thank you justin, who know if M30 TB is a bolt-on affair? What is its diameter?
I remember reading 63mm stock and the 633 guys were doing a group buy for 66.x mm bored out throttles.
I don't think its a direct swap because the bottom of the M42 throttle bolts are further apart than the top. But at least we know that the top bolts match up. M30 TB gasket is essentially square.
http://www.autopartswarehouse.com/search/?N=9740+1580+4294967005+7004VS M42 heater plate as reference.
http://farm3.static.flickr.com/2273/2113768490_0e79cfd0c4_o.jpgSo you will need to use an adapter plate. Maybe a very thin one.
One way to look at it is the that the M42 has a 35mm + 54mm tb or 1.37" + 2.1" TBs. The M42 total thorttle surface area is 1.47"^2 + 3.46"^2 =
4.93"^2. The M30 has a 63mm or 2.48" diameter throttle plate with a total surface area of
4.83"^2. So in rough terms the M30 TB is marginally smaller but thats not the whole story. This doesn't take into account how the air flows through 2 different size TBs instead of one large TB. If you put both TBs on a flow bench I suspect the M30 TB will be more efficient. I'll pick one up at the JY and give it a try.
Another thing to consider the the snorkel that connects the back of the headlights to the airbox is just 2.1" wide at its narrowest point. Using a simple vacuum gauge I measure 5" of vacuum in the lower airbox with the stock snorkel, WOT, 2nd gear @ 6000rpm. I took that thing off and got an immediate gain in throttle response. No more vacuum in the airbox. Maybe its because I'm running larger injectors so my engine can handle the extra air flow but I think the snorkel is the first restriction to deal with. Right now mine is just a hot air intake until I find a 3" hose to connect to the airbox.
BMW doesn't call it a muffler for nothing. 2" at one end, 3" at the other.
http://farm3.static.flickr.com/2395/2113883286_71ab8b38d5_o.jpghttp://farm3.static.flickr.com/2080/2113883340_98aab2e2b9_o.jpg
Topic: WOW, clean m42! (Read 17463 times)