Open versus closed loop

[Ed Curtis]

OK boys... have at it.... Technical only... any flame wars and I'll go PSJ on ya!

Ed

[CollinsAuto]

Depends on the application. Some you can and some you shouldn't

[highperf]

if your tuning it... it's in Open Loop damn'it

if it's got it.

I'll go PSJ on ya!

Ed:wtf[1]:

[viper99ta]

PSJ is a dood from another board.

Myself I feel open loop if you race it alot and monitor it alot.

Closed loop for daily drivers who don't monitor very often and drive in many conditions.

Some morning I leave for work it's 45 out but by afternoon it's 75-80. So I prefer closed loop.

[highperf]

Ok now we need clarification

Are we talking simply "Open Loop" or MAFless/Speed Density ? Ed how about a ruling here :banana:

Speed Density is my choice

but IMO it's not for everyone?

[Ed Curtis]

Don't ask me... I'm an old "stink-pot" carburetor guy. :D

Actually, everything is really speed density with a MAF helping band-aid the peculiarities of the day. Late model HEMI is an exception though.

At least that's what I see when I crack open a file.

Ed

[wkmcd]

Don't ask me... I'm an old "stink-pot" carburetor guy. :D

Actually, everything is really speed density with a MAF helping band-aid the peculiarities of the day. Late model HEMI is an exception though.

At least that's what I see when I crack open a file.

Ed

I'm running open loop MAF - No 02's. Just to confuse things more.

[Injected1]

I <3 My MAF....it makes things so EASY!!! It hasn't let me down yet, and the car is fairly consistent in any weather...Of course I have also done some different stuff in my tune that I wouldn't do in other peoples tunes.

[viper99ta]

What does <3 mean? No more MAF?

[Black_Knight]

I think it's a heart.

[viper99ta]

Damn, I have to keep up on my emoticons

[redhardsupra]

I <3 My MAF....it makes things so EASY!!! It hasn't let me down yet, and the car is fairly consistent in any weather...Of course I have also done some different stuff in my tune that I wouldn't do in other peoples tunes.
i've spent a lot of time going back and forth between MAF and SD and I gotta say they both suck ;)

MAF looked like a winner because of a clear relationship between the independent control variable (the maf's frequency) and what everyone believed automatic accounting for environmental changes. unfortunatelly, it looks like both in SD and in MAF modes, temps have to be taken into account. granted, in MAF the accounting is just kinda there, while in SD it's very explicit, but temps are still there. if you don't believe me, scan your car for both MAF airflow and MAF airflow (SAE), and you'll notice the two are different (unless you're driving at precise SAE-like conditions). I'm not sure why the MAF wouldn't automatically account for the temps, afterall more air should cool the hot element quicker. Any ideas?

[Injected1]

i've spent a lot of time going back and forth between MAF and SD and I gotta say they both suck ;)

MAF looked like a winner because of a clear relationship between the independent control variable (the maf's frequency) and what everyone believed automatic accounting for environmental changes. unfortunatelly, it looks like both in SD and in MAF modes, temps have to be taken into account. granted, in MAF the accounting is just kinda there, while in SD it's very explicit, but temps are still there. if you don't believe me, scan your car for both MAF airflow and MAF airflow (SAE), and you'll notice the two are different (unless you're driving at precise SAE-like conditions). I'm not sure why the MAF wouldn't automatically account for the temps, afterall more air should cool the hot element quicker. Any ideas?


and the answer is....Hummidity, thats really the only thing I can come up with. Unless that element gets hot enough to vaporize water that his it, some water particles will stick to the element and water has a slower heat transfer than air (hence a 70* pool is freaking cold, while 70* air is nice). Sounds like I need an IR temp sensor.

[redhardsupra]

wouldnt it still take more energy (higher maf freq) to vaporize the water off the sensor tho? even if it's for a brief moment, you'd see sudden jump in maffreq, which i'm not sure if it was interpreted as extra airflow.

[Injected1]

yes, but higher MAF Freq points to more/colder air, water is not air, hence it continues to throw off the ammount of air actually entering the engine

[02sierra]

and the answer is....Hummidity, thats really the only thing I can come up with. Unless that element gets hot enough to vaporize water that his it, some water particles will stick to the element and water has a slower heat transfer than air (hence a 70* pool is freaking cold, while 70* air is nice). Sounds like I need an IR temp sensor.
As soon as someone brings a hygrometer into play I want to know about it. Higher temps means the air can hold more water but its not a rule that the higher temp means more water, Im sure you could develop a climate model for a specific region and not have to measure relative humidity.

Im still left wondering about how much humidity actually effects commanded fueling? Its almost symantics, the larger factor is temp and that is taken into account with adder tables.

I personally like the MAF it does its job very well and is simple, why anyone would take it out of the picture permanently (except for power limits) is beyond me. Ive noticed it adds a level of cushioning and fueling transitions seem more linear vs without it. Its there for a reason and anyone with less than 600hp removing just to say I run in SD is a jackass. Most guys who say I run in only SD fall into this category.
my .02
//chris

[Injected1]

As soon as someone brings a hygrometer into play I want to know about it. Higher temps means the air can hold more water but its not a rule that the higher temp means more water, Im sure you could develop a climate model for a specific region and not have to measure relative humidity.

Im still left wondering about how much humidity actually effects commanded fueling? Its almost symantics, the larger factor is temp and that is taken into account with adder tables.

I personally like the MAF it does its job very well and is simple, why anyone would take it out of the picture permanently (except for power limits) is beyond me. Ive noticed it adds a level of cushioning and fueling transitions seem more linear vs without it. Its there for a reason and anyone with less than 600hp removing just to say I run in SD is a jackass. Most guys who say I run in only SD fall into this category.
my .02
//chris

I am hitting the research here soon.

[highperf]

As soon as someone brings a hygrometer into play I want to know about it. Higher temps means the air can hold more water but its not a rule that the higher temp means more water, Im sure you could develop a climate model for a specific region and not have to measure relative humidity.

Im still left wondering about how much humidity actually effects commanded fueling? Its almost symantics, the larger factor is temp and that is taken into account with adder tables.

I personally like the MAF it does its job very well and is simple, why anyone would take it out of the picture permanently (except for power limits) is beyond me. Ive noticed it adds a level of cushioning and fueling transitions seem more linear vs without it. Its there for a reason and anyone with less than 600hp removing just to say I run in SD is a jackass. Most guys who say I run in only SD fall into this category.
my .02
//chrisinteresting take...

SD can be a way to nail things down and remove some of the dynamic variability. Then it leads to being able to make better adjustments during condition changes and/or when logging the engines response on a particular day.

Also you can have a decision point when upgrades result in the engine taking in more air. changing the size of the intake path would require changing the size of the MAF. Do you upgrade the MAF ? or nail the tune down and open the intake path wide but deleting it (the MAF) and laying down speed density.

but for 98% of the people GO MAF!

[02sierra]

interesting take...

SD can be a way to nail things down and remove some of the dynamic variability. Then it leads to being able to make better adjustments during condition changes and/or when logging the engines response on a particular day.
I agree SD has its tuning uses and it is cool to see how much of a factor the maf actually plays by swapping back and forth. I like to tune on a day with average temps and humidity for my region, both the ve table and maf line get tweaked.

[grfperformance]

I've gone back and forth between SD and MAF and by far, the MAF only, open loop, has been the best for my application. SD is much more susceptable to temperature changes unless you can dial in the bias tables (that's a whole different thread).

For most simple applications, like cam only or heads and cam, I like to keep the tune in closed loop.

[highperf]

A SD vs MAF conversation with 20 posts and no name calling or foul language.

That must be some kind of record :)

[redhardsupra]

or maybe the other threads have said everything that needed to be said? it's really not that complicated, people just like to make it into another chevy vs ford/pepsi vs coke religious argument. i'm surprised that with all that's been written on the topic there's people that still dont understand the differences.

[Injected1]

A SD vs MAF conversation with 20 posts and no name calling or foul language.

That must be some kind of record :)

SHUT IT GOAT ROAPER!!!
LOL:devil[3]:

I just think everyone here agrees, just like anything else on a car, there is no ONE answer.

[ringram]

Well I like open loop because you can run lean at low loads and save some cash with little performance loss :)
At higher loads you are in open loop anyway.
Closed loop is another one of those bandaids for emissions, its not there for economy or performance. Though it does help as the engine wears, or for some mods to keep fueling constant.

[TAQuickness]

As soon as someone brings a hygrometer into play I want to know about it. Higher temps means the air can hold more water but its not a rule that the higher temp means more water, Im sure you could develop a climate model for a specific region and not have to measure relative humidity.

The key thing here is absolute vs. relative humidity. Simply put, absolute humidity is the total amount of water vapor in the air. Relative humidity is the relationship of absolute humidity to temperature, specifically the dew point (the point at which the water vapor will condense).

For given absolute humidity, as temperature increases above dew point, relative humidity decreases, and the air feels dry(er). As temperature approaches due point, relative humidity increases and the air feels (more) wet. However, the amount of water vapor in the air has not changed.

Im still left wondering about how much humidity actually effects commanded fueling? Its almost symantics, the larger factor is temp and that is taken into account with adder tables.

I did the math on this a while back and a full swing of 0% - 100% humidity, all other variables constant, makes about 2% difference in air density. Elevation and temperature are much more the dominating factors in determining air density.

[02sierra]

The key thing here is absolute vs. relative humidity. Simply put, absolute humidity is the total amount of water vapor in the air. Relative humidity is the relationship of absolute humidity to temperature, specifically the dew point (the point at which the water vapor will condense).

For given absolute humidity, as temperature increases above dew point, relative humidity decreases, and the air feels dry(er). As temperature approaches due point, relative humidity increases and the air feels (more) wet. However, the amount of water vapor in the air has not changed.



I did the math on this a while back and a full swing of 0% - 100% humidity, all other variables constant, makes about 2% difference in air density. Elevation and temperature are much more the dominating factors in determining air density.

Thats good info, nice to see some empirical numbers vs just opinions.

[highperf]

The key thing here is absolute vs. relative humidity. Simply put, absolute humidity is the total amount of water vapor in the air. Relative humidity is the relationship of absolute humidity to temperature, specifically the dew point (the point at which the water vapor will condense).

For given absolute humidity, as temperature increases above dew point, relative humidity decreases, and the air feels dry(er). As temperature approaches due point, relative humidity increases and the air feels (more) wet. However, the amount of water vapor in the air has not changed.



I did the math on this a while back and a full swing of 0% - 100% humidity, all other variables constant, makes about 2% difference in air density. Elevation and temperature are much more the dominating factors in determining air density.
TA... I would think Atmospheric pressure probably has more impact to most of us VS pure altitude ? Unless Density Altitude is the model of measurement.

IMO Pressure systems change, influence and can be used as a "indicator" of air density.

Jim

[TAQuickness]

Symantics on my part. I think simpler thoughts early in the morning

[highperf]

I hear ya. The best simple thoughts are the ones that include a High Pressure system on a crisp cool Fall Morning :joy:

Hot Damn we like it. :)

[viperbluelx]

Newbie question. The ecm isn't in closed loop at WOT ever is it? I thought at WOT the car would always be in open loop?

[redhardsupra]

it isn't, because there is no point for it with narrowbands, since they cannot measure non-stoich. with standalones you can have a real-time AFR correction (aka closed loop) because you're using a wideband to measure AFR so it's actually precise.

if you play with PE triggers you don't have to go into OL, or better yet the ECT based tables you dont ever have to go into CL at all.

[viperbluelx]

Yeah I had a FAST system on my Cobra, but for whatever reason I thought most of this discussion involved stock ECU's.