So why is everyone so anti-CAI?

[moatilliatta]

there is no MAF conversion that works well with the stock ECU - a MAF conversion isn't "going big" either.

unless you like blowing $700 for a minor increase in throttle response..

safc2

[tjts1]

If properly designed and built forward facing CAI works better than stock.

http://autospeed.com/A_110824/cms/article.html

http://www.autospeed.com/cms/A_0663/article.html

http://www.mz3.net/articles/149.html

[mdok]

with no other change whatsoever, 15deg f is 1.8% more air by CFM at any standardized pressure going into your engine. 50degF is 3.8% more air. If the mapping accomodates it, there is power to be had, though small. Moreover, any air flow restriction that is improved upon will cause a ripple effect right downstream. You will put more air through a TB if more air gets to it, because all upstream parts have parasitic losses. if you couple a tb with a maf that flow the same , the two together will flow less, an substantially. The loss is because the air going through the maf loses energy (parasitic loss) so the raw supply of air getting to the TB is reduced. The AFM is extremely parasitic, an maf system that has appropriatesoftware will make more power, as more air will get into the engine. On inlets, provided the design is reasonable in sizing, any reduction in temperature and airflow restriction will result in more air in the chamber. A well done CAI/maf/high flow inlet is a good thing, with good software. Stock is good with stock.

On an s50US/m50 throttle body, a decent commercial 3" CAI, which could be readily improved further, delivered over 20% more air to the plenum @ whatever test pressure you choose to use, than the stock system. A 3.5"maf yielded over 30% more than stock, and a light modification of the 3" to 3.5" adaptor yielded another 1.5% . That is all going throught the same TB, which flows less by itself than any of the tubes, mafs, adaptors, elbows by themselves,exceptthe stock airbox, which is more restrictive. Although all the parts flow more than the TB, their collective parasitic losses cause the TB to only pass 82% of its capability with 3.5" stuff. If you cut the grids out of the MAF, eliminate the elbow, and use a long taper large entry radius airhorn, and no filter, you can get a substantial amount of that lost 18% . The temperature will also drop as all the drag inducing parts also raise the heat of the air passing through, not to be confused with the wind chill factor in there.

If you can get the full flow value of the TB into the manifold, you would have almost 56% more air in the manifold than the stock system can get in there, all through the very same TB. Put on a bigger TB, you get more. These are S50 numbers, the restriction of barn door AFMs are way worse. The s50/m50 head doesn't flow what you can get to it, so head improvements are needed.

You should always go after the worst cork, in M20s case, the AFM, which is hugely parasitic.FWIW stock 885 heads flow pretty decently for the valve size they have. They can be improved.

Just because something doesn't work on a stock car, doesn't mean it is worthless. Good intakes need software, as noted in this thread by many. The stock system and map are an excellent compromise between power and noise, it loses a tiny amount of power for a significant noise reduction. any driveability can be restored through mapping , unlike carburettors, because fuelflow relative to airflow is controlled by the guy doing the mapping. If more air gets to the chamber, with appropriate fuel and timing, there is more power.

Air flow restrictions are not absolute, you can always get more or less air through an orifice by varying the local pressure of the air. It's not like trying to stick a 3"rod in a 2"hole, because they are essentially incompressible, and air is highly compressible. The air squeezes down or expands as needed to pass, the biggest losses come when those expansions and contractions are uneven, because as the air accelerates or slows, it loses energy in each transfer. You can never regain 100% of the loss, but good head/inlet guys can get very high amounts back, and thus lose less. Nascar guys get almost 500bhp through an incredibly small restrictor plate playing this game to the hilt. The velocities must be amazing.

Because of the compressability, if you improve just the air filter, you will get more air all the way to the plenum, even if it is one molecule. The temperature works the same way, more molecules all the way in. And it applies to each part as they all have parasitic losses. It only approaches no gain if the worst restriction is absolutely tiny relative to the rest of the system.

Any racecar allowed by the rules has some sort of CAI, usually custom made. An F1 airbox is a CAI. We have always been concerned about the pressure we can get in there (good) more than temperature. Temperature is easy with good isolation, and it looks like kamotors is doing the work there. getting the air from a good and isolated location is how you get the pressure. For temp, you can't get lower than the ambient, so you get in some good ambient, Near the road is hot on hot days.

lastly as far as how much power increase is possible from all these flow improvements, it is limited by how much headroom (if any) the flow value from the outer components (front of car to throttle body) has over the engine's ability to process air, how much air it pumps at peak rate through the engine. If there is no headroom, the gains are big, because the whole damn thing is a restrictor. If inlet system already flows substantially more than the engine needs, the parasitic losses are smaller relatively, and the gains can be tiny. If the temperature is dropped, the gains from that drop are available regardless of flow. Except for the AFM, bmw's inlet systems flow pretty decently, so you need to get the engine to process more air to see the real gains a CAI can give. And that ain't bolt on.

or turbo it.

[SpecRaceM5]

kamotors: I understand you have a product to put out and it's success affects your income. I have worked in the aftermarket industry for both high end sports cars as well as older BMW's for a few years now. With all due respect, your product does look much better then most intakes I see out there. However, it's getting back to my point earlier. You have basically created a box with filter in it, similar to the factory intake. Now I do see benefits such as lower maintenance with the filter you have chosen, and the fact that you have a more direct ducting system for air to flow into the filter, not to mention the "bling" factor you get with the sound and appearance. If I were to purchase an aftermarket intake, I would definitely consider yours for the M20. However, I still personally prefer to either leave the intake stock, or go with FI. In my opinion BMW did a great job engineering their intakes and for a relatively stock motor, there is not much that can be done to improve them.

Cheers,

Brian

[nando]

there is no MAF conversion that works well with the stock ECU - a MAF conversion isn't "going big" either.

unless you like blowing $700 for a minor increase in throttle response..

[JAM]

the reason cai's dont do anything is because there is still restricted flow with the archaic afm w/flapper. if you want to go big, do a maf conversion with a cone filter

[kamotors]

No, I agree, that was my point. You rarely see BBtbs anymore b/c of that simple fact. I am saying that those components pretty much make the CAI idea the same as leaving the stock stuff on with a paper filter. Only so much volume can pass through those two restrictions, and the stock airbox has enough area to comply.

with a cold air intake it doesn't even have to be with a cone filter, the AFM and throttle body aren't going be blocking cold air.I dont sell kits as high flow intake kits I sell them as cold air intakes because it makes your intake temps roughly 10-15 degrees cooler than the OEM setup and 40-50 degrees cooler than a plain cone filter in all driving conditions. if warm air is going to decrease power isn't cold air going to help?

[delatlanta1281]

if you still have an AFM and a stock motor, the TB isn't a restriction either. Increasing the size of the TB and leaving everything else stock is just going to reduce throttle response.

This has been argued hundreds of times already on E30s - the stock airbox is a good design when coupled with the stock engine. A true "cold air" (really ambient air) intake is only going to see mild gains. And most people just run a cone filter with no heat shield which just sucks in hot air from the radiator, which is worse than stock.

BMWs are not fords - there are no huge gains to be had with any bolt ons. You either need a bigger engine or forced induction for anything more than 10-15whp.

No, I agree, that was my point. You rarely see BBtbs anymore b/c of that simple fact. I am saying that those components pretty much make the CAI idea the same as leaving the stock stuff on with a paper filter. Only so much volume can pass through those two restrictions, and the stock airbox has enough area to comply.

[delatlanta1281]

all you have to do to get cooler I.A.T's is introduce a larger volume of outside air.

what is the temp difference from the front of that inlet to the tb? How much does it differ from the stock airbox?

[nando]

considering the size of out throttle bodies, I wouldn't expect any gains whatsoever. If you leave the airbox on, the air coming in is cool enough. Unless you do what KAmotors is saying, but still... without a supercharger, I can't see any real gains. The TB and the barn door are a problem before cold air is.

if you still have an AFM and a stock motor, the TB isn't a restriction either. Increasing the size of the TB and leaving everything else stock is just going to reduce throttle response.

This has been argued hundreds of times already on E30s - the stock airbox is a good design when coupled with the stock engine. A true "cold air" (really ambient air) intake is only going to see mild gains. And most people just run a cone filter with no heat shield which just sucks in hot air from the radiator, which is worse than stock.

BMWs are not fords - there are no huge gains to be had with any bolt ons. You either need a bigger engine or forced induction for anything more than 10-15whp.

[moving3e]

so is this CAI discussion only m20/m42....who has experience with one on an m50/s52???

[kamotors]

all you have to do to get cooler I.A.T's is introduce a larger volume of outside air.

[delatlanta1281]

considering the size of out throttle bodies, I wouldn't expect any gains whatsoever. If you leave the airbox on, the air coming in is cool enough. Unless you do what KAmotors is saying, but still... without a supercharger, I can't see any real gains. The TB and the barn door are a problem before cold air is.

[kamotors]

Was your OEM setup missing the plastic tube that directs cold air from beside the driver side highbeam directly into the OEM airbox? Can't get much colder than that...

yes it had everything, its the fact there isn't enough air getting to it. if you notice as soon as you put the grill on, it block all the air that would be entering from the front. The OEM setup just catches what ever air goes by it, ive done the I.A.T testing, the temps on the OEM setup dont start really dropping until your traveling at 50-60mph.yes the airbox never really gets super hot but it still heats up.

[Lobstrosity]

with a proper CAI you can get colder air than the OEM setup.

Was your OEM setup missing the plastic tube that directs cold air from beside the driver side highbeam directly into the OEM airbox? Can't get much colder than that...