Tech help on Inlet manifolds

[hough]

Hi i was looking on the net the other day in reguards to doing a manifold conversion on my BMW E46 328 by putting an inlet manifold on it from a E46 330i which is ment to give my car an extra 20 bhp....

but this my question while looking on the net i found a few different styles of inlet manifold but besides the shape what is the difference and would it give any extra performance????

the two picture are,
1st, are picture of the standard and E46 330i manifold back to back
2nd is a custom inlet manifold on a E36 engine

 

[Prince]

It's all about getting air into the engine. The reason changing the inlet on the 328 gives extra power is because they were made to be restrictive.

 

[hough]

thanks prince but thats not quite what i ment, i know the old manifold on the M52tuc28 is very restrictive thats why im looking at getting a inlet manifold from a M54b30, but what im trying to find out is the 2 pictures shown the left standard bmw inlet manifolds and the right shows a custom manifold for a bmw but is the type on the right better if so why????

 

[Prince]

The s/s alternative looks less restrictive meaning the air will flow better. I would be interested to see full setup from the picture on the right. A reason most just use an inlet from a different BMW is cost.

 

[Loz]

The custom one has a larger plenum & it will have been designed to move/flow more than the plastic version. Looking at the plastic version you have seem to have 6 thin looking tubes with very little volume when compared to the larger beefier looking ally set up.
Stamford's your man to ask he's got a fair bit of experience with intake systems.

 

[Loz]

Looking at the two plastic ones the difference is quite distinct, the one on the right will be choking the engine, the holes look a good (conservative) 10% larger on the left so multiply that by 6 cylinders that will give you 60% increase in air flow, wouldn't it?

 

[Prince]

BMW inlets were designed to be restrictive. It was to pass some sort of law that I can't remember in Europe.

**Edit. They are restricted as it brings them down in taxation classes in Germany. **

 

[hough]

well im thinking of making my own inlet manifold if i dont go for a M54B30 inlet

 

[Prince]

I would get the BMW inlet, then try to make your own. That way you can test them both to see if you can actually improve power.