Performance improvements on 4d33...any experiences?

Good old 4d33, already turboed but still struggles in the hills at highway speeds. Is there scope for effective improvements. Don't want stupid power but the ability to hold gears and not become a mobile chicane would ease the drive.
What is the performance/reliability cut off for an engine not originally designed for any kind of functional performance?
 

Aussie Iron

Explorer
They are a good solid engine and I don't know where the cut off is to engine mods to reliability. Unless you are heavier than me I'm not having that problem. Even loaded with 2.5 tonnes of sweet potatoes on board I can hold 100Klm/hour except on the really steepest hills.
Even though you are turboed ( how much boost ) all you can do is get more air into the engine and increase fuel. Watch your Egt on really hard uphill pulls. So get the engine to breathe better 3" exhaust, maybe a bigger or better turbo.

Dan.
 
Thanks Dan. Pretty close to GVM 5.5 tonne. Running a MTQ turbo set up (Toowoomba) . It certainly improved driveability, its just been wanting in the hills over the last few days. ( Can't imagine even trying those hills in non turbo mode). Kind of wondering the improvements with obvious mods like larger exhaust and intercooler, though the consensus from MTQ and Turboglide was an intercooler wasn't required. I feel it needs another 20% to get the job done modestly.
 
No idea how you maintain 100kmh Dan esp in SWB!😁 How much do you reckon the gearing changes contribute to your trucks ability? I find the torque/ power band pretty narrow 2000 to 2600 ish, below and above, nothing much happens.

Thanks Joe. Do you have any anecdotal comments about the improvement an intercooler makes, same for 3" exhaust? These are the most logical and possibly easiest to do but if the gains are minimal perhaps not cost effective.
 

javajoe79

Fabricator
I’ve only messed with a few diesels but they like intercoolers for sure.The bigger exhaust will probably help too. An EGT gauge is important to have when you turn up a diesel.
 

Aussie Iron

Explorer
My believe is turbo setups from the major suppliers are fairly conservative in performance gain as they don't want problems with the customers. Yes they improve performance some.

Definitely need an intercooler, I can't see where they can say an intercooler doesn't help performance (cooler air). 3" exhaust helps the turbo spool better and also gets the exhaust away and the turbo will probably spool higher. Egt very important to know whether you can feed more fuel in or not.

Yes major torque is around 2000 to 2750 Rpm and above that it needs to wind out (usually not real usable unless getting some speed up on the flats). Below 2000 it should accelerate fairly well unless it's under a lot of load.

Because you are sitting on 3000 odd Rpm at 100K's you have no torque left in the engine to keep it there so it slows down on even the smallest hills. Mine is running at around 2500 Rpm's at 100K's right in the torque band so it tends to hold it there better.

My idea :- Intercooler, Egt, 3" exhaust from the back of the Turbo, Feed in more fuel, Then Regear to get even better performance.
Dan.
 
Thanks Joe/Dan. I'll make a few enquiries.

Dan, a vague one. Light rapid ticking kind of noise, especially on trailing throttle when the motor is a bit quieter. Fluctuates with revs. Potential valve adjustments???. Thanks for any thoughts. Neil.
 

Aussie Iron

Explorer
That is where I would look first. Warm the engine up and then remove the tappet cover, start the engine with cover off and use the handle of a screw driver to apply a little pressure to the rocker arm above the valve and see if you get a noise change, do this to all valves and you should pick up which one it is. But saying that you might as well adjust them all while you have the cover off.

Dan.
 

gait

Explorer
another use for the screwdriver is to place the sharp end on parts of the engine (like rocker cover) and the other end against the bone in front of ear. Works like a low tech stethoscope.
 
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