Divemaster1
Well-Known Member
Simples really ...
DD 2-strokes are 1 base engine in different configurations ... all with individual cylinder volumes the same. So all 92 series will have same single cylinder volume weather a V6 or a V16... makes parts simple.
Then there comes the issue of how air is introduced.. Natural Aspireated DD's are not "natural" ... they have a roots komppressor (blower) that forces air in to the cylinders through scavenging ports in the cylinder and this force does two things ... get's rid of exhaust gases and gives new air for the compression& ignition stroke in one function. This allows for injection of fuel and combustion each time the piston moves upwards (2 strokes -- 1x Ignited powerstroke downwards & 1x compression stroke upwards).
As fuel / air combination drives power, DD introduce fuel through injectors which are a combination of seperate fuel pumps and injector in one (keeping these in sync is key to fuel economy and if not "in-tune" she will not perform as designed...). As each injector therefore is a fuel pump, DD can size up/down the pumps with ease.. Bigger injectors = more fuel .... more fuel = bigger bang = more HP... Injetors for the 71 & 92 series engines are interchangable so easy to replace at approx £100 a piece (or less if you do a part exchange. This means you can easly and quite reasonable tune up or down a DD engine by simply buying bigger / smaller injectors.
At the higher HP ranges (bigger injectors), one introduce turbo chargers (perhaps one for each cylinder bank) and intercoolers to provide more air into the combustion chamber for a clean combustion (this as the roots blower itself is not big enough to provide enough air for the fuel delivered by the bigger injectors to combust properly and thus give you extra HP.
... based upon this you get a base engine (71 series for example).. that was made in everything from a single cylinder to V12's and each of the cylinder numbers ... let's say a straight six was delivered with a range from around 200 HP ("Naturally Aspirated) and up to 485 HP... and the V12 between 400 and up to over 700 HP
I have seen a pair of 8V92's with injectors called 9260, which are bigger than stock engines was delivered with, and these were pushing about 780 HP .... and there are bigger injectors out there that can be used ... and you can introduce more air into the cylinders for even more power ... (not that i would want those engines as thewy will require frequent re-builds, but is an indication of what you can do with these engines for a relatively small sum of money).. Ie a 550 HP 8V92 with turbo and intercooler is the same as a 700 Hp one .. but the 700 hp one have bigger injectors and a uprated cooling system.
You will find that the main difference between a low rated engine vs a high rated in the same series are the cooling systems (to get rid of heat .... actually the injectors and the extra fuel they can pump... read diesel returned to the tank ...... form part of the cooling system), turbo's and intercoolers.... turbo charged engines do have different pistons when compared with Naturally aspirated ones....
A bit piecemeal, but may answer your questions on the ratings ... but I have not covered the engines with lower governed RPM in here ... these are also same base engine, but with max RPM restricted...
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