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Ecobust Analysis

Jaymar

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Your description is largely depended on cam centerlines and valve timing which on the new cars is variable so there are scenarios that can lead to increased combustion pressure over the normal limits from high velocity intake charge and extreme exhaust backpressure both over filling the cylinder before both valves close resulting in gasket failure/head lift and cylinder distortion.

Headers work by tuning the exhaust pulses in the header to work in conjunction with the intake pulses so that in an ideal world the pulse in the header will be just arriving at the exhaust valve as the fresh intake charge is about to exit past the exhaust valve right as it closes to keep the most air/fuel charge in the cylinder. Just as the intake valve should be timed to close just as the intake charge is beginning to slow its velocity into the cylinder to capture the greatest amount of air/fuel charge. The cam is the heartbeat of the engine, and the intake and header combo must be matched to that heartbeat to achieve the overall best performance.

BD
It still doesn't add up, take the most fouled cat you've ever seen and it was nowhere close to blowing a head gasket because of cylinder overpressure. And that's far worse than an Ecoboost head design. This video is just some yahoo trying to sell a hair-brained idea that has no facts to back it up. Ecoboom just doesn't exist without people forcing too much air or timing on the motor or "tuners" that have no idea what they're tweaking with. I'm sure someone somewhere has blown up a factory engine, maybe they drove it like grandma going to church even but it just doesn't happen as often as the internet would like you to believe. And Bob the budget builder usually leaves out all of the details when he does cry to the world about blowing his motor. You've been working on cars long enough to know how to read between the lines of the customer report, read what isn't there.
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Ecto1

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Wow! Touchy subject. Thanks for all the feedback.

I guess I'm still trying to understand the cause/effect claimed in the video. The exhaust "manifold" is integral with the cylinder head in these cars to support the twin scroll turbo design. (Well, more to save money WHILE supporting the twin scroll design I guess. That's another story.) The firing order for the engine is listed as 1,3,4,2. The 2&3 cylinders feed one 'scroll' of the turbine while the 1&4 cylinders fee the other 'scroll'. Due to the firing order the cylinder pairs are not fired back-to-back creating a 1 cylinder firing gap to allow exhaust gases to be separated. At higher RPMs less separation. At higher boost pressures AND higher RPM less separation AND more air flow. However, due to valve overlap between the exhaust and intake strokes both valves are open simultaneously for a little while. According to descriptions of the engine's operation there is a negative pressure (vacuum) inside the cylinder while the intake & exhaust valves are both open. So under ALL conditions a little exhaust gas will be drawn back into the cylinder. At least I think it will. Inertia will move most of the exhaust gases out but back pressure will prevent at least some exhaust gas from being expelled, especially at higher RPMs under substantial boost. But if there is sufficient back pressure more than just a little exhaust gas will remain (or be drawn) in to the cylinder. I think this is the gist of the "reversion" argument. While the turbo will attempt to force fresh intake air into the cylinder the exhaust gas will put a limit on the amount of the fresh air that can be drawn/forced into the cylinder. Even though the intake is under boost it's not more than a full atmosphere of pressure (14.7 psi is 1 atmosphere). Unless these tunes are running well above 29.4 psi (2 atmospheres). I don't think they are. So if a trace amount of exhaust gas remains in the cylinder the turbo forces in an almost full cylinder of fresh air. But if a significant amount of exhaust gas remains from back pressure or being drawn back in under 'reversion' now there is much less fresh air in the cylinder. Since this is a direct injection engine the computer will spray in the requisite amount of fuel based on the RPM, MAF, engine temp, etc. It can't measure the amount of fresh air vs exhaust air in the cylinder. At least I don't think it can. If this were a port injected engine then the air fuel ratio would be established in the intake but here it's established inside the cylinder. I don't know what happens when the air charge is contaminated with a significant amount of exhaust gases. The computer is forcing in fuel based on a specific Air/Fuel Ratio. But the computer assumes that the air is fresh air, or almost 100% fresh air. What happens when the concentration of fresh air is less than 90%? Or less than 75%. Will this cause detonation? Remember that the amount of fuel injected is the same regardless of the percentage of fresh air in the cylinder.

In the EGR systems of yore the AFR was established outside the cylinder. Either in the carb, TB, or PI. If significant exhaust gas remained in the cylinder the intake air charge would be reduced but the fuel charge would be reduced proportionally since it was mixed outside the cylinder. I think this results in the same AFR inside the cylinder regardless of the percentage of exhaust gases remaining. Here the AFR is established solely by the amount of fuel sprayed into the cylinder based on assumptions about the air charge being forced in by the turbo. If exhaust gases are significant then the AFR calculations are kaflooey. There is a much higher AFR than predicted. At least I think this is the case. I'm hoping that the engine builders out there understand this WAY better than I do and can offer some constructive criticisms.
 

Jaymar

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The car determines fueling based on manifold pressure and RPM mostly, from that it determines how much air is going in and fuels accordingly. Regardless of any restrictions or port velocity VE, an amount of air goes in therefore an amount of fuel goes in. This is further trimmed by the reading at the first O2 sensor Incase it didn't get it quite right. Other cars actually measure the air mass going in with a MAF but with the turbo Ford went back to speed-density on the Ecoboost which means it doesn't go all apeshit when the recirc valve blows off.
 

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explanation of pressure ratios


explanation of detonation & boundary layer (0:00- 4:00ish)


i suspect the small turbo on our cars creates a lot of backpressure.
 
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Ecto1

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The car determines fueling based on manifold pressure and RPM mostly, from that it determines how much air is going in and fuels accordingly. Regardless of any restrictions or port velocity VE, an amount of air goes in therefore an amount of fuel goes in. This is further trimmed by the reading at the first O2 sensor Incase it didn't get it quite right. Other cars actually measure the air mass going in with a MAF but with the turbo Ford went back to speed-density on the Ecoboost which means it doesn't go all apeshit when the recirc valve blows off.
So the computer can detect how much fresh air is drawn/forced in during a cycle? Even in the presence of a significant amount of left over exhaust gas?

Thanks.
 

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Jaymar

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So the computer can detect how much fresh air is drawn/forced in during a cycle? Even in the presence of a significant amount of left over exhaust gas?

Thanks.
Yes, exactly. Unless you have a boost leak, all of the air that goes through the induction system ends up in the cylinders. Measure that and you know how much fuel to inject. The methods by which we do that have slightly improved over the years but the basic principles remain the same since the first mass-produced fuel injection systems.
 

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... How many years have you been building/racing vehicles for a career/living.

BD
I assembled a class winning IMSA RS car when I was still in high school. I've performed the calculations and tuned both intake and exhaust runner lengths to improve volumetric efficiency. I was building/tuning dual Weber 4 cylinder engines before you were born. I'm a recognized expert in the nuclear power industry regarding acoustic phenomena in steam lines.
Your turn.
 

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I assembled a class winning IMSA RS car when I was still in high school. I've performed the calculations and tuned both intake and exhaust runner lengths to improve volumetric efficiency. I was building/tuning dual Weber 4 cylinder engines before you were born. I'm a recognized expert in the nuclear power industry regarding acoustic phenomena in steam lines.
Your turn.
And now, after all this time your name makes sense!

I made my living in automotive when I was younger. Now I build machines that park atoms in tight spaces next to each other. You'd be surprised just how similar the two are. Sometimes I even wish I could use some of the components from the automotive world that I feel are superior.
 

Radiation Joe

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I could have made a career in racing, but common sense ruled that I get an engineering degree and make a decent living. Most of my friends from early life worked as mechanics early on and then moved on to other, sometimes related, industries. Only a small few of the people I worked with early on were successful in racing careers. Such is your lot when you have to start from the bottom.
I also did a stint parking atoms for military devices while in college. Grew up in Silicon Valley before it was "Silicon Valley". I was a Skyline Blvd terrorist for all those familiar with that road.
 

ice445

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With anything mass produced you will have cars that are at the very lower end of tolerance stackup and ones that are at the high end of stackups. so never said that completely stock could not suffer ecoboom from excessive tolerance stackups that put the safety limit right on the edge of failure from the very start. It's the reason no 2 identical cars run exactly the same.

BD
I found out last night that Ford actually changed the design of their 4 cyl long blocks to remove the "steam relief" slit that goes in between the cylinders, instead replacing it with a cross drilled hole below the deck. I guess they were having so many failures that they had to redesign it. This goes far beyond simple tolerances unfortunately.
 

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My Ecoboost bit the dust at 74k miles. It had a Ford Performance tune and old man driving style. As others have said, it probably comes down to tolerance stack-up and poor quality control. Head gasket failure between 1 and 2.
 

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i don't buy off the cuff the "turbo backpressure creates similar effect to EGR" comment. EGR controlled by the computer only at partial load reduces overall exhaust temperature. i dont see any left over hot air being left in the cylinder because of backpressure doing anything to increase the stability of combustion, which denonation is the opposite of stable
 

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I assembled a class winning IMSA RS car when I was still in high school. I've performed the calculations and tuned both intake and exhaust runner lengths to improve volumetric efficiency. I was building/tuning dual Weber 4 cylinder engines before you were born. I'm a recognized expert in the nuclear power industry regarding acoustic phenomena in steam lines.
Your turn.

Well, its odd that you seem to know just how old or when I was born by thinking you were racing in IMSA before I was born when IMSA was not formed until 1969 in Daytona Florida and it just so happens I was racing in local two stroke dirt bike motocross racing in 69 as a junior racer and was tuning and building my own race bikes up until my early twenties when the beatings took its toll on my body. In the two strokes of the day, you did the majority of tuning with the exhaust pipe and backpressure/reversion pulses in the expansion chambers to dial in the powerbands you needed to a particular track. So, exhaust reversion/backpressure is very real and does influence engine performance/tuning to a large extent. I also raced Datsun L20bs with weber carbs and was out running V8 at the strip with them so very familiar with both webers and SU carbs on four bangers.

I then went to working on cars for a living and have been an ASE master tech for 45 years as well as GM master tech and Harley master tech. I was the one that had to fix the mistakes the engineers made in designs of the new cars that were being sold. I cannot remember all the times I had a customer's car come in with a complaint that could not be diagnosed with the service manuals procedures or flow charts. So, when I would call the tech line for assistance from an engineer and described what was occurring and what I had found as a failure I would be told it was not possible for that to occur or my findings were incorrect, yet when I did my repairs that fixed the complaint, I was again told it could not work or be possible as a fix by said engineers. But the customers never came back for the same issue with their cars again. While at Harley as a research and development mechanic I also had numerous times that an engineer sent me a prototype part to install per a Workorder that either did not work or would not fit the bike properly even though they said the CAD/CAM program stated it would fit and they tested it before sending to the test facility. So, I put little faith in what most engineers say unless they have actually worked in the trenches with us grunts.

I know what I know from years of hands-on experience and knowledge from actually doing the work but by no means am any expert at all, but have proved many an engineer wrong more times than I can count.

I am not saying the video is absolute fact but that it does hold some insight to cause of ecoboom in certain situations that are very likely the result of overzealous tuners or individuals that throw parts at a car without understanding the interaction all those parts have when combined for better or worse. Bottom line is the ecoboost motors specifically in the mustang are tuned very close to the edge of self-destruction and if more power is added in the wrong way with boost or timing it will fail.

I do not believe everything I see or read or am told by anyone either.

Never "assume" anything as you make an ass of you and me.

BD
 
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Buldawg76

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I found out last night that Ford actually changed the design of their 4 cyl long blocks to remove the "steam relief" slit that goes in between the cylinders, instead replacing it with a cross drilled hole below the deck. I guess they were having so many failures that they had to redesign it. This goes far beyond simple tolerances unfortunately.
AFIK right now that only pertains to the 2.0L block used in the 2020+ Escapes, edges and fusions and some Lincolns. I have yet to confirm the 2020 2.3L has received the cross drilled block but am going to contact my part buddy to do some research to find out. My 2020 service manual shows the pic of the block still having the slit cut between the cylinders, but it may be just an old pic used in the manual also.

Bottom line is Ford should have kept the original closed deck block from the early Focus RS cars for all the eco block design. Just another cost cutting corner IMO by the bean counters.

BD
 
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Ecto1

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Yes, exactly. Unless you have a boost leak, all of the air that goes through the induction system ends up in the cylinders. Measure that and you know how much fuel to inject. The methods by which we do that have slightly improved over the years but the basic principles remain the same since the first mass-produced fuel injection systems.
Impressive. If that is true then the detonation from exhaust "reversion" doesn't hold up. The AFR should be correct regardless of the amount of left over exhaust gases remaining in the cylinder or how they got there. Doesn't explain the causes for the detonation, particularly if it is most prevalent in the #2/#3 cylinders, but it should rule out the "reversion" theory.

Thanks. That's VERY helpful.
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