Based on the fact that the Aeromotive FMU reacts to increased pressure from the manifold, would I be correct to assume that this unit is basically an Absolute Manifold Pressure sensor? If this is the case, depending on your needs and the HP limits of this system it seems as if you actually can use this unit with the ATI procharger without a problem as long as you find some way of tunning it in accordance with the timing..I am wondering if there is a way to retard the timing based on the pressure the FMU senses???I dont know what to do at this point....I was really looking to get rid of this FMU but I may keep it and tune my piggy back unit I am working on along with the FMU to contro EXTRA injectors..I dont know...Any of you technical Gurus feel free to jump in and give me your 2 cents...

 

This was the very same dilemma I started with a month ago. The factory timing can be adjusted a bunch of different ways. I ended up using the E-Manage for the future possibility of other adjustments it can make. For right now it is only be used as a very accurate, tunable boost retard unit. When I get the new injectors and fuel pump I will be able to turn off or down adjust the DFMU and associated fuel pump. If you go with a fixed setting solution for the timing curve and you make other improvements you are stuck with a device that is not adjustable otherwise. There are a few other adjustable timing devices out there for this, the E-Manage is the one I went with.

 

So the E-manage does your timing and the FMU does your fuel..Are your detonation problems solved and how did you DYNO?

 

This is the whole reason some of us are using the J&S.

-J&S will do it, has its own map sensor like the dfmu

-E-manage will do it with optional map sensor

-Your piggyback should do it if it uses a map sensor

 

The piggy back can use a MAP sensor and it can retard the timing based on rpm and additional retard on boost..It is very tunable to exact rpms and you can see exactly what is going on.But I think the only advantage I would have over the J&S would be the control of A/F mixtures for a fine tune and a switchable MAP for 2 different states of tune on the fly...I just dont know if its worth it for me to keep the DFMU at this point as it is a very good unit after doing some research..I just dont know what the limits of the DFMU and the STOCK injectors and PUMP are...Is anyone familiar with how reliable overdriving the stock injectors is?

 

If your unit can control bigger injectors, you may as well run them IMHO. A lot of people use fmu setups on numerous types of cars without any problems, but it is possible that you could eventually have problems because of the elevated fuel pressures. There are a lot of things that will affect this, so I personally think that only time will tell. If you're going for a lot more power over the standard kit, then you'll probably have to run bigger injectors anyway since you only have so much pulsewidth and fuel pressure available.

 

I forgot to ask if this unit can TRIM the injector pulse at low rpms to compensate for the larger injectors...I dont want to run like crap at idle, and I dont feel like spending cash on the TS reflash..This is where my problem lies..I know the DFMU can run ito problems but I would also assume anything you put on the car can run ito problems at some point..I just dont know how reliable the DMFU is..
The solution I see most cost effective is the EXTRA injectors controlled by the Piggy back, and leave the stock injectors for idle and low rpms..Kind of like a dual stage injector set up like the Vettes used to run, or still do..I am not sure..This method I would assume would also require a new fuel pump or an extra one..Do you know the limits of the stock fuel pump??
Oh my..decisions decisions....

 

oh..ps in case anyone was wondering that little Aeromotive DFMU cost like $399-499!!!

 

Actually to be anally technical, the DFMU doesn't actually actually have a MAP, it has a differential pressure transducer in there. A MAP is something that takes measurements from absolute zero pressure(vacuum) and measures up from that point. The differential pressure sensor simply makes a comparison between outside air pressure to manifold pressure and calculates the appropriate slider to use based on the scale setting.

My plan is to continue to use the FMU for fuel tuning and a J&S box to control timing. There are a lot of ways to do it and yes I am mildly concerned about the effects of long term high fuel pressures on the injectors, but I'm holding out for a fuel system that is proven to work, inexpensive and totally tunable by the end user. Right now the FMU is the only thing IMO that meets those criteria for me. Granted, I may be waiting a loooonnnng time for something else, but my FMU will work fine until then.

 

alright!!!Jesse and Gary are her!!Let the technical mudslinging begin!!
On a serious note..How do you feel about the Extra injector method?either in the rail or into the manifold???Seems like the guy I am dealing with is a big fan of it and has used it on some really serious hot rods for some serious customers..Just a thought that would still require the addition of another fuel pump right?

 

I don't see a problem with the additional injector thing at all. I would actually tend to favor that over a modification of the stock ECU and larger injectors. Mainly because it's generally a cheaper route and less chance of screwups.

I don't really know where the best location for the extra injector would be. I would assume right after the throttle body, but not in the plenum itself so the fuel can atomize.

The only bad thing about it that I could come up with is that now you're engines health is relying on that single injector.

It might require an aux fuel pump, depending on the fuel pressures the piggyback ECU is relying on to calculate the pulse widths for the additional injector. The stock pump can flow enough fuel, but will the stock Fuel pressures be appropriate for the piggyback controller?? That's a question only the manufacturer of the piggyback can answer.

 

I think the extra injector method sounds promising.......perhaps you could find out how Stillen did it, and try it the same way

i'm not sure how i feel about the additional fuel pump.....i've always found that the less amount of moving parts in a system, the better......perhaps a larger in-tank pump would do the trick

i can't really agree with jesse about the entire engines life depending on that one injector.......there's already six in the system that could kill the engine if one of them were to go partially bad.......but i understand what he's saying.......i just think that applies to all the injectors

 

Have not dyno'd yet. Other than a need for a little more fuel my problems are solved. I do not get detonation anymore. I still need more fuel to get all the HP I should be getting.

 

I'm not sure were we are here so I will throw in this. The E-Manage has a larger injector swap feature built in especially for injector swaps and it has a special function that does some trick stuff with larger injectors and idling problems. I don’t know how that works at this point but it seems interesting.

 

What do you concider inexpensive?

 

Well, not spending $900 on injectors for a start.

 

Well, kinda. The difference is, if a regular injector fails, that cylinder will have no fuel period. Thus won't run lean because there's no fuel to burn. With an additional injector failure, you'll still have fuel in that cylinder, from the stock injectors, but not enough because the additional injector went kaput. Without that additional injector, you'd be running all six cylinders lean the second you went into boost. Now will the additional injector fail? Probably not for years and years and years. Injectors have a VERY long lifetime of operation. So a maintenance schedule, maybe have the injector tested every 3 years or something would help to eliminate the possibility of failure.

Edit: just reread EJ's post. Yes if an injector partially went bad (meaning slow to open) it would cause the same problem. Because it's just a solenoid, when injectors go bad, they generally either just stop working entirely or only work every once in a while. They are designed that way so a single bad fuel injector won't blow up an engine.

 

If the new fuel injector is placed just after the throttle body, yet not in the plenum, then it will be supplying additional fuel to all of the cylinders.......if one of those cylinders' original injectors were to go bad, there would be a small amount of fuel in that cylinder anyway from the additional injector

 

Ahh, I see what you're saying. You're right, I guess I should've said that adding the 7th injector creates a situation where if a single injector fails, you will run lean. In your above quote I was comparing a seventh injector setup to an upgraded stock injector scenario. It's still a weakest link in the chain type thing and if any of them go you're up **** creek. Whereas upgraded injectors and flashed ECU will not cause an engine to blow if an injector fails.