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Discussion and questions related to the course Diesel Tuning Fundamentals
I have see on the courses video using Motec M1 that on dyno pulls, when TPS goes to 0, it activates "overrun" that normally this is anti lag on Motec. Sense i cant find nothing abouth this want to talk abouth it to try to work with it sense im working on a rally race truck and will be nice to use this option. I understand how it work on a petrol engine and know that on diesel this is set using Post Injection, just want to know if someone can help me to use this, like min and max injection and timing to start using this. Its a stock 1KD 3.0 Toyota engine with a non VNT turbo
If diesel engines had sparkplug you could maybe set a post injection ablaze but as they don’t you still need to inject fuel on a point that it will ignite so close to TDC and it will make power and as you do not need this if your off throttle and you want to slow down this is not wanted. Also take in mind in order to evaporate diesel you need a load heat so a small combustion around TDC will not provide this and all you get is white smoke so than you would say why the need for post injections???. Well the DOC or diesel oxidation cat will convert diesel into heat but not in a way that it’s a massive flamethrower able to drive your turbo.
On launch control your able to use post injections but your running a load more RPM @ that point. This is what it looks like. [url=https://www.youtube.com/watch?v=rnZDfK42S9k]https://www.youtube.com/watch?v=rnZDfK42S9k
What we use on big bore engines is a function that you could call a turbo kicker where the ECU changes several times to different injection modes depending if your in transient static or deceleration modes or any in-between and all that dos in turbo kick modes it runs the engine less efficient directing the combustion towards the exhaust stroke and it will work well for a turbo that is able to support 120Hp per L. Any bigger and your will be burning more fuel as the ECU try to maintain boost on part load by dropping fuel in less efficient all the time.
Also take note bigger a turbo have more rotation mass so keeping it up to speed is more important. On small bore engines the turbo in comparison is a lot smaller and spools a lot faster so a lot easer to get things op to speed with the turbo.
For example a motec diesel ECU is very basic with only the main functions to run a diesel engine as for fuel quantity/timing and fuel/boost pressure only able to dial in engine efficiency as in 3D mode. In our basic diesel ECU there is the option to set any load conditions until X boost pressure is present but reality tells us having >50% torque under your accelerator peddle @ part load sounds exiting but we easy making 800Nm out of a 3L CR Toyota engine so over 50% torque Makes 400Nm+ that can make your engine very jerky so we came up with a control strategy that maintains a hi ready state of boost but still able to control torque and inlet pressure on low RPM dos tell a story as not a lot is needed as example below.
In this picture you get 388Nm @ 1373Rpm on transient @ only 170Kpa inlet pressure. I have done 700Nm @ 1500Rpm on the dyno and these 3L CR Toyota engine like any other small engines are not build for this. It’s not a truck engine build for max low-end performance.
Also being a 4 line engine its very hard on the gearbox as well as often customers destroy 3e gear so we limit torque under 2000Rpm.
Thats perfect, thanks for that answer. I also see that the plug and play kit that i use, it does all the injection calculation based on MAF sensor and maybe it does "slow" reaction instead of a map, so i need to keep testing all this. I start the truck with no MAF sensor for the first time and notice that was very quick reaction to the peddal, as soon i conect everything (maf) i see that was much slower reaction, a "normal" behavior of maf tune, as im new on diesel, its the way the kit works and all courses talk too much abouth maf
First of all I like to say the motec tuning software is excellent in the way they try to explain things among with there youtube stuff so I do not sound all negative.
You just conformed what I was expecting using MAF not MAP to smooth thing up with what we call torque control getting slow transient response on load chance using MAF. Try to run it on MAP with some boost and chance is it will be very jerky on the peddle.
Also like to explain why mainly MAF is used when EGR is active as MAP will not longer give a reference in combination with manifold temp what air mass is entering your engine as exhaust gas is recalculated but even as MAF can be used MAP can be used not only for boost control as end of compression temp play an important part on how fast combustion takes place and there is a direct link with manifold pressure on that part.
As this topic is about ALS and hard to do on diesel the next best thing is to use the combustion and its delay to spool the turbo and as you can see in the picture of my first post where fuel mass (dark blue line) travels in front of air mass MAP (green line) and under normal 3D condition you pull a load of smoke so setting lambda number as smoke limit dos not do the job and even a 4e element will not do the trick so a 5e or even 6e element is needed to prevent smoke and get faster spool-up and get torque response out of your engine. As a 3L Toyota is a small bore engine we do not have a load of room in the combustion chamber before we hit the wall with fuel so we are limited and the result is that torque response from the engine is related to manifold/end of compression temp as my picture show as well looking @ the RPM increase over time. On a big bore engine we have more room in the combustion chamber so we can do the same trick more efficient giving an almost instantaneous massive torque response and able to pull o2 as low as 13:1 AFR getting some smoke on older engines but having low exhaust gas speed out of the downpipe that is facing toward the tarmac part of the diesel partials will land on the tarmac and the rest will burn off as it hits oxygen so most of the time no visible smoke can be seen.
Do understand diesel tuning can become very complicated and not a load if information is out there so what ever is out there on information is taken also in support and I favour to the ECU system used during training sessions. Also most training courses are given by followers not developers so most of stuff on what is going on with the combustion dates back up to 2012 technology from what I have seen and yes most of this still apply today but in 2020 a lot of progress has been made on diesel engines so we are constant looking on how to use these improvement to the max so keep an open mind and explore do not aim for given number but aim for result.
I have too much to learn yet, and need more practical hours to find all those little things that make difference. Thanks one more time. Hope that this changes helps turbo spool a little faster