Electromotive TEC3 vs. F.A.S.T.

[LinearX]

I've got a friend that is building a turbo motor for his car and he's asked me to help him figure out which EFI system to get. I know tons of people who are using the F.A.S.T. stuff so if we need help with it, I know we can get it. However, he's found this thing called the Total Engine Control 3 (TEC3) from Electromotive. I downloaded their demo software and the instruction manual and have reading it over. One of the things in the manual really confuses me, and I wanted to run it by some of you guys in here to see what you think.

This has to do with O2 correction under WOT.

It is strongly recommended that the High MAP Switch reading be set to a value BELOW 95kPa. This will turn off the oxygen sensor correction at full-load conditions. It will save an engine from having a lean-out condition due to the oxygen sensor reading. Never run a boosted engine in closed-loop during high-boost situations.

Now call me kooky here, but I thought that F.A.S.T. runs in closed loop no matter how high the boost is. I've got another friend with a turbo Mustang, and I'm pretty sure he is in closed loop when he's making his pass, and he's running 30 psi. Am I wrong on this?

Also these Electromotive people say not to use a rising rate fuel pressure regulator. Instead get a nonadjustable fuel pressure regulator set at the PSI rating for maximum flow of your injectors. For instance, they say if your injectors are 160lb/hr @ 70 psi, then get a nonadjustable fuel pressure regulator set to 70 psi and let it go. That's kind of backwards from what all the Turbo Regals have going, and backwards from some of the guys running big turbos on their drag cars that I know.

Are these Electromotive people crazy? Is their stuff any count? What I want to avoid is getting in a situation where we may need some help with it, and finding no one that knows anything about it. Now if we go to the track with F.A.S.T. I know a ton of guys running it and can get help from them. This other stuff I'm not too sure of. Thanks, guys.

 

[Scott231]

You are comparing Apples to Oranges. I run the Electromotive TEC2 on my 87 GN. Electromotive is making that first comment because their system uses a "dumb" oxygen sensor that is only accurate at stoichiometric air/fuel ratios (just like the stock computer). The Electromtive untis are much more akin to the standard Accel DFI but with more bells and whistles.

The FAST units can run Closed loop at WOT becuase they use the high-dollar "intelligent" oxygen sensor that has a very wide band of accruracy.

Electromotive does recommend an adjustable fuel pressure regulator.

Electromotive's theory of operation works a little different than how the other companies advise you to set up your system. The Electromotive instruction manual goes to great length to assist you in pickingo ut the correct fuel injector to begin with. The other systems allow you to throw any injector in there and modify the fuel curve based on results.

No, the people at Electro are not crazy. They are just selling a product that works a little differently from all the other ECM use that dumb O2 sensor. I use the TEC2 on my hi-10 second GN, Alan Whitter used it on his 9-second GN, and Jim D'Allesandro had a TEC unit on his 7-second white GN.

Someone that can tune a DFI controlled motor can tune a TEC controlled motor. Again, TEC vs. FAST = Apples vs. Oranges

 

[LinearX]

Unlike a stock OEM computer, the TEC3 generally does not require an adjustable fuel pressure regulator. The reason for this is quite simple: the TEC3 allows you to set the precise fuel injector pulse width for a given RPM/load point. In so doing, you do not need to change the fuel pressure to change the amount of fuel introduced into the cylinders; you simply need to change the injector pulse width. There are, however, some guidelines to be followed for selecting a regulator. When you select the injector size needed for an engine, you will need to know the pressure for which the flow rate was established. Typically, injector sizes are rated at 3-Bar or 43.5psi. Therefore, an injector rated at 55 lb/hr at 43.5psi will only flow 55 lb/hr when it is at 43.5psi. More accurately, it will only flow 55 lb/hr when the pressure gradient across the injector is 43.5psi. The pressure gradient is defined as the difference between the injector spray tip pressure
(this is generally the same as the intake manifold pressure) and the fuel rail pressure (often referred to as “gauge pressure”). For a naturally aspirated engine at idle making 15” of Hg (about -7.5psi) vacuum, you will need to decrease your fuel rail pressure by 15” of Hg (about – 7.5psi) to obtain the same pressure gradient across the injector. So for the 55 lb/hr injector to actually flow 55 lb/hr when the manifold is under –7.5psi vacuum, you will need to decrease the fuel rail pressure by 7.5psi. The rail pressure should therefore be reduced from 43.5psi to 36psi.
The same holds true for engines under boost: for an engine with 10psi of boost pressure in the intake manifold, the injectors will need to have 10psi added to the fuel rail pressure. The fuel rail pressure would then have to be 53.5psi. Though this all may sound complicated, maintaining a constant pressure gradient sounds more difficult than it really is. Since 99% of all fuel pressure regulators have a vacuum hose port on them, all you need to do is run a vacuum hose from your intake manifold (after the throttle) to the regulator. On boosted applications using a draw-through throttle, place the vacuum hose after the turbo compressor. To be totally accurate, the vacuum/boost reference for the port on the regulator should be experiencing the same vacuum/boost as the injector tip. Plumb the hose accordingly.
Be aware that when you use a fuel pressure regulator that regulates the fuel pressure to a value that is not the same as the fuel injector flow rating pressure, the injector will no longer run
at it’s rated flow. That is, higher pressure will cause a higher flow rate. To keep things straightforward, try to run the fuel pressure for which your injectors are rated. Electromotive offers several regulators with different pressure ratings to make your search as easy as possible.

Sorry for the long quote, but that's straight from the user manual for the TEC3. The first line says you generally do NOT need an adjustable regulator like OEM, and then they go on to explain how to determine what fuel pressure regulator rating to get, and that they sell a variety of pressure rated regulators.

The other thing that the user manual says it not to use the on-board data logging above 7000rpm as it will cause the injectors to misfire. That is one of the big feature that my friend was turned on by, but he's going to turn his motor to well past 7000rpm so that's not going to help much. It doesn't say anything about the laptop working or not.

I wasn't aware that Alan was running it in his car, but I've not seen him race in a long while. Most of the racing my friend is going to be doing is Outlaw Limited Street on 1/8th mile tracks. He'd have to weight too much to go run NMCA Limited Street anymore like he used to.

I think 99% of the Outlaw guys down here that are running EFI are using F.A.S.T. so I know we can get help from them if we need it. Plus, I think we can get a map to get his car running fairly quickly.

I think he was really caught by the price of the TEC3 vs. F.A.S.T. with the WB o2 option. I guess I'll just have to wait and see what he does and try to adapt accordingly. Thanks for the reply, Scott.

 

[Scott231]

Yeah, well there is the "generally is not needed" quote from the manual that is intended for the masses. Then there is common sense for race cars...and Fred at the Electromotive Tech department will agree that on a race car, an adjustable fuel pressure regulator is "generally advisable".