Is The 280Z Fuel Injection a "Good" System?

[Captain Obvious]

If the 280Z fuel injection system is in good shape and is working as originally intended, do people consider it a "good" system? Another way to ask that question is... If everything is working properly, is there any reason to be wanting something different or is the original Bosch system the best choice for a stock 280Z motor?

I do see people pulling the FI system off and replacing with carbs, but that seems to only be in cases where the FI isn't working properly. What about when it IS working properly? Do people feel the reason to change to something else?

I assume the FI system is expected to:

Provide better gas mileage vs carbs.

Provide better drivability over seasonal temperature swings vs. carbs

Produce lower emissions vs carbs.

What about performance vs. carbs?

[240260280z]

I have read many reports (including dyno data and mileage data) that newer EFI systems are capable of more fuel efficient operation and also capable of drawing more power from the engine than carbs and the stock EFI system.

The stock system is "good" ..... especially relative to 1976.

[FastWoman]

Performance? Probably a bit better than carbs. One of the bigger issues with the L-Jetronic system is the flow-restrictive airflow meter. A more modern EFI system with a MAP sensor or hot wire anenometer is going to be less flow restrictive. The same sort of flow restriction exists in the workings of any carburetor.

As far as I can tell from my computer, a more modern EFI does increase efficiency and performance over the L-Jet, but the improvement is not so great as to justify the effort (in many people's view). I'm told that our L28 engines, with their fixed-timing 2-valve/cyl architecture, are simply not going to deliver 30 mpg performance like a modern engine. I don't know whether that's true.

In my own experience, the properly functioning L-Jet functions as well as the best carburetors I've ever owned and far better than the other 80% of carburetors I've owned, with the possible exception of hot restarts. Could it be better? Sure. However, it's still pretty good.

[jmortensen]

The problem with the factory FI is that it cannot compensate for a large cam. A cam is critical to making power in the L, so if you're looking for power, stock FI is not where it's at. I think there are other issues like AFM restriction, plumbing, runner size, plenum volume, etc. Aftermarket programmable injection is a different story. The most powerful L-series that I've seen used a triple manifold with ITBs and Electromotive FI and ignition. I think the FI has come along since I was really looking at these things, so there might be better choices, but that was the thing to do about 10 years ago.

Gas mileage can be really good with carbs, and I think there is more power in a cammed L28 with SU's than you'll ever get out of the stock FI. Weather/altitude driveability, and emissions are always going to go to FI.

[Captain Obvious]

Thanks all. That's exactly the kind of info I was looking for. I'm not surprised at all that newer systems from today are much better than the L-Jet using technology from the early 70's. And it also makes sense that the stock system will run out of adjustability if you make significant enough engine modifications that it's not expecting.

Another question... Is the L-Jet brain analog or digital? In other words, is there a microprocessor in there, or is the whole thing done analog? I suspect it's digital, but just have to ask.

I just bought a 280 and now I gotta start my whole learning curve over again.

[sblake01]

It's analog, nothing but circuit boards. Think about the era it was designed/built in.....nothing 'micro' about the processors in use then and certainly there would have been no way to utilize any of that technology in an automobile.

Edited January 4, 2012 by sblake01

[Z train]

For the day,it was a really,REALLY good piece.But as mentioned,it doesn't like big sticks.THe newer systems will make more power only because they can adapt to bigger cams,change timing & the like.But bottom line is HP is a result of "airflow-not fuel delivery method".On a stock motor,putting carbs on isn't really a bright idea-absolutely no benefit.

CO-if you search under "ECM" i posted an article awhile back about some internal issues on the "computer".

[John Coffey]

In SCCA ITS trim a L28 with the OEM fuel injection can make 195 hp and still have very good driveability and fuel economy.

[Captain Obvious]

It's analog, nothing but circuit boards. Think about the era it was designed/built in.....nothing 'micro' about the processors in use then and certainly there would have been no way to utilize any of that technology in an automobile.

sblake01, I'm not sure what you meant by "nothing but circuit boards" and equating that to an analog design. Both an analog and a digital design could utilize a circuit board. "Digital" doesn't have to look like a PC. You're right about 'micro', but it's time relative, right? Haha!

So, just to be sure. Another way to ask the same question... Are there any software programmable devices inside that box, or not?

Z train, is this the post you were talking about?

http://www.classiczcars.com/forums/showthread.php?36903-280Z-ZX-ECM-tech

[sblake01]

There is nothing programmable. I wasn't equating "nothing but circuit boards" to analog but it's an analog circuit board. There are no microprocessors or anything else that can be communicated with. I should have been clearer.

Edited January 4, 2012 by sblake01

[jmortensen]

I was pretty sure the FI systems could be chipped if not programmed. In fact, I thought they changed the rules a couple years ago to allow that in ITS, and that's what they're doing to get the kind of power John mentioned.

[doradox]

http://en.wikipedia.org/wiki/Jetronic

Looks like L-Jet is analog.