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Holden Colorado 2.8 diesel

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I’m using HPTuners and my BASE FUELING tables go up to 122mm3 and at stock it will only fuel at 98mm3 max after increasing the max torque numbers in Torque Management I can get 105mm3 out of it now, any idea what is now limiting me getting to 122mm3. It’s not DRIVER DEMAND as I have played with this and no increase at the top end.


Not an engine many of us are familiar with - any chance it's reached it's limit of being able to actually supply the fuel? You 'may' be lucky and gain a little from replacing fuel line filters, if they're restricting it a little. However, just forcing more fuel into the engine is foolish without looking at the whole engine build, and can actually cause many other problems, even failures - what have you done to increase airflow/charge density?

In NZ, you can also get a $150 fine for excessive smoke - https://www.police.govt.nz/faq/it-illegal-cars-have-smoky-exhaust - you may have noticed very few smokey Jap' imports nowadays, or trucks, compared to back in the day.

That engine is the 2.8 litre Duromax, there is a lot on-line about it, and tuning/performance options - you may be better to check that side of it out? For example - https://www.youtube.com/watch?v=wRi-9DOHic8

Thanks for the reply Gord, I have done shit loads of research but my question is a bit specific to the engine and was hoping someone who has tuned one would know the answer. Yes it could be 105mm3 is the max for the ecu and the amounts up to 120 are there just to fill in the tables? In a diesel more fuel means more power, won’t smoke if I get the AFR right.

I had in mind more the capacity of the pumps and injectors to meet that demand.

With a diesel, more fuel - to a point - can give more torque/power BUT it also means a whole lot of negatives, like excessively high EGTs that can literally melt turbines and crack housings, excessive fuel consumption, excessive particulates (smoke), very high carbon monoxide levels, oil contamination, ring wear, etc.

The trick is to balance the additional fuel with sufficient air to oxidise that fuel - that allows the AFRs, EGTs, etc, to be kept in check. My personal focus, in your place, would be on maximising, where I could, air flow into the engine and out the exhaust.

Have you been following the Gale Banks engine builds - he goes into a lot of the detail on how to make, and lose, torque/power with diesel engines as he discussed his builds.

Are you up early, or up late?

I’m an early riser.

My research into the 2.8 Duramax is they respond very well with a tune alone without any hardware upgrades. Most tuning shops here in NZ and Australia report a 20% gain that’s all I’m after not going to push it. They say the turbo is good for 29psi and stock is running about 24psi so a bit of room there.

Not as much info on the net about diesel tuning compared to petrol.

Modern utility diesels still respond favorably to a turbo back exhaust, even on a factory tune there is significant improvement.

Yeah I’ve done a muffler delete but going to retain the DPF 3” from there back, just decided to go with a high flow air filter also.

You may need to work on the smoke map. It may be limiting fuel by air flow. I saw you asked in another thread of this map was expressed in lambda which I honestly can't recall, been a while since I've tuned one. Try and make a drastic change in either direction and see if it makes a difference. If that doesn't work, you can just add a little injection ms to get more fuel in, although this won't be shown in the scanner. Proceed with caution.