These are made out of great plastic and keep the air cool too. bmwman91 is absolutely correct when he is typing all of this while he is pulling his hair out and turning blue all at the same time:)  He is 100% CORRECT. Leave things alone that aren't broken yet because BMW spent a lot of time R&D'ing this stuff.  They're Germans for cryin' out loud...you know they got everything out of it that they could have.  The de-tuning is done on purpose to make the cars last a looooooooong time.  You increase timing and fuel and start pushing the rpm limits, then the longevity of the motor will ultimately come down in miles or kilometers.

Another big miss in the BMW world is ...."I just bought this car and I need to make it faster.....I guess I should add a muffler!" NO!!! The power is in the Head. Port your head and leave the muffler alone and tell me what you gained. Then change your muffler and see what you actually haven't gained after doing so.  If you do a complete motor rebuild and do head work and run Alpha N, then I would think that you might need an exhaust modification. But definitely not headers until you get into about the 250HP range?

I have played with so many options on the S14 from stock to my current 2.5L race motor so this is real world knowledge, not some guess work or I read it on the internet kind of thing.
Keep it simple stupid...KISS.  It does work.  I'm all for making power and making things better, but you really have to look at what makes sense vs wasting your time.

Just trying to help save time on projects.  I'm all for everyone doing what they want to, but in an effort for the best running BMW you are better off leaving some things stock.

Cheers,
~Ralph

PS I'm installing and tuning my MSII v.3.0 next weekend to test on my stockish (Conforti Chip and LW flywheel) M42 which will eventually see its way to being on my stroker motor. I will post a thread with a complete write up of mods and running conditions. Everything from modified cam trays and buckets to...Alpha N....to E30M3 exhaust and even Dbilas ITB's.

[flyinglizard]

They sound louder and faster. Thats important..
 Ths stock box is very good. No way to make morepower by grabbing air from under the hood. If you get air from the head light, keep it cool into the AFM, than you may gain 1or 2 hp over stock.
  The stock box keeps out intake noise  and resonance, drawing air from a cool area.  Tough to improve . The 3 in straight tube may help a wee bit . Some racers put the filter out in front of the core, in a pressure area, then run the air to the meter.
 Cold air makes a big difference in power in these  little , weak engines.
 Some help, would be to cool the intake manifold, by either adding gaskets, spraying the outside with water, or engineering something along those lines.( hood scoop!!)
 Power is made by changing the temp of the burn gases. More temp change makes more power.
 All of my race cars, now use at least two intake gaskets to reduce the charge temps, along with a heat shield of some sort, drawing cold air as is deemed legal, etc.  
 It may be only 5hp total, but on 150 it makes enough  to play with it.

[bmwman91]

Excellent post, Warsteiner.  It is a good read.

Flyinglizard, I completely agree that keeping intake air temperatures as low as possible is ideal.  I built some data acquisition hardware & software when I was doing my MAF conversion & it is really easy to read the intake air temperature.  I think I need to do some tests with the stock setup & whatnot.  I am hypothesizing that the stock setup will have a statistically insignificant difference in average intake air temperature over a tube sucking air from under the car or something.  Anyway, it sounds like a fun little test.

[Ricer Ennemi]

I will put a BIG cone with the head open in a "bowl"
surrouding it.Right trougt the Hi-beam.It should create
cold pressurized air around the cone.I'll probably put heat
shield under the piping.The results will be test on the 1\4 mile.

[bmwman91]

If possible, can you try swapping in the stock setup after a few runs?  The 1/4 mile test is of course subject to the variances in the driver's timing :p.  Those are probably bigger then the differences form the intake, so the driver factor might mask the intake's effects.

[1991 E30 M42]

Drag racing a BMW is like going fishing with a hooker, it's fun but it's not what you got her for

[bmwman91]

LOL

Depends.  Are you on a boat, and is anyone else around?

[flyinglizard]

The best way to judge is a 3rd gear roll on from 3000 to 6500, with some else timing. Go both directions on the same road. Make 4 passes for the baseline. Change the goods, make 4 more passes. After about 8 passes add 2 gal fuel.   HTH, MM