M325is 0 Report post Posted October 10, 2007 Why the hell is the exhaust manafold Iron on the E30? How dumb is that?!! Apparently its a commom arse problem for a bolt to go cos iron doesnt expand the same as aluminium under heat. Isn't that a simple fix that a german engineer shouldnt have missed!!! Oh my god, what a mission it has turned into. I cant believe a German designed this! Quote Share this post Link to post Share on other sites
320guy 0 Report post Posted October 10, 2007 Um, I think that you will find that almost every car has an iron exhaust manifold. Douche. Quote Share this post Link to post Share on other sites
OLLIE 26 Report post Posted October 10, 2007 haha Quote Share this post Link to post Share on other sites
M325is 0 Report post Posted October 10, 2007 Why is this? Why can you not have an Aluminium manifold? Quote Share this post Link to post Share on other sites
hotwire 352 Report post Posted October 10, 2007 Cant say I remember seeing any car with an alloy exhaust manifold - only cast or steel - would be to do with the heat generated I would say Quote Share this post Link to post Share on other sites
Gus 5 Report post Posted October 10, 2007 alloy cant cope with the stresses...its too brittle and wouldnt handle heat cycling as well. (correct me if im wrong) virtually all OEM manifolds are cast iron, cant think of many that arent. steel or stainless are really the only other options. what is such a mission? just take manifold off and get it outta there if its snapped...there is meant to be torque values that allow for expansion (ie not too tight) Quote Share this post Link to post Share on other sites
QuickSilver 0 Report post Posted October 10, 2007 rant backfire? Quote Share this post Link to post Share on other sites
hybrid 1039 Report post Posted October 10, 2007 titanium is another common metal for the higher end systems. Quote Share this post Link to post Share on other sites
Gus 5 Report post Posted October 10, 2007 but manifolds? exhausts yes but never seen a ti manifold. seems too light/hard to work with/$$. any pics? Quote Share this post Link to post Share on other sites
M325is 0 Report post Posted October 10, 2007 Mission because only 6months ago we replaced all the bolts and exhaust gaskets, now one bolt has blowen and half is left in the block which we have tried to drill but accidently a little off centre which means taking it off etc. and replaing gaskets again bla bla bla, im sure if it wasnt iron it wouldnt have happened. Now I have to wait till labour weekend as the rally is this weekend in Wangarei, bad timing. Quote Share this post Link to post Share on other sites
kiwi535 538 Report post Posted October 10, 2007 the exhaust is 5 or six hundred degrees as it exits the cylinder so the manifold has to be able to cope with being that hot...Maybe aluminium would melt!. Quote Share this post Link to post Share on other sites
mark247 38 Report post Posted October 10, 2007 exhaust manifolds are overrated anyway =P Quote Share this post Link to post Share on other sites
320guy 0 Report post Posted October 11, 2007 What is this i see? More cast iron exhaust manifolds?!?!?! Stupid engineers!! Quote Share this post Link to post Share on other sites
M325is 0 Report post Posted October 11, 2007 320guy I get your point it isnt just german cars, im a chick for christ sakes I dont know everything about every car lol Quote Share this post Link to post Share on other sites
Surge 1 Report post Posted October 11, 2007 Don't let your gender be an issue. I'm a guy and don't know every thing about cars. But for future reference, learn everything about every car. Quote Share this post Link to post Share on other sites
mark247 38 Report post Posted October 11, 2007 hahaha quite amusing. But i cant say i would know any better, i know pretty much all exhaust manifolds are made of the same metal, i didnt know it was iron tho I suck when it comes to metals. Quote Share this post Link to post Share on other sites
bravo 34 Report post Posted October 11, 2007 (edited) Hey Shelley. I think what 320 guy is saying is: You are a n00b. :P Hah Best thread in a while. Edited October 11, 2007 by bravo Quote Share this post Link to post Share on other sites
Rod 0 Report post Posted October 11, 2007 Cast iron has some very desirable properties. It is a relatively inexpensive material to cast and machine. Generally it is less prone to corrosion when compared to steel or aluminium when subjected to corrosive environments, this is due to the presence of intergranular graphite. Thermal cycling can result in corrosion, hence one reason why exhaust systems can corrode from the outside in. The corrosive compounts in the exhaust gasses will cause corrosion on the inside. Due to cast iron also being porrous it attenuates noise, in the case of an exhaust manifold noise radiating from within. The ability to cast thick wall sections means that the engine can be quite quiet, a definite advantage when marketing a car to a conservative public. Aluminium however is notorious for transmitting noise, and would probably not tolerate the heat of the exhaust gases, given that it is not actively cooled like the engine. Aluminium in this application would most likely fail from fatigue due to thermal cycling. Aluminium exhaust manifolds have been used with success on some two stroke engines, where the exhaust gases are cooler due to the greater presence of unburnt fuel and oil. Aluminium does have some definite weight advantages where it can successfully be used. Titanium is the ultmate answer, however it is extremely expensive. Stainless steel can also be used however one must allow for the fact that it is inferior in terms of heat conduction, which depending upon the integrity design may result in hotspots or meltdowns. Same old story really, the best is the most difficult to work with and is the most expensive. Cast iron is a friendly material, just do not subject it to mechanical shock as it is relatively brittle. Rod Quote Share this post Link to post Share on other sites
M325is 0 Report post Posted October 11, 2007 Is that like calling a dude a dick? Quote Share this post Link to post Share on other sites
bravo 34 Report post Posted October 11, 2007 You're thinking of b00b. Quote Share this post Link to post Share on other sites
320guy 0 Report post Posted October 11, 2007 Is that like calling a dude a dick? You mean, is like calling someone a noob like calling a guy a dick? No its not, it was first used in computer gaming, where someone new to a game was called a "noob", "newbie" etc. I didnt realise you were female, so I dont expect you to know as much as a guy. I just found it ironic for you to call the bmw engineers stupid for using iron for the exhaust manifold when you obviuosly didnt know much about it yourself. I dont know much either, but im learning new stuff every day. Chur. Quote Share this post Link to post Share on other sites
Gus 5 Report post Posted October 11, 2007 you wont need to replace the exhaust gasket to change the stud, they're still good. and be happy you have a stock manifold and not headers..they're not fun Quote Share this post Link to post Share on other sites
M325is 0 Report post Posted October 11, 2007 I didnt realise you were female, so I dont expect you to know as much as a guy. I just found it ironic for you to call the bmw engineers stupid for using iron for the exhaust manifold when you obviuosly didnt know much about it yourself Haha thats why im the graphic designer and they're the engineers Gus, there is high chance by the time it comes off (labour weekend) it will have blowen the gasket also. Better safe then sorry, only $60 for both gaskets anywho. I think this topic has seen its day. Hooroo Quote Share this post Link to post Share on other sites
Driftit 1950 Report post Posted October 12, 2007 At least the E30 Manifold is dead easy to get off. Pulling one off an SR20DET is such a pain in the ass. Putting the water and oil lines back on the block never goes right. Quote Share this post Link to post Share on other sites
