Affordable Fuel Injection

**Mr Badpliers** · 03-05-2015

Hello,
I am working for an aircraft company and their tugs have been having issues with longevity, and also have been having issues with their affordable fuel injection setups being high maintenance.

The setup being used is a ford 300 I6, with AFI's gm throttle body, and their biggest problem has been poor install, and sensor issues, and lack of oil checking causing engine failure. My goal is to build drop in crate engines that are broken in on a test stand, with the fuel injection system wired and installed, with all the electrical set up so all they have to do is connect fuel lines, radiator, battery, and body ground. My thought is to have AFI provide me with the base tune for these engines but with a few modifications.

1. Delete O2 sensor input and just go with a base map that utilized outside air temp, manifold pressure, engine coolant temp, and throttle body position.
2. Do I need knock sensor input, these engines spend most of their time at idle, and at mid RPM high load conditions pulling airplanes.

Is their any input that can be modified/mapped to monitor the oil pressure and shut off the fuel pump if the oil pressure is lost?

Thank you in advance for any help/criticism/information provided.

Mr. Badpliers Stripbolt

**Skinny Pedal** · 03-05-2015

With the exposure to the elements you see up there, I would look at building good durable harnesses as well. Building the tunes for an engine like these would not be hard at all, especially if you are going to use the dizzy for timing control and not the ecm.

With your oil pressure, the best you could do is a switch that would kill fuel or ignition to the ecm.

You could run the engines without O2 feed back, Open Loop, but your tunes till need to be dead on for that. Since you are not going to be changing elevation and or climate with them it wouldn't be a problem.

You won't need a knock sensor if you are not controlling timing with the ECM.

**dave w** · 03-05-2015

From the factory, most all GM TBI engines used both an oil pressure switch and a fuel pump relay to provide power to the fuel pump. The factory TBI fuel pump power design provided a redundant source of power to the fuel pump. If the relay failed, long periods of start up cranking was required until the oil pressure switch closed. I supposed a manual "Prime" switch could be used so the engine would require less cold cranking until the engine started, then the "Prime" switch could be turned off. Maybe the "Prime" switch could work as a backup power source for the fuel pump, if the switch controlled a fuel pump relay?

dave w

**1project2many** · 03-05-2015

Howdy.

What a neat project. I work with a man that maintained aircraft support equipment on carriers in the Navy. One of the stories he loves to tell is how the mechanics installed an oil pressure cutoff bypass to allow the tug engines to be started faster when cold. It worked well until some of the operators figured out how to wedge the bypass so the pressure monitors were never active and they started killing engines. This was in the early '70s so it sounds like some things never change.

Engines can be run with alpha-N control... essentially using throttle position and RPM to calculate required fuel. These systems are simple and do not adjust to varying climate conditions but they work well enough for some of the world's fastest racecars. With that in mind, any additional sensors are really going to help an alpha-n system adapt to variations. How much adaptation you want is up to you. I'd include the coolant temp if these engines are likely to run in cold and war5m temps. Since you've already decided on intake air, it's not going to hurt to include that as well. Oxygen sensors are primarily to keep fuel delivery correct for emissions reasons, not for best driveability. There are plenty of open loop calibrations that run just fine. And at wide open throttle most computers are switched to open loop anyway so don't feel bad about removing it. Just remember that you might need to spend additional time with your calibrator making tuning changes as the seasons progress.

As far as the knock sensor, it's your call to leave or remove it. The conditions you describe, sustained periods at medium to high throttle under load, are exactly the conditions that can initiate knock. But I'm wondering if these vehicles will be using aviation gasoline or just cheap, automotive grade stuff. With better quality gas the odds that you'll have a knock problem decrease. Either way, a tune intended to run without knock and without the benefit of careful, knowledgeable operators, should be set up with conservative spark advance curves to reduce the odds of a problem. Long story short, a good calibration intended to run sans knock sensor will sacrifice some power for reliability. Enough to be a problem? Probably not.

I think I agree with Dave regarding the oil pressure shutoff. I believe the easiest route will be to use the switch in series with the relay to cut power if oil pressure drops. The programming for automotive ecm's really isn't set up to recognize a "kill" input. If you use an oil pressure switch to provide ground to the control side of the fuel pump relay then you could put in a second relay that bypasses the pressure switch only when the starter solenoid is engaged, thus reducing crank time until fuel pressure is available. I would recommend considering a Ford pump over a GM model. They seem to last longer and in my experience they have better check valves to retain pressure when the system is shut off. It's not necessary to change the pump though. If you have GM pumps installed already they'll work fine.

I do recommend you get a laptop and tuning software at some point. It will be easier for you if you learn to make some basic changes. Over time you might want some tweaks or mild modifications and if you can do them yourself, what a savings in time that would be.

Good luck. Please keep us posted.

**Mr Badpliers** · 03-05-2015

It should be an interesting project indeed. The fun will come after the company has paid me to learn all this so I can fit a tbi to a vintage Hamilton jet boat with an old Aussie ford 250. Setting the fuel curve for that shouldn't be too involved since a jet acts just like a fluid dyno, and load vs rpm is a constant curve. I like the relay ground through the oil pressure switch idea, that would work well. I could make a secondary relay ground by sending power to a relay when the key is turned to start so that the fuel pump runs when the starter is cranked, or just use a push button and install a placard with starting instructions. The biggest issue I see is adaptability to rapid intake temperature changes from a warm start in a hanger, to going outside in -40.
I do want to get chip programmer and software for sure, that will make it easier than calling Affordable if I want to make a few tweeks.

**1project2many** · 03-05-2015

The biggest issue I see is adaptability to rapid intake temperature changes from a warm start in a hanger, to going outside in -40.

This could be an issue. When I lived in an area with this type of temperature extreme we had to face false codes set when the ecm measured -43 deg for an extended time. If the tugs are currently experiencing repeated or frequent coolant or air temp sensor failures in cold weather, it's probably a similar issue. You might want to ask AFI about altering the conditions required before the ecm signals a problem. I don't believe I'd have the codes disabled unless there was no other workable solution.

You probably know that the early light duty GM TBI trucks had no air temp sensing. GM used a thermal valve and placed the air breather inlet over the exhaust manifold so incoming air below 90 deg F could be heated by the manifold. Heating intake air would help engine longevity in those cold conditions.

The jet boat will be fun. I love seeing well executed marine adaptations of automotive EFI.

Tunerpro is a very capable tuning and data monitoring package. It is well worth the suggested donation price. The hardware you choose to use may depend on your final plans. An emulator is very nice for real time tuning. You could use the emulator with the tugs if you have to work out changes then have AFI burn chips with your changes added. For the boat I'd say having an emulator on board, at least in the beginning, will be very helpful.

**Fast355** · 03-05-2015

I know I might be out on a limb here, I would not use a TBI type fuel system on an I6, especially with the extreme cold temperatures you are talking about. I have been around these airport type tugs before and the ones I have been around have all been propane powered. The advantages of propane if you can get it in this application are actually numerous. First propane vaporizes completely at a very low temperature. You might wonder why that is important, well with the long intake manifold an centrally mounted throttle body your center cylinders will have to run richer than the end cylinders, especially on a cold engine making them more prone to bore wear. On top of that with a warm engine the end cylinders will be leaner and tend to be more detonation prone. With the high load, low rpm running you are talking about the engine will be prone to spark knock unless you are careful with the timing advance. Being careful means being conservative and that will reduce your lugging power. Propane is very high octane allowing for more compression and therefore more power at lower rpms without being octane limited. Closed loop fuel control is also very simple with propane and works quite well. With the temperature/weather extremes I would have a hard time ditching the closed loop feedback of an 02 sensor.

If you want to run gasoline, I would have a hard time not sourcing the factory ford MPFI intake that came on the later trucks. I feel the I6 would greatly benefit from running port fuel injection at a minimum.

As for your oiling system trouble, in the cold temps you experience and the lack of attention it might not be bad to install a 2-3 quart oil accumulator for prelubing the engine before cold starts and run an additional 2-3 quarts in the crankcase that gets pushed into the accumulator when the engine starts. If the oil sloshes away from the pickup with the engine running the accumulator will immediately release the oil and keep the engine lubricated. You could add a 12v solenoid valve to make this process automatic. With the key on the solenoid valve is open, with the key off the valve is closed.

http://www.jegs.com/i/Moroso/710/239...oductId=745635

**Mr Badpliers** · 03-06-2015

Wow, every overhead cam engine in cold temps could benefit from that pre-oiler. Propane is out, due to it's sourcing issues in some communities. Removing O2 sensors was brought about by the damage caused to them by 100LL (100 octane low lead), and also the run time of the tugs in places with only a few airplanes may not be long enough to reach closed loop anyway. Good call on heated air intake, not sure if it is installed on these tug engines or not, but can be accomplished easily. I was informed that GM didn't use intake air temp sensor, so the base map must be done pretty rich it looks like. I have been mulling over the used of ford's efi system on the trucks, but I would need the tug in order to see if it would all fit, as it seems like it took up a bit of space. All good points, I need to do a little research and see where it all goes.

Chris

**dave w** · 03-06-2015

The most common TBI computer, 1227747, does not use an IAT. The TBI Camaro computer, 1228746, uses an IAT.

dave w

**Fast355** · 03-06-2015

Originally Posted by Mr Badpliers

Wow, every overhead cam engine in cold temps could benefit from that pre-oiler. Propane is out, due to it's sourcing issues in some communities. Removing O2 sensors was brought about by the damage caused to them by 100LL (100 octane low lead), and also the run time of the tugs in places with only a few airplanes may not be long enough to reach closed loop anyway. Good call on heated air intake, not sure if it is installed on these tug engines or not, but can be accomplished easily. I was informed that GM didn't use intake air temp sensor, so the base map must be done pretty rich it looks like. I have been mulling over the used of ford's efi system on the trucks, but I would need the tug in order to see if it would all fit, as it seems like it took up a bit of space. All good points, I need to do a little research and see where it all goes.

Chris

Yea leaded fuel will contaminate an o2 sensor so I can understand the desire to remove them if that is the only fuel available.

Some of the GM TBI cars used the air temperature sensor. Camaro Firebird and the B-car clones (Caprice/Roadmaster/Oldsmobile/Cadillac) come to mind.

**Mr Badpliers** · 03-06-2015

It looks like I can source the computers that have IAT fairly easily, then find a base tune that is close and modify it. Any recommendations on software/hardware for this?

**1project2many** · 03-06-2015

I was informed that GM didn't use intake air temp sensor, so the base map must be done pretty rich it looks like.

GM uses coolant temp as an adjustment to fuel. Air temp is primarily an adjustment to spark. Most OEM applications are ingesting warm underhood air most of the time. In most cases air temp is very close to coolant temp by the time the air gets to the valves.

In my experience, a TBI replacement for a carb on an inline engine produces a dramatic difference in performance. There are better ways, but computer controlled timing and fuel generally makes a remarkable difference over carb and mechanical timing.

**lionelhutz** · 03-13-2015

Here's another option besides AFI.

http://www.fitechefi.com/

Costs about the same but you get a more advanced controller and the system is mostly self contained and suitable for outdoor applications which better suits your application. The downside is that it's a new company so there's no history behind the products.

**delcowizzid** · 03-13-2015

not the greatest system looking at it fuel pudling on the throttle blades at anything but full throttle and look at the a/f ratio swing on the dyno run a whole 1.0 a/f ratio swing on boost as it struggles to hold itself in range