what is open loop and closed loop
 

trying to get to the bottom of my motor issues without having to go the long way about it.

when a motor is running...
What is open loop?

What is closed loop?
are these only to do with fuel injection?

The motor I have was running fine in open loop when first started... as it warms up the motor goes into closed loop. If the closed loop does something to the injectors and creates ringwash could that be what caused all the smoke, misfires, hesitation etc...?

Open loop and Closed loop are YES fuel Injection only.

Open loop is when your car is cold as in the first fire of the day, or if the engine is not at it's full operating temp. It usually kicks over to closed loop when reaching 255 milliseconds.

So to break it down for you....

Operational Modes
The EEC operates in three distinct modes.

1) In closed loop mode the EEC uses the MAF sensor to determine the amount of air entering the engine to calculate a "guess" of how much fuel to inject. It uses facts about the engine (number of cylinders, injector size) to calculate the injector pulse width to deliver the right amount of fuel, and then at the appropriate instant when the cam position sensor says the engine is at the right point in the 4 stroke cycle, the EEC switches on +12V to the particular fuel injector and holds it there for just the right amount of time - the pulse width. Then it continuously uses the too-rich / too-lean signals from the O2 sensors to add a bit or subtract a bit of time to the injector PWs to achieve 14.64 A/F ratio. [14.64 A/F ratio is called stoichiometric mixture. It is the chemical mixture where gasoline burns with best emissions. :rolleyes:15.1 results in slightly better fuel economy, but creates more emissions. And you can't by an O2 sensor calibrated for 15.1 anyway.]

The EEC operates in closed loop mode almost all of the time.

2) In open loop mode the EEC completely ignores the O2 sensors and hopes to achieve some specific A/F ratio just by using the MAF sensor voltage, RPM, number of cylinders, and injector size to calculate fuel injector PW. I say hope because it is typical for your MAF transfer function and / or injector slope to be as much as 10% off. Without the O2 sensor feedback used in closed loop, open loop commanded A/F ratios are never very precise. Open loop mode is used whenever the EEC needs to achieve A/F other than 14.64.

Typically open loop is used at startup and at WOT when the engine needs an A/F ratio mixture richer than stoichiometric. Richer A/F is needed at engine startup, especially with a cold engine, just like a carbureted engine has a choke. Richer A/F is needed at WOT: Maximum HP at WOT typically occurs somewhere between 12 and 13. Also, this slightly richer mixture helps cool the combustion chamber and exhaust valves at the higher combustion temperatures of WOT.

3) Another mode the EEC may operate in is called limp mode. As the name implies, this mode is only invoked when the EEC thinks something is wrong. A typical reason for limp mode is failure of one or more sensors. Depending on what sensors failed, the EEC may refuse to operate or may operate in limp mode. [The Check Engine light always accompanies limp mode.] For example, if O2 sensors fail the EEC operates but cannot run in closed loop. The EEC can even run in limp mode with the MAF disconnected by using TPS and RPM to estimate PW - It just won't run very well.

Hope this helps you understand the three different operation modes.:tup

well thanks for that. The reason I'm asking is because of a motor I had some hack mechanic build.

The motor runs fine when first started. BLows no smoke and is just a dream... until it warms up. Then all hell breaks loose and she starts smokin like crazzy and coughs and sputters and hesitates until it hits around 3200 rpms at WOT and then it goes back to runnimg like a dream and screams to the point where I just dont want to keep my foot in it do to lack of experience with my 5oh and 340hp est.

I'm really hopin that throwing a carb unit on this motor will solve the issue.

This is going to kill your love for the hobby. Shitty shops did it for me.

Think positive man..... :)

Instead of giving up and putting a junk carb on it, lets try some trouble shooting.
There are many smart people on this forum that might be able to chime in and help.

First of all if the engine light on, and does the engine light even work...? When you first turn your key to the on position before starting does it come on?
This would be a great start :)

uh perhaps I should enlighten you as to where the motor is now.
on my engine stand... The mechanic dropped a stock motor in and gave me back mine complete.

and yes the check engine light comes on... randomly it comes on with this stock motor as well.

I have a spare car and was just going to drop a 750 carb on this beast and call it a day.

The carb is not going to fix your issues if it smokes at higher rpm you might have a broken oil ring.Closed loop is when o2 sensor kick in if it is getting to much gas check pressure on fuel rail then check your injectors one mihgt be have a small piece of dirt causing a sticking ball floods out one cylinder smoke show.750 is way to big for 302 on street no throttle response 650 is big enough.Check firing order seen it happen runs good till you give it throttle ecu will keep it running at low rpm and sounds alright.

Don't throw that 750 on there. It will kill your cars performance. There was a 750 holley on my Mustang when I bought it. I guess the guy thought bigger was better. I put on a new holley 650 and the car is like night and day. All that said find someone with a scan tool and some knowledge before you give up on your EFI

Yep agreed, carb is old school!!!
750 is to big, I agree with a 650..but I don't agree with the Holley part I would put on a Edelbrock. Best bang for the buck and its bolt on and go no bs screwing with it.

Again don't give up on the EFI, you will regret it in the end.
Good luck man, and keep us updated.

Don't do it. Keep the efi. You can get it fixed don't worry I see this kind of thing everyday- you just need to find the right guy.

If you can bolt a carb on and it runs right to begin with, You've done something wrong. They are never set up right out of the box, and need to be setup right per application.

Edelbrock carbs are a waste of money.

These people that are telling you to leave it EFI appear to be completely biased. If you are more comfortable with a carb, then switch it. If you need help to get it running right pm me. Hell with a little time and effort we can even make the 750 that everyone here says is to big work on there.

Nothing will be better then a fuely! carbs are out dated pieces of scrap material IMO!
750 on a stock 302 motor.....LOL cant wait to pull beside hes gonna smash on the throttle and your gonna see all this fuel get dumped in its gonna cough, choke, puke, right on the spot and the fuely at this time will be lets say......near finished :laughhard
But if this is what he wants to do....well this is ONE out of ten million problems to look forward too
[YOUTUBE]http://www.youtube.com/watch?v=T8G2KQmOZ-Q[/YOUTUBE]
LMFAO......

you talk like you really have a clue. you have 500 hp and ran what? And now your trying to call people out? You really need to expand your knowledge base before posting crap like this!

I have something with an outdated carb on it your more than welcome to play with. Not to start a pissing match, but get a clue! There is way too many uninformed opinions on this site lately.

can you even count to 10 million? I don't think there is that many things that can go wrong on a car.

Coming from a guy who likes both, they both have their places.

If somebody enjoys tuning their own vehicle, doesn't want to spend 1200 bucks on a tuning device, then a laptop....etc and is more comfortable with a carb, then by all means, a carb swap makes sense.

I've got feet in both boats. I was going EFI with the Capri; had been EFI, that WORKED WELL with my '87 GT, but have now decided to go carbureted.

Why?

1. Well, I sold HALF of my EFI stuff and was able to buy my ENTIRE carb swap. I'm MAKING MONEY doing this.

2. I will have the car RUNNING shortly. No more parts to buy.

3. Cleaner engine bay due to less wiring.



I'm running a 750 Holley HP. I wouldn't touch an Edelbrock (Carter) carb with a 10ft pole. They are great for Grandpa's hot-rod for tootin' around car shows, but for any real PERFORMANCE build, there is always a Holley or BG on there.


Nothing wrong with wanting to go carbureted, and for your MODIFIED engine (which sounds like the one you want to go carb'd on? Not the stocker that is in there?) the 750 can be made to work.

Don't sweat the propaganda, there are advantages to both sides of the fence, go to where you feel the most comfortable.

Oh Nick comon lol
Well actually its 511, and it is only a little 302 nothing special...

So this is the only car ive owned?? Ive never had a carb before??
I only blab on from experience not from guess's

Like I said go carb and we'll see what happen's and when I say this, im saying a 750 on a stock 302.

What does this have to do with running my car??
My car vs. a stock mustang? anything is possible I guess I could spit a belt right?
Pull beside anyone is a figure of speech....

Oh, and I always use Youtube for my sources for tech.......... ???? WTF Keith?

A stuck needle and Holley's are "junk"???

Here's my junk:

http://www.darkfibrecommunications.c...carbswap01.jpg

its an ignorant "figure of speech". I guess I am not most people and take comments like that quite literal. You never did say what you ran?


And, if your a carb expert, how do you tune one? thats 95% of the problem with them, is people don't know the first thing about them, and then class them as junk.

Jet it down, put in mild AP cams and smaller squirters and the 750 will work. But of course you knew that already right?

of course he did!

I would definitely agree this is the cheaper way to go!!! WAY CHEAPER!
Do what you feel is best as mentioned...personally myself I would not use a Holley but thats just me, If I were to use a carb..."IF"... I would use a DeMon carb! But thats me!
Some people like Holleys, some like others! :tup

DUDE! showing more ignorance. A demon is a knock off holley. They are the same thing. Do some research.

Fallow the leader....

you still haven't answered my question?

Your right, they are ALL a knock off of holley...

And a Holley is a knock off of a Rochester! :laughhard

Notice how all carb vehicles carry a fire extinguisher with them :bleh:

I've had no issues with Holley carbs. My old '78 Glasstron has one!

We've had three different Holley carbs on the S10 and one Edelbrock. The Holley carbs have ALL worked well. The Edelbrock, not so much.

My two friends with Edelbrock carbs, who both had nothing but issues now run a Holley and a Demon.

BTW, as Nick stated, a BG Demon carb is basically a modified Holley.

There are companies like Prosystems that make modified Holley carburetors for specific setups, and the products are phenomenal.

They are the predominant choice of racers for a reason.

actually none. But surround myself with people who know how to work on both carbs and fuel injection

You seem to be avoiding my question......................:bleh:

Holleys are nothing like a Rochester.

Have you LOOKED at the two side-by-side?

Holley was established in 1897 and made the carburetor for the Model T Ford.

Rochester is a GM brand. The Quadrajet was conceived in the 1960's......

1897, 1960, I can see how you'd be confused.........?????????

Notice how all race vehicles carry a fire extinguisher? That's because it is class-mandated, not because the cars are carbureted. Run EFI, you still need the extinguisher dude.

What question do you want me to answer?

What did my car run?....I cant answer that cause I am not about to hack my car together just to beat it down the track to give you an answer! I like to take my time with things and do things the right way.
I have THOUSANDS of dollars sitting there and im not ready to race it yet...but when I do ill let you know what I ran, hey you never know when I do race you might be the first I land beside ;)

Does this answer your question?

Now why you getting all worked up? cause I said fuelly is better....its my opinion he or you don't have to listen to me...
Chris seams to be doing fine, he gave is input witch is true and great advice and what he has seen/heard from experience. BTW Chris your engine looks nice and clean I just wont run it myself....simple!

Maybe you should just not give advice, until you get your own stuff working right. And I would be proud to end up beside you! whats that phrase? "pull beside"

In the mean time, open a book and do some more learning. You need to get rid of the ignorance.

HAHAHA Ok thanks for the advice Nick

Anything else I can learn today?

Watch what you say....you could end up with a rude awakening :chacha:

Apparently not. You are the pro. Teach me something Kieth. If you grow some balls, maybe I will see you at the track.

and you know what it ran.

With your closed minded attitude. Not likely. You keep standing on your pedestal though.

What do you want race me with? your dads S10?

whatever you want. I sold my car, but can still put something together. its in the process of getting a fuel system upgrade right now.

Its got a carb. Its slow. lol

How can you call out a race when you don't even own your own vehicle? Like so what does it bother you I haven't raced me car?

Remember THOUSANDS, and THOUSANDS of dollars...lets see what you can whip up :laughhard

Not to be a dick, but I'm pretty sure we all have "thousands and thousands" into our junk.

Tell me you don't really want to find out. Sometimes, keith, its not about money.

BTW The truck is a co project between my father and myself. We both have money invested in it. We use it to bond. So even though his name is on the ownership. It is actaully both of ours.

I wouldn't call that rude, some people just have more in there junk then others...

I unfortunately just have more then what a 04 Cobra costs :banghead: