Re: Fuel injection? Open or Closed loop?
 

Longest lasting I've ever seen were the sensors that came with the NGK PowerDex kit. Things were tough enough to go about two years, on C-12, maybe 350-400 passes. Lasted until a huge wheelstand got them and the collectors they were in.

Re: Fuel injection? Open or Closed loop?
 

Since I got my Stahl headers, that isn't near the problem. They are tucked up closer to the floor than the Hedman Hustlers. Oil pan will hit before anything else now. They should all be built like Stahl stuff. I could not find 1 7/8" headers from anybody but Hedman before Stahl. I tried to order a set from Jere originally, but he had no jigs for the 4th gen F body until Woodro took his up there. Jere told me "Just bring the car, we will build them on the car." Just a short jog from Tulsa, OK, to York, PA. Shorter tow for Woodro. Thanks Woodie! LOL

Re: Fuel injection? Open or Closed loop?
 

I get about 200 or so passes on an NTK sensor using unleaded race fuel, sometimes more. This is with the Holley system. The Bosch sensor is about half that. If you limit your correction to +-5% or less, then if a sensor does go south, it won't kill the tune that bad. But, you do have to look at your datalogs and keep an eye on things....... I run Closed Loop in both of my cars, but also limit what I allow it to do.

Re: Fuel injection? Open or Closed loop?
 

I agree. I would never allow it to make more than 5% correction. NTK sensors are great.

Re: Fuel injection? Open or Closed loop?
 

Thanks for the info.!

Re: Fuel injection? Open or Closed loop?
 

Thanks as well for the information.

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

Sean

Re: Fuel injection? Open or Closed loop?
 

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.

Re: Fuel injection? Open or Closed loop?
 

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".

Re: Fuel injection? Open or Closed loop?
 

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.

Re: Fuel injection? Open or Closed loop?
 

amen!

Re: Fuel injection? Open or Closed loop?
 

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

Re: Fuel injection? Open or Closed loop?
 

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!

Re: Fuel injection? Open or Closed loop?
 

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.

Re: Fuel injection? Open or Closed loop?
 

You're a 'tweener, which is just fine.

They can probably tolerate 12.1 A/F at the launch, but play-around. See what happens as it approaches 12.5 to 12.8 at the hit. If the 60's don't like it, go the other way.

I imagine you run C11. You can normally go up to 13.0 A/F with that fuel without hurting power. Heck, I have seen up to 14.0 A/F and not hurt the engine, but it did slow down. Again, find out what it likes. Some engines like a flat fuel curve from start to finish, others like to change A/F though the pass. With EFI we are free to experiment with just a few keystrokes! :)

I have found the higher the octane, the leaner it likes. I have not used oxygenated fuels so I can't speak for tuning them.

Re: Fuel injection? Open or Closed loop?
 

Thanks. I plan to run Sunoco Turbo Blue. That's what I've been running in the Camaro LT1. I'm still using C-11 in the LS1 but plan on switching to Turbo Blue at the next race.

Re: Fuel injection? Open or Closed loop?
 

How does the LT1 compare to the LS1? The LS engines have a terrific head, but have they been killed with HP? Do they hold-up without oil pressure issues? I have seen several munch cam bearings for no reason..... And these were just 500-600 hp street engines spinning less than 7000.

Re: Fuel injection? Open or Closed loop?
 

Sorry to say, but I don't know a lot about either engine.

Re: Fuel injection? Open or Closed loop?
 

Darrel, you have not had problems with Sunoco passing fuel check? Maybe it's better now. I tried that stuff when it first became "the official fuel of NHRA", to prevent hauling fuel in my trailer. Saftey issue. Lost two qualifying runs, at two different races. Bought the fuel from Sunoco at that track. Maybe it's better now.

C11, in my LT1 SS car, runs the same times between 12.8-1 and 13.0-1. Maybe half a MPH faster at 13.2-1 above 7500. I use Speed Density mode, Open Loop.

Re: Fuel injection? Open or Closed loop?
 

I have never failed a fuel check with Sunoco or VP. Remember I've only been doing this Stock thing for a couple of years. In the Nova 402 I drove for most of 2 seasons we normally used VP C12 but changed back and forth with Sunoco Supreme 3 times and could see no performance difference. I'm not planning on buying C11 (because of price) even if it means not racing Super Stock unless somehow, magically I obtain some outside funding or if I can find a tune that will qualify in bad air. Last weekend in Topeka it ran a best of 10.58 on C11 in good air and a best of 10.73 (SS/IA index is 10.70) in worse air with 15-20 mph head wind and 75 lbs. heavy. All I care about at this point is being able to run the index. I'll be trying some Supreme next weekend to see if it's closer to C11 in ET. This is in my Firebird LS1 Stock car that I want to run in SS. I've been running Turbo Blue in my Camaro LT1 Stock car. I'll also try Supreme in the Camaro for ET comparison.

I thought you were using closed loop now?

Re: Fuel injection? Open or Closed loop?
 

Played with closed loop, saw no need. Once I ran in enough different conditions to get runs in enough different Baro conditions, to get each cell corrected, logs always show correct air/fuel anyway. If it were in Closed Loop, it would not be making any corrections anyway.
The manifold air temp sensor helps consistency a lot. All weekend at Houston recently, it varied exactly one hundredth. First three passes over two days at No Problem Raceway last week, it only varied four thousandths, then it broke a lifter. Did not repeat that close without the manifold air temp.

Re: Fuel injection? Open or Closed loop?
 

Interesting. My LS1 did not have a MAT on it. I put one on it but have since learned it isn't controlling anything anyway. You have your MAT modifying fuel at different temps?

Re: Fuel injection? Open or Closed loop?
 

I don't know about others, but the FAST uses it to control air/fuel vs intake air temp. The Intake Air Temp Air/Fuel correction table has a straight line across it, at zero correction. You alter the correction at a given temp by moving that up or down for more or less fuel.

Re: Fuel injection? Open or Closed loop?
 

The Holley system can do the same thing but both of mine are set flat line with no correction. I didn't know anyone used that in race applications.

Re: Fuel injection? Open or Closed loop?
 

I have worked with the Holley system on a couple of COPO cars. Not real crazy about it. Maybe if I had more time with it.
I don't know how anybody could expect the guys building the system to have any idea how a given engine would respond to air temp changes. Too many variables. Just because that is a straight line does not mean it isn't using the data. You would have to, I would assume, change that baseline for your application. I could be full of crap (wife says I am) but have altered that line in colder and warmer than normal (70 to 80 deg F, I consider normal) air temps. I just figured everybody altered that. Wife is likely correct, I'm just full of crap.

Re: Fuel injection? Open or Closed loop?
 

How much air temp decline do you see on a typical pass?

Re: Fuel injection? Open or Closed loop?
 

Depends. Usually more in cool weather. In my case, FAST XFI (with the straight line across the Manifold Air Temp correction table/"map"), "compensated" a little too much. (Added just a little too much fuel in lower temps, etc) It would take somebody much sharper than myself to simply dyno tune one on a given day to get that part dialed in right. I guess some dyno rooms could have the inlet air temps adjusted that much?
I have to do it the hard way.

Re: Fuel injection? Open or Closed loop?
 

I saw this post last year and always meant to respond. I see it's back from the dead!

I prefer closed loop. While I am not very consistent the system has been. I suggest to most racers to use a CTS and IAT modifiers if their engine combination is temperature sensitive. In a street application it can help drivability at various air temps. In the race car not so much.

Our system reacts very quickly to input from the 02 sensors. Probably faster than most of our competitors. Once you have a good base tune the closed loop will chase the target within 1 to 2 percent. Like someone previously stated you can limit the parameters of the amount of correction either up or down in air fuel ratio.

The Holley also has a learn table. It's exists on top of the base fuel table. The learn table retains the correction that the ECU uses to attain the target A/F ratio. This table can be transferred to the base or deleted. It can be left alone as many street cars use this as their "self learning" or "self tuning" function. The latter being very overused in the EFI Market. The learn function is similar to long term learning in early to mid 2000 year cars. It's a great feature to get a map within a few percent of the target. I use it on the dyno and then turn it off after I have a good base map. The system reacts faster when in Closed Loop with the Learn feature turned off.

I have seen many tuners have very radical air temp correction tables. Unless you are running a supercharger where the temps change dramatically during the run I would not spend a ton of time on that.

Robin

Re: Fuel injection? Open or Closed loop?
 

Same here. About 23/24* drop in cool weather, 18/20* in hot/humid weather. But, this is in a Bracket Car with a cowl hoodscoop and an air pan sealed to the hood.

I do very little compensation for air temp, in fact, in the range it is in for racing it does nothing. When its really cold (below 50*) I add 2% just to help it. We don't race in that cold of weather though.

Same thing for coolant temp. Below 80* I add fuel to help with warmup, but above 80*, no change.

It is interesting Robin mentioned not using the Learn function once the engine is tuned. I still use it, but it is severely limited in what I let it do. I may as well turn it off and just let the Closed Loop take care of things but still limit it's range like present, +-2%.

Re: Fuel injection? Open or Closed loop?
 

This is a great post so I thought I would bring it back to the top and add some information that is missing here about Air Temperature and its impact on fuel needs.

There is no need to guess or add "Corrections" for air temperature!

Air Temperature does have a proven, direct, and significant impact on Air Density.

The Ideal Gas Law was formulated way back in 1834. It defines how pressure and temperature changes affect the density of a given volume of air.

Since we measure the fueling of an engine in Air / Fuel ratio (? parts of air to one part of fuel), if the Air becomes cooler, or more dense, or heavier, then the only way to maintain the same Air/Fuel Ratio is to add more fuel.

In a TRUE Speed Density EFI system, the Air Temperature reading plays a part in the equation that is calculating fuel needs behind the scenes.

There is a fuel correction vs Air Temp table in the FAST software just like most any EFI software, but just because you have this table zeroed out, that doesn't mean that the Air Temp is not impacting fueling (This statement is only true if you are running in Speed Density).
That table is there for those who run in Alpha-N mode and wish to build in some manual correction for changes in air temperature. I always run in Speed Density mode and leave this table zeroed out.

This is not some black magic that FAST or any other EFI company invented. It is basic physics and it works as long as the system is set up correctly and you have all the correct basic information in your tune (Cubic Inch, Injector size, Fuel type used, etc.)

An incident happened a few years ago that prompted me to do an experiment to validate how the Air Temperature is used to maintain a constant Air Fuel Ratio while Air Temp is changing.

I have two customers with very similar LT1 SS combinations. Both run my system, Both run Speed Density in Open Loop, Both have tunes that have been extensively calibrated so their actual Air/Fuel ratios run right on target with no O2 correction in all conditions at different tracks without changing their tunes. Both are very FAST, consistent, and dependable.

One of the racers decided to try Icing down his manifold to squeeze a little more ET out of his car. He staged the car and when he let go of the transbrake, it was so lean that it coughed and died. Let it warm back up and all was well. I asked where his Air Temp sensor was located and he said it was out near the entry of the throttle body. That would ordinarily be a fine location for it as that is sampling the air entering the throttle body. The issue here was that the ECU was being lied to. The Air Temp sensor was telling the ECU that 100 degree air was entering the engine when the air going into the intake ports was actually much colder than that. He had increased the density or weight of the air without adding any fuel. More parts of air for the same one part of fuel = a leaner Air/Fuel ratio!

So here is the test we conducted. Took the other car, put the Air Temp Sensor in the intake manifold, Iced it down, made a run, and it picked up big time! We got the car back and looked at a datalog of a previous run with no ice, compared to the run with ice. Here is what we found that was different on the run with ice:
The Air temp was obviously a lot cooler.
The Pulsewidth and #s per hour of fuel delivered was a lot higher.
The Air/Fuel ratio was EXACTLY THE SAME!!!
This is with the O2 correction turned off, so what happened was the Ideal Gas Law was once again proven to be true and the True Speed Density strategy was proven to maintain a constant Air/Fuel ratio as the density (Temperature) of the air changed.

Don't believe any of this, I've got a couple of witnesses who can testify.

Hope this comes across as helpful and informative as I intended it to be.

Re: Fuel injection? Open or Closed loop?
 

Mine is Speed Density as well, Open Loop. Leaving the line across the Manifold Air Temp table straight @ zero, my air/fuel ratio was going too rich in cold air, too lean in hot air. I now have it repeating in all air temps I have encountered so far. Car is much deadlier in bracket mode than the driver.
The tweaks I made were pretty small.
I'm probably doing something wrong. LOL

Re: Fuel injection? Open or Closed loop?
 

Ed, What style of manifold do you run and where exactly is the Air Temp Sensor loacated?

Re: Fuel injection? Open or Closed loop?
 

Hogan sheet metal, the sensor is in one of the bungs, above the distributor, on the back end of the plenum.

Re: Fuel injection? Open or Closed loop?
 

I'm curious.....how often do you look at your data logs once you have it tuned? I'm still new so looking at most of the data logs but now they all are looking the same. Thanks.

Re: Fuel injection? Open or Closed loop?
 

Darrel,
I log every run and generally look at the graph after every run. I run a FAST system in open loop and like being able to review the data after each run!

Nick

Re: Fuel injection? Open or Closed loop?
 

That's what I've been doing except when I'm lucky enough not to have time between runs to look at them ;)

Re: Fuel injection? Open or Closed loop?
 

Darell, are you running it in speed Density, or Alpha N?

Re: Fuel injection? Open or Closed loop?
 

Density

Re: Fuel injection? Open or Closed loop?
 

Me too. Once I have run it, and got my A/F right on the row for that Baro, next time I run there (Great Bend, KS, Noble, don't use the same row in my VE table as Ennis, Houston, etc. Don't have to touch it. I have just about quit logging every run. Never have to touch it anymore.
In low gear, Closed Loop doesn't make corrections fast enough. If off at (for instance)7000, the ordectuon would end up at 7500, when it's referencing the 7500 cel, which needed no correction. I ended up trying to set the delay so corrections would not start until 2nd gear. I got it so Closed Loop was not making corrections in the upper gears anyway. I just put it back into Open Loop. With the IAT sensor, it's always dead nuts. The car repeats really well. Wish the driver did.

Re: Fuel injection? Open or Closed loop?
 

I'm getting very little correction at WOT. I've tried shutting off closed loop but it barely runs in the pits then so I have to turn it back on. I just need to get that area tuned in OL. So if you go to say Denver would you turn CL back on for a couple passes or just select the whole table and take a percentage of fuel out? Do you save a tune for every track? In CL I think my launch AFR is way messed up because of 2 step. As soon as I launch it adds quite a bit of fuel. Here's my thought at this point and please correct me if I'm wrong. Footbrake a couple passes to get launch area AFR close, turn off CL and get pit area tuned and then slowly adjust AFR according to data log? Racing gets critical now starting with Topeka Nationals. ;)

Re: Fuel injection? Open or Closed loop?
 

More thoughts......

Since I most likely can't win a heads up based on performance I should quit worrying about getting every last hundredths of ET out of my cars. I should just get them tuned to where it's consistent and leave it alone. Agree?