Idea for EFI mod

[conedodger]

I know a couple people who put the Megasquirt board inside the stock box to drive the stock sensors. Looks original 'cept it's digital.

[FastWoman]

Really! OK, that changes everything. I suspect a MegaSquirt system is in my future -- or at least a MicroSquirt mounted inside the OEM ECU box.

That said, my car is running pretty well right now, so I think that's a project I'll save for (much) later. Of course I'll keep a lazy eye on what Cozye is doing too.

Maybe by the time I'm ready to convert, some kind soul will sell a turn-key, plug-n-play ECU retrofit. That would be nice.

[Pomorza]

Cozye, yes, you're that special "someone!"

Rob, I agree that the L-Jetronic system is pretty dumb, but I have a strange affinity for primitive technologies. I want a system that utilizes the stock, vane-type AFM, just because it's old and different. I have no special affinity for the analog electronics in the ECU. I suppose my ideal system would be a MegaSquirt digital ECU that would utilize the signal from the vane AFM and perhaps also fine-tune via an O2 sensor.

Another possibility, since it's just a dumb analog ECU, would be to build a fully adjustable analog ECU with modern linear circuitry design. This would require that I reverse-engineer the original ECU, of course.

FAIW, I made a special extension cord for my AFR adjustment potentiometer, so that I could have my wonderful assistant drive my car while I made AFR adjustments from the passenger seat -- e.g. seeking out the fastest cruising speed at constant throttle. I found that the ideal settings under load were pretty similar to the ideal settings in the driveway. (I was rather surprised by that.)

BTW, I can buy a "rebuilt" ECU through AutoZone and am certain I can find one elsewhere too. However, all the electronics are proprietary, mysterious, and obsolete. I suspect the "rebuilding" process amounts to little more than cleaning the thing up, making it look pretty, fixing anything obvious (e.g. a bad solder joint), putting it in a nice box, selling it, and hoping it doesn't get returned. Short of having Hitachi's documentation and a stock of NOS replacement parts, I doubt there's anything else that can be done.

Fastchick, I agree with nearly everything you've said above except for the fact that you called the F.I system dumb. (I guess Ron said that) You must realize that this was pretty much cutting edge technology back in the 70's. Hell I don't believe the U.S even had F.I cars back then. (I don't know I was born in 87). But it is rather simple, (I guess your term for dumb) as it is just a basic input output device. This has it's ups and downs. (I just came home from the mechanic where someones 99 Eclipse was going to cost 3K to fix computer related things).

As the old saying goes, if one is determined enough one can accomplish anything. I'm pretty sure if one tired you could get a modern EFI system to resemble the old school L-Jets. I've done "some" work on the EFI system on the Z but I usually go down to my mechanic if I need something clarified (or pass emissions here in Arizona).

Jan

[sblake01]

Hell I don't believe the U.S even had F.I cars back then.

G.M. had F.I. as early as 1957 on Corvettes and Pontiac Bonnevilles almost 2 decades years before Datsuns L-jetronic based JECS.

[Powerglide]

GM's foray into fuel injection began with the 1957 model year. However, it was strictly a mechanical/analog system. Fuel metering was MUCH more precise than a carburator. But the design still relied on vacuum/venturi effect. AMC and Chrysler implemented ELECTRONIC fuel injection that was released for the 1957 and 1958 model years, respectively. It was expensive. didn't sell and was difficult for contemporary dealer service departments to service. Look here: http://en.wikipedia.org/wiki/Fuel_injection

Caddilac had EFI in the early to mid 1970s. Mercedes in 1968!

Your Megasqirit project seems like an interesting technical exercise. But other than that---I fail to see the practical gains you perceive once you spend all that time and money. On a STOCK motor, you WILL get slightly enhanced driveability and milage and perhaps cleaner emmissions. Power gains will be VERY modest. The stock EFI definitely has it's limitations---I know that from experience. I own a '76 EFI Z car. But---if the motor is in good mechanical condition and it's TUNED PROPERLY---the stock EFI will deliver good power, milage in the 16-27 MPG range (depending on gearing) and is DEAD RELAIBLE. It's so simple too.

If your car is "car is running pretty well right now"...why go through the hassle???

Edited December 10, 2010 by Powerglide

[sblake01]

Agreed and agreed. A modern engine has other things to go with the modern fuel injection. Distributor-less ignition, variable valve timing, etc. I had no problem with the two Datsun EFI cars I owned. Their engines and EFI components were in above average condition and they both did what they were supposed to do. I seemed to be lucky enough during my ownership to avoid many of the problems I see being discussed here and also was able to solve the minor ones that did come up.

Edited December 10, 2010 by sblake01

[FastWoman]

Jan, there's dumb and dumber, so to speak. The early ECUs with linear circuitry and no lambda feedback are dumb, but carbs are dumber. Either can meter fuel rather accurately when in good repair. The problem is that both are subject to inaccuracies and become tempermental over time. Cozye and I have just discovered that our ECUs have drifted over time in their output properties and required rather strong corrections to the mix through the coolant temp circuit.

My comment about "dumb" wasn't meant to be disparaging. I remember when I bought my '75 Z (not the one I currently own) in 1982. It was my first EFI car, and I thought it was the cat's pajamas! Even then (with an 8 year old car) the EFI was quite tempermental, but there was a certain magic about it that I loved.

I also don't want to disparage linear circuitry too much, because I've designed and built so much of it. I suppose familiarity breeds contempt. I know how these sorts of circuits fail, and I understand what toll is exacted with time and usage. There is a HUGE difference between linear and digital control. Both have their respective strengths and weaknesses. However, a digital system will be very stable until it fails. The linear sensors are of course subject to deterioration and drift, but those are all individually serviceable. Ultimately the O2 sensor is the calibration point, so if all the sensors are within reasonable range, the engine will run very well.

Anyway, the question was posed as to the purpose of such an exercise. My answer is that our ECUs are starting to degrade in very predictable ways that I've seen over and over again in multitudes of linear devices. They're elderly and probably nearing the end of their service life, even with bandaid patches like Cozye and I have used. And once these devices fail, they will not be repairable, owing to proprietary circuitry. (You are warned! ) Anyone interested in preserving the old hardware, rather than retrofitting with new technology, is faced with this reality. There is no absolute solution to this problem, but offloading power demands from the device is one possible way to delay the inevitable.

Please note that the huge investment of time and money I'm proposing is probably 30 min and a few bucks in parts.

To go totally nerdy on y'all, I see our Z's as examples of V-GER from the original Star Trek movie. They are humble devices that are patched, augmented and retrofitted to remain functional. But at their core is the same charming core device. I like preserving as much of that device as possible, or at least that's the way I feel about it at this stage in my life.

Edited December 10, 2010 by FastWoman

[Pomorza]

Thanks guys for the explanation here I did forget that Vettes had fuel injection back in the day.

[Powerglide]

Values typically drift with OLD oil filled capacitors. I have a TV built in 1947. The vacuum tubes are rock solid for MANY hours of use. It's the paper caps that drift and require replacement from time to time---mostly from DIS-use.

Have you PERSONALLY observed said drift in ICs on a Z car ECU? I think this highly unlikely---but I really can't speak with much authority on that. Certainly specific circuits within the ECU can and do fail for a variety of reasons (like voltage spikes, poor grounding, etc.). But electronic drift within the ECU or the AFM? That would REALLY surprise me. NOW---changes in resisatance in the WTS or the CHTS or the Thermotime-switch??? That is quite COMMON..! The results of which we are all familiar.

Edited December 10, 2010 by Powerglide

[LeonV]

To add some more to the history aspect of this post, the first mass-market EFI system was the Bosch D-Jetronic in the 1967 VW Type 3. Mercedes used direct fuel injection in 1954 (300SL)!

[FastWoman]

Powerglide, Cozye and I have just been through the mill on this issue. Both of us have restored our intake/fuel systems to rock-solid, within OEM specs status. Mine might even be more so, as I redid my entire system from the fuel tank to the injector, including completely new injectors and electrical connectors. We've both found that both of our ECUs ran our engines quite lean -- lean enough to create backfire and a vacuum of 14 or 15 in Hg, but not lean enough to keep my local Z specialist from commenting that my engine ran well (go figure!). In addition, my spare ECU ran the engine just as lean.

The fix for both of us was resistors in series with the coolant temp sensor, which lengthened the output pulse proportionally at all delivery levels. In my case, the needed resistance was substantial -- about 2.4 kOhms. According to Cozye, who has researched the issue far more than I have, this is a known issue with our ECUs and a very common fix. So yes, these black boxes do drift. Semiconductors do break down and lose both gain and linearity. I've refurbed enough early hybrid tube/solid state oscilloscopes (similar generation of component solid state electronics) to have seen this with some predictability and regularity.

They're not all linear ICs in the ECU, BTW. There's a lot of plain vanilla component transistor circuitry as well. It's impossible to know much about these circuits without schematics and components data, and as such, they would be really hard to service. One might be able to replace some of the 1st gen oil-canned transistors (of unknown identity), for instance, but at what current gain? Forget replacing the ICs, except with little daughter boards. They are canned in oil, like the transistors -- first I've ever seen packaged like that. You won't find THOSE anywhere. I think when our boards finally start dying, we're going to have to switch over to Megasquirt/Microsquirt retrofits.

I think it'd be great if someone figured out a Microsquirt retrofit for a plug and play ECU -- i.e. by retrofitting the board in the stock box, with the stock connections and program suitable for the 280Z. It's my understanding that these systems can run on the old vane AFMs and w/o O2 sensor.

Edited December 10, 2010 by FastWoman

[Powerglide]

FORGIVE ME... But, NOPE. I don't buy it. The ECU is not causing your car to run lean. There are other factors at work here. A motor pulling 14 or 15 inches of vacuum has an air leak, retarded ignition timing, incorrect valve timing or LOW compression. The AFM controls injector pulse width below 3000 rpm. Suggest you check voltages and adjustment there too. Also consider the fact that a worn motor wants more fuel throughout it's RPM range. Especially at and just off idle. If your motor is old/worn/poorly rebuilt it will want/need more fuel to run well. Your stock ECU (and the entire EFI system) is having a difficult time coping with your worn/out of spec motor. The external inputs and the ECU are designed to work within certain somewhat narrow parameters that were built into the engines by the the engineers. When an L-Series motor wears, it wants MORE FUEL. When an L-Series motor is out of adjustment, it wants more fuel. That's why your motor is lean. It's NOT the fault of some circuit that may have drifted inside the ECU. I'd bet money on it.