Carbs or Fuel injection ? Options

[ILM914]

Hi folks a 914"expert said carbs will burn the valves on a 914 and not run well. Is this true? is the fuel economy worse when using duel carbs? Would you run orig fuel injection on a 2.0 or carbs thank you, Joe

[bbrock]

My advice is to forget you ever heard the word "carb" and just go FI. Either modern or stock; your choice.

I'm one of those who was perplexed by how to repair an aging D-Jet so in the mid-80s bought a pair of Webers like many people at the time, and installed a mild carb cam in the engine I was rebuilding. Then the project was mothballed for 35 years. In spring of 2021 I finally had my car ready for the road and was excited to finally try out my fancy carbs. After 7,000 miles, I hate them and plan to convert to megasquirt FI over the winter.

It took some work to dial them in with a wideband but my car runs fabulously with the carbs and I'm getting low to mid 30s mpg highway. So why do I hate them? Several reasons:

1. they stink - as previously noted, my car and garage stink like gasoline. Oh the nostalgia of the 70s when we were all breathing leaded gasoline. And this is with a custom air cleaner that is sealed and not open to the atmosphere like the crappy K&N filters most carb conversions run.

2. no altitude adjustment - I live where a day's drive can take me through a range of several thousand feet elevation. My carbs are adjusted at 6,000 ft. but when I go over high mountain passes, the engine gets wimpy, and I worry about running too lean if I go too low. I honestly don't know how D-Jet compares as I never drove my car at altitude when I was running it, but the megasquirt I plan will have real time barometric adjustment.

3. cold start woes - When the car sits in sub-freezing temps for a long time, it is a bitch to get started. No doubt this is because I spent a lot of time dialing in the accelerator pumps for efficiency. They squirt just enough to provide smooth acceleration transitioning from the idle to main circuits, but no more. That's the problem with carbs. I have to choose between efficiency or cold start. With FI, you don't have to choose. You get both.

4. Unpredictable idle - I get smooth idle at 600-800 rpm which is great. But when the weather changes, so does the idle. I find myself having to feather the throttle at stop signs some days, and other days not. Wouldn't it be great if there was a way to monitor idle speed and adjust the fuel mix to keep it where you want? Oh right, there is.

5. too much compromise - driving around with wide band to dial in the carbs showed me just how crude carbs are at managing AFR. All they can do is provide an average that is acceptable through the rpm range. As others have said, the real strength of FI is being able to more precisely meter fuel through varying conditions. These compromises show in my fuel economy. 32 mpg highway seems pretty good, but my old records show the same engine with over 100k miles on the clock was consistently returning 36-37 mpg highway with the D-Jet.

Our 914s were an early first step to a future beyond carbs. Why downgrade the engine by stepping backward?

[JamesM]

2. no altitude adjustment - I live where a day's drive can take me through a range of several thousand feet elevation. My carbs are adjusted at 6,000 ft. but when I go over high mountain passes, the engine gets wimpy, and I worry about running too lean if I go too low. I honestly don't know how D-Jet compares as I never drove my car at altitude when I was running it, but the megasquirt I plan will have real time barometric adjustment.

D-jet used on 914s has altitude correction built in as a function of the MPS. It works very well.

On more than one Colorado mountain pass my D-jet 1.7 has zipped by carb conversion guys stalled out on the side of the road.