GKD Legend - BMW 4 Cyl engines from E36 / E46

[Richard]

Here is a brief high level summary of the 4 cyl engines BMW used in the E36 and E46 series. The post will come in a few edits.



Within each engine there are a few variants and they were used in differing capacities and models.

There are a range of tuning mods available but they are not all compatible with each engine so if you are thinking about supercharging for example you either have to be more mechanically minded and creative or choose carefully for available kits for the model of engine you pick.

All the engines were only ever made with <2000 cc and varied from 1596 – 1997.

The M40 and M43 are SOHC 8v all the others are DOHC 16v.

The weight of engines varies between ~80kg - ~100kg.

The M40, M43 and N43 are all about 80kg  the  rest are around the 100kg mark.

In standard form the bhp of the engines varies from 102 to 173 in the more modern engines and torque ranges from 105 to 154.

If the August 1995 date is something you wish to pay attention to then the choice is limited as depicted in the graphic above.

The more powerful older engines are the M42 and M44 with either 136/140 bhp depending on cat and whose figures you believe. The M42 is a 1.8 and the M44 a 1.9.  I'm not aware of them coming in differing capacities unlike the M43 for example.

Choosing a 4 cylinder engine then has a wide variety of power / weight combinations. The general rule has been that the coupe gets the more powerful engine in the older models. I'd personally recommend the M42 and M44 for decent price performance and tuning potential at the moment. They both have naturally high compression so if thinking about the Forced Injection(FI) route then you should plan ahead.

I believe that BMW created in the M42 with a large amount of potential for their racing intentions and then proceeded to handicap the engine to keep the 0-60 times down and keep the performance of the 318is down to avoid taking sales from the 325/323.  The gearing/diff that was put with the engine don't help acceleration along with a few other "restirictions" put in place to "boost economy" and to keep it away from eating into the 325 sales, just my opinion. 

I have to mention the incredible S42 engine here. Go search it out and you'll understand what an achievement it was, starting its life as 285 and rising 315 bhp from a 4 cyl NA engine, this puts it in the bhp per litre bracket that so few engines achieve. It is possible with a lot of know how and a degree of money to recreate this. You can still get substantial performance improvements from other efforts.

The N42 won an award, I'm never to sure if awards are valuable or worthless but given the engines in its era it does indicate it was among the best engines. This and other of the more modern engines are still in my view relatively expensive for the donor route but without much doubt the N series of engines will in future be great kit car material.

I do think that bringing BMW running gear and engines into the kit car world is a good thing for both car worlds.
There are very few running BMWs that weigh under 800kg let alone under 600kg, a recent article on a car in Australia in one magazine (it also features on a couple of the forums, one in particular) is quite a quick machine even with its lowly engine capacity and is very stripped out (not quite as much as my donor car is now).

There is so much material on tuning in the BMW world of forums/ magazines / independent specialists that I'll leave this post as more of an introduction and hopefully an interest to find out more. One thing that comes up very frequently in the BMW performance world is upgrading the engine from 4 pot to 6 pot, it is very effective in road cars, so it takes a lot more searching to find the 4 cyl improvements. One thing this does show is that the way the whole set of mechanicals can work together brings a lot to the kit car builder.

I have various favourite BMW forums and magazines, I'll leave anyone interested enough to research this some more to make their own mind up.


Engine Map with some power information added