Reply With QuoteOriginally Posted by Bush65
John, do you mean the Isuzu will outlast the smaller engines, even with mods for more power?
YarnMaster
There are a few things relating to diesel combustion that determine engine torque. Basically getting fuel in quickly before top dead centre and burning it more or less completely - to create high combustion pressures at the most effective part of the stroke.
With old school fuel injection getting a lot of fuel in quickly creates loud diesel knock and creates excessive nitrous oxide emission, so our pumps are made for the necessary compromises.
Modern injection systems (e.g. unit injectors or common rail) can overcome this to suit common use - but for drag racing or tractor pulls then mechanical pumps modified for very high pressures and fast injection rule and modified common rail have so far been unable to compete - note this last comment is not relative to this thread, but it illustrates how much the injection rate and time relate to torque.
Tweaking our injection systems for more fuel has a limit to increasing torque because the extra fuel is injected later, i.e. injecting over a greater time, rather than more fuel in the same (or shorter) time.
The modern injection systems operate at higher pressure, which coupled with smaller nozzle holes gives finer atomisation of the fuel, which allows it to burn quicker and more thoroughly - this (better combustion) produces more torque (and power). It is also a problem if fuel quality is not too good.
In order to burn extra fuel, additional air is required and this is where turbos are required. VNT turbos can help with more air at lower engine rpm. Effectively turbos increase volumetric efficiency so a smaller displacement engine can produce the torque of a larger displacement normally aspirated engine - as others have said, off boost, the smaller displacement turbo engine would not produce as much torque.
It is not difficult or expensive to get 600+ Nm torque from a 4BD1T and it will not require internal changes (basically turbo, intercooler and injection pump tuning) and the engine will not still outlive the smaller alternatives spoken about in this thread.
In the later years of 300Tdi use in rovers the engines were produced by International in Brazil. The 2.8 was based on this. The 300 Tdi linage goes back to much older rover engines and some parts are still the same.
ForumSage
John, do you mean the Isuzu will outlast the smaller engines, even with mods for more power?
YarnMaster
Most certainly will. Comparing the 4BD1T to any of the 300Tdi, 2.8TVG, TD5 or Puma is chalk and cheese.
The extra engine mass and cast iron head of the 4BD1 provides greater thermal mass that provides considerable immunity to damage from overheating (e.g. following coolant loss) that would kill the others. The stock head gasket is good for more than 40 psi (probably 50 psi).
Mechanical strength of non-turbo engines is an issue when their power is increased because much increase can only be achieved from running to higher rpm. The greatest component loads are due to inertia of the reciprocating parts, which is greatest when the pistons change direction at the top and bottom of the stroke. The inertia loads increase as rpm increases. The inertia due direction change at TDC (top dead centre) creates tensile load/stress in the con rod and at BDC compression load/stress.
With a turbo engine the power and torque can be increased without increasing rpm and the resulting inertial loads. The increase comes from increasing BMEP (brake mean effective pressure) from burning more fuel (air + diesel) at the same rpm. The highest pressure occurs just after TDC and the direction of the load due to combustion pressure is opposite to the inertial load at that position, i.e. the increased pressure reduces the load/stress due to inertia. At BDC, when the compression load/stress due to inertial is greatest the pressure is not increased.
Remember that the 4BD1T in an Isuzu truck rated for 4 tonne payload and 12 tonne when towing has a very long life between overhauls if serviced properly. If you look at what they are like inside you can easily see why this is - very robust, nitrided crankshaft, alfin pistons (steel inserts for rings), hard chrome plated liners, bypass oil filtration, etc.
If I decided to go this route with my Defender, who would be able to fit one of these motors. Who have put these in for people that do have them?
Davis performance or graeme cooper or would my local landy machanic be able to do it??
Thanks
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