Fuel Inj v Carbs v Drivability, What's easier for new teener to drive? Options

[c12croft]

[i][b] When it comes to drivability and general ease of driving for my wife's sake, chosing between 46 Dellortos, Webbers, and properly fuctioning fuel injection is a no brainer I assume.
Has anyone been successful with getting their better half to master driving their 914 carb conversions?
It's only my physical disablity that's forcing me to give up my driver's seat.
(IMG:style_emoticons/default/driving-girl.gif)

[byndbad914]

frankly, a well-tuned carburetor will run just as well as f.i. so you really shouldn't sense much difference IMO. That said, the issue with carbs is that it is really hard to tune for every situation (idle v. mid-range v. WOT) so you tend to tune for what you use the most and let the one used the least be sacrificed a bit. For example, if you are always on it, then tune for WOT and it may be rather fat thru the mid-range. you won't feel it per se while driving at mid-range, but the fuel curve isn't as efficient there so you may be rich. Tune for normal driving, then you might be a bit lean at WOT.

F.I. is nice from an efficiency standpoint as with enough feedback loops the fuel mixture can be tuned for max efficiency at all data points. If you are good with carbs, then tuning shouldn't be that tough for the "best of all worlds".

[toon1]

Is there a drivability prob. now? if so wht is it?

[Tobra]

FI is superior in general. If you are going up and down in altitude, no question FI would be the best choice, to get carbs to run decent at altitude requires rejet

[Brando]

With the right FI setup, you can meet and/or exceed carbureted power. Both systems tuned properly will net reliability.

A properly configured PEFI system will run excellent.
A properly configured carb system will run excellent.

Only differences would be... How many possible failure points in each? How tuneable are they? How expensive are they?

Carbs you get three settings usually. 1) Idle 2) Midrange 3) WOT.
PEFI you get... Wow, the whole RPM range can be configured.

But I like FI, and would love to switch to a PEFI system.

[r_towle]

I would leave it the way it is.
If you can still drive an automatic car, lets make your 914 an automatic.

I am close enough to help with that project.

Rich

[toon1]

With the right FI setup, you can meet and/or exceed carbureted power. Both systems tuned properly will net reliability.

A properly configured PEFI system will run excellent.
A properly configured carb system will run excellent.

Only differences would be... How many possible failure points in each? How tuneable are they? How expensive are they?

Carbs you get three settings usually. 1) Idle 2) Midrange 3) WOT.
PEFI you get... Wow, the whole RPM range can be configured.

But I like FI, and would love to switch to a PEFI system.

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)


I like FI! (no offense carb. guy's, personal opinion) I have just switched to a MS, MAN what a difference! WAY more drivablity over stock EFI.

They can be done for a modest price. A base PEFI is probably cheaper than carbs.

And if your disability prevents you from driving you can do all the tuning in the world with your wife driving (IMG:style_emoticons/default/biggrin.gif)



Hey Brando , what's preventing you from going to a PEFI?

[Bleyseng]

Carbs suffer from changing conditions....cold/hot, elevation etc..no chokes makes cold starts a headache until warmup.

Djet starts up easy, runs fine cold and hot, up or down as its self adjusting and provides excellent hp and Mpg.

My fiance Monique only drives the 914 when its running sweet as she has a hard enough time with the shifting. (IMG:style_emoticons/default/chairfall.gif)

[pbanders]

Overall, FI is better in theory and often in practice. However, as our cars are now nearly 40 years old, getting your FI system in proper order can be difficult and expensive. Another issue is that the FI systems on our cars, D-Jet and L-Jet, were the earliest electronic injection systems, and are both essentially "open-loop" systems. Unlike modern systems, they have limited ability to adapt to the aging of the engine, and have no active control of the idle. As a result, the system requires precise adjustment to operate at its best. It's still better than carbs at dealing with the full load range of the engine, and altitude compensation, as well as warm-up (when adjusted correctly).

[IronHillRestorations]

Good stock injection is quieter, generally more fuel efficient, and gives good throttle response. In theory your engine should last longer too, with the precise fuel metering of injection. Personally I think the biggest problem you've got with the stock injection system is age of components and replacement parts. Also you are limited on what you can do to increase performance. All in all though a stock injected 914 is a fun driving car, BUT a dual Weber'd 914 has never left me stranded due to a fuel problem.

As far as "driveability" I agree with Bynbad. A properly matched (meaning correct venturi & jet pkg for the engine) set of carbs and a fuel injected engine shouldn't run that much different. The biggest problem you get into with carbs is having the wrong venturi and jet package, or even the wrong carb size (usually too big). You've got to match the carbs to the engine (cam & displacement). Too often you see too big carbs on a stock engine, running like crap.

I don't know enough about the PEFI systems out there, but I'm sure we'll see more inprovements in the future. The biggest problem I see with some of that stuff is user development, which I mean to be the user having to develop their own solution for the problems they have with system they have chosen. But again I'm fairly ignorant on aftermarket injection systems.

[Brando]

With the right FI setup, you can meet and/or exceed carbureted power. Both systems tuned properly will net reliability.

A properly configured PEFI system will run excellent.
A properly configured carb system will run excellent.

Only differences would be... How many possible failure points in each? How tuneable are they? How expensive are they?

Carbs you get three settings usually. 1) Idle 2) Midrange 3) WOT.
PEFI you get... Wow, the whole RPM range can be configured.

But I like FI, and would love to switch to a PEFI system.

(IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif) (IMG:style_emoticons/default/agree.gif)


I like FI! (no offense carb. guy's, personal opinion) I have just switched to a MS, MAN what a difference! WAY more drivablity over stock EFI.

They can be done for a modest price. A base PEFI is probably cheaper than carbs.

And if your disability prevents you from driving you can do all the tuning in the world with your wife driving (IMG:style_emoticons/default/biggrin.gif)



Hey Brando , what's preventing you from going to a PEFI?

What's stopping me? Same thing that stops most people... Cost and time of install. I can't be without a vehicle for more than a day and a PEFI install would take maybe a week for me, because I'd have to tune it too.

[pbanders]

With the right FI setup, you can meet and/or exceed carbureted power. Both systems tuned properly will net reliability.

A properly configured PEFI system will run excellent.
A properly configured carb system will run excellent.

Only differences would be... How many possible failure points in each? How tuneable are they? How expensive are they?

Carbs you get three settings usually. 1) Idle 2) Midrange 3) WOT.
PEFI you get... Wow, the whole RPM range can be configured.

But I like FI, and would love to switch to a PEFI system.

I hear you - I'd like to go to PEFI on my 914, too.

There are a lot of different operating conditions that a fuel system needs to accomodate, and many of these conditions are interactive:

1. Cold start (sitting overnight)
2. Cold-cold start (engine temperature under 32 deg. F)
3. Warm start (engine not fully warmed up)
4. Hot start (engine fully warmed up)
5. Warm-up (affects all load and engine speed mixtures)
6. Part-load (low throttle angle)
7. Moderate load (transition region)
8. Full-load (WOT)
9. Overrun (closed throttle, coasting)
10. Acceleration (rapid throttle closing)
11. Altitude compensation
12. Ambient air temperature

Oh, and you've got to do all of this while optimizing performance, maintaining good fuel economy, and producing low HC, CO, and NOx emissions.

Doing all that with carbs proved impossible for auto manufacturers as emissions regulations tightened, hence the move to EFI through the 70's and 80's. I was always impressed by Honda, how long they held out against going to EFI. Some of the carbs they put on the Accord in the '80s were freakin' insane, with about a billion vacuum hoses and all kinds of little gizmos attached.

I had a 2.2L with 40IDF Webers before I converted back to D-Jet FI. I really liked that motor, it had gobs of power and sounded great. Wasn't that bad to tune and maintain, but you did have to stay on it. But it didn't have a warm-up system, drank fuel like booze, and put out gobs of pollution. Carbs also are intrinsicallly unable to be as efficient as FI due to poor fuel atomization.

I think carbs are great for modder's, but as people have become more familiar with FI, PEFI systems are now the tool of choice. Even better are systems that permit full engine management, with active control (e.g. idle speed control, and active mixture control w/oxygen sensors).

[toon1]

Here is a choice a dyed in the wool carb user might find interesting, Using an o2 sensor to tune!

A freind of mine put two fittings in his Olds. cutlass. when he does a tune up or adjusts the carbs, he takes his sensor to a freind and they put it on a meter to see the emissions.

Just an option. I still like FI better (IMG:style_emoticons/default/biggrin.gif)

[c12croft]

I would leave it the way it is.
If you can still drive an automatic car, lets make your 914 an automatic.

I am close enough to help with that project.

Rich

thanks but i'm a quadriplegic due to an atv accident

[bd1308]

You know something--I work with a quadriplegic, he uses a hand throttle to do throttle.

I can ask him and take pics of his car (he drives a mustang)....i know it can be done and some amazing things have come from this club

[JoeSharp]

If you want the car to start every time you turn the key Put 2 40mm Solex's on it with a 050 dist. an for get it.
One of the cars I play with has gotten over 49 MPG.

[Bleyseng]

I know you post those results all the time Joe but FI provides better fuel management than carbs hands down due to the engineering. (IMG:style_emoticons/default/chair.gif)
A Djet FI thats is proper condition will be as trouble free as you can get for a car.

[rhodyguy]

that *proper condition* can set you back with either carbs or any fi setup. if the fuel injection works well, consistantly, stay with it. just adjusting to driving a 914, whether carb or fi can take a bit of practice. jeanne worked the carb driving out on the run to cal in the silver car.

k

[c12croft]

thank you much for your well wishes and engineering commentaries.,
sounds like i'll follow the D-jet route.
i must revert back to the stock cam?

[Brando]

No, you don't have to. Raby makes an excellent cam for stock fuel injection (9550) that works much better.