Now that we've pushed the tuning potential of the BMW 2.8 to the limit using red paint and flower pots, it's probably worth looking elsewhere for gains.
Maximum power potential of the 2.8 was deliberately limited by BMW by fitting the inlet manifold from the 2 litre version. On this, the inlet tracts are much smaller in diameter and many people have found gains of 20bhp when fitting a manifold from the 2.5 litre motors, which have larger inlet tracts. In BMW terms, the M52 28 and M52 20 (2.8 and 2.0 litre motors) have the smaller manifolds, whilst the M50 25 - the earlier 2.5 litre motor - has the larger tracts.
Here's a power plot of a typical gain:
I bought a 2.5 manifold before buying my Z3 and then bought a facelift car with the M52TU motor meaning the manifold won't fit my car.- it only fits pre-facelift models- I bought it at a good price and I'm offering it for sale here at the same price I paid before putting on eBay at a higher price if it doesn't sell.
I'll add pics in a moment, but it's yours for £120 plus carriage at cost. You're welcome to collect from Port Talbot.
It's a straight forward swap except for some new vacuum pipes and fittings being needed - details in the next post.
The power potential of a remap is even greater with this fitted. The manifold, remap, CAI and exhaust is expected to gain 40bhp or more.