Zetor 4718 performance tuning

[gnusi]

Hi there

I own a zetor 4718 that i am building up to use only for a race, i am modifying the engine to the limit i think, but i need some advice if anyone has done this before. But maybe i am the only one. The engine will be built from the ground up with new 4 ring pistons, main and con rod bearings, turbo head gaskets, ported heads, turbo inlet manifold, tube exhaust headers, intercooler, electic fan instead of the fixed one, modified injection pump and a VGT turbine from a 2.0L diesel engine. And if i am not satisfied with the power i will consider using nitro. Does anyone know of anyone who has done this or has some tips for me what to be ware of? I am little bit confused about how much boost is safe for the engine so i will not be throwing out the pistons

So if anyone has any tips for me please tell me

 

[Renze]

I am less afraid of the power than the speed...

You can use heads of a 4911 or newer, it has bigger valves. Four cylinder heads would work too, but then you have to drill and tap new holes for the intake manifold, these are 20 or 30 rotated versus the 4 cylinder. (both are made from the same casting)
Just, you have to drill a new recess for a frost plug, to cover a coolant passage which the 4718 engine block doesnt have..

You could also bore out the piston swirl bowl to lower the compression ratio to lessen the force on the connecting rods. The compression you loose from increasing the piston swirl bowl volume, you win by pumping extra air into the engine.

With a VGT turbo i would certainly turn out the pistons a mm or so, it saves both compression temperatures, and force on the connecting rods.

Also, if revving real high, weigh your connecting rod and piston sets so they will have the same weight, and have an engine shop balance the crankshaft. When doubling the speed, the mass inertia forces quadruple, so balance is of key importance in any race engine, especially truck and tractor engines.

 

[gnusi]

I am not really afraid of the compression ratio of the engine. The original compression is around 16-16.5:1. And with a turbo head gasket that is thicker than the non turbo, non turbo 1.25mm and the turbo 1.5mm.

What do you think that the turbo boost should be? any way to increase the oil flow from the injection pump to the extreme?

 

[Renze]

Normal compression ratio is 1:16.5 or 1:17
In tractor pulling they normally use 1:14 or so, to compensate for the huge boost level.

You can achieve max fuel by simply removing the cold start device from the far end of the pump: Then it will allways inject the full plunger stroke. I dont know if the units are cut so they increase injection timing too at that point, but thats the easiest way.
The cold start button is the max fuel stop: when you push it, a pin falls into a recess in the control rod, allowing it to give more fuel at starting. If you remove it entirely, you can allways have max fuel possible when pushing the throttle.

===edit:
i dont think the plungers are set to advance the injection timing: the 3011 and 4712 use exactly the same fuel pump, though at a different setting: Even with the button pressed, it is still the end stop for the control rod, so at a 4712 it also turns the fuel plungers further than in a 3011 which is adjusted at less control rod stroke.

 

[gnusi]

Thanks, i have already throw away the cold start plunger and i have also taken apart the return flow valve from the top of the injection pump and fitted a stiffer spring to increase the fuel pressure on the plungers. So that is probably stretched to the max?

 

[Renze]

injector return pressure is a fairy tale, it doesnt add any. Fuel is injected at 160 bar, so increasing the return line back pressure by 0.5 bar doesnt add anything.

 

[grumpy6711]

surely the extra power gained will be offset by the weight of the giant anchor you will need to throw off the back when you need to stop the thing