wemay
Site Donor 2023
True, especially the LSPI for which the entire industry developed a amended spec.
Shearing, dilution and low cSt questions
- Thread starter Flashlightboy
- Start date
Since last month, the Russian oil-club.ru has been testing shear stability. KO method, 90 cycles.
First 0W-20 results look very interesting
First 0W-20 results look very interesting
0W-20 Shear Stability Test
Сводная таблица лабораторных анализов масел вязкостью 0W-20 Shear Stability Test Проделана громадная работа, на которую потрачено очень много средств и времени, форумчан Oil-Club.ru. Спасибо Вам всем! 1. Extreme A.M.G. VR2 0W-20 GTE Shear Stability Test 2. Idemitsu Zepro 0W-20 API SN Shear Stabil...
www.oil-club.ru
That's quite contrary to the supposed efficiency advantage of GDI over MPI?
I think the main problem with GDI is that the fuel is not well atomized and mixed with air. MPI seems more stable at lower speeds, whereas at higher loads and speeds GDI is definitely better
They should be since they contain relatively little VII. 0W-8 oils are even more stable since they are essentially a 0W-20 oil without any VII. Monograde oils do not shear.
I pay more attention to the KV100 in relation to the HTHS. If you have two 30 grades, one 9.5 cSt and one 11.5 cSt, and both have an HTHS of 3.1 cP, then the 9.5 cSt obviously uses superior base oils with less VII and thus, more desirable. The flip side of that is also true with two 30 grades, both 11.5 cSt, but one 3.1 cP and the other 3.5 cP HTHS. The higher HTHS in relation to KV100 tells you a lot more about the quality of the oil.
I'd rather have an oil that starts at 9.5 cSt and ends at 9.0 cSt than one that starts at 10.5 cSt and ends at 8.5 cSt.
I'd rather have an oil that starts at 9.5 cSt and ends at 9.0 cSt than one that starts at 10.5 cSt and ends at 8.5 cSt.
OVERKILL
$100 Site Donor 2021
GDI allows higher static compression ratios and manipulation of injection timing that's independent from the operation of the intake valve, which allows a level of optimization not possible with a port injected configuration and a considerable bump in power, particularly when paired with a turbo or turbos.
On the other hand, because GDI directs fuel directly into the cylinder rather than into a flow of air, there is the tendency for some of that fuel to:
A. Not combust properly, creating soot
B. Wash down the walls and get by the rings, making its way into the oil.
"B" seems to be even more prevalent on TGDI applications where enrichment levels are higher due to boost and cylinder pressures are also higher, likely aiding in more blow-by and more fuel making its way into the oil.
Of course GDI has also had other issues, which vary in severity depending on marque, such as intake valve deposits and LSPI in turbocharged applications.
In general yes. But Idemitsu Zepro 0W-20 has 11,4% of viscosity decrease and Shell Helix Ultra 5W-40 API SP has only 1,7%.
Shell Helix Ultra 5W-40 API SP свежее Shear Stability
Shell Helix Ultra 5W-40 API SP свежее Shear Stability за анализ спасибо Filyan, parziv, Дюпелек, a-ha, ai_gelios. Масло закупал в емексе у поставщика NICQ по цене 821р. Масло заявлено как: API SP ; ACEA A3/B3, A3/B4; BMW Longlife-01, MB-Approval 229.5, 226.5; VW 502.00/505.00; Porsche A40, Renaul...
www.oil-club.ru
”relatively little VII” does not always mean “more shear stable”. It also depends from VII type.
Definitely. But also on the other hand mechanical shear is relatively rare in most engines. A few have a problem but most do not.
If the wear metals on UOA's have never been lower with GDI, and the increasing amount of timing chains wearing out, why doesn't the timing chain wear elevate the wear metals on UOA? Probably because the UOA's have shortcomings and isn't really that good of a source.
That seems to go against what I’ve read. Todays fuel injection is computerized and the injections are variable depending on conditions. They tend to run rich if the engine is cold but that is short lived.
Yes the higher compression ratio allowed by GDI results in higher output.
However, the compromises with GDI are quite considerable that they had to reintroduce MPI to address the issues.
Last edited:
The air/fuel mIxture of GDI can be so poor, particularly during cold start that engine designers resort to adding tumble valves at the intake to enhance & aid air/fuel mix by creating turbulent air.
The rich mixture and the ensuing GDI diesel rumble during cold start is to conform to certain emission standards by allowing quicker warming of the catalytic converter.
Even standard port injection (MPI) arr just as computerised as GDI
OVERKILL
$100 Site Donor 2021
Toyota is the only marque I know of off the top of my head that has a hybrid GDI/MPFI setup. I outlined the caveats of GDI quite clearly in the post you responded to.
It's not just higher compression, it's the ability to manipulate the timing of the injection of the fuel to facilitate it, which you can't do with MPFI because it depends on the timing of the intake valve. That's how you can get away with higher compression ratios, boost, and 87 octane with GDI.
Ford was/is using reversion to "wash" the intake valves with the air/fuel charge on the EcoBoost as their way to mitigate IVD's, this was done with manipulation of the camshaft timing. Toyota has claimed their hybrid setup is to improve low speed performance/drivability, which is where their engines use MPFI, but of course keeping the intake valves clean is an obvious benefit of that system.
Personally, despite the performance benefits, I'm wary of GDI. Honda has had some considerable issues with fuel dilution, then there is LSPI, costly injection pumps, injectors...etc. While it shouldn't be a technology in its infancy at this point, given the considerable time that has elapsed since its introduction, in many ways it still feels like it is.
There are ways to manipulate fuel timing with port EFI if you have enough injector. You set the injector to spray it's entire cycle while the intake valve is closed. The fuel hits the back of the hot intake valve which helps it vaporize and cool the intake valve at the same time. When the valve opens, the fuel gets pulled in right away allowing just air to fill the cylinder the rest of the intake cycle. Not as good as GDI obviously, but a little bit to play with. The injector duty cycle needs to be <50% to pull that off.
Ford uses both GDI and MPI on the 2018+ Coyote.
- Joined
- Aug 12, 2020
- Messages
- 167
Let's not forget superior atomization due to much higher fuel pressures.
The ideal system is definitely a dual system.
I feel like factory engines have more problems than engines that are tuned for power, possibly they run less rich and therefore have less fuel dilution? I'm not sure. For instance, the DAZA 2.5 TFSI engines seem to be supremely reliable when tuned.
The ideal system is definitely a dual system.
I feel like factory engines have more problems than engines that are tuned for power, possibly they run less rich and therefore have less fuel dilution? I'm not sure. For instance, the DAZA 2.5 TFSI engines seem to be supremely reliable when tuned.
All engines shear oil, and some engines shear oil pretty good. And of course the amount of shear is also dependent on the oil. Any time an oil layer is between two moving parts it's being mechanically sheared. Here's UOA data collection of different oils used in 1st Gen Coyotes (2011-2014). Shear rate data is in the last column.
Last edited:
OVERKILL
$100 Site Donor 2021
Was unaware, that's interesting. So we have two brands doing it now I guess. Of course the Gen 2 Coyote was port injected, so for the Gen 3 they've tacked on DI, apparently, to take advantage of the higher compression ratio:
OVERKILL
$100 Site Donor 2021
Without fuel being accounted for there, it's very hard to ascribe change in viscosity exclusively to shear. This is made even more opaque by the fact that these are different cars with different operating conditions. It is in no way a controlled data set and lacks any corresponding GC data.
True, a fuel dillution column would be nice. But at lease they are all 1st Gen Coyote engines (only MPI) which IIRC don't suffer from fuel dilution like a typical GDI engine.
Similar threads
