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

[914Sixer]

No carbs will not burn valves. Fuel economy is worse with carbs. Good running 2.0L should get 28 mpg or better. Factory got it right all along for street cars. Big engines are another story all together.

[dr914@autoatlanta.com]

I second the reply. Carbs will NOT burn the valves, burned valves can occur from miles and miles and miles of use and infrequent valve adjustments, carbs will lead to shorter engine life because they do not precisely control the mixture and are usually running richer

Fuel injection is always the best bet for a 914

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

[GregAmy]

20 years ago the world was generally perplexed by 1970s fuel injection (coupled to its inability to handle much mods) and was wholeheartedly supporting converting to carbs.

Today, this community has realized the value of those early-gen systems and their better driveability and economy. Further, many/most of the degradation problems have been identified and solutions provided by the aftermarket.

This thread will be filled with "keep the FI" comments (including from me) with sprinklings of "I prefer carbs".

IMO, if you still have the original parts, and there's no plans for significant modifications (e.g., big cams and compression) then the stock D-Jet is my preference.

[fiacra]

No carbs will not burn valves. Fuel economy is worse with carbs. Good running 2.0L should get 28 mpg or better. Factory got it right all along for street cars. Big engines are another story all together.

(IMG:style_emoticons/default/agree.gif) I've driven both and I vastly prefer FI. Once the FI is nicely sorted and you have gained a good understanding of the intricacies of the system it will serve you well. I suspect that most carb conversions are done out of frustration with trouble sourcing FI parts and troubleshooting D-Jet/L-Jet systems. Also carbed systems tend to have the lingering smell of gasoline at all times. I personally hate that, although I know some people think of it like perfume.

I see you already PM'd the person selling a full FI system in the classified section. It looks like a decent system at a good price. There are lots of resources and vendors on this site that can be of help in getting the original FI system sorted out. Good luck whichever way you decide to go!

[TheCabinetmaker]

20 years ago the world was generally perplexed by 1970s fuel injection (coupled to its inability to handle much mods) and was wholeheartedly supporting converting to carbs.

Today, this community has realized the value of those early-gen systems and their better driveability and economy. Further, many/most of the degradation problems have been identified and solutions provided by the aftermarket.

This thread will be filled with "keep the FI" comments (including from me) with sprinklings of "I prefer carbs".

IMO, if you still have the original parts, and there's no plans for significant modifications (e.g., big cams and compression) then the stock D-Jet is my preference.

I for one, have known that since the 70's, and still believe it.

[Root_Werks]

Some threads on the subject:

http://www.914world.com/bbs2/index.php?sho...29&hl=carbs

http://www.914world.com/bbs2/index.php?sho...=211615&hl=

http://www.914world.com/bbs2/index.php?sho...=212060&hl=

[Shivers]

I've been running carbs since 83'. No burnt valves. Now I wish I'd kept all of those parts for FI. You'd need a proper cam to run carbs. Running on the freeway and staying out of it, I got pretty good mileage. Running around town is a different story.

[Jack Standz]

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

Sorry, but FI isn't always best for a 914!! Try telling that to anyone with an original 914/6. As I remember it, they all came with carbs. So, run what you want. Either FI or carbs can be a good choice.

Dual carbs will run well, if you properly tune them even on a modified motor. Why? Because you can tune the heck out of them. You can't do that with stock fuel injection. Once the stock fuel injection hits its limits, you'll need to go to an after market FI system or modify the stock FI system.

Stay away from the single carb systems. Burnt valves can happen from running the motor too lean (either carb or FI), which causes the motor to run too hot and the exhaust valves can just get cooked til they die. Also, as mentioned, not checking valve clearances often enough and running the lash too tight can also burn the valves.

As to fuel economy, FI generally has the slight edge. But, again you can tune the carbs to optimize fuell economy and considering the form of FI the stock 914/4 came with (not as good as modern FI systems), you'll be just fine, if you choose to run carbs.

So, if you have FI, run it. If you have carbs, run them.

[Lockwodo]

I've had my '74 2.0 for almost a year now. It took a while to get the DJet system sorted, but having done that the car runs great now. I tested each FI component, and replaced the MPS, the TPS board, all the vacuum tubing, plugs and wires, and installed a 123 distributor to eliminate runability issues caused by the stock worn disty.

[NARP74]

The decision was made for me when I bought my first 914, old race car, dual carbs. Not sure I have the patience to go back to original FI. Eric at PMB is doing some cool stuff with modern FI, looks like dual carbs with all the advantages of a modern programmable FI system. Probably pricey in the 1st version, but something to watch as it evolves and the price comes down a bit.

[lesorubcheek]

Sorry, but FI isn't always best for a 914!! Try telling that to anyone with an original 914/6. As I remember it, they all came with carbs. So, run what you want. Either FI or carbs can be a good choice.

Dual carbs will run well, if you properly tune them even on a modified motor. Why? Because you can tune the heck out of them. You can't do that with stock fuel injection. Once the stock fuel injection hits its limits, you'll need to go to an after market FI system or modify the stock FI system.

Stay away from the single carb systems. Burnt valves can happen from running the motor too lean (either carb or FI), which causes the motor to run too hot and the exhaust valves can just get cooked til they die. Also, as mentioned, not checking valve clearances often enough and running the lash too tight can also burn the valves.

As to fuel economy, FI generally has the slight edge. But, again you can tune the carbs to optimize fuell economy and considering the form of FI the stock 914/4 came with (not as good as modern FI systems), you'll be just fine, if you choose to run carbs.

So, if you have FI, run it. If you have carbs, run them.

(IMG:style_emoticons/default/agree.gif)

It really comes down to what you want from your car. If you want a pristine original example, FI is the obvious choice. If you want a little more power and getting that on a budget, a new cam and carbs is a relatively easy path. Our car was fitted with dual IDFs ever since we got it in 1980, so I can't compare to an original FI car, but it was reliable and fun with plenty of pep. Highway driving was easy to get around 30mpg. City was obviously worse, but never tried to calculate since never drove just in town. Carbs are not evil, just not as efficient as a properly setup FI system. You could make the same argument that old D and L jet FIs are not as efficient as newer systems. Use whatever you decide is the best overall choice based upon your criteria, after all, it's your car. Just enjoy it.

Dan

[VaccaRabite]

Carbs have been run on 914s for decades. You can run them just fine.

But you will run BETTER with fuel injection. Period.

Zach

[mlindner]

Ran dual Webers on my old 1.8 with a cam, always ran great, lots of power. Went the same route with the new 2.2L six with S pistons, Mod-Solex cams and 40 PMO's.

[JamesJ]

I have one of each. My carb'd car has performance enhancements that require carbs or aftermarket EFI. My stock FI car is smoother to drive and gets better gas mileage. If you are keeping the car stock, then I would recommend keeping the FI.

[ILM914]

Thank you guys Much appreciated

[mb911]

Can’t wait to put fuel injection on my -6 but it needs to wait for now. Inflation is killing me lol

[ClayPerrine]

The 911 engine used in the 914-6 was designed to use carburetors, and was later converted to CIS (on the 73.5 911T), then Motronic fuel injection (on the 3.2 Carrera). Both fuel injection changes improved both performance and fuel mileage.

The VW based Type IV motor was designed with fuel injection from the start. When it is backdated to carbs, both the performance and fuel mileage suffer. When you change the internals on the engine and exceed the limits of the stock injection then you justify going to carbs. And these days, the programmable EFI out there is a far better choice than carbs.

There is a reason that carbs are no longer sold on any production vehicles in the US. Fuel injection is a far better, more efficient system. Why would you want to go back to something more primitive? Gas is too expensive to waste these days.

The only reason we still have the factory Weber carbs on our 914-6 is it came from the factory that way, and we are trying to preserve it and keep it as original as possible.

Clay

[Rand]

I don't know if there is a more highly-debated subject. Of course FI is better DUH, like ALL car manufactures have figured out LOL IDjUTS...

[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?