Slant Six Forum

Analog fuel injection controller with 555 timer
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Author:  lgu32 [ Sun Nov 10, 2013 9:55 am ]
Post subject:  Analog fuel injection controller with 555 timer

This topic was originally "1st time out of garage since 2012".

Here comes my Dart out of garage after sitting there for 18 months. I had to replace a bent exhaust valve and when I took the head off it was easy to install the fuel injection with the same gaskets.


The base engine is the same. I did a head porting, installed Clifford manifold with Bosch injectors, fuel rail, -pump, -lines, -regulator, -surge tank, -filters and a top of all, a home designed and soldered "ECU" based on "old school" 555 timer circuit. Just a little of leaning as the lambda shows that this is absolutely too rich now.

I also switched from gasoline to ethanol with the fuel injection. The local ethanol fuel called RE85 and it is made from organic waste.

Author:  Reed [ Sun Nov 10, 2013 10:35 am ]
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Tell us more about the fuel injection system!

Author:  lgu32 [ Mon Nov 11, 2013 7:36 am ]
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Here you can see my fuel feeding system under installation. An aluminium surge tank is taking the place of the alternator. Alternator is now located to the driver's side of the engine as it has been with very first slants.


The original mechanic pump is the one which moves the ethanol from the main tank to the surge tank. There is also a return line built with 1/4" rubber hose that the fuel can flow back to the main tank. You can also see an electric pump. The coarse filter is before surge tank and then I have a fine filter before fuel rail. All of this is a normal stuff.

Note the hand pump. This was used before 1st start. It also helps if I run out of ethanol and I have to do the surge tank fill again.

Here you see my fuel feeder.


I have had this hanging in my garage almost a decade. The injectors were "unknown". They said to be from Cadillac V8 but I could not find that Bosch part n:o from catalogs. I measured them to be 230cc which I thought to be enough for test trials. For measuring I needed not only pressurized fuel but also electic pulses. Why not a 555? YES!

Throttle body is from Chrysler/Jeep 318 V8 and then there is some hand fabricated links as this was the best positioning for the TB. Note the finger screw at the fuel rail side of the throtte body. It is replacing the idle motor in this application. This has a manually adjustable idle air needle valve.

Remember I am doing it with the 555...

The original plan was to built a sequential injection with six pieces of 555's. Against trigger wheels I had a plan to use spark plug wires as sensors for the engine crank location status (1/3 rev accuracy for 2 circles). I did those sensors. They were inductive coils plus some other stuff, molded to insulative plastics. But because I am so lazy to soldering so much components and because the 6 separate injector circuits have to test and calibrate and so on, I decided to go to "single bank", all injectors have to be run same time. This sequential injection with so many components could also kill my slant as one of six 555 circuits could die and then I have a cylinder lean and so on...

I do not have a sensor for the engine positioning. Against trigger wheel I am using the ignition pulses from the ignition coil for my "ECU" to inform the current engine speed.

As there was a bent valve I did the complete head work.


The head and block are now both "milled". The static compression is above 10:1 and the tester shows about 14 bars (200PSI I think) which make me easy to choose between gasoline and ethanol. Ethanol seems to like high compression.

I have there cold spark plugs now as I had some pinging with carb and gasoline/ethanol mix before going to EFI. I have to found a new value for the spark plugs for ethanol. It would need some test runs to find the correct value plugs on it.

Almost finished installation. Already tested with '555' circuit...


And then comes the controller.


Updated [dec 8. 2013]: This is a quite finished controller which I have tested. I DO NOT RECOMMEND ANYBODY TO BUILD SIMILAR. If you do one, please understand its your own fault if you damage your slant six car!

This is still a prototype for just testing the A/F ratio adjustment. I have some plans to mix the lambda sensor signal to the ECU later.

This controller has for example

- Cold engine enrichment plus engine primer with extra fuel at start
- Incoming air temp compensation
- adjustable MAP sensor min-gain-max, which I estimate to be enough for acceptable A/F settings in normal conditions. No RPM compensation yet.
- "Power valve" for full throttle (uses TPS signal)
- Separated idle fuel feeding circuit with adjustment (air and fuel)
- Syncronized fuel feeding (1 fuel pulse for 1 and 2/3 revs of engine).
- Injectors are compensated against battery voltage variations.
- Automatic shut off of fuel pump when engine stops

To get the idle speed controlled both the gear on and the gear in neutral I have set the idle feed pulse string for slow. There is now 125ms in between pulses. That is enough to feed well the slant for 800-900 rpm idle but not enough for 1300 rpm in neutral (which this engine tries to get). So it could not and the speed in neutral is about 1000 rpm. My engin has MP268 cam and with automatic and factory turbine is a bit problematic but I can live with it.

This project has been made for fun. Now I can say I know the basics of the fuel injection. The literature for this project was just couple of old Bosch injection handbooks. I also used some Megasquirt map suggestions from this forum to calculate start values as estimations for fuel settings. Lot of practical tests at the garage were done to get the secrets opened for the one of most simplest fuel injection controllers.

Author:  Dart270 [ Mon Nov 11, 2013 12:07 pm ]
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Very cool project! It is satisfying to design and build things like this yourself, so that you know how every little feature and component works.

Enjoy the drive...


Author:  Sam Powell [ Fri Nov 15, 2013 5:04 am ]
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I am impressed with all aspects of this. The engineering is cool, and the craftsmanship appears excellent. As Lou said, this must feel really rewarding. Very well thought out, and clever ideas. Keep us up to speed with the project.

I suspect you may get better results in the end with smaller injectors. I started my project with 36 pound injectors, and ended up with 24. Mine may still be a bit large. The stock chevy small block comes with 18 pounders. The economy and drivability got better. Smaller ones have a longer open time at idle, which improves the ratio of transition time to open time, thus making it all more predictable and consistent. If you can monitor your open time at idle, it is best to keep this at 2 ms or above to maintain your target AF ratio at idle. Smaller injectors will allow you to use longer times, and get a leaner idle that is still smooth.

Again, congratulations!


Author:  lgu32 [ Sat Nov 16, 2013 7:43 am ]
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Yes, I noted during the "development" that there is something I have to know about the injectors. I have also seen Megasquirt user manual and as there was parameters for injectors I did some investigations with my set. At first I measured the flow.


I used a dental chair clean water bottle system to get constant pressure (with air) to the gasoline/ethanol. Note the orange hose at the picture. I was surpriced with flow numbers and non linearity of the results. Soon I noted that the small 2mm hose for injector feeding at my test bench was absolutely too small. With 4mm hose and bigger there was no differences with flow and Bosch injector measurements continued. Of course this was only the flow bench error. The tubing for fuel rail is 8mm in diameter and there is no flow problem.

I flow tested all eight injectors (I have a complete V8 set. I used 6 for slant) to be good (as they were used) and noted also that they were equal in flow. The DCI bottle and test glass with a scale at the side was very good tool for flow bench job.

Next I tested their opening and closing times, see graph:


"Virtaus" is a finnish word and means "flow". I tested the injectors with 8, 11 and 14 volts supply voltage. As I have the old style Mopar alternator which does not make enough current at idle the car voltage has its changes. I compensated most of the the operating voltage difference variation in my electronics. As well I noted that the injectors have looong closing time (note the purple line at the graph) which could get the adjustment nonlinear. I fixed that in my electronics. Against just a mosfet and diode I used a resistor with the diode circuit to minimize the free rolling current flow time at the closing edge of the injector drive.

Injectors are high impedance type, so there was no need to operate with PWM drive with them.


There is now about 4ms pulses at the idle, period time is 125ms. I assume the injectors quite close to the 4ms open and the fuel consumption is about 2,5liters per hour at the idle. The lambda is at the 0,5 volt area with this adjustment, much leaner that I got with a carburetor.

Here is a picture of the tested engine position sensor "development". As I told there was originally a plan to make "sequential" injection (like 1958 Chrysler/Bendix) for individual control of each injector. I did couple of tests to get a "sensor" developed for spark signal detection. I tested both a ferrite ring (brown thick one at the picture) as well a normal keyring (similar as used to keep several keys together, steelring) . Both were usable.


Anyway I left the idea for sequential injection as the electronics would be come too complex. So there is no sensors on the spark plug wires on my control system. The engine speed signal comes from coil -terminal.

Author:  Sam Powell [ Sun Nov 17, 2013 6:47 am ]
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Very well thought out, and mostly above my head technically. Explain the keyring thing please. Did you make that? I notice it is on the coil wire only. Is it for suppression of interference? I had great difficulty with this on my set up. Also, explain the inductor core as well. Thanks.


Author:  lgu32 [ Sun Nov 17, 2013 7:26 am ]
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The round keyring over the spark plug wire will take a small part of the electrical energy of the spark in to it. Every electric wire which carries current have a magnetic field around the wire. If the current is alternative (AC) the magnetic field is also alternative. A small part of this alternative magnetic field will go to the metallic circle over the wire. Anything magnetic will do it. As soon there is some alternative magnetic field in the metallic ring, another wire thru the ring will generate voltage. The complete set, ingition plug wire, metallic ring and the "other" wire are together a transformer.

This transformer will "stole" a small part of ignition energy and this energy can be used as a signal to ECU. So this transformer is acting like a sensor. Of course its possible to put a connection direct to plug wire but it will have its challenges as the voltage there is about 15'000 volts and the signal level good for ECU is just few volts.

Use a keyring (you can find a chromed ring there over one plug wire as well a thick brown/orange thing, that's the inductor core). Depending of needs, physicians and chemists have developed for electricians many kinds of magnetic materials with different features. An old style transformer core for 115V/60Hz mains is made from steel plates which are not so far away the sheet metal Chrysler used for cars. That metal is good enough because that mains electic is doing changes so slow. Modern transformers are made materials which are also based to "iron" but the construction of the material is closer to ceramics than steel. That material, ferrite is faster and better for electonic transformers and inductors. There is lot of different ferrites. This one used in my example was special (and expensive) material which makes much more inductance than conventional ferrite. It has like the best parts of conventional transformer sheet metal and ferrite together. I just had a set of different cores in an electricians test set, then I went to the garage to make tests. All were usable and then I did a look to my Dodge keys. Could that keyring work? Yes it did but the signal was so weak I rather will use "more professional" inductor cores than keyrings.

Playing with ignition signals includes always some risks. Either the spark can kill some electronics and it isnt really healty to get that voltage to human body especially the person has heart problems. A dead electrician is not either a good thing at all.

I have had some test drives at friday and saturday. I have pretty good mixture now and the warm engine feels strong. Of course the engine is a bit complicated as the camshaft and the stock turbine are not the best pair, but as I mentioned I can live with it,

But the starting with dead cold engine is hard to do. I have to made some soldering again to make 1st start extra fuel circuit to my ECU. How easy it would be with Megasquirt! But I have choosen my way and I will keep it to the end...

I have to do it as some of my friends are still thinking I cant with survive this project...

Updated. I have finished my fuel injection project and the car is ready for fun. As it is just snowing and getting cold I probably keep this Dart garaged until spring.

I also have updated my controller schematics above in my previous postings. Someone with some electronics experience can now read better the schematics. Before trying yourself I will write few words of operation of this type "almost-analog" controllers. This kind of stuff has to be tuned in a car with several road tests. So I do not recommmend anybody build a similar thing as it could cause harm to the car or person itself if something goes wrong - it was little confusing to drive with all meters and oscilloscopes on the dashboard. It could also be illegal to build such a things in a car. In Finland we dont have pollution rules for such an old car like my '66 Dart. So I was free to play with injection and ethanol.

But if you feel so, why not. I have done my "electrojector" as they called the first electric fuel injection at 1950's. And what happened? All of them were collected back as the quality was ...

Author:  lgu32 [ Sun Dec 15, 2013 5:11 am ]
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I have done some street and road tests. At first I refueled the tank up with fresh ethanol fuel. The local "RE85" mix contains 70-85% ethanol depending of the season, the rest of it is premium fuel. Just couple of checks with lambda and then I went to the streets and roads:

Everything above 2000 rpm was fine, even better than with a (318 V8 BBD) carburetor and gasoline. Road driving was the best. Even I have 3,55 gears and only 185/70R14 tires the driving was fine. The best comes just when it is WOT and engine speed goes over 3500rpm. There comes the power peak and seems it continues well above 5000rpm which I used shift point with my tests.

A engine with MP268 cam and 318 BBD is "under carbureted" in my opinion. The engine does not get air/fuel as much the cam like to deliver at high engine speeds. It feels its going to die. With my home made efi the high engine speeds felt more "natural".

The engine didnt stop once without shutting it down by key. Reliable, yes.

Either I didint get not one firing inside the intake manifold or exhaust pipe during my 1st test day.

The idle is quite worse as well driving with lowest engine speeds below 1500 rpm is not very comfort either. It is probably because the weather was below freezing point (-5 centigrades) and this car does not have heater for manifold or even for the air cleaner. I have used only one day and about 40-50 miles for tune up so there is still potential improment as I get more test sessions done. Even the ignition timing is still as it was with gasoline and carburetor.

I am little surprised how easy it was built a "home made" fuel injection...

To do: together with low speed improvements I have tune the transmission link to get more line pressure for 904. Now it feels to run up with 1-2 as well 2-3 shifts in some conditions. Probably I will add later a shut off (motor braking) feature so that the fuel delivery is off at high vacuum and high rpm. Otherwise I will need more brake pads and shoes.

Narrow band lambda was pretty close to 0,5 volts at road test. i think i will not go any leaner until summer conditions.

As the car was "so nice" I went for official inspection which we have to here for all cars annually. Everything was fine except the left rear brake was lost the friction. Probably there is some hypoid oil from diff gears. Its good that it was found there as this car really needs all the braking power it can get.

Author:  lgu32 [ Sun Feb 09, 2014 3:20 am ]
Post subject:  Greetings from Helsinki!

I have had success with my fuel injection project. :D :D :D

Even the weather has been the best for test drives. During one month the temperature has been everything from +5 centigrades to -20 centigrades => I have had possibities to test how E85 slant runs in cold weather. It runs well!

The latest schematics of the "555" controller is above.

Even the road tests were fine (previous posting) it came clear quite soon that I cant get the fuel/air ratio not close to the optimum at all conditions. This simple controller does not support any possibilities to made fine tuning by numbers in a VE table like a Megasquirt. As this controller does just a vacuum measurement by converting the vacuum value to the voltage and then converting that value to the opening time for injector I got "good" AFR just in one narrow RPM area.

I have to use oxygen sensor to fix this problem! I did some changes and now the controller keeps the AFR pretty close to ideal with wide RPM area.

This controller is measuring the engine speed from the ignition.

It makes an injection periodically for each 1 and 2/3 engine revs. All injectors are fired at the same time. The engine gets "RPM limiter" at 5500 (full throttle) at the time when injector open time reaches 100%. Over that point the controller drops down every second injection pulse. I feels like RPM limiter usually does. Because it is cutting the fuel delivery but not the ignition, there is no series of explodes in the muffler. Or flame behind the car.

If the lambda sensor dies suddenly, the AFR goes pretty rich but I can drive the car back to my garage. This is what I call fail safe design.

Of course I have a spare controller at the trunk if there comes electronics failure.

For full acceleration the oxygen sensor control is set off. Above that the controller adds some extra fuel.

As soon the asphalt gets dry I'll do tests with accelerometer to get the best fuel ratio and ignition advance for full throttle operations. :D :D :D

Author:  sandy in BC [ Sun Feb 09, 2014 7:43 am ]
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Your work is inspirational! Its nice to see someone using science and simple parts to make a sophisticated and unique system.

Author:  lgu32 [ Wed Apr 09, 2014 9:38 am ]
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Hello all you slant people. There comes my measured performance:

I did just a couple of test rides. I have a G-tech performance meter for results. No tuning of car or engine, no other tricks but just tests with different shift rpms. This was done with 5200 rpm shifts. 15,94s and 144km/h (89,5mph). I am pretty sure there is some tenths of improvement after fuel mixture and ignition adjustment.

I havent "thought" the absolute performance when building this. I have used what I already have in my storage. I am happy with this performance.

Author:  Dart270 [ Wed Apr 09, 2014 1:27 pm ]
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Excellent work. You must have done a good job porting your head, in addition to the nice EFI.


Author:  Matt Cramer [ Fri Apr 18, 2014 9:30 am ]
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This thing is like a home-engineered and homemade Bosch D-Jetronic. Very cool.

Author:  lgu32 [ Sat Jun 14, 2014 5:01 am ]
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Now the performance is confirmed at race track. It was my 2nd trial and the result was 15.987s and 138.3km/h. As usually also this time it started rain so no there was no possibility to test anything like AFR or ignition timing.

Next point of this project should be to built in car test bench to compare acceleration/speed/engine rpm to get this tuned "in garage or near it".

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