Staged extra Injector control + other goodies design. Input wanted
Engine Management, Fuel, Spark, EGTs, and Air/Fuel RatiosThis forum includes modification, tuning, repair, replacement, identification and restoration of all components mentioned above including SMEC, SBEC, Logic Modules, aftermarket engine management, etc. Nitrous oxide posts go in here. This is the place
Ok, at first, I was like I am not sharing this design because I wanted to make some money on it. I have had a change of heart.
Since that is not your goal, design needs to be simple in nature.
Since the fuel needed will be under very spirited driving and/or drag racing, we will assume high throttle positions. (approaching WOT)
Design basis resembles that of cold start and other jery rig setups.
Two most important inputs are needed RPM and MAP.
Use of injectors instead of coldstarts are needed for control.
Injectors need pulsewidth modulations
Well lets start with a common circuit that would resemble frequency and adjustments like duty cycle. Look familiar?
If you subsititue the motor with 1-3 injectors, and change the transistor design for driving the injector, you have a pretty good variable frequency and duty cycle injector controller.
So how do we break this down into be controlled? Well RPM can be thought of as frequency! That means the frequency driver (first 555 timer circuit) is now substitued by RPM (coil driver from computer) into Pin2 of the duty cycle 555 circuit. There is a problem. Unlike injectors, ignition thrives off of coil flyback. That means you can easily fry the 555's Pin 2. This means transistor. You will need a transistor that translates the coil driver from your computer onto Pin 2 of the 555 timer.
So how do we get MAP into there? That is the easy part. The duty cycle 555 circuit allows for adjustment by the ammount of potential on pin 6 and 7. Since this is normally done through a potentiometer that is connected to Vs, you can remove it and put in an OpAmp circuit as the driver to Pin 6 & 7. The OpAmp will then be driven from the MAP's output. This will have to be additional to the one already on the car, but who cares. A properly sized diode will need to be placed at the output of the OpAmp to act as a cutoff. This is to keep the 555 timer inactive until a certain MAP voltage is reached.
A very rough diagram is shown below of the circuit. If you were to pursue this, you would need lots of other sizing of resistors, and selection of proper transistors for the job.
I'd can the 4 injector idea. too complicated too many things to go wrong. You want power and reliability?? Stay as simple as you can. I saw a car on the DYNO make 400 hp & 460+ ft lbs with only +40's and a NOS 5th injector set-up. The 5th was using the SMALLEST jet we could find in his collection... .020. Started with an .025 and was too much fuel.
I am only helping to assist him in his design. I didnt build it because my focus is STALO. But point well taken. You sound like Brian - always giving me crap about how I will build a circuit, it works, then I try to make it better! It never works again! LMAO.
-Frank
PS. You should see the sig now. Couldnt help myself. HEHEHEHE
Thanks for the input Frank, that approach is more of an analog design compared to what i was thinking of doing but it's definitely practical when it comes to helping me figure out some control measures for this thing so kudo's to you
And Ken the main reason i'm doing this is cuz in the end, for me anyways, its going to be a LOT cheaper then getting a set of +40's and the AFPR to go with it. I have the injectors already, and i have the know-how to build this controller. Before i ever get this thing into a car it's gonna be tested pretty thoroughly to ensure that it works as i need it to. I do agree it's a little complicated, much moreso then just putting higher flow injectors in, but if us TD'ers did everything the easy way we'd all have the electronic boost controllers, spearco intercoolers custom built for us, and other goodies that in general cost more but make things simpler in the long run. So I guess I'm a sucker for punishment
That means the frequency driver (first 555 timer circuit) is now substitued by RPM (coil driver from computer) into Pin2 of the duty cycle 555 circuit. There is a problem. Unlike injectors, ignition thrives off of coil flyback. That means you can easily fry the 555's Pin 2. This means transistor. You will need a transistor that translates the coil driver from your computer onto Pin 2 of the 555 timer.
There is something i was wondering about the output from the coil driver from the computer. First off where can i Find it (I have the PM/LM setup on my car) I'm thinking its based off the Power module but could you wire it from the coil itself? Secondly how "pretty" of a pulse are we dealing with here. I actually designed a very good filter circuit which i thought would work on the coil (it sent out a perfect 5 volt flat output if the input was between 2 voltage limits which i could adjust) but I couldnt get it to output a clean signal when connected to the tach. Could be that i just was reading from the wrong place. What i wouldnt give for an oscilloscope at home But yeah, any info on this front would be great.
Just basic staged injectors (maybe up to three) with input from O2, TPS, MAP would be wonderful. One can make the mistake of over-complicating this... Although paired with a staged boost controller might be nice at launch.
There is something i was wondering about the output from the coil driver from the computer. First off where can i Find it (I have the PM/LM setup on my car) I'm thinking its based off the Power module but could you wire it from the coil itself? Secondly how "pretty" of a pulse are we dealing with here. I actually designed a very good filter circuit which i thought would work on the coil (it sent out a perfect 5 volt flat output if the input was between 2 voltage limits which i could adjust) but I couldnt get it to output a clean signal when connected to the tach. Could be that i just was reading from the wrong place. What i wouldnt give for an oscilloscope at home But yeah, any info on this front would be great.
Thanks again
From the coil itself would work. You could expect as high as 130 volts from the coil itself as the flyback from the colapsing field in the secondary's coil translates back into the primary coil.
If you go with a logic level type of conversion where you look at the rising edge of the ignition pulse, it doesnt matter how clean.
id use an optoisolator to protect the circuits and a schmitt trigger to clean it up. as for the tach drive you were talking about earlier, you might need something like a op-amp/transistor combo to provide the current to actually drive the tach.
Similar in application and response but mine was just a transistor and some resistors. Simple and moderately effective. Only worry being high voltage on the base, but that shouldnt be a problem either.
I don't have any electronics background...just a fertile imagination. Have you ever thought of tapping all the electronic signals that already exist in the system and use them to literally run a second computer controlling 4 other injectors? I thought it sounded interesting, but no one wants a second set coming on when they aren't making boost; if there were some way to modify the input from the sensors (say, cut all the readings in half, especially the map signal, making the second computer think you were not at wot), then the second computer (minus or with the timing disabled) would take care of pretty much everything else...good welding skills for a second set of bungs would be handy for sure.
This too far out in left field? Sometimes I get a bit out of hand...
Well actually I think a whole second computer (if I'm understanding you here) is alittle excessive. But you pretty much have the general idea of this controller. I've got a couple really nice features that i'm thinking of building in like lean/detonation protection system and possibly the idea of running all 4 injectors as soon as it needs it and adjusting the fuel input using PWM, instead of firing one at a time. Both of these options would be fairly easy to implement actually and I must say I'm getting pretty excited about the potential for this thing.
Even if all it does is monitor your engine and protect it from running too lean (user adjustable level for this of course) it would be worth having. So I'll keep you all posted on how it goes Wish me luck
You could keep on running your stock 2 bar MAP sensor for your regular computer, right? Then Get a 3 Bar MAP and supply it with 5 volts from a power source from a switch inside the car. To get the 5 volts to the 3bar map, go to radio shack and get some sort of resistor set at 5 volts.
Following me??? basicly you are having the 3 bar map sensor running independintly of the computer.
Get a volt meter and record the boost level and what voltage.
At .X amount of voltage (lbs of boost) have injector number 1 kick on. Get some sort of sensor to kick on at say 3.7 volts (just a guess) and trigger the first injector, same for the next injector. Make sure to use relays for each injector for minimal voltage drop.
TurboDodge.com 
But yeah, any info on this front would be great. 
Wish me luck
