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Megasquirt as secondary injection controller?

4.7K views 11 replies 4 participants last post by  matt167  
#1 · (Edited)
I have an ECU that cannot be tuned to run larger injectors/ has to pass inspection with OBD-II.. Can I put 4 extra fuel injectors in the port runners of the intake manifold? probably 200cc each, but I have another set of Subaru injectors which are 280cc if I could use those. Then trigger them with just the tach signal? And batch fire them?

I only want it to fire those injectors as secondary and only under boost, so a second MAP sensor would be needed.. I don't event think I'd need an O2 sensor for it, just a wideband for tuning/ gauge to dial in the fueling correctly... I wonder how far off I really am.


This is for a 4cyl Subaru 2.5L. Not a standard hotrod but hopefully will end up a very quick parts chaser
 
#3 · (Edited)
Some Subaru computers can be tuned, but not the one for a 2001 Forester. Rom raider and taxtrix cables can be used starting in '04. Cobb discontinued the accessport for them.. The only way to put bigger injectors on one like mine is with a piggy back like greddy emanage, then scale back bigger injectors while off boost, but due to the way the greddy works, it wont idle well.. That's what I've found out so far.. I know a simple voltage clamp on the map sensor takes care of ecu seeing boost, and then 75% throttle the system goes open loop, so its just dumb enough to do anything without codes.. The emanage is $700 without any options, and its the size of a notebook computer. A microsquirt would be a lot easier to hide and wire. Its $369 with a harness.

I know a FMU can work, but stock injectors run out of fuel at 6 Psi. Even if I found a set of side feed 370cc ej22t injectors and got a fuel rail to work, they might not even idle and would still run out of fuel around 8 psi.. The engine ill put together will hold 10 psi without any issue
 
#4 ·
All the Subaru people either just use a FMU and a split sec voltage. clamp, piggy back, standalone or swap the entire engine over to a Turbo engine, which involves merging the wiring harnesses.

Going by the proven builds, the MAP cars like mine use a 12:1 FMU with the MAP clamped. IDC would be near 100% at that.. Fuel pressure is 43 PSI while running. Subaru guys use the Walboro 255LPH in tank pump..I could probably find a set of 370cc injectors. I have a set of side feed Subaru rails that I think will fit. they are only +90cc so the ECU might handle them..

I meant that Cobb had an accessport for the N/A cars 2004+. Nobody has been able to crack the older Subaru. Essentially the same 1996-2002 but wiring changed a bit in 1999-2000
 
#6 ·
You could run the microsquirt to run a second set of injectors and it should be quite simple to set up. The issue is going to be can your stock injectors correct enough and quickly enough when in boost. I don't know the answer.

But the local dyno shops works on Subura's nonstop. I'll check with them and see what they have to say. I know that they tune the 2.5 turbos in WRX's with some type of software, but not sure of the vintage though.
 
#7 ·
Well, with the map signal clamped in boost, the injectors would be at 100% injector duty cycle, so in theory the only time there could be an issue would be right when the secondary injection comes on which would have to be just prior to positive pressure so the engine was never lean
 
#12 ·
So this is more or less a go at this point.

Engine in my car is now loosing compression, backfiring and when it's cold it smokes like Uncle Bucks ( John Candy movie ) old Mercury coming from a stop, so I either have to let it warm up or hope nobodys behind me.

But a couple changes to my plans and the biggest is that I'm gonna run a factory turbo engine since they really are not much more expensive than the N/A counterparts when you go to the import JDM engines and come complete..
The EJ205 ( US WRX 2.0L ) in japan was used on the low density crank/ cam triggers that my ECU uses on their older version WRX the US never got. It has waste spark ignition and otherwise is just a bit different than any USDM EJ205. Different enough to make it a not so popular WRX replacement compared to the newer fully compatible one, and so they are cheaper. and so to run the engine as a swap, I can just swap my engine wiring loom from stock engine to EJ205 and I have to manipulate the tuning. I may actually use an Emanage to be able to run the EJ205 injectors which are 440cc or 550cc depending on color, compared to stock 280cc.. The Emanage is supposed to be able to scale them good enough.. I'm gonna get the engine with a transmission attached since the turbo trans are stronger and they have a steeper gear. Also adds very little to the cost to get it that way.