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Suitable mods for 4.2 engine

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I am new (as a member) to the forum however followed it for long time.

I have read the post from Dronus4x4 on nads mods which I found excellent -best I have seen for a long time however I am after the same for the 4.2. I am in the process of fitting a new 3" exhaust to the vehicle ( it has had one from new) and having pulled everything off I felt it the best time to do some mods.

Does anyone  know where I can find a post that discusses the mods and issues with the 4.2 (2004 model)

I look forward to your i put.

Roland Cox

Edited by rolandcox
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G'day mate,

4.2 L is pretty much NADS mod free as it is quite reliable. Most people mod 4.2 L to gain more power out of it not extend its reliability.

Mods for TD42 (4.2 L) are far from little simple things. Most if not all require major hardware changes comparing to NADS where these are just little add ons. EGR mod is simple enough though and gives extra gain in low to mid torque except not entirely legal.

Because TD42 is pure mechanical beast it is also limited by those mechanicals. I'm assuming yours is turbo version aka TD42T. First going on by bigger exhaust certainly helps the thing but major problem with TD42 is the fuel limiting factor.

Cheap and nasty mod is to fiddle with adjustment of the "smoke compensator" on the injection pump, another is advancing injection timing by moving pump on its elongated mounting holes to increae advance etc,

Very positive change reported is to add good quality auxilliary fuel lift pump, changing to bigger intercooler, resizing the intake starting from snorkel piping to replacing airbox and associated piping and then proceding to change to UEFI turbo and inlet manifold.

TBH, increasing power output also put extra strain on cooling system  and TD42 is known for overheating so aftermarket radiator with increased capacity and properly functioning engine fan is a must.

The next level is scary (exensive as if the other mods aren't) as that involves the fuel pump insides modifications (fuel plunger size up).

Me personally, I'd fit catch can, 3' exhaust and better intercooler with decent snorkel/intake piping and airbox and that's it as far as the mods are concerned. Of course the usual as boost and EGT gauges fit applies. I'd also invest is some sort of low coolant level warning, custom coolant temp gauge (factory one is useless) and perhaps oil pressure gauge.



Edited by Rumcajs
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Many thanks for the detail, I had to read it several times to make sure I had it all in order.

When I bought the car new I had the 3"exhaust put on and the turbo modified and boost to 14psi.

I have to say I was a little dissapointed with the outcome. The first trip we did the thing over heated going up  Cunninghams gap and we pulled into nissan at Warrick to have fhe vehicle checked. We did have the campertrailer on and it was a hot day.

This issue has plagued us ever since and I sometimes wonder if the engine timing is actually correct.I have just replaced the exhaust system and thought while I am under the car i may as well see what else can be done to get the power up. I have noticed some oil leaking from around the turbo, I found it was leaking from the boost controller. I am not sure if this is reasonable . Your thoughts would be most welcome.

Regards Roland









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There should no oil leaking out of boost controller. I'm assuming you mean waste gate actuator piston. If that's the case that means either turbo is not OK or better the amount of blow-by gases contain so much oil that it now contaminates the intake side of the turbo where it then gets to the actuator via the boost controller pressure hose.

Possible solution to that if thats the case is to fit catch can or oil separator to the breather hose between rocker cover and intake hose before turbo charger compressor housing.


As for the overheating issue just make sure the fan is working (you should feel certain resistance in viscous coupling clutch when engine is cold and stationary if it spins easily check for tell tale traces of dust build up on the fan hub around the center of the shaft, that means silicon oil has leaked out, or  and this is crucial you don't have the radiator blocked either externally (easily checked with workshop light) or internally (common problem) blocked which requires specialist to confirm.





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First and most important, in my opinion is to fit a EGT Gauge (pyro gauge). The TD42 with aftermarket turbo if set up incorrectly will push HIGH egt's which can cause major problems.

I have a bigger radiator fitted in mine, and that makes a HUGE difference. Viscous coupling also needs to be in good working order too. 

Oil blowby is a problem on mine too as I have the boost set quite at 12psi, but so far other than sweating around the turbo, all is good so far. An oil catch can is also a good mod to do and adds piece of mind.

At 12 psi I have pretty decent pulling power, even with my big camping trailer, but on a long uphill I can see my EGT's climb easily into the early 600 deg C ( probe pre turbo)

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Seems my reply got lost in the ether.

When I had the original mods done to the car in 04 they fitted a GBF boost controller and wound the pressure up to 14 psi - good or bad. The oil is leaking out of the small hole in the side of the controller ( I assume when it reached boost pressure) which means there must be a lot of oil coming out of the turbo to the intercooler. As you suggest, I will fit a catch can to the PCV line and see what happens.

I have had a look at all the points for leaks as per your diagrams, other than the oil from the boost controller, there are no other leaks so we will watch this space as I have finally got it back together. (I lost the E clip on the boost arm and it took me 3 days to get a new one, problems of living in the bush)

Next time I have my head under the bonnet, I will check the fan, I have had it tested however, again I am not convinced.

One last thing, is there a way to check the timing of the Injector pump???

Once again, thanks for the advice.

Hi Ricster,

Thanks for the reply.

All this has convinced me to fit a few gauges so I can see what is going on. I will start with the boost and Temp. I know the temp has been up high when climbing and I have had to back off on the pedal just to get to the top. One hill I had to stop twice to let the motor cool.

It seems everyone else's patrol goes better than mine especially when towing so I am going to get to the bottom of it this time. (gives me a reason to use the new hoist)

At least the car is back on the road and it seems to be a lot quieter, except for a thump in the rear but another story for another day.

Thanks for the interest.



Edited by rolandcox
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