GR Yaris LSPI - is it a problem with GRY and D-4S?

[GRunt]

Hey folks, i was wondering if the GRY is prone to LSPI.

LSPI is quite a problem for low displacement, force inducted engines with direct fuel injection when running high loads at low engine speeds.

I am aware the GRY is meant do be driven on load in higher RPM and many of the problems with LSPI can be avoided by proper driving behavior. But does in general the GRY also has some problems with it or is the combined injection system D-4S wich runs port injection at low speeds and load and port and direct at low speed and high load a possibility to lower the probability of occurrence.

Many oil suppliers are aware of LSPI and have developed API SP formulations as an improvement to API SN to tackle it. But how effective is the changed oil? Does it really make a difference?

 

[Michael Knight]

Not an oil expert but assuming oil can tolerate something but it is not preventing as it is fuel that is igniting. Would assume it is managed by ECU though.
Would this be visible via knock sensors ? sad that they did not include any in our great engine as it would give good insight of any problems occurring..

 

[Onehp]

Older oil spec additives could make LSPI worse as oil residue sticks to the cylinder walls.
Our engines have knock sensors for sure, but LSPI has nothing to do with normal spark plug intiated knock afaik, as is a form of self combustion?

Adding up to 30% ethanol to the fuel supposedly helps, as does keeping charge temps low... Haven't seen the hard science research papers though.

The port injection is active in low rpm but not sure if active on high load, at least there is a choice to try to avoid it. It also means the engineers made the engine strong in case there is LSPI....

 

[GRunt]

Knock occurs after ignition. LSPI just before and therefore is extremely lateral to engine health.

The upwards movement of the piston collide with the expanding flame front of the pre ignition.

LSPI arise from interactions of oil drops fuel and engine design. Downsized forcefully inducted engines are prone to LSPI because of their design and the driving behaviour resulting from this.

Small turbo charged engines trade power from size and speed for power from low end torque through compression. Therefore they are driven in much lower rpm and also accelerating from them compared to a larger NA engine. So they give excellent environment for LSPI.

Research has shown, LSPI events occur quite randomly but frequently in the combustion chamber and not only at the cylinder walls as thought earlier. It seems small droplets of oil and fuel are ignited by high compression at high load and low speed.

"When the fuel is injected directly into the combustion chamber, it dilutes the oil film lining the cylinder. This fuel dilution reduces the surface tension and viscosity of the oil, causing an oil-fuel mixture to accumulate in the upper reaches of the piston top land crevice. The mechanical energy of the upstroke during compression pushes droplets into the combustion chamber, where they vaporize and can auto-ignite prior to spark ignition and subsequent engine damage. The team used high-speed video, crevice sampling and other specialized tools to better determine the source of the problem. Captured video showed that droplets of material were coming out of the piston crevice in the engine. Sometimes those droplets burned, leading to LSPI and strong engine knock. The video also showed that the material was a complex cocktail of fluids—fuel, lubricant, soot and other material. It’s clear to us now that resolving LSPI issues will require addressing lubricants, fuels, engine design and more.”

From Thomas Briggs, Jr. manager of engine systems research and development at Southwest Research Institute (SWRI) in San Antonio, TX. Briggs led SWRI’s Pre-ignition Prevention Program team that includes industry partners (GM, Ford, Honda, Infineum International, Afton Chemical and others) that began investigating LSPI in 2011.

Also "We already know that LSPI arises when engines are in the 1500-2000 rpm range, a relatively slow speed, while still exerting plenty of torque. That’s also when a large supply of fuel is present. Yesterday’s engines spent little time in these operating conditions, but it’s very possible they too would experience LSPI if they had.”

I would conclude from this information, hard accelerating from low end, below 2k rpm, should be avoided if possible. Especially on a high compression small displacement high boost engine like the lovely G16E GTS... well that's no news.

But what options does the engine have to prevent LSPI, combined injection? Knock sensor? Reduced injection amount from low end or reduced boost?

What options do we as a driver have beside accelerating from proper speeds and the right oil?

I am curious!

 

[Painkiller]

This is what i researched....a time ago​

What is it ?​

Low speed pre ignition
Premature self-ignition of the fuel-air-mixture before ignition by the spark plug by low engine speed
Not to confuse with high speed engine knocking.

What happens with engine ?​

Engine can easyly get damaged, cause the highest cylinder-pressure thats usually about 60 bar increases up to 200 bar and more.

Which motors are affected ?​

Direct injected, turbocharged, downsized high output engines.

When does it happen ?​

Only by low motorspeed (about 1250 - 2500 rpm)...
...and high load (full acceleration) at the same time.

What are the reasons ?​

Hotspots from sediments
uncorrect fuel-air mixture
Detachment of oil drops from the piston ring gap
Oil-fuel-interactions
Particles
Residual gas

So, what helps preventing ?​

we can not influence:

1) the number of injections per working stroke - but the danger of LSPI by only one injection is 4 times higher than by two injections (becauce of much better fuel distribution and circulation)

but we can influence many things:

2) do not demand the engine at low rpm (1250-2500) with heavy acceleration - and everything is good !
(why? by full acceleration at low rpm, there is much fuel injected, by low circulation at the same time)

3) the danger of LSPI sinks with warm engine (oiltemp over or at least 100°C, watertemp over or at least 90°C) - so always take care of good tempered engine, before having fun.

4) use premium fuel (high octane is good) becsauce premium fuel has good volality and good detergents

5) fuel with up to 30% Ethanol is very good against LSPI (over 30% LSPI increases again)

6) use oil that prevents LSPI (API-SP - good, Dexos1Gen2 - stronger)...they have no Calcium as detergent - cauce calcium changes the size of oiltrops, that may be detached...

7) oil with low volality and high flashpoint decreases oil-fuel interactions (my faforite: Ravenol-DFE)

8) dont use foam-filters with bad filtration-rate - so you dont get any Silicium in your intake-air

So, is the GR Yaris engine endangered of LSPI ?​

I do not know, but becauce of the additional port-injection by low rpm (but this just till middle load) it may be better prepared against LSPI than other engines...but who knows?
Still if he had no LSPI-Problem...if you take the above standing to heart, your engine will live longer...

Sorry for bad English...

Regards Painkiller