Looking for 2.3 owners input

[Brian_B]

If you read the fine print for ProCal, it defines Premium gas as 91 octane.

If you are using a third party tune they are usually much more transparent and explicit about what you need to run for various tuning levels.

Sponsored

 

[Brian_B]

Also, I don’t know if the ECM has an “octane sensor” or anything like that.

I don’t know for certain but I think the only way it can really evaluate what octane your running is by watching the knock sensors and seeing what it’s doing in real time. It just adjusts to whatever is burning.

 

[userdude]

Yes, the base tune is accounting for 87 to 85 octane. I don’t know how advanced our Bronco ECUs are, but when I was tuning Focus STs / Subarus it’ll start at a base value and gradually increase timing (On subaru it’s viewable by the DAM (dynamic advance multiplier) ) and adjust fueling tables until it reaches the desired target fueling and timing. The engine will continue to learn and adjust timing until it detects a knock value over a certain amount of time / severity. That will be the “values” it looks for. Anything past that knock value or consistent knock the engine goes *oh hell* and drops timing


When you throw in 91/93 it’ll see that spot of fueling and go “oh hey, i knocked there before. i’ll see if i knock again” and if you get no knock, it’ll adjust timing further.

How does the engine know what octane the gas is currently?

 

[userdude]

Also, I don’t know if the ECM has an “octane sensor” or anything like that.

I don’t know for certain but I think the only way it can really evaluate what octane your running is by watching the knock sensors and seeing what it’s doing in real time. It just adjusts to whatever is burning.

This is what I thought you saying previously. Really, I hadn't ever thought about it, but just assumed the engine used the different octanes the same with fewer issues... Now I'm like, that doesn't make sense. But that does beg the question, how does it prevent knocking without the tune any better than with the tune? Unless it's just defaulting to more aggressive programming, but then... When does the engine expecting 87 make use of 91 without experiencing knocks?

 

[zyglyrox]

This is what I thought you saying previously. Really, I hadn't ever thought about it, but just assumed the engine used the different octanes the same with fewer issues... Now I'm like, that doesn't make sense. But that does beg the question, how does it prevent knocking without the tune any better than with the tune? Unless it's just defaulting to more aggressive programming, but then... When does the engine expecting 87 make use of 91 without experiencing knocks?

“An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compression the fuel can withstand before detonating. Octane rating does not relate directly to the power output or the energy content of the fuel per unit mass or volume, but simply indicates the resistance to detonating under pressure without a spark.”

per wikipedia, a better definition than i could give you

 

[userdude]

“An octane rating, or octane number, is a standard measure of a fuel's ability to withstand compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compression the fuel can withstand before detonating. Octane rating does not relate directly to the power output or the energy content of the fuel per unit mass or volume, but simply indicates the resistance to detonating under pressure without a spark.”

per wikipedia, a better definition than i could give you

I was asking about the computer.

 

[zyglyrox]

I was asking about the computer.

It’s looking for knock. If it sees knock -> less timing. no more knock or no knock where it used to see knock consistently -> more timing and boost.

 

[Brian_B]

This is what I thought you saying previously. Really, I hadn't ever thought about it, but just assumed the engine used the different octanes the same with fewer issues... Now I'm like, that doesn't make sense. But that does beg the question, how does it prevent knocking without the tune any better than with the tune? Unless it's just defaulting to more aggressive programming, but then... When does the engine expecting 87 make use of 91 without experiencing knocks?

My understanding from working on bigger engines (so if someone here knows better I'm all ears):

Engine has a default setting. The stock tune assumes 87, the ProCal 91. And the default timing curve is based around that.

Now, while running, if the engine starts to detect knock, it will retard the timing (and reduce power). It can detect very small levels of pinging, so it's pretty sensitive, much more sensitive than you'd normally be able to hear while driving. If you can hear it (definitely possible in severe cases of knock), something has gone really really wrong.

If the engine doesn't detect anything, and all parameters align just right, it can advance the timing (increase the power). If it starts to detect knock, it stops that advancement and backs off a bit. There is a ceiling on how far it will ramp up - so there isn't infinite gains by using ever-increasing octane fuels.

These adjustments can happen very quickly - hundreds of times a second even. And it's all dynamic based on air temp, throttle position, fuel flow, MAP pressure, etc.

Over time, I don't know if the ECM can adjust the default setting on startup, or if it always just starts from default and ramps up/down

 

[userdude]

My understanding from working on bigger engines (so if someone here knows better I'm all ears):

Engine has a default setting. The stock tune assumes 87, the ProCal 91. And the default timing curve is based around that.

Now, while running, if the engine starts to detect knock, it will retard the timing (and reduce power). It can detect very small levels of pinging, so it's pretty sensitive, much more sensitive than you'd normally be able to hear while driving. If you can hear it (definitely possible in severe cases of knock), something has gone really really wrong.

If the engine doesn't detect anything, and all parameters align just right, it can advance the timing (increase the power). If it starts to detect knock, it stops that advancement and backs off a bit. There is a ceiling on how far it will ramp up - so there isn't infinite gains by using ever-increasing octane fuels.

These adjustments can happen very quickly - hundreds of times a second even. And it's all dynamic based on air temp, throttle position, fuel flow, MAP pressure, etc.

Over time, I don't know if the ECM can adjust the default setting on startup, or if it always just starts from default and ramps up/down

So would you expect a tuned Bronco to see more knocking using 93 and 87 every other tank than a stock tune using 87 and 91 every other tank? If you get my drift... My confusion a little bit is that knocking over time is worse with a non-stock tune running lower octane gas, which is what I had thought we were discussing before.

 

[heavyD]

The people that choose to fill up with 87 are driving all the time with the timing retarded and lower boost levels. People filling up with 91+ are driving all the time with timing advance and higher boost levels. No need to complicate this discussion any more than that.

 

[zyglyrox]

So would you expect a tuned Bronco to see more knocking using 93 and 87 every other tank than a stock tune using 87 and 91 every other tank? If you get my drift... My confusion a little bit is that knocking over time is worse with a non-stock tune running lower octane gas, which is what I had thought we were discussing before.

Absolutely. the difference in the factory tune and the FP tune is where the ecu starting values are. Switching back and forth from lower to higher gas when the engine expects 87 isn’t bad, it’ll usually compensate within a few minutes. But the other way around is a huge red flag to the engine and causes pre-detonation or drivability issues. stumbling, stuttering, etc.

in a perfect world you want to NEVER see knock. however we don’t live there and it is not escapable which is why the sensors are sensitive and things like harmonics inside the chassis can cause false knock. i’ve had a subaru with just slightly bad motor mounts give me headaches of false knock because the engine registered it “knocking” against the metal on metal mounts.

i don’t have the FP tuner yet, but on devices from Cobb you can monitor in real time those values. I’d be happy to help you figure those out or anyone else who’s curious that way you can monitor.


it’s also why we LOVE e85 for turbo engines. E85 has a cooler intake charge, and a higher octane rating (e85 is like 106-115 depending) coupled with its high stability level from its high octane rating. resists knock less, allows more fuel and air, which means more power.

 

[Brian_B]

So would you expect a tuned Bronco to see more knocking using 93 and 87 every other tank than a stock tune using 87 and 91 every other tank? If you get my drift... My confusion a little bit is that knocking over time is worse with a non-stock tune running lower octane gas, which is what I had thought we were discussing before.

I would expect them to knock more or less identically - to whatever limit the ECM is tuned to allow. But they would be operating on very different timing curves and power levels.

But your assumption is correct - the severity of the initial knocking would be more severe on a tuned engine that is timed more aggressively initially and needs to detune to get back in the envelope, than on a tame engine that is trying to ramp up.

Knock sensors are analog outputs. The ones I'm familiar with have 4 levels of severity. If they see Level 0's, they will advance timing. Level 1, they maintain current timing, Level 2, they retard, Level 3, they shut down the engine. -- I don't know if Ford is exactly the same way, but that's how CAT does it with their high efficiency gas engines.

So they will keep adjust the curve until they see some Level 1s, but no Level 2s -- or they hit the limit of their timing adjustment range.

 

[Brian_B]

in a perfect world you want to NEVER see knock. however we don’t live there and it is not escapable which is why the sensors are sensitive and things like harmonics inside the chassis can cause false knock. i’ve had a subaru with just slightly bad motor mounts give me headaches of false knock because the engine registered it “knocking” against the metal on metal mounts.

This is true - knock sensors are just microphones bolted against the block. They "hear" everything, so distinguishing between, say, someone tapping on the block with a hammer and pinging from pre-detonation is difficult.

On our CAT engines, we see a lot of "Detontation" shutdowns from the knock sensors, and they can be just about anything mechanical - a bad bearing on a water pump, a failing valve spring, etc. But often they are detonation-related, and usually a sign that the spark plug is failing (incomplete combustion, and we start to see low levels of backfire) or that we are just running too hard in a really hot environment.

 

[xtreme_exploder]

Yeah, that isn’t how it works once you install the FP tune. It is EXPECTING 93/91. Since you wanna be pedantic about that difference. The vehicle only has a certain amount of knock correction before timing is adjusted. Timing is power. Pull too much timing and you’re now adjusting your entire power curve. Then you start getting into pre-detonation (a HUGE issue on these Ecoboost motors. You command 100% throttle and it sends 17psi of boost at 2100 rpm, but you can’t handle 17psi of boost because you don’t have enough energy in the gasoline.

I can't tell if you're trolling or not. Not being pedantic, just want to make sure people get correct information. The stock calibration is also "expecting" 91 octane. If you run lower octane, the computer pulls timing to adjust. The tune does not alter this. It simply enables more aggressive timing to utilize 93, as you correctly said timing is power. I'm not sure what you meant by "The vehicle only has a certain amount of knock correction before timing is adjusted", as knock correction is literally equal to timing removed. Maybe you meant to say something else? I believe you meant pre-ignition and not pre-detonation, as "pre-detonation" is not a thing. As someone already said, octane has nothing to do with energy content. I fully agree that it would be dumb to use the FRPP tune and not run 93 most of the time, but to say it's required for vehicle safety is incorrect.

You mention that ecoboosts operate best at 91 octane. So I'm wondering how the knock sensors and tuning works stock. Does it assume 87? How does it know it has 91 without allowing knocks to occur and deprogram back to programming anticipating lower octane? It all seems confusing to me how this stuff works in practice. Hopefully that makes sense.

All modern vehicles that utilize knock sensors have a similar strategy. They start off "assuming" a certain octane and work back or forward timing as knock events are detected. I do not know if the Bronco starts off with 91 or 87 octane timing tables but it doesn't much matter, as it will add or remove timing as knock is detected. It is not possible to know this without allowing and detecting knock. The big thing that people don't understand is that these systems are extremely sensitive and detect singular knock events (literally one abnormal combustion event in one cylinder) and can immediately dial back timing before the engine makes another revolution. Depending on the exact calibration, a small number of events may be allowed before the computer takes action, so that it is not overreacting. The level of knock that triggers the computer to take action is low enough that no damage happens, even cumulatively. This means that the engine can operate at these low levels of detonation forever without damage. It's not something that "adds up" over time. When detonation is allowed to progress to higher pressures and temperatures is when the damage starts, and this is certainly cumulative in nature. It typically damages the edges of the pistons and the ringlands of the top ring.

 

[Brian_B]

The stock calibration is also "expecting" 91 octane. If you run lower octane, the computer pulls timing to adjust.

No. The stock calibration is expecting 87 octane.

Sponsored