What are we interested in when building a new engine? This is what parts we can use.
I will try to state as briefly as possible, because. if you describe everything in detail, few will master the article to the end, although in fact a lot of information is needed for the construction.
M20 engines have two types of cylinder blocks – with cylinders of 80mm (m20b20 and m20b23) and 84mm (m20b25 and m20b27 eta). Naturally, to build a more powerful naturally aspirated engine, the larger the cylinder diameter, the better. The m20b20 block, in principle, can be bored up to 84mm, but at your own peril and risk, the walls turn out to be a bit thin, and given the age of the blocks, you can end up with problems. Although there are engines successfully assembled and driven with such a block.
Therefore, it is better to choose the m20b25 or m20b27 block. It’s not a problem to buy them (there are still enough of them in e34 bodies), they don’t cost much money.
Okay, we have the block, what else do you need? That’s right – the crankshaft. Four types of crankshafts were installed on the M20 – with a rise of 66, 75, 76.8 and 81 mm. To get a volume of 2.7 liters, we need a crankshaft from an ETA motor (m20b27) with a rise of 81 mm. Of course, you can go further and make 2.8 l – for this you need a knee from m52b28, but just like that it will not fall into our block, it needs to be finalized. At a reasonable price, I did not find this, but there were a pair of 81 mm knees for ridiculous money.
Next are the connecting rods and pistons. Everything here is very individual, there are a lot of options. Depends on what kind of engine you want to get (the adored R / S ratio), what compression ratio you need.
In my engine, I used m20b25 135mm connecting rods (simply because they were). I chose m42b18 pistons for construction with a compression height of 31.7mm. The Kolbenschmidt catalogs helped me a lot in choosing pistons – I recommend them for use. They contain all the parameters that you will need when choosing.
So, in the lower part we still have an oil pump – there are two options – standard or from a diesel engine (m21b24). The diesel has more performance – I put it.
Now the top of the motor.
Cylinder head – there were three types – 200, 731 and 885. It is advisable to use the 885 head, because. it used valves of a larger diameter than the other two, the air channels are wider. We take the intake manifold from m20b25.
The throttle valve was also used from the m20b25, although some seem to be installed from the M30 motor.
On the camshaft — of course, it would be chic to use Schrick, but the budget can crack)) Where are you, Santa Claus?!
Information on regular camshafts is contradictory and rather vague. They seem to differ in opening angles, but there is no clear picture and numbers for them. I used m20b25 shaft.
For the time being, I will install nozzles from m20b25, if they are not enough, I will change them to more productive ones. Again, they are selected individually – we look at the Bosch table for performance.
Everything will be controlled by Motronic 1.3
. I will replace the standard shovel with a MAF with a Pilot controller.
Everything seems to have been forgotten. In short, it didn’t work. Who mastered – well done))