I keep thinking about builing my own engine control computer. While musing this over I wonder if the geometries of the Fiero 2.8 fuel system would work with a sequential fuel injection scheme? I'm just considering a setup that gives full control over each cylinder.
Ideas anyone?
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11:04 PM
PFF
System Bot
PBJ Member
Posts: 4167 From: London, On., Canada Registered: Jan 2001
I don't know for sure but I think that you would need bigger injectors. The reason why I think this is because the mpi constantly sprays fuel and spi does it all at once and in order to do it all at once you would need a larger injector. my thoughts.
I'm not worried about injectors. The first issue to resolve is air flow patterns - hence why I'm curious about the geometries of the fuel system. This is going to require some research.
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12:10 AM
artherd Member
Posts: 4159 From: Petaluma, CA. USA Registered: Apr 2001
I don't see why it wouldn't *work* (though you'd either need to find a block that has a hall effect crank position sensor, or retrofit one on there somewhere...)
What would be really neat: Individual throttle bodies and injectors per cylinder, with Velocity Stacks!
Best! Ben.
------------------ Ben Cannon 88 Formula, T-top, Metalic Red. "Every Man Dies, not every man really Lives" 88 Formula, Northstar, Silver, In-Progreess. -Mel Gibson, "Braveheart"
Sequential fuel injection only functions at lower rpm's, a GM PCM reverts to batch fire after that. SFI's benefits are in emissions and fuel mileage improvements, and no real performance or hp increase will be obtained by switching from a MPFI system to SFI.
Prior to the switch to OBDII in 96 (94-95) there were a few application's that used SFI on the 60 degree V6. If one were really dead set on using SFI (not sure why), they could probably just modify this code a bit and pigyback the corresponding PCM into the Fiero harness. You would still have to use a DIS capable block or compatible harmonic balancer mount type crank trigger. (3.4 camaro/bird and 3100/3400 blocks are all DIS capable since they have a hole for crank sensor.) Unless you are using the 3100/3400 block, you would also need to invent some method for supplying a cam position signal.
[This message has been edited by 00lE (edited 01-21-2002).]
One magic word, fuel mileage improvement. Why use SFI, why have more control over each cylinder? It's a project - because I want to build my own engine control computer that will do SFI, MPI, and TBI. This semester for software design I'm going to design a flexible engine control system. This summer I'll implement the hardware and software; testing will be the fun part
What processor are you planning on using? Are you going to look for something with PWM and A to D built in or use seperate components. If I were going to build my own... I would use an ARM.
One other thing to consider for the project is the injector response over pressure differentials between manifold vacuum and fuel pressure. Getting air flow characteristics sounds doable through research but I think you will need injector vendors help for the second piece of info, or some fairly sophisticated measurement equipment to gather the needed data.
Also one other question from my previous post and that is are you just building fuel management or the whole enchilada?
[This message has been edited by 87GTZ34 (edited 01-21-2002).]
The goal of the project is not a replacement control just for the Fiero, but a flexible engine control for engine swap applications. The goal is to be able to control fuel and ignition - amongst other desirables. Consider,would it not be nice to be able to tune each cylinder of an engine - fuel delivery and ignition timing.
I haven't selected a microcontroller as that will be part of the detailed design. Currently I'm working on the architecture - high-level design. The design has to be flexible enough to work with OEM sensors and/or other modifications for performance applications.
I'm also curious if this could be a marketable product. I know of other products for converting to fuel injection, but know of none that offer the level of control, if so desired, that I would like to achieve.
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05:37 PM
Fiero STS Member
Posts: 2045 From: Wyoming, MN. usa Registered: Nov 2001
The Holley 950 control IS as well as fuel. I suggest you go to their web site and download the tech manual for the 950. You need to see all of the technical aspects of designing your own computer. There must be about 25 functions BESIDES fuel management. The Holley is a Batch fire system. Other than the design exercise, I don't see why you want SFI. It is not a higher performance system. In fact, it is lower performance. One of the main reasons GM went to SFI was torque management. They could selectively shut down various functions of the fuel process to limit torque for traction control, coast down, etc.
Individual cylinder control is where the production electronic systems are going. They use direct injection (designed for gasoline) for precise fuel control and ion monitoring systems (100 volt) to detect A/F, detonation, VE and combustion burn among other things. I think they might start arriving as early as 2004 if current development is on track. The ion monitoring will eventually replace MAF, MAP MAT and O2 sensors. This engines are to be true SFI with much higher performance mainly due to high pressure direct injection. You should look into the main developers of sensors like Bosch to see what development packages would go for. Of course this would add a high level reqt for a signal processor.
The original idea was SFI, but the new goal is a controller flexible to encompass a broad set of requirements. Designing the computer is not an issue as I have expertise in computer engineering and software engineering.
Inspiration for this project has come from seeing the different types of engine swaps people are doing and some of the problems they have encountered. Why not build a system flexible enough to read a variety of OEM sensors and control a variety of OEM actuators, not to mention aftermarket equipment. Plus, for a car that you actually want to drive on a weekly/daily basis why not be fuel efficient and still have performance. In a sense you could say I want my cake and to eat it too!
The descriptions of SFI thus far sounds like a mixed mode operation. The architecture of my system should be flexible enough to encompass this type of operation as well. I also favor the idea of being able to finely tune my engine for efficiency and performance.
Just a few thoughts...
Okay folks, how about pointers to technical data on the operation of SFI, MPFI, and TBI engines? Maybe a good book on engines?
