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