So I am spitballing here. For a challenge car, does anyone have any experience with running a second set of injectors using a combo of stock parts/cheap electronics in an challenge car or similarly cheap configuration. The thought here is to use parts from a zeroed out donor car to double the fueling to handle boost. A rising rate FPR is an easier option for sure up to a point but I thought if anyone knew about such things, it would be this group!
We did that aeons ago in NB Miatas. Stock ECU with a piggyback controller to fire off four extra injectors plus play with timing. The expensive part will be the electronics, relatively speaking. If you can find one of the old Link piggybacks, they're not terribly highly valued.
FPR is the easy button, though. Just make sure you have enough fuel pump to handle the pressure levels.
In reply to Keith Tanner :
That is definitely something that will require an upgrade.
Some discussion elsewhere pointed towards a single injector running off an arduino that is boost referenced.
This is mostly speculative as the Crown vic has a pretty well know ECU that can be hacked cheaply.
singleslammer said:So I am spitballing here. For a challenge car, does anyone have any experience with running a second set of injectors using a combo of stock parts/cheap electronics in an challenge car or similarly cheap configuration. The thought here is to use parts from a zeroed out donor car to double the fueling to handle boost. A rising rate FPR is an easier option for sure up to a point but I thought if anyone knew about such things, it would be this group!
No a challenge car, but a while back I had a turbo kit on my Miata that used a second set of injectors controlled by a piggyback ECU to add fuel under boost.
How are you going to control them? A piggyback computer faces some challenges because OEM computers are complicated and it can be difficult to predict how much fuel they're going to run in all situations. This can lead to lean conditions and driveability problems at the transition points into and out of boost.
Later on I replaced the piggyback system with a full aftermarket ECU (Hydra) that supported staged injection using the secondary injectors. This fixed the driveability problems, but I'm not sure it makes a lot of sense to go that way from scratch because it adds a lot of complexity to the car for no really good reason. There were some mechanical challenges with the system, over time it had a tendency to break the mounting tabs that held the fuel rail to the manifold presumably due to vibration. Mine mostly held together, but another guy with the same kit had several major fuel leaks while driving as a result (fortunately no fire -- it was the intake side of the engine, but still scary)
The setup Codrus was running is the same one I mentioned. Yes, it had some long term problems due to fatigue of some less-than-ideally mounted aluminum parts.
Keith Tanner said:The setup Codrus was running is the same one I mentioned. Yes, it had some long term problems due to fatigue of some less-than-ideally mounted aluminum parts.
Yeah, OEM engines are packaged pretty tightly so "less than ideal" is about the best you're going to get trying to add another set of injectors and a fuel rail.
A singleton injector is mechanically a bit easier, but will tend to fuel different cylinders unevenly. If you're up to doing Arduino-level electronics then you might want to look into "speeduino". It's an open engine management system using Arduinos, that should in principle allow you to use larger injectors in the stock locations.
Well, a gusset would have gone a long way. It wasn't packaging, there was loads of room. It was bad design work.
That kit actually started off with two throttle body injectors instead of the four injectors in the runners. When I referred to the electronics being expensive, I was referring to buying something off-the-shelf. There's a lot to be said for leaving the stock ECU in place to deal with all the hard corners of the map and just having a piggyback add more fuel/reduce timing when needed.
This is just brainstorming, so not based on experience, but...
I wonder if you could use one of the GM spiders with poppet type injector from the 90s as your supplemental system?
GM computers tend to be pretty well understood and the spider would eliminate the mounting of a fuel rail and could be fed with a separate pump or line.
How tuneable is the ECU, can you easily change out the injector information for larger injectors? Decapping flex fuel injectors from most GM trucks will leave you with roughly 80lb/hr injectors.
In reply to RacetruckRon :
An add on chip will allow 40 lbs without doing anything funky. After that, apparently there is a way to scale the output to run larger injectors. That is on the Ford EEC IV. If I manage to swap on the EEC V that I am likely to get on a parts car later this week, I think that HP tuners can handle most anything.
With my chump car Jaguar XJS I used the stock early VW Rabbit system where Jaguar tripled up the ECU's.
It had a knob on it that allowed the system to be dialed rich. By using Gold pladium spark plugs the plugs wouldn't foul when it was rich enough to meet 2 PSI. BOOST once boost reached 2 PSI the cold start injector was triggered and that provided enough additional fuel to get to 5&1/2 PSI which was all we could get from the little T2's used in Saabs.
It was really a kluge job. You could feel the power band go from too rich to to almost too lean times on the way up. No way could you drive that around a long corner. The best technique was to drive in deep into the corner and more or less coast around. Until you were more or less pointed in the right direction.
That was before E85.
With E85 I think that could have dealt with up to 6 psi in a much more stable way.
You can increase fuel pressure ( and with it richer fuel) by using a boost sensor to control voltage going to the fuel pump. And for boost above 6 PSI you could supplement it with Methanol, a set of clipped injectors, and a trigger mechanism.
You can't control fuel pressure with fuel pump voltage unless there's no regulator in the system. Increasing flow from the pump will just mean more fuel gets returned from the tank, promoting more fuel heating.
Jaguar fuel pump works at 30PSI. GM is 60? Psi I don't know about other cars.
However, one approach that was explained to me is fuel pressure increases fuel delivered. The ECU tells the injector how long to remain open and the fuel pressure determines how much fuel is delivered during that period.
Unless I don't understand things correctly. Which very well could be.
The fuel pressure is controlled by a fuel pressure regulator - basically, it allows x psi through and bleeds the rest back to the pump. It's a mechanical device. You can run a pump capable of 100+ psi on a GM, but the regulator will drop that down to 60 psi. You're right that increasing pressure will increase fuel delivery - all else being equal - but you don't do that by putting more voltage into the pump. You do it by making changes at the fuel pressure regulator.
I have a hard time believing Jaguar was using simple fuel pump voltage to manage fuel pressure, that would have to be a closed loop system or you'd have some nice fluctuations in the pressure. Even then, I suspect you'd have lean tip-in problems. I think Mazda is using some trickery on the low pressure pump in their newest cars but that's far beyond what we're talking about here.
There are no good ways to do this. There are a lot of bad ways to do this:
1) wire injectors in parallel and use a hobbs switch to kick power on the 2nd set under boost, only helpful if you run a lot and can tolerate running very rich like with methanol
2) same as above and just have the stupid things on all the time after set boost, even worse than 1
3) same as 1 but use two smaller sets of injectors like 20% lower than stock so your fuel trims take some base fuel out and the jump isnt' so big
4) rrfpr - I think this is the easy button without some kind of programmable management
5) cheap used MS - probably the slickest way
You missed x) add a separate controller for the auxiliary injectors.
The problem with 5) is that you're now responsible for everything. Probably okay for a Challenge car that only has to operate during a very short period under simple conditions, but it's a massive step in terms of complexity.
In reply to Keith Tanner :
Thanks! You just lit up another light bulb.
I assume pressure regulators can be controlled by the ECU? That's how they control the amount of fuel an injector squirts?
So a normally aspirated engine controls the duty cycle time and a boosted engine controls the pressure regulator?
Doug was the guy who helped me get the Champ car engine running under boost. We could spend only $500 back in those days. On the whole car. So any system like Megasquirt was way too expensive. Luckily we had a whole junkyard to find bits and pieces. In the end Doug wound up with the whole car and he still shows up once in a while at the drive in burning the rubber off the tires.
So Alpine used a 5th injector to adjust fuel for boost with their supercharger kits on the Beta 2.0 in Elantras and Tiburons. Those ECU's were NOT hackable, so they ran a piggy back to add fuel for the extra air and intercept and interpet the MAP signal.
frenchyd said:Thanks! You just lit up another light bulb.
I assume pressure regulators can be controlled by the ECU? That's how they control the amount of fuel an injector squirts?
So a normally aspirated engine controls the duty cycle time and a boosted engine controls the pressure regulator?
Generally no, the regulator is normally a purely mechanical/hydraulic/pneumatic device with no computer input. At least it is on port injection cars, DI may be different.
The regulator mechanically sets the fuel pressure to a particular reference value. That reference value may be fixed, but it may also vary, for example many cars will reference manifold pressure. Rising rate regulators are those which will increase the fuel pressure by some multiple of the reference value, but they are still purely mechanical.
In theory you could have a pump to create pressure and then use a solenoid to bleed some of it off before feeding it to the regulator (like how an electronic boost control works) so that the computer could drive the fuel pressure, but I've never seen that done. It doesn't seem like it would work very well.
I have seen people use a "solid state relay" (basically a big transistor) in place of the normal fuel pump relay and then duty cycle that with the ECU to control fuel pressure. I'm not sure how precisely you can manage it with normal pumps (that is, pumps not specifically intended to be used this way), but it's useful if you have a pump that's too big for the regulator to control properly when the engine is at idle. It's also not clear how long the pump lasts if you run it this way. :)
Keith Tanner said:You missed x) add a separate controller for the auxiliary injectors.
The problem with 5) is that you're now responsible for everything. Probably okay for a Challenge car that only has to operate during a very short period under simple conditions, but it's a massive step in terms of complexity.
Honestly 5 is easier than X but that is IMO having done it a few hundred times.
Frenchy, cis-lambda and CIS-e were basically that there was an electronic pressure regulator (bypass in cis-l and actual pressure in cis-e) that was controlled by the engine ecu in parallel to the flapper that got the basic airflow. Maybe there is a way to take these over for port EFI but I never tried.
In reply to codrus (Forum Supporter) :
OK. That's helpful and I really do appreciate your input.
But here is where I'm confused. I watched many tuners on Chassis Dyno's and all I see them do is type a few commands into their lap tops and change boost and mixture, sometimes even timing.
I sorta understand what part of the graph controls mixture under normal aspiration and which part is under boost etc.
But I never see them go under the hood and change anything. It's always in the laptop.
What am I missing or not understanding properly?
The laptop is sending data to a control unit in the car. If you don't see a data cable from the laptop, the tuner is probably using a Bluetooth or WiFi connection.
Normally, to change fueling, you change injector pulse width - that is, howuch time the injectors stay open. The fuel pressure usually stays the same, although you sometimes see that controlled too. Older ECUs sometimes have the tuner set pulse width directly, but usually the fuel table is one variable in a longer equation to calculate pulse width. This allows the tuner to swap injectors without changing the fuel table - instead, the tuner sets a much smaller set of numbers that define the injector flow rate.
There's a company out of Canada that used to make exactly what you want. www.sdsefi.com
They had an aux injector controller with a knob to set at what MAP pressure the injectors started opening, and another knob for the slope vs. MAP for duty cycle. They don't make it anymore but you might find a used one. It's also something you could whip up with an arduino in an afternoon.
frenchyd said:
But I never see them go under the hood and change anything. It's always in the laptop.
What the heck is changed under the hood other than the plugs? 
It's a bit true, other than doing a preflight check and verifying nothing mechanically or electrically stupid is going on there is little to do to the actual engine itself unless something breaks. Even then, it's not like you put a rod and piston back in if something goes wrong. 
I tuned a car in Australia a few weeks ago from my basement in Pennsylvania. The hardest part was the time zones.
MadScientistMatt said:The laptop is sending data to a control unit in the car. If you don't see a data cable from the laptop, the tuner is probably using a Bluetooth or WiFi connection.
Normally, to change fueling, you change injector pulse width - that is, howuch time the injectors stay open. The fuel pressure usually stays the same, although you sometimes see that controlled too. Older ECUs sometimes have the tuner set pulse width directly, but usually the fuel table is one variable in a longer equation to calculate pulse width. This allows the tuner to swap injectors without changing the fuel table - instead, the tuner sets a much smaller set of numbers that define the injector flow rate.
Thank you. I've seen both blue tooth and a data cable. Luckily that doesn't blow my mind.
I can understand how you can control pulse width to richen or lean fuel delivery. That's helpful. Knowing the horsepower ( and fuel type ) you intend to make allows you to select various sized injectors to fit your situation, that too I can understand. I'm also aware that a person shouldn't exceed 80% duty cycle on the injectors. (See I really do pay attention to what I read and watch).
What my mind fails to grasp though is the variation from warm idle to full tilt boogie making 5-6-700+ horsepower. Or a little partial chirp of fuel to a full throated fire hose of alcohol and fuel. All done with a little injector? I mean the feed hose is 5/16's ? That's enough?
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