Hi everybody,


I suppose that for everyone who lives on the topside of the globe it's also pretty cold right now...
Because of this cold I notice that my engine shakes more when it's not on temperature.
By logging I can see that the SOI in earlier than in my SOI maps


When looking in the mapping I can see that the SOI is corrected and advanced the engine is not at optimum temperature (90°) and/or when the air temperature is lower then 18°c.

So off course this explains why the engine shakes more and makes more noise.

Now I whas wondering why this is configuerd and if this an and/or situation.

I suppose that the timing is advanced so you have more heat in the chamber so you can heat up the cylinders faster. Is that rigth?

Also, as stated, there are different maps correcting this, the engine temperature and the air temperature.
Both say to advance from 0,5 up to 2,5 degrees of cranck depending on the conditions.



What i whas wondering is if this is cumulative or not?

Meaning that: If it says to advance 1° when Air temp is -10° and, it says to advance 1° when the enginetemp is at 0° that it advances the timing from 2°?

Would i hurt to reduce the advancement of the SOI correction to reduce vibrations in cold weather or would this just result in my engine taking more time to get up to temperature? Or would i be better to simply increase the pilot injection to reduce vibrations ?

Thank you for you input.

It is all about flame speed - cold air with more oxygen cause fuel burn faster it also causes higher noise as Bang of fuel stronger with higher burn temperature. EGR has one of objectives to slow down flame and lower burn temperature - it also makes engine run smoother. If EGR not in car you work - learn live with more noise and vibration.

Hello Pukis,

Thanks for your imput.
Correct, the EGR is disabled on my car.

If EGR really has the effect of slowing down the burn, that means that the top peak pressure the bang creates is later in the cycle.

Shouldn't I then not need to retard the SOI so that the peak pressure happens at about the same time?

I'm not convinced that you should learn to live with the fact that the engine shakes more and makes more noise.

I know that retarding the soi decreases vibrations and noise. Also adding pilot injection has this effect. Both are more implemented on newer diesels where there is less noise and vibrations.

Retarding has also, if I'm not wrong, a negative effect on emissions, higher EGT and off course less Torque. But if this can prevent from making my engine sound like an old used diesel, while in the summer or when the engine reaches 90° it sounds good and runs smooth, why not.

Modern diesel engine is state of art balancing lot of parameters - there no single easy way make it run smooth as petrol. Retard will produce more smoke - lambda will not be happy where ecu will reduce IQ. Fuel CT also will start play role with retard. To be more accurate - modern CM engine use arround 7 injections per cycle in total.

With EGR-off combustion is faster-harder because cylinder pressure and temp is higher. You must check if you EGR-off method considered that difference, if not you must to tune combustion a little when cold (soi, rail etc).

Hi Ceecee,

Thank you for your reply and your words of wisdom. You have already helped me a lot and I don't think I have thanked you enough for it!

This does make more sense. Indeed, the EGR-removal was not corrected and unless it's very cold I never noticed this excess of noise and shaking, or any other inconvenience .

I'm glad you advise me to modify the SOI, rail etc. For me I don't find it logic that you have to live with this because EGR is off. IMO there are different things that can be done to reduce this.

As previously stated timing retard and pilot injection. For these I can find correction maps that are regarding to engine and IAT. In these maps you can already see that there is a compensation for cold temperatures. For the rail pressure I can not find these maps.

So I have different options as I understand (always in EGR zone) :
I can retard the SOI correction maps
I can decrease rail pressure correction
I can inject less (but that's less fun :D)
And I think could increase pilot injection a bit. I know for sure that this reduces vibrations and noise. These are also most active in the EGR region.

Thank you in advance and stay healthy everyone!

Here you have SOI dependencies.

Recently I had a HDI engine with EGR off by hysteresis minimization, with severe knocking/pinging when cold, gets better when hot but you can still hear pings under load. Interesting while no load there is no knock/ping hearable.

What I did is played with SOI correction and got nowhere, so I compared distances of crack angles between hot SOI map and PI SOI map on normal working engine, then I compared "distances" on this knocking engine; guess what? PI SOI map was advanced up to 7°ca in pinging egr region, I recalculated PI SOI map so PI was retarded 1 to 7 °ca on specific points and guess what? severe knock was gone.

I did not try with rail pressure or temp correction for PI as I thing it will not work well.

I love ICE Theory.
Friends, you noticed here that recirculation helps the diesel to be quieter, and rightly so. If you know how the filling and combustion processes go, it will be easier to tune the motor.
EGR raises compression temperature! And the fact that the EGR can lower the combustion temperature, in this case, here, is not interesting. Let's leave that to the environmentalists. And so, what will we hear from a diesel with poor compression, with large spray from the injectors? Yes, detonation. Detonation occurs due to a significant part of the fuel evaporated from the drops into the "cold", and after the accumulation of steam, detonation ignition occurs in the volume, but there should be a flame right next to each drop, and not the absence of a flame. That is why they came up with the EGR for a diesel engine, which, due to the turbocharger, has a relatively low compression ratio and has weak compression before boost. In the cold, we hear the "charms" of the imperfections of such a design. That's why pilot injection (heating up the combustion chamber) helps us.
In the cold, the diesel will be quieter if we adjust the injection to the moment of the highest compression, and here is a paradox, the compression begins to weaken to TDC (cooling of the compressed against the cold walls of the Combustion Chamber). Hard to compress exhaust gases, they are not cold and they raise the compression! There is a second and main effect of the EGR - even if an undesirable evaporation occurred not in front of the flame, but behind the fading flame, then the inert exhaust gases cause such a mixture to "smolder" and not detonate.
Congratulations to all fans to turn off the EGR. It must be adjusted, and not turned off, so as not to burn the intake at partial loads, but to have a quiet warm-up and idle

ceecee wrote:With EGR-off combustion is faster-harder because cylinder pressure and temp is higher. You must check if you EGR-off method considered that difference, if not you must to tune combustion a little when cold (soi, rail etc).

The advice is correct, but the reasoning is wrong.
I tuned such an old motor with a phased noise meter, and the offset of the pilot injection did not help, increasing the ramp helped a little, and a little early main injection (by 2 degrees) helped. The exhaust support (boot in the pipe) immediately calmed the detonation both in the version with stock injection and with early, equally