Fuel injection? Open or Closed loop?

[Sean Marconette]

Thanks as well for the information.

Ed are you planning on racing at the Topeka National open in May?

Sean

[Ed Wright]

Originally Posted by Sean Marconette

Thanks as well for the information.

Ed are you planning on racing at the Topeka National open in May?

Sean

I don't know, Sean. Jeanie says I'm done. Says I'm too old to be going off like that. Still in discussion. LOL I will if I'm still racing. No AHFS at those. :-)

On the closed Loop thing, The RPM vs Load tables, for + & minus fuel correction limits, I have +4 & -4 percent in the top few cells at 6400, nowhere else. No cells above 6400.
Won't correct on the 2 step or return road. Or, 5600 & down. My converter hits at 6200/6300.

[pbp1]

Neither closed or open loop offer a performance advantage. In a properly set up and tuned Speed Density system, closed loop is just a tuning tool to help guide the building of your VE table, which is simply an airflow model of your engine.
I am not satisfied until the O2 correction is less than + or - 2%. At that point, your VE table is properly calibrated and you should be able to put it in open loop and the engine will perform the same.
The argument that one mode has a performance advantage over the other is completely invalid.
As for the durability of sensors, NTK is the best, and while the NTK sensor is an upgrade on some systems, it is STANDARD EQUIPMENT with the FAST XFI, always has been.
It is basically a personal choice, running in closed loop offers some protection in the event of injector or fuel system failure. The other side of that is if the O2 fails or if you develop a leak in your header, you are going to have a rich condition as a result. Live by the O2, Die by the O2.
As for it being a good or bad idea, two of the top 5 qualifiers in Super Stock at Indy last year were running Closed Loop (and Speed Density) including the #1 qualifier.

The purpose of closed loop IS NOT to correct for changes in air. Speed Demsity does that automatically and in Alpha-N, the tuner does that manually when needed.

The biggest issue that people experience when trying to run in closed loop is the correction overshooting, and then see-sawing up and down. There are gain controls and corrrection limits that you can use to get the "speed" of the correction dialed in for your application to prevent over/under correction. It also works better as you get your base numbers closer so it doesn't have "so far to go".

[pbp1]

On the location of the O2, it will definitely read leaner in a slip fit collector than it will in a primary even at higher TPM and under load, but it takes having 8 O2s plus one in each collector to see that. I have seen an average of one point leaner reading in the collector.
This doesn't mean that the collector is not an OK place for the sensor, you just need to know that and set your A/F targets accordingly.

At the end of the discussion, all that matters is that you find what A/F reading makes your car run the best no matter where you put the sensor.

[cmracing]

Originally Posted by pbp1

on the location of the o2, it will definitely read leaner in a slip fit collector than it will in a primary even at higher tpm and under load, but it takes having 8 o2s plus one in each collector to see that. I have seen an average of one point leaner reading in the collector.
This doesn't mean that the collector is not an ok place for the sensor, you just need to know that and set your a/f targets accordingly.

at the end of the discussion, all that matters is that you find what a/f reading makes your car run the best no matter where you put the sensor.

amen!

[Darrel Goheen]

Originally Posted by pbp1

At the end of the discussion, all that matters is that you find what A/F reading makes your car run the best no matter where you put the sensor.

How much to you change the target AF at a time when trying to find the best AFR? Thanks.

[cmracing]

Lower compression/horse power engines have a wider A/F range that they will operate in than high compression/horse power engines do.

You may find that the low power combo will tolerate an A/F swing of .6 total (.3 A/F rich or lean from mean) and be just fine, may not even show on the timeslip.

A high power combo may barf if it is run too rich (and that can be .2 A/F from mean). I'm not talking down a little bit in power, I am talking about it being flatter than flat and not moving in the first 60/330 ft.......

So, to be safe, vary it .2 A/F up or down and keep track of conditions. Learn what your combo likes.

I don't travel much so I make very few changes during the season. Unless I go to Numidia which has a much higher altitude than the other tracks I race at, I really don't touch the tune. Rarely do we get huge swings in temp/humidity around here, but it does happen.

I lock down the wide open throttle correction at 2%. After a pass I look at what it tried to correct. If I see it pinned at +2% or -2% I may make a slight change. Usually it will show nothing on the timeslip, but I am after consistency which I have no problem with using EFI.

I don't believe in the "fast tune" or "killer tune". I give the engine what it wants each and every pass. Every 500-600 passes it gets pulled and freshened. Bearings and rings/pistons tell me if they are happy and after 20 years of this they (and my wallet) have always been happy!

[Darrel Goheen]

Thanks for the info. I really appreciate it. I don't know if my engines are considered low or high hp or somewhere between. They are both Stock Eliminator engines. One is a LT1 and one is LS1. I'm assuming they are considered low hp. I really don't even know where to start on WOT AFR. I have them both on 12.7 after about 6000 rpm and about 12.1 on launch (3500) and then take fuel away to 12.7. The O2 sensors on both cars are in a header tube.