Doubledip

Hi , i have searched but none of the answers have answered my question. Is it possible to run 16 injectors off a LS1 PCM. either wiring them in series or parallel? - dont want to have to run another box if i dont have to...

both sets of injectors will be high impedance

abbaskhan

good question id like to know also

Juiced

iTrader: (2)

as long as you can keep the IPW high enough for the PCM to read and within the amperage limitations of the injector driver you may be able to.

stevieturbo

I would guess the standard drivers could do it wired in parallel. But unless you stage the injectors, you will still run into control difficulties due to high flow, at low rpm's

2002_Z28_Six_Speed

iTrader: (19)

low impedance = high current. :-( I'd say no intially. But there are high speed relays out there you might be able to implement if you find the right person.

Doubledip

sorry for asking possibly a silly question but IPW - is that injection pulse width?

and secondly i have been thinking about this as well as seeing what you guys think/have experienced and one problem i feel i may run into is that (back to basic electronics) when you put two resistors (the injectors) in series you increse the resistance that will be across the injector driver (which i feel could be bad or may cause the injectors to not open/operate fully or fast enough) and if you were to run them in parallel then you halve the resistance (like running a low impedance injector - although would be round the 6 ohm resistance not 2.5 that a low impedance one is). To get round this if you ran the injectors in parallel like mentioned before but then ran a hefty power rated 6 ohm resistor in series to raise the resitance back up it may work... early toyota efi engines had a dropping resistor like this for their injectors.

Vents

iTrader: (9)

also it more so has to do with your intent for doing so. if your simply trying to cut the inj. duty cycle in half, it would work great. If you'd somehow attained the mindset that you could wire in and tune for staged injection events based off of map/rpm/tps/cts, ect, that IMO wouldn't be worth it.

You could wire in relays triggered by the PCM. Grounding out the injector, and running the switched (grounded) sides of that relay to a pair of high imp 60#'s you'd effectifely have a set of H.I. 120#'s. ;D But then you'd have to figure you new IFR, & IPW in the pcm.

Progressing to wire those relays on a rpm, boost, tps or other switch system and you've sucessfully created a young frankenstien to troubleshoot, should anything fail. I think that you'll realize the KISS principle really is a wonderful philosophy. Sure anything is possible though, do you really want to mess with it?

Doubledip

not trying to get any form of staged injection... more after the flow as this is for a drag car with fairly big HP .. the perfect injector is the 160lb injectors i.e. indy blue.... but they are low impedance... so the though of just running 2 injectors per cylinder to make up the flow

stevieturbo

Where are you getting low impedance from ?


And FWIW....if you are going to the trouble of 2 injectors per cylinder. May as well just buy an ecu capable of controlling them.

One option would be, to use the likes of a cheapy ecu, in piggyback fashion to control the extra set. Staging them that way.

Although a single ecu to do it all, is the most sensible approach.

Doubledip

I know it may be easier to go after market ECU and if that is the case then might as well go single injector 160lb's each but the point question is "is it possible to run to injectors per driver on a LS1 PCM".

the previous setup on this car was running after market ecu , accelronics driver box and big low impedance injectors.. the car ran fine but have EGT probes on each cylinder and there was upto 200 degrees temp diff in some of the cylinders. where as back to running the standard PCM and injectors there was very minimal temp diff..

stevieturbo

how can an engine that requires big low impedance injectors, run the same on a std ecu and std injectors ???

And are you sure that each injector flowed exactly the same fuel ? If not, did you trim cylinders accordingly ?

Doubledip

the engine that is being rebuilt now has a huge single turbo as opposed 2 too smaller turbo's (old setup) with the boost at a certain level there was enoguh fuel with the LS1 and hi impedance injectors (not standard - 60lbs)... then when the other computer setup with driver box and injectors was connected the boost could be upped. "And are you sure that each injector flowed exactly the same fuel ? If not, did you trim cylinders accordingly ? " the tuner.. who is the car owner would have done all that.

cast iron

The facts that remain to be determined:

-can the factory driver handle 2x the current? 1A becomes 2A

-will it be happy "seeing" 7 Ohms of resistance? R1*R2/R1+R2

The initial problem with running a resistor in series with the circuit, you are limiting the total current to about half of what it should be. That's going to make for some very sloppy injector characteristics (they would be running at an equivalent of 7 volts battery power if operating voltage was 14V, 12 Ohm injector coils)

Doubledip

Thanks for that Cast Iron

that has been one of our concerns ,but we are going to try on a standard road car to run 2 injectors per driver and see what happens. We dont mind if we ruin a ECU but will data log it all any way.

Beaflag VonRathburg

iTrader: (176)

I'm glad I noticed this thread. I was thinking of something very similar today except with a slight variation. You could add an extra wire to each sensor and run a secon PCM for strictly fueling the extra 8 injectors. Tuning it would be interesting, but it sounds like a decent idea. Keep in mind I have no idea what so ever about tuning. Would it work?

Doubledip

you could never say never with anything... but it would be an absolute pain in the A#$# to tune as you have 2 brains trying to control one thing (engine)

be like have 2 brains in you head and each controlled a leg and you tried to walk .. how would one know what the other has done and where it is... poor example but you can get the general idea.

cast iron

That would be a rad idea, but I'm not sure what problems you would create with splicing into vitals like cam / crank / maf / map / vss / O2 etc...


Be neat to see if setting the MAF airflow table vs Hz to 0 until you needed the additional fueling would provide "staged" injection

Also - since the additional computer isn't being used to drive engine load based calculation (spark timing, transmission, trac control), you could have a very wide range of load resolution - hacking the MAF values down 75%, and boosting the IFR table by 75%

bad ***.

cast iron

If they are reading from the same sensors, they should be provided with same inputs and outputs.

Doubledip

yes but remember that when one PCM makes an adjustment to the fuel trim for what ever reason the other pcm is going to make the same adjustment so effectively make either double the adjustment.. so would be constantly fighting with each other...

i.e. accelerate so PCM 1 says ok we need this much fuel to go that fast and delivers the correct ammount of fuel but at the same time PCM 2 is doing the exact same thing ... so you would have to be mucking around even longer to get mixtures right etc... on two computers at the same time.. would be a nightmare

then trying to share all these other sensors would probably lead to other signal problems.

as i said ... you can never say never but....

stevieturbo

As I said in post 9...its very do-able to use a second ecu. There are also piggyback ecu's capable of driving injectors.

The fuel curve on the second ecu doesnt need to be accurate, or perfect. Just tune it to dump fuel in progressively, and fine tune on the primary ecu, just as normal.


Megasquirt could probably do it on a budget.

Or the likes of a Haltech Interceptor/Miniceptor. These have no problem using existing cam/crank triggers etc, and could run additional injectors.

For 2 ecu's There is a guy here in the UK who has been using 2 Apexi PFC's on his Subaru, and is running very low 9's at circa 160mph. So he has managed to get it to work ok