How hot does an engine need to get to eliminate fuel dilution?
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Mazda has programmed these SkyActiv engines to heat up quickly from a cold start. I don't recall the exact method.
I also cannot remember if your year has the 4-2-1 exhaust header known as the bundle of snakes. I seem to recall the early years did not have this as it wouldn't fit. Shortly afterwards they designed the engine bay to allow it. That's why Mazdas have a longer hood.
I also cannot remember if your year has the 4-2-1 exhaust header known as the bundle of snakes. I seem to recall the early years did not have this as it wouldn't fit. Shortly afterwards they designed the engine bay to allow it. That's why Mazdas have a longer hood.
Correct. In 2012MY they introduced the 2.0L skyactiv engine as an option (rather standard on the i Touring and i Grand Touring trim levels) on the Mazda3. In 2014MY they introduced a new Mazda3 with a longer hood and part of the firewall reshaped to make room for that large header. Then all Mazda3's came with a skyactiv engine, either 2.0L or 2.5L. I wish I had the 4-2-1 header.
I'm not delighted with what I'm hearing about the new 2019 Mazda3 with a torsion beam rear suspension, no hope of a Mazdaspeed version, and a move towards 'mature' luxury NVH, interior design, and materials, away from an affordable and efficient zoomzoom driving experience. I may rush my next car purchase to buy a discounted 2018 Mazda3 touring or Fiesta ST.
My skyactiv engine heats up somewhat quickly by running rich with delayed ignition timing and high RPMs when cold. On cold days the idle at start up consumes around 1.5 gallons per hour. When warmed up idling consumes only .2 or .3 GPH. The keep the delaying ignition timing till the coolant temp exceeds 60C, on very cold days it waits till the coolant is even hotter. Average fuel economy is heavily impacted by cold starts. When running in an Atkinson cycle after warmed up using timing around 40 BTDC with a moderate load (8-12psi manifold absolute pressure), they are so efficient that they produce little waste heat, leading them to run cold in the winter, especially if one is drawing off heat to warm the cabin. On the up side I routinely get 35-40 MPG with mild hypermiling techniques and have once gone 702 miles on 13.9 gallons of gas (all highway, all hypermiling.)
I'm not delighted with what I'm hearing about the new 2019 Mazda3 with a torsion beam rear suspension, no hope of a Mazdaspeed version, and a move towards 'mature' luxury NVH, interior design, and materials, away from an affordable and efficient zoomzoom driving experience. I may rush my next car purchase to buy a discounted 2018 Mazda3 touring or Fiesta ST.
My skyactiv engine heats up somewhat quickly by running rich with delayed ignition timing and high RPMs when cold. On cold days the idle at start up consumes around 1.5 gallons per hour. When warmed up idling consumes only .2 or .3 GPH. The keep the delaying ignition timing till the coolant temp exceeds 60C, on very cold days it waits till the coolant is even hotter. Average fuel economy is heavily impacted by cold starts. When running in an Atkinson cycle after warmed up using timing around 40 BTDC with a moderate load (8-12psi manifold absolute pressure), they are so efficient that they produce little waste heat, leading them to run cold in the winter, especially if one is drawing off heat to warm the cabin. On the up side I routinely get 35-40 MPG with mild hypermiling techniques and have once gone 702 miles on 13.9 gallons of gas (all highway, all hypermiling.)
Couple of things to consider:
1- the impact of coolant temp (ie playing with the thermostat) may not be as significant as you may think. ie there won't be a one to one impact. For example there may not be much oil temp diff between hot /cold (20°F) thermostats some used to switch (winter/summer) in the old days. Don't expect to see 20°F higher/lower oil temps. If you do this, and tell me that the oil temps hardly ever changed, I'll believe you.
2- oil temp may typically be running 20-30°F above the coolant temp. I've seen it anywhere from 10 or 20°F to as high as 50°F above the coolant temp depending on the car. Keep that in mind when using Shannow's charts. I am typing and can't look at the graphs but I'm pretty sure they are engine oil temperatures and not coolant.
1- the impact of coolant temp (ie playing with the thermostat) may not be as significant as you may think. ie there won't be a one to one impact. For example there may not be much oil temp diff between hot /cold (20°F) thermostats some used to switch (winter/summer) in the old days. Don't expect to see 20°F higher/lower oil temps. If you do this, and tell me that the oil temps hardly ever changed, I'll believe you.
2- oil temp may typically be running 20-30°F above the coolant temp. I've seen it anywhere from 10 or 20°F to as high as 50°F above the coolant temp depending on the car. Keep that in mind when using Shannow's charts. I am typing and can't look at the graphs but I'm pretty sure they are engine oil temperatures and not coolant.
Originally Posted by OilUzer
2- oil temp may typically be running 20-30°F above the coolant temp. I've seen it anywhere from 10 or 20°F to as high as 50°F above the coolant temp depending on the car. Keep that in mind when using Shannow's charts. I am typing and can't look at the graphs but I'm pretty sure they are engine oil temperatures and not coolant.
That they are...and bear in mind that the big end temperatures could well be 20+ degrees C above the bulk oil temperatures.
So SonofJoe's conjecture that blowby heat and volume is sound.
The spray of oil from the big end, counterflow with the blowby is the perfect recipe for "stripping" the volatiles from the oil.
(Also with the CO and NOx, perfect place to make varnish precursors)
2- oil temp may typically be running 20-30°F above the coolant temp. I've seen it anywhere from 10 or 20°F to as high as 50°F above the coolant temp depending on the car. Keep that in mind when using Shannow's charts. I am typing and can't look at the graphs but I'm pretty sure they are engine oil temperatures and not coolant.
That they are...and bear in mind that the big end temperatures could well be 20+ degrees C above the bulk oil temperatures.
So SonofJoe's conjecture that blowby heat and volume is sound.
The spray of oil from the big end, counterflow with the blowby is the perfect recipe for "stripping" the volatiles from the oil.
(Also with the CO and NOx, perfect place to make varnish precursors)
I had a 2012 Skyactiv and I controlled the fuel dilution and deposits (verified with UOAs and boroscopes) doing the following:
1) Run 91 octane or higher. This pretty much eliminates the fuel dilution issue completely.
2) every 5k miles, do a 3,500-4,000 RPM run on the highway for 20 minutes.
Worked great for me. I can't prove #2 did anything for my situation as the valves stayed clean. It may or may not have been necessary.
1) Run 91 octane or higher. This pretty much eliminates the fuel dilution issue completely.
2) every 5k miles, do a 3,500-4,000 RPM run on the highway for 20 minutes.
Worked great for me. I can't prove #2 did anything for my situation as the valves stayed clean. It may or may not have been necessary.
I also run premium in my 2.5 SkyActiv. I can tell the response has improved. I'm also fortunate to have a couple of long hills nearby. Going up those in sport mode gives the engine the workout it needs.
The only evidence I can provide, and it's not scientific, is that the oil doesn't smell like gasoline when I have changed it. My oci are 5k.
The only evidence I can provide, and it's not scientific, is that the oil doesn't smell like gasoline when I have changed it. My oci are 5k.
Originally Posted by badtlc
I had a 2012 Skyactiv and I controlled the fuel dilution and deposits (verified with UOAs and boroscopes) doing the following:
1) Run 91 octane or higher. This pretty much eliminates the fuel dilution issue completely.
2) every 5k miles, do a 3,500-4,000 RPM run on the highway for 20 minutes.
Worked great for me. I can't prove #2 did anything for my situation as the valves stayed clean. It may or may not have been necessary.
This is the key. NO turbocharged, high compression engine should be ran on junk 87 octane fuel, regardless if the darn manual tells you that you can! All these manufacturers coming out with these turbocharged engines and very high compression using 87 for efficiency is dialing the timing back so far it is causing a multitude of other issues. LSPI and dilution being two big concerns. Run 91/93 octane fuel and flog the thing once or twice a month as in the old "Italian tune up" and many of these issues will cease to exist.
I had a 2012 Skyactiv and I controlled the fuel dilution and deposits (verified with UOAs and boroscopes) doing the following:
1) Run 91 octane or higher. This pretty much eliminates the fuel dilution issue completely.
2) every 5k miles, do a 3,500-4,000 RPM run on the highway for 20 minutes.
Worked great for me. I can't prove #2 did anything for my situation as the valves stayed clean. It may or may not have been necessary.
This is the key. NO turbocharged, high compression engine should be ran on junk 87 octane fuel, regardless if the darn manual tells you that you can! All these manufacturers coming out with these turbocharged engines and very high compression using 87 for efficiency is dialing the timing back so far it is causing a multitude of other issues. LSPI and dilution being two big concerns. Run 91/93 octane fuel and flog the thing once or twice a month as in the old "Italian tune up" and many of these issues will cease to exist.
Originally Posted by racin4ds
Originally Posted by badtlc
I had a 2012 Skyactiv and I controlled the fuel dilution and deposits (verified with UOAs and boroscopes) doing the following:
1) Run 91 octane or higher. This pretty much eliminates the fuel dilution issue completely.
2) every 5k miles, do a 3,500-4,000 RPM run on the highway for 20 minutes.
Worked great for me. I can't prove #2 did anything for my situation as the valves stayed clean. It may or may not have been necessary.
This is the key. NO turbocharged, high compression engine should be ran on junk 87 octane fuel, regardless if the darn manual tells you that you can! All these manufacturers coming out with these turbocharged engines and very high compression using 87 for efficiency is dialing the timing back so far it is causing a multitude of other issues. LSPI and dilution being two big concerns. Run 91/93 octane fuel and flog the thing once or twice a month as in the old "Italian tune up" and many of these issues will cease to exist.
It is more the A:F ratio than the timing. They run much leaner on higher octanes.
Originally Posted by badtlc
I had a 2012 Skyactiv and I controlled the fuel dilution and deposits (verified with UOAs and boroscopes) doing the following:
1) Run 91 octane or higher. This pretty much eliminates the fuel dilution issue completely.
2) every 5k miles, do a 3,500-4,000 RPM run on the highway for 20 minutes.
Worked great for me. I can't prove #2 did anything for my situation as the valves stayed clean. It may or may not have been necessary.
This is the key. NO turbocharged, high compression engine should be ran on junk 87 octane fuel, regardless if the darn manual tells you that you can! All these manufacturers coming out with these turbocharged engines and very high compression using 87 for efficiency is dialing the timing back so far it is causing a multitude of other issues. LSPI and dilution being two big concerns. Run 91/93 octane fuel and flog the thing once or twice a month as in the old "Italian tune up" and many of these issues will cease to exist.
It is more the A:F ratio than the timing. They run much leaner on higher octanes.
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