Conclusions on Ecoboost Engine Oil - Gas Turbo Direct Injection

[SubieRubyRoo]

I believe the speed of the vehicle has nothing to do with determining which fuel injection method to use.

My understanding is that DI is used during moderate to heavy acceleration, and MPI is used under light/part throttle conditions.

I think you’ve got it reversed, but I don’t think there’s a lot of consensus. MPI was “too dirty” at low RPM because the fuel wouldn’t stay in suspension at low port velocities and you’d get droplets in the chamber. Liquid gas doesn’t burn well. This is why they came up with DI, so the fuel is introduced as close to combustion location and timing as possible. Once port velocity is increased due to higher RPM, the fuel from MPI stays in suspension much better.

The reason why I believe this is on my EB is that to go over 30% ethanol the in-tank (lift pump/low pressure) must be upgraded.

 

[twX]

2.5% dilution in 1,000 miles is not what I would call minor.

7500 miles, sure, 1000 miles, no.

Fuel dilution doesn't keep going up indefinitely over an OCI. It happens rapidly, then reaches a steady state level. Notice how the fuel dilution was the same on your 1,000 mile OCI as on your 2,000 mile OCI? It would measure about the same at 7,500 miles.

Use a thicker grade of oil to deal with the dilution if you think it's warranted, but you shouldn't base your OCI on fuel dilution.

 

[Nchockeyfan]

I think you’ve got it reversed, but I don’t think there’s a lot of consensus. MPI was “too dirty” at low RPM because the fuel wouldn’t stay in suspension at low port velocities and you’d get droplets in the chamber. Liquid gas doesn’t burn well. This is why they came up with DI, so the fuel is introduced as close to combustion location and timing as possible. Once port velocity is increased due to higher RPM, the fuel from MPI stays in suspension much better.

The reason why I believe this is on my EB is that to go over 30% ethanol the in-tank (lift pump/low pressure) must be upgraded.

I certainly could be mistaken. My understanding is that air flow inside the intake is swirling around more during part throttle, which leads to better fuel suspension. Under full throttle conditions, the air flow doesn't swirl as much, and the velocity is higher as well. That inherently leads to fuel dropout, since there is less time for the fuel to mix with the air. Again, I might be mistaken on this. Also, under full throttle conditions, the intake pressures are much higher with the turbo.

 

[MNgopher]

I think you’ve got it reversed, but I don’t think there’s a lot of consensus. MPI was “too dirty” at low RPM because the fuel wouldn’t stay in suspension at low port velocities and you’d get droplets in the chamber. Liquid gas doesn’t burn well. This is why they came up with DI, so the fuel is introduced as close to combustion location and timing as possible. Once port velocity is increased due to higher RPM, the fuel from MPI stays in suspension much better.

The reason why I believe this is on my EB is that to go over 30% ethanol the in-tank (lift pump/low pressure) must be upgraded.

This study from NHTSA on a 2017 3.5 Ecoboost may be of interest to you. Check out the histogram on page 42 included below. PFI dominates to absolute engine load below 40%, then DI takes over, with a maximum of 70 to 80% of the fuel coming from direct injection, and then leaning more on PFI, with almost 40% of of the fuel being PFI when at maximum loads...

https://www.nhtsa.gov/sites/nhtsa.gov/files/documents/812520.pdf

 

[OVERKILL]

I think you’ve got it reversed, but I don’t think there’s a lot of consensus. MPI was “too dirty” at low RPM because the fuel wouldn’t stay in suspension at low port velocities and you’d get droplets in the chamber. Liquid gas doesn’t burn well. This is why they came up with DI, so the fuel is introduced as close to combustion location and timing as possible. Once port velocity is increased due to higher RPM, the fuel from MPI stays in suspension much better.

The reason why I believe this is on my EB is that to go over 30% ethanol the in-tank (lift pump/low pressure) must be upgraded.

MPI puts far less fuel in the oil at low speed than DI does, but doesn't allow for as wide a ratio or effective CR, because you can't control WHEN the fuel is injected into the chamber. MPI is cleaner (this is why you don't generally see soot on the bumpers of MPI vehicles like you do with DI) but limits CR, and HP. The ability to control when the fuel is injected, allows for higher CR and HP with DI, but the byproduct is of course fuel dilution.

Ergo, my understanding with these hybrid setups is that MPI is used at idle and low RPM and load. When you get into higher load situations and approach conditions where the engine design would naturally knock, you have already been transitioned to DI, where its ability to better control when fueling occurs, avoids it.

 

[Danh]

MPI puts far less fuel in the oil at low speed than DI does, but doesn't allow for as wide a ratio or effective CR, because you can't control WHEN the fuel is injected into the chamber. MPI is cleaner (this is why you don't generally see soot on the bumpers of MPI vehicles like you do with DI) but limits CR, and HP. The ability to control when the fuel is injected, allows for higher CR and HP with DI, but the byproduct is of course fuel dilution.

Ergo, my understanding with these hybrid setups is that MPI is used at idle and low RPM and load. When you get into higher load situations and approach conditions where the engine design would naturally knock, you have already been transitioned to DI, where its ability to better control when fueling occurs, avoids it.

As an additional “benefit” I understand MPI allows for a smoother idle than DI and is so used in dual applications.

 

[OVERKILL]

As an additional “benefit” I understand MPI allows for a smoother idle than DI and is so used in dual applications.

Which makes sense, since MPI is spraying a fuel "mist" into a moving column of air, whilst with DI, you are blasting fuel into the middle of what is essentially a static column of compressed air.

 

[SubieRubyRoo]

This study from NHTSA on a 2017 3.5 Ecoboost may be of interest to you. Check out the histogram on page 42 included below. PFI dominates to absolute engine load below 40%, then DI takes over, with a maximum of 70 to 80% of the fuel coming from direct injection, and then leaning more on PFI, with almost 40% of of the fuel being PFI when at maximum loads...

https://www.nhtsa.gov/sites/nhtsa.gov/files/documents/812520.pdf

View attachment 191537

Thanks!

 

[TiGeo]

I believe fuel % happens quickly and stays relatively constant over a typical OCI on many engines.

 

[Sandstorm]

I believe fuel % happens quickly and stays relatively constant over a typical OCI on many engines.

I tend to agree with this assessment but I would like to know the mechanism of action behind it

 

[odie]

A time for P.U.P. , even w/o the Dexos 1 , Gen3 emblem on their bottles .

 

[CarbonSteel]

Fuel dilution doesn't keep going up indefinitely over an OCI. It happens rapidly, then reaches a steady state level. Notice how the fuel dilution was the same on your 1,000 mile OCI as on your 2,000 mile OCI? It would measure about the same at 7,500 miles.

Use a thicker grade of oil to deal with the dilution if you think it's warranted, but you shouldn't base your OCI on fuel dilution.

It was two separate 1,000 mile OCIs, not the continuation of the first 1,000 mile OCI.

I would love to know how fuel dilution doesn't continue to rise over the term of an OCI, given that nothing happens during the course of the OCI to reduce it. Both of the 1,000 mi runs were on the highway where the least amount of dilution should occur.

My next UOA which is a separate 3000 mile run will give some insight into that.

 

[CarbonSteel]

I believe fuel % happens quickly and stays relatively constant over a typical OCI on many engines.

I hope your opinion is correct, but I'll have to wait to get my next UOA to see how that pans out.

 

[odie]

A time for P.U.P. , even w/o the Dexos 1 , Gen3 emblem on their bottles .

Found this . No mention of DEXOS 1 , GEN 3 . Does apply to needs of D.I. engines .

https://www.pennzoil.com/en_us/latest/ilsac-gf6-compliant.html

 

[twX]

I would love to know how fuel dilution doesn't continue to rise over the term of an OCI, but next UOA which is a separate 3000 mile run will give some insight into that.

Fuel evaporates from the oil when the engine is warm. It can then either get past the piston rings, or go through the PCV system. In either case it will get burned up in the combustion chamber.

Here's what dilution looks like over an OCI. Ignoring the extreme cases with only 5 minute trips, most of the dilution happens in the first 5 hours or so, and it's nearly at equilibrium levels after around 25 hours (1,000 miles at 40 mph).

Here's an example of dilution going up rapidly and reaching near-equilibrium dilution in about 10 hours when the engine is operated cold, then dropping rapidly over the next 10 hours with a warm engine.

 

[mr_boring]

2013 Ford Focus...130K/11 years....5W20...most reliable lowest cost to own I've ever had. Yes...built Ford Tough.

I agree. I'm driving a 2018 F150 2.7 with close to 80k on it. I've done zero mechanical work to it other than a set of brake pads and caliper pins and spark plugs. My last 500k ish miles driven have all been in Fords. In those 500k miles, I've had to replace one part that cost me about 50$ on a 2012 F150 (Y connector on radiator hose) and 2 coil packs on a mid 2000's Taurus. Did have a transmission issue on the 2012 F150 at ~98k miles, but it was a CPO (100k mile powertrain warranty) vehicle so I took it in to get it fixed then traded it on a 2018 F150 with the 5.0 while it was still in the shop.

That first 2018 F150 5.0 was a lemon, but I honestly don't hold that against Ford. Sometimes you get a bad one.

Current ride gets 5W-30 every ~7500 miles. Even with the dual injection I smell a little gas in the used oil - but heck, that's my nose chromatograph and for all I know it could be lying. Oil level never changes measurably on the dipstick. It probably burns 3-5oz of oil and has 3-5oz of gas in it at the end of the interval.

 

[CarbonSteel]

Fuel evaporates from the oil when the engine is warm. It can then either get past the piston rings, or go through the PCV system. In either case it will get burned up in the combustion chamber.

Here's what dilution looks like over an OCI. Ignoring the extreme cases with only 5 minute trips, most of the dilution happens in the first 5 hours or so, and it's nearly at equilibrium levels after around 25 hours (1,000 miles at 40 mph).

View attachment 191578

Here's an example of dilution going up rapidly and reaching near-equilibrium dilution in about 10 hours when the engine is operated cold, then dropping rapidly over the next 10 hours with a warm engine.

View attachment 191579

We shall see...I hope you are correct. Given that I drove two different 1,000 road trips, the engine was as hot as it was ever going to be and for extended times, and under conditions where dilution should be the least.

If that was the best it is ever going to be, then this winter in CO should prove interesting to say the least.

 

[Kalle.J]

MPI puts far less fuel in the oil at low speed than DI does, but doesn't allow for as wide a ratio or effective CR, because you can't control WHEN the fuel is injected into the chamber. MPI is cleaner (this is why you don't generally see soot on the bumpers of MPI vehicles like you do with DI) but limits CR, and HP. The ability to control when the fuel is injected, allows for higher CR and HP with DI, but the byproduct is of course fuel dilution.

Ergo, my understanding with these hybrid setups is that MPI is used at idle and low RPM and load. When you get into higher load situations and approach conditions where the engine design would naturally knock, you have already been transitioned to DI, where its ability to better control when fueling occurs, avoids it.

Could argue that DI limits HP. At really high rpm high boost situations there is not enough time too inject fuel and have it blend in CC .
So PI takes over again at high rpm.

Plenty of 4cyl 2.3T Saabs with 500hp+ on port injection with stock ecu even. Guessing you mean DI increases HP/torque at lower rpm?

 

[OVERKILL]

Could argue that DI limits HP. At really high rpm high boost situations there is not enough time too inject fuel and have it blend in CC

Plenty of 4cyl 2.3T Saabs with 500hp+ on port injection.

View attachment 191586

I'm thinking more like the bump in power GM saw with the LSx engines going from PI to DI. We are constrained by "practical" in this case, but the increase in static compression ratios helps.

The chart @MNgopher posted shows it (a hybrid system) shifting back toward MPI at higher RPM, so I expect if the RPM ceiling were elevated like in your example, what you've noted would apply and the system would go completely off DI in favour of MPI.

So, I think the answer to the Porsche slide would be a hybrid setup.

 

[SubieRubyRoo]

Fuel evaporates from the oil when the engine is warm. It can then either get past the piston rings, or go through the PCV system. In either case it will get burned up in the combustion chamber.

Here's what dilution looks like over an OCI. Ignoring the extreme cases with only 5 minute trips, most of the dilution happens in the first 5 hours or so, and it's nearly at equilibrium levels after around 25 hours (1,000 miles at 40 mph).

View attachment 191578

Here's an example of dilution going up rapidly and reaching near-equilibrium dilution in about 10 hours when the engine is operated cold, then dropping rapidly over the next 10 hours with a warm engine.

View attachment 191579

Where are these “predicted” charts from? Just wondering, because I’ve never really seen any UOA data here that proves fuel % comes down. There are plenty of members who say they’ve taken their vehicle for long highway drives once per week or even for an hour or so just before an oil change, and yet there’s no appreciable difference in fuel compared to OCIs on those same vehicles when the oil was drained cold. They are even shocked at their high dilution because they thought the “common knowledge” that a long highway drive would boil off fuel, but that doesn’t seem to be the case with the limited control of samples available here.