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HENRYNBMW

Cold air intake

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Finally got around to installing a cold air intake for my M10 with Alpina itb injection.  

I purchased generic intake hose, and  flanged piece from Amazon that fits through the  3 inch hole I cut into the radiator support.

Alpina originally used a metal tube with mounting tabs that angled it into the oncoming air flow. Mine is at a slight angle to the front of the car and might not be optimal. If I only had a 3D printer!

Cutting into the radiator support was fraught with peril but really ended up not being too hard. I purchased a fresh 3 inch hole saw and despite a little awkwardness with the angle of attack, it came out fine. I guess that will be a modification that I could never undo, oh well.

I have a 304 Dr. Schrick camshaft, Alpina/Bosch modified pump, and above 4000 rpm the throttle response is immediate.

 

Henry

 

Current:

2015 X5

2012 335 XDrive Coupe

1988 E30 M3

1973 2002tii

 

Previous:

1971 2002 Colorado orange, early model,short bumpers. 

1974 2002tii Verona red, Recaros, 5-speed sport trans, limited slip.

1976 2002 Sahara beige, Miller and Norburn downdraft Weber kit. Stahl headers.  Purchased from the dealer with a bent control arm and a defective center resonator. 

1980 320i Tii engine transplant that ended up with triple webers 2.7L engine. 

1986 325es 2.7L with Alpina headers and exhaust and ECU. Body colored euro bumpers full M-tech kit. 

1988 325ix Automatic,still great in snow.

1989 325ix Stick,great in snow and a blast to drive.

1988 E30 M3 Purchased new, 25K, dealer couldn't sell it. Salmon Silver.

1993 325i With S50 engine.

2000 M5 What a great car!

2008 335xi Coupe Totaled by some idiot in a Toyota Tundra. 

 

 

post-37745-0-11580500-1452630925_thumb.j

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Henry, that is super clean looking (like new).  I believe used an aluminum backed paper duct (similar to some of the stuff they use on air cooled Porsche's) tried to locate it for a few A4 users but no dice.  Hopefully you will bring your car to Monterey this summer for the Historics,  I would love to check it out.  Nice work.  BTW, ex tii Regsiter guy Jeff Mulcahy wrote a piece on that cold air intake on a Tii/A4 motor, with the testing he did (at Road Atlanta) he was able to get a couple of extra mph out of the car with the cold air as opposed to without - I don't recall now the science he did to determine that - he was a smart guy so I am sure it was something tangible.  Will have to look for that article.

 

http://www.alpinabmw2002.com

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I was going to give you shit for not using the factory snorkel on the nose, but....  whups...

 

that looks nice!

 

t

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It won't be as clean looking and professional as yours but I am planning one from a pair of sidedrafts through the gap in the front panel by the battery to a remote filter pod behind the front grill.

Is there any down sides from turbulence being right in the front of the car?

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You do not want to "pressurize" the intake side of your FI or Carburetors.  You want to supply them with the coolest air you can but if you are trying for some kind of "ram air" system you will have HUGE problems with fuel mixture.  Think about it:  at higher speeds the air pressure will go up and you will actually pressurize the carburetors and if you Jet the carbs or set the Fuel injection to supply the correct amount of fuel at 6000 rpm @ 110mph you will be horribly rich at 6000 rpm @ 40mph in 2nd gear.  Modern fuel injection systems can compensate for this by using Air Mass Sensors, Pressure sensors in the intake track and O2 sensors and thus make use of the "ram effect". 

 

This is not theoretical it has been tested over an over by everyone from street car guys to racers and without fail IT DOES NOT WORK!  I found this out in 1977 with a B sedan 2002, we had a new engine we set up on an engine dyno,  put it in the car and it went like stink up though 3rd gear, would not go over 7000 rpm in 4th and would not pull more than 6500 in 5th.  We took the lid off the airbox so we were still getting the cold air but just not pressurizing the carbs and we were getting 7800 at the engine of the straight in 5th gear. 

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You do not want to "pressurize" the intake side of your FI or Carburetors.  You want to supply them with the coolest air you can but if you are trying for some kind of "ram air" system you will have HUGE problems with fuel mixture.  Think about it:  at higher speeds the air pressure will go up and you will actually pressurize the carburetors and if you Jet the carbs or set the Fuel injection to supply the correct amount of fuel at 6000 rpm @ 110mph you will be horribly rich at 6000 rpm @ 40mph in 2nd gear.  Modern fuel injection systems can compensate for this by using Air Mass Sensors, Pressure sensors in the intake track and O2 sensors and thus make use of the "ram effect". 

 

This is not theoretical it has been tested over an over by everyone from street car guys to racers and without fail IT DOES NOT WORK!  I found this out in 1977 with a B sedan 2002, we had a new engine we set up on an engine dyno,  put it in the car and it went like stink up though 3rd gear, would not go over 7000 rpm in 4th and would not pull more than 6500 in 5th.  We took the lid off the airbox so we were still getting the cold air but just not pressurizing the carbs and we were getting 7800 at the engine of the straight in 5th gear.

Interesting. I thought that this arrangement could bring issues but didn't appreciate from that direction. Problem here is that aerodynamically there are areas when the car is moving at different speeds that are higher and lower air pressure. If you did an arrangement as I described, I would expect that area behind the grill to all be high(er) pressure compared to within the engine compartment but if I left the filter in the same place but put a shield over the front this would then be at a lower pressure due to the effect of the higher pressure air passing around the outside (like The low pressure on the top of a plane's wing). Perhaps I can avoid the issue with having a small filter, like a crankcase ventilation filter local to the airbox on the carbs. This would allow any pressurisation to equalise but maintain integrity of filtration at lower speeds.

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Oh, yeah, I have had that happen, too-

the nose DOES build some pressure in it,

 

especially when you start blanking off the radiator,

which was when I ran into it. The intake was in the grille area, beside where the headlight wasn't,

the hood rested on the front support to keep frontal area... well, less frontal, I guess,

and when air couldn't get out through the radiator, jetting went to hell.

 

The immediate fix was to unblank the rad, the longer- term was

to get the pickup somewhere else.  And then retune out what we'd jetted in to

try to compensate for the reduced effect we'd already created.

 

It doesn't take psi, it takes a mm or 2 of water for the effect to be measurable

on a wbo2- carbs aren't compensated for it, like they are for almost everything else.

 

Also, the 'tuned port' volume effect of the intake can mess with reversion in front of the carbs,

and create lean and rich spots.  The rather cobbled- together intake that came

with my race car was miles better than several commercial ones at that, simply by accident.

 

t

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