Texas_WS6

iTrader: (9)

I am to the point with my engine that I think I need to run two sets of fuel injectors. This is because the power out put of the engine will demand an injector that will still deliver too much fuel at idle and maybe even at part throttle. I have looked into different aftermarket controlers and have found that none will work the stock dash and most will not work my trans the way I want it to.
So here is my thoughts:
Use the stock PCM with a set of 8 small injectors, probably my stock injectors with the factory settings(that way I will know the injector data is correct). Let the stock PCM continue to control the ignition, trans, and dash. No MAF and still use the 3barSD OS.
Use an aftermarket PCM to run the 8 very large injectors (220# or bigger), the waistgate controler, and methonal injection.
I would like the stock PCM to only fuel the engine at idle, low load, and not at all during boost, but to do all ignition and other normal functions.
I am thinking I can let it run with the STFT's on, and maybe even with the LTFT's on and that by doing this the car will drive smoothly around the city.
So the first question I have is, for those that have done this, how did you attack this?
Can you completly shut the fueling off with the stock PCM or do you have to basicaly flatline the VE table in the areas the smaller injectors reach say 70% and then start bringing on the second injectors?
I would love any advise to this.
Thanks

minytrker

iTrader: (13)

I havent seen a street car need 16 injectors yet. What kind of horsepower are you making?

Texas_WS6

iTrader: (9)

Made 844rwhp and 817rwtq last year.Will be making over 1000rwhp and tq this year. I am already having issues with my #80 injectors over fueling at idle. I am going to 120# injectors (if I stay with gasoline, 220# if I change fuel). I have no doubt the 120# injectors will overfuel at idle. I am also toying with the idea of running pump gas threw the small injectors and PCM, and alcohol threw the large injectors and aftermarket PCM.

The main thing here is over fueling at idle, and during normal driving conditions.

minytrker

iTrader: (13)

With that size injector you shouldnt have any problems with fueling. You dont have the tune right or you have some cheap injectors. I have used 90+lb injectors with no problems when they are setup right. I would either change brand injectors or work on tuning the ones you have correctly.

What your wanting to do with 2 pcm is way more trouble than its worth. There is no way I would keep the stock pcm if I had an aftermarket pcm in the car also.

Texas_WS6

iTrader: (9)

I am not asking if I should do this but how people have gone about running two different injector sizes. I have my reasons for wanting to do this. There is nothing wrong with my current tune or my tuning abilities. There are things that you have to live with when you run large injectors with the stock PCM. I want better control at idle then what you can get with the large injectors and a stock PCM and keep the stock dash working. I am also toying with the idea of running two different fuels.

I would only use the aftermarket PCM if it would in fact run my 4L80 AND run my dash. It will not without a second trans controler and they will not work the dash. Why pay for another controler when my stock PCM will run the trans perfectly and work the dash correctly? I will need an aftermarket controler (which I already have in hand, also one of the reasons for wanting to do this) to run the second set of injectors and to consolidate all of the other controlers I have in the car now into one device.

Please, lets not get side tracket with why I do not need to do this. Lets use our knowledge and figure out how to do this.

Thanks

SSpdDmon

iTrader: (10)

If you flat lined your VE table by RPM at the point of atmospheric pressure (0kPa manvac), in theory I would think you could use an external system to provide the extra fuel when in boost. This would allow you to use the PCM and stock injectors (or something close to factory) for normal driving. The difference in this and what you're proposing above is, the factory injectors would still be working in boost....but at a flat rate based on RPM. The supplimental fuel system provided by your aftermarket controller would need to be boost referenced and capable of fueling ONLY when in boost. I don't know if there are systems out there that are capable of this. I would guess there are. But, I'd kind of envision this working in the same way a wet nitrous kit works. There's extra air coming in (boost / N2O) and you're going to add the extra fuel needed without the factory PCM knowing what's going on.

What you may find in doing this with a larger injector is, you'll need to have the aftermarket unit come in a little early or the primary injectors stay on a little extra after 0kPa because the secondary injectors are going to have the same small pulse problems you're trying to avoid. If they do, low boost scenarios might not get sufficient fueling.

minytrker

iTrader: (13)

There is no need to go through all that, thats the point your missing. There are plenty of boosted cars out there running 80+lb injectors with the stock pcm with no problems at idle or part throttle. Why wont yours? Its either the injector choice, tuning or both.

I don't think it will work, I think you will reach some hard limits in the stock pcm that most tuning software doesnt give you access to. I think you will have to many things out of limits or maxed out trying to run two pcm's even if one isnt stock. You would also need double of; sensors, fuel systems, data logging software, wiring harness's just as a start. Why go through any of this when the stock pcm can do it with 8 injectors.

Texas_WS6

iTrader: (9)

The issue I see with the Aftermarket system is minimal pulse width. It would still be fireing the injectors at low manifold pressure if if the table was zeroed out. Now the system I have has tables for a second set of injectors. I think if I use that table it will shut off the injector 100% when outside of those parameters. I will call them and get more detail.

Minytrker, there are other reasons that I have not gone into that makes me want to run 16 injectors. It is not just an issue of injector data. I can not go into these reasons at this time. That is why I am trying to skirt around your point and avoid a debate about it. I agree with you that if the injectors are quality, and the injector data is of high quality, then it should be able to be tuned to work right. But the definition of work right for some people is different then for others. So please lets not debate something that will not lead us to achieving the goal I am after, which is to run 16 injectors, keep the stock dash working as it came from the factory, and control the 4L80E as the stock PCM does, and condence all of the extra aftermarket control systems to one PCM. I do appreciate your comments and agree with what you are saying. Please stay in this thread.

Maybe the thing to do is run both sets of injectors with the aftermarket PCM, maybe even the ignition system. Use the stock PCM for the trans and dash. I do not know if I can piggy back the cam and crank signal off the engine. I think I will have to install a crank trigger for the aftermarket PCM, and come up with a symple cam trigger, which either would be symple to do. Manifold pressure sensor is not a problem, and the TPS is symple, as well as intake temp and engine temp sensors.

The negative to utilizing the aftermarket PCM for the ignition is it has no detination protection. The negative to leaving the ignition control in the stock PCM is I would still have to use the MSD 2 step.

Hmm.

white01ss

iTrader: (37)

The 16 injector setup is ideal for a high horse street/strip car hands down. There is no debate as far as I'm concerned. If it was easy everyone would do it.

You might contact Lingenfelter as they have built a few 16 injector turbo cars. I don't know if they would give out info for free but it doesn't hurt to ask.

ramairJP

iTrader: (3)

Pretty badass. I don't have much direct experience with that level of build, but it sounds like a BS3 is the way you would want to go. It will handle the engine control like you're asking, and it will also pick up the trans control. I agree with above, though, LPE would be a good starting point.

Jason Haines @ LPE

On our 1000 hp twin turbo Z06 C6 Corvettes we use a fabricated intake manifold that has provisions for 16 injectors. We then run 16 stock Z06 injectors. The second set of injectors is controlled by an auxiliary controller (PCS XFC) and is programmed to come in as we start to max out the stock injector duty cycle. We used a MAP based control strategy for the secondary injectors although we could also have used MAF based but that would have needed some more software and hardware development. The advantage of MAF based is that it would have been a potentially smoother transition from one system to the other (but we didn't run into any transition problems with the MAP based system). The primary injectors are controlled by the OEM ECM (with MAF) and the secondary injectors never come in during any closed loop operation so the ECM is unaware that they exist. This gives us great injector linearity since our idle and light load pulse widths are like stock.

Here is a picture of the 16 injector LS7 manifold on a 1000 hp twin turbo Z06 Corvette (sorry about the size - it is the only one I could find up on the Net):



We used a similar system on our 1600 hp standing mile Z06 Corvette although we had larger injectors in the secondary position (and maybe in the primary - I don't remember right now).

If you are using an auxiliary fuel control system you need to be careful about how you do the RPM limiter. You don't want to use a fuel based RPM limiter because making sure both systems cut off at the same time is difficult. Lots of fuel is ok, no fuel is ok but some fuel is dangerous (aka lean and damaging). You want to make sure you use a spark based RPM limit (or throttle or both).

Some aftermarket engine management systems can control 16 injectors. We did a roughly 1500 hp 540 BBC engine using BigStuff3 EFI and had 8 primary and 8 secondary injectors (again in a custom fabricated manifold). In this application we also staggered the injector operation so that we were not using the secondary 8 injectors except at higher boost levels when the first 8 were near maximum duty cycle. The BigStuff3 software allows you to adjust how the two sets of injectors are controlled. In this application we also had the fuel rails separated so that if the customer wanted we could add a second fuel tank, pump and feed/return line and then the second set of injectors could be fed with race fuel. This would allow you to run low boost/standard octane on the primary injectors and then run high boost/race gas with the secondary injectors.

Hard to see the intake and fuel rail but here is a video of that engine on the dyno:
VIDEO LINK

You could have the BigStuff3 control the engine and leave the OEM ECM/PCM in the vehicle to run the dash etc. You might have to run a few redundant sensors etc. or run signals to both EFI systems.

As an example of how nothing is ever new, the 1990-1995 ZR1 Corvettes (LT5 engine) have 16 injectors. The engine is a 4 valve DOHC engine with an intake manifold that has individual runners to each valve. Each injector feeds a valve/port. The secondary ports have a bypass valve in them. When the bypass is closed the secondary port is closed and the secondary injectors are not operating. When the secondary port opens the secondary injectors become operational. GM uses the same size injectors in both locations and then just halves the pulse width when the secondary injectors come one so that the effective fuel flow stays roughly the same (easy way to do it given the ECM processor power and IO they had available back then).

white01ss

iTrader: (37)

moehorsepower

iTrader: (3)

Not doubting your tuning abilities but unless like you say for reasons you want to run 16 injectors, maybe ask to see how others have run large injectors with good manners? Only reason I ask is because when I was supercharged, I pulled off my SP and ran NA with the same 80lb injectors with absolutely no problems on the street. Of course I had to tune for this. But like I say, if you are set on the 16 then maybe some one can help you out....This would be most interesting. Good Luck, I hope it works out for you..

Texas_WS6

iTrader: (9)

Thanks to all. I am even more interested in doing this now. please subscribe to this. I am sure I will have a few questions needed answered as I move forward with this.