Achieving the maximum potential of your diesel tuning with Trundles – Part 2

In Part 1, we touched base on some maintenance that may be required prior to chasing more power out of your diesel!
With that out of the way, I am now going to touch base on associated modifications that you may like to consider prior to getting your truck to the Dyno that may effect the tune if done at a later date.

For the larger percentage of people, a piggy back ECU or remap of some kind may give more than enough grunt for the average wheeler, some people just want that bit more or plan on doing other modifications in the future. The most popular modifications that we will initially touch base on are exhaust upgrades, intercoolers and air intake upgrades!

For high flow exhaust systems you may be left disappointed in return on investment (ROI) depending on what vehicle you are dealing with. Believe it or not on a lot of common rail vehicles with VNT turbos the factory exhausts are reasonably well designed, although an upgrade will give you slight power and torque increases above 1500rpm and also help drop EGT (exhaust gas temp), you will loose a bit of bottom end below the 1500rpm mark. I know there are a lot of internet mechanics that would beg to differ, but we have proven it time and time again with metrics on the Dyno. Other undesirable results may also be the note or sound may not suit what you have in your head, ideally it may pay to ask to hear a truck with that exhaust before you invest your hard earned cash.

Don’t get me wrong if I was modifying a small cube CRD I would definitely run with an aftermarket system. Some vehicles however, get great improvements across the board. Most 1KZ powered trucks (KZN130, 165, 167 etc) have a turbo down pipe that could not possibly be worse. The likes of the 80 series Landcruiser, which the system drops down to 1.75 ” in places which is simply hopeless when you are dealing with big cube engines like the 1HDT.

Once you have made the call if an exhaust is for you or not, another very common upgrade is an intercooler. Although some of your trucks won’t even have intercoolers from factory, and others will, ask yourself “why do I need an upgrade I already have one fitted”?, both examples have large room for improvements. If you don’t have an intercooler and plan on reasonable gains or using the vehicle under wide open throttle conditions for long periods of time, your exhaust gas temps will increase to the point that you can cause costly engine damage. When your turbo is working hard air temps in the vicinity of 1-200 degrees Celsius can be forced into your inlet.

Most late model trucks have intercoolers, as previously mentioned, however when increasing boost levels we have seen post intercooler temps reach over 100 degrees Celsius which means less dense air and the motor is under more strain. Although most common rail and EFI motors have provision for raising air temps, mechanically injected motors do not, either way watch your power figures drop by the second as the air temps increase! Now we have touched base on the negative effects of hot air, lets look at the benefits of fitting or upgrading an intercooler. Low air temps means more air density which gives the ability to add more fuel which in turn will make more power. Low air temps will result in significant EGT drop, we have seen drops as large as 150 degrees just in upgrading intercoolers from say 450-600mm wide and/or quality and/or location improvements. A key point is that the real benefits of the intercooler will only be truly noticed when the tune is matched to suit.

Finally for the basic modifications we will touch on the inlet. I cannot comment for any one vehicle in particular but when chasing gains we often disconnect certain sections to eliminate restrictions. Some factory air box systems we have seen even on a mild tune have been taking 50nm of torque. An air box upgrade can be a wise investment, however some people choose to upgrade air filters which I hate to say can be a complete waste of money. Most of the later model trucks we have tested at moderate states of tune have zero HP difference with the air filter completely removed if the vehicle is in a well serviced state. The final piece of the inlet system that is often fitted to our trucks is the snorkel. Whilst crucial when doing water crossings, running with the cheapest option often can often be a poor investment in the long run. If you are only after moderate gains a nice Safari unit will be fine, but if you want a 200 plus KW fire breather any off the shelf plastic snorkel unit will not even come close to giving the result you are wanting.

We are not trying to scare monger you into purchasing a specific product, but simply getting you to consider your options on where you should be saving or spending your money.

Next week we will touch on my favorite section, fuel system and turbo upgrades! And also follow up with where all the pieces to the puzzle get put together on the Dyno!











Part 1

– Trundles Automotive

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