Re: Fuel injection? Open or Closed loop?
 

Don't really know anybody pulling timing with it. Most slightly tweak air/ fuel with it.

Re: Fuel injection? Open or Closed loop?
 

Just thinking, since we have always run closed loop, that could explain our inconsistency run to run when weather changes a little, but doesnt seem like enough to cause the kind of changes we have seen.

Our tune is tight enough, that we could certainly run open loop without worrying about breaking anything.

Hmmmm, next time out, whenever that might be, I think I will try open loop to see.

David
The New Hemi Guy

Re: Fuel injection? Open or Closed loop?
 

NEVER run a race car in closed loop.

Re: Fuel injection? Open or Closed loop?
 

I thought you could only run 1 loop as the other would adjust the fuel for the weather?

Re: Fuel injection? Open or Closed loop?
 

Micky, open loop makes no corrections.
Closed loop attempts to always correct to the values in the Target Air/Fuel ratio table.
I'm surprised at how many use closed loop in this poll.

Re: Fuel injection? Open or Closed loop?
 

you guys might want to read the rulebook....

FUEL INJECTION
Fuel injection must retain OEM throttle body(s), plenum, and
manifold. If OEM throttle body(s) was equipped with electronic
throttle control (i.e., drive by wire), the throttle body(s) may be
adapted to mechanical throttle linkage if an aftermarket OEM-type
electronic-fuel-injection system is used. Larger fuel injectors
permitted, provided no modification or redrilling of manifolds is
performed. Electronic fuel injection must be closed, OEM-type
system; i.e., may monitor only engine functions. Monitoring of
vehicle performance criteria, wheel speed, driveshaft speed,
vehicle acceleration, etc. by fuel-injection system prohibited. All
aftermarket OEM-type electronic fuel injection must be NHRAaccepted. A current list of NHRA-accepted electronic-fuel-injection
systems is available on NHRARacer.com. Open-loop systems
permitted on production vehicles as equipped with OEM electronic
fuel injection. See General Regulations 9:1.

not saying it could be checked very easily but 99% of you are illegal running in open loop..

Brad

Re: Fuel injection? Open or Closed loop?
 

as i read all this i'm reminded of some classes/training i've took over the years......when you go WFO, oem stuff IS in open loop.

Re: Fuel injection? Open or Closed loop?
 

You are absolutely correct Tom. P.E. (Power Enrichment) mode is Open Loop. Closed loop target air/ fuel ratio is always 14.7-1 unless they have a Lean Cruise Mode. Then usually over 15-1 or leaner. Those are normally "Export" calibrations, as the cats used now are not efficient that lean. Most factory calibrations are actually overly rich in P.E. mode. Richer than we run our cars. Most GM calibrations are closer to 12-1 from the factory.

Re: Fuel injection? Open or Closed loop?
 

Brad,

I am not sure you are reading that right. It says that it must be a closed system reading only engine functions, not driveshaft speed etc.... The "closed" system part of the rule doesn't have anything to do with "Open loop/Closed loop" as far as O2 monitoring.

The later part of the rule that you put in bold clarifies that.

Re: Fuel injection? Open or Closed loop?
 

Yep. It says "closed system", not closed loop system .

Re: Fuel injection? Open or Closed loop?
 

Some stock systems run in open loop. Till certain parameters are met. The turbododges are in open loop at wide open throttle.
We are not illegal. I had went through an NHRA electronics teardown. And they had asked it I running open loop.

Re: Fuel injection? Open or Closed loop?
 

Open loop.

Unless you have an o2 sensor for each cylinder (with correction factors to support each cylinder) then you could argue some advantages to running it closed loop.

Re: Fuel injection? Open or Closed loop?
 

Open loop is probably better for bracket racing consistency I would think because the car doesn't adjust itself going down track.. however, would closed loop be better in a heads up run or when you need that extra power if the car is properly tuning itself downtrack? Has anyone ever tested to see which method was strictly quicker?

Re: Fuel injection? Open or Closed loop?
 

I'm no expert tuner. But I would be cautious using closed loop to go faster. I don't think the O2 sensors most of us use are fast reading enough. I have changed brands of O2 sensors and seen a difference, when tuning off the datalogger.

Re: Fuel injection? Open or Closed loop?
 

Art is right.

Re: Fuel injection? Open or Closed loop?
 

In my opinion the tuner should always have full control of the fuel map and timing .

But on the new cars from the factory the oem computer controls everthing . If its oem the the computer can control the car down track and its more consistenbut not faster . NHRA has allowed both , but if its a aftermarket computer the computer is not allowed to make changes going down the track unless the car came with a computer that did .

I like were I have full control of the car bracket mode or heads up . I vote open loop

Re: Fuel injection? Open or Closed loop?
 

Unless the new Fords are different, from the factory they all go to open loop in P.E. (Power Enrichment) mode, or wide open throttle.

Re: Fuel injection? Open or Closed loop?
 

Gentlemen,

The question of closed or open loop is not really valid when the engine is using a narrow band O2 sensor. The stock systems normally use this narrow band sensor that is accurate only in a very narrow target area of about stoichiometric (14.68:1 with pump gasolne).The wide band sensors can be used with the appropriate control system, but I would think you want absolute control to be consistanrt. Some of you racers hit it on the head, mentioning that at WOT the system had better be in open loop, using the base fuel tables with its modifiers. The operational parameters regardng PE and the closed loop threshold are probably the areas that are highly tuned (along with base fuel and spark), that the successful guys paying attention to. Forced open loop would cerntainly be my choice!

Just an old racers two cents, Dennis Baccus
Former F/S record holder - 1969 Z28,
Current calibration engineer on GM MEFI systems and engine builder

Re: Fuel injection? Open or Closed loop?
 

There's an electronics teardown? I never heard that one before. Was this in stock with a TD or with the Neon?

Re: Fuel injection? Open or Closed loop?
 

This was with the Neon. Jake Hairston did it at Englishtown in 2010. It took about 1 1/2 hours. They wanted me to connect my laptop to it to show the program. He wrote some stuff down, serial numbers etc..And traced all wiring. Which in my case gave them fits.
But I passed.

Re: Fuel injection? Open or Closed loop?
 

That is a very tough question. I believe the most efficient way to run is in selective closed loop. So, it is not open or closed but open when it 'should" be and closed when it is necessary.:)

Re: Fuel injection? Open or Closed loop?
 

Not a tough question. And, nothing difficult about doing that at all.

Re: Fuel injection? Open or Closed loop?
 

Sorry did not understand this high level question

Re: Fuel injection? Open or Closed loop?
 

I believe that in my case at least. If I run in closed loop at low rpms the O2 sensor is to close to the end of the collector. When idling, the over lap allows air to get to the sensor causing the mixture to show very lean. It doesn't read correct till about 4000 rpms.
I put a 4 foot extension on the collector to tune it at idle.
If it was in closed loop it would tune the mixture all wrong. Plus most (if not all) ) O2 sensors don't read fast enough to correct going down a dragstrip. RPMS and load are constantly changing.
I get back from a run. Read the data, then correct it for the next run. If I'm trying to get every .001 out of it. If not I just look at the logger for anomolies and if there are none, leave it.

Re: Fuel injection? Open or Closed loop?
 

They all do that Art. I've seen guys to that running closed loop, and wonder why their spark plugs are always black.

Re: Fuel injection? Open or Closed loop?
 

Search the tech forum for user name pbp1. This guy works at F.A.S.T. It is a very good tutorial on fuel inj. and will clear up any misunderstanding of how the FI. works.


Gary

Re: Fuel injection? Open or Closed loop?
 

If you can't get it right in open loop, set the minimum RPM for closed loop just above your 2 step RPM. You DON'T want it in closed loop on the 2 step, at idle, or on the return road if your O2 sensor is in the collector.

Re: Fuel injection? Open or Closed loop?
 

Yep, David Page is a great guy, and he helps a lot of racers.

Re: Fuel injection? Open or Closed loop?
 

Ed, I recently bought a '94 Mustang N/SA car that is currently set up on closed loop. The o2 is in the # 2 primary pipe and the afr is 12.2 or so on the two step and 12.9 at the finish line, the target setting is12.8. Does it take a major revamp of the fuel map when changing from closed to open loop? The car is very consistent but in reading this thread I became concerned that I'm giving up some performance running it closed.


Any info will be appreciated but remember I'm a novice when talking FI.


Jimmy Parker

Re: Fuel injection? Open or Closed loop?
 

Jimmy, I would set the min RPM for closed loop above your 2 step RPM. The misfiring on the 2 step gives a false lean indication, at least on mine. A misfire, incomplete combustion, puts more oxygen out the exhaust than a complete burn. Higher oxygen to an O2 sensor = lean mixture to the ECU. Closed loop during a misfire in closed loop means more fuel added. Since your O2 is in a primary tube, it may not show as lean then.

If your engine has been dynoed with 8 wide bands, and they knew all 8 cylinders had the same air/fuel ratio (mine did not) putting in in a primary tube would be better than the collector.

Mine had a 9% spread between cylinders on Patterson's dyno, with 8 wide bands. I run mine in Sequential mode so I could make them all the same. We tried to pull mine down to 3000 to get them all the air/fuel right in the 2 step RPM range. Would not pull down that low. Seems like 5000 is as low as we actually pulled it.

Yours being in one primary, it may not see as big a false lean indication as mine does. Mine looks like ~15-1 on the 2 step. Also looks very lean in the bottom of each gear. We pulled it past that RPM (~6200) so I know it is actually correct there. In closed loop mine adds fuel there, and slows my car down. If I were to try closed loop again, I think I would set my minimum closed loop RPM to 6500.
Edit: had a brain fart. Forgot about FAST's ten second delay. Setting my min RPM to 6500, the run would be (or close to) over before it went into closed loop.
You should talk to David Page about this. LOL

Re: Fuel injection? Open or Closed loop?
 

Thanks Ed, I think I know enough now to be dangerous.


Jimmy

Re: Fuel injection? Open or Closed loop?
 

Who's ECU are you using?

Re: Fuel injection? Open or Closed loop?
 

Ed, it's a FAST XL1. Matt Maxwell with FAST did some upgrades on it this past weekend in Atlanta.


Jimmy

Re: Fuel injection? Open or Closed loop?
 

Great system. you should be good.

Re: Fuel injection? Open or Closed loop?
 

Sounds like you should be a lot more consistent in open loop. So do you do a couple of TT's or qualifying runs in closed loop for learning and then go to open loop for elims. to get the consistency?

Re: Fuel injection? Open or Closed loop?
 

That was 2012, learned what I was doing wrong. I've run it both ways now. If you have it tuned correctly, it makes almost no corrections in closed loop anyway. Makes no difference I can see now.

Re: Fuel injection? Open or Closed loop?
 

So do you normally run closed loop now? I know it's an old thread. I was just going through old posts trying to learn. Thanks.

Re: Fuel injection? Open or Closed loop?
 

Closed Loop. O2 sensors don't live long with leaded fuel. I replace mine at the start of each season. Runs the same both ways. Once the tuning is right, it makes no difference. Hit some strange weather conditions, may help.

Re: Fuel injection? Open or Closed loop?
 

I did buy an extra Bosch sensor. Do you use Bosch sensors or NTK. Maybe NTK isn't an option with FAST. Holley offers a NTK for double the price but is suppose to last longer with leaded fuel.

Re: Fuel injection? Open or Closed loop?
 

My Holley Bosch sensor lasted thru 2 dyno sessions and driving the car in and out of the shop then the car fell on its face while testing. The logs showed strange readings and I already had a NTK with me at the track. I switched to the NTK and it was back to normal. This is with C-16. I was wondering about how often the NTK should be replaced as well.

Sean