What size Webbers?

AlexO · 05-22-2000, 05:03 PM

Well, I'm finally considering the option of swithching to carbs. I'm running a '74 2.0 with a mild FI cam, Crane XR3000, slightly oversize valves, SS exchangers and Bursch exaust. What size carbs should I use?

MJHanna · 05-22-2000, 06:27 PM

40’s will work in this application. Main Venturi 32, Aux. Venturi 4.5, Main jet 125, Em Tube F16, Air correction 180, idle jet 50, Acc pump jet 50, pump ex Value 55. You could go with 44 much the 40 will better on the street with your cam.

Rouser · Rouser's Garage

Why the switch to carbs? Is the FI not functioning properly?

All too often many owners regret switching to carbs after having to deal with syncing, jetting, morning cold-bloodedness (no choke), and occasional tuning hassles.

Webers DON'T react well to neglect, and although they may have a hot-looking, racy appearance in the engine bay, they do bring additional mechanical complexity.

Even though the D-Jet FI may've not allowed for a whole lot of "growth", it IS a well-thought-out system for the 2L engine's size. Unless you're punching out way past that, you really can't beat it.

AlexO · 05-23-2000, 09:26 AM

That's exactally why I'm debating the switch. After checking all my wiring conections, I still can't get my injectors to fire. So I think I'm down to either replacing the ECU, or putting on a set of carbs. I've ridden in a friends 914 1.8 and it ran rather well, even during its warm up period. My only reservation is that this is a daily driver, and I've never set up a set of carbs. Everything I've driven has had Bosch injection.

Neal Colingham · 05-23-2000, 10:11 AM

Alex, I have a 76 2.0 with Weber 40's, I just
installed the XR3000. I don't have warm up
problems and the car runs great. The webers
are very easy to tune. I had them adjusted and the guy I use spent about 5 minutes
adjusting the air and then synching the carbs
If the intial jetting is done properly for your driving habits I think they will be very
reliable for daily driving. Mileage has suffered on mine. My dad used to get 30+
with the FI and I can only get 25 mpg. I don't know how much the condition of my motor is a factor (it's toast). If you don't have to worry about emissions then the carbs might be a viable choice.
Neal

david c. · 05-24-2000, 03:38 PM

I have the same 2.0 in my 912E, and I went to twin 40 Webers. The power is a bit more immediate, and there is a noticeable increase in suction noise. The mileage isn't appreciably less. The car runs rough for 1-3 minutes in the morning (I drive mine daily also). But, typically, it warms up quickly. I have an old Permatune on it, with a stock coil, and it idles fine and truly has only stalled one single time since installation. The overall effect is positive, in my experience. I certainly respect the opinions of those with functional F.I., but when your F.I. craps out, I don't think it's a poor alternative at all. Regards,...

B Frye · 05-24-2000, 07:22 PM

I don't know how much you would pay for a set of Weber carbs (with all of the installation goodies included) but before you commit your money, check out Simple Digital Systems FI http://www.sdsefi.com .

For just under a grand you can have your cake and eat it too. This digital FI system is completely tunable and will support cams that range from stock to high lift and duration 'race' profile.

AlexO · 05-24-2000, 08:02 PM

Well guys, thanks for the info. I haven't made a decision yet, but it sounds like I may be going to carbs if my ECU is fubar.

JP Noonan · 05-24-2000, 09:14 PM

See if the distributor is putting out a signal from the FI trigger points in the bottom of the dizzy. There are three pins, the outside pins should alternate between open and continuity to the center pin as the engine rotates. If the points work, check wire continuity from the injectors to the brain, then see if the grounds from the injectors to the block have continuity, finally (never heard of it, but I guess it's possible) see that the block is grounded to the battery.

If in fact the injectors are getting a signal and still don't click, are they old? I have some that sat with gas in them for many many years, and I guess rust or varnish froze them shut. The injectors run on something much less than 12 volts, Personally I use a rechargable 3.6 volt battery and short it to the injectors to see if they click. Good ones do, bad ones don't. Listen carefully and don't confuse the snapping of the battery shorting to a bad injector with the clicking of the injector pintle. BTW I really don't know if this is a good thing to do to the injectors, it may burn up the coil inside them. So hook them up to a battery at your own risk.

Gheck out the D-Jet article on the 914 fans web site

http://www.914fan.net/djet.html

willisb914 · 05-25-2000, 04:52 AM

JP, I use a 6v lantern battery to chack the injectors, shouldnt hurt that if you only connect them intemitantly (sp?)......

Are you sure that your ECU relay is good? If it isnt getting 12volts then you wont get any signal to the injectors.

The 12v supply relay is the second one from the front on the relay board.....

If you are in fack getting power to the ECU, then try turning on the ignition and depress the throttle. Make a smooth transition from idle to WOT you should hear clicks from the injectors. If you dont then check continuity from the injectors to ground pin #11, and from injectors to ECU plug #3,4,5,6 not in that order but those are the pins....

Hope this helps????

Ben

[This message has been edited by willisb914 (edited 05-25-2000).]

AlexO · 05-25-2000, 07:47 PM

Well, the ECU clicks when I swing the throttle, so its got juice. I checked the injector plugs with a test light and nothing. I haven't checked the FI points yet, but I'll do that soon and let ya' know. JP: not sure what you mean by the continuity between the injector and the brain.

I just put my BMW up for sale to cover the possibility of needing carbs or a new ECU. Any takers?

Dave at Pelican Parts · Dave at Pelican Parts's Garage

The ECU is not what clicks when you open the throttle. The injectors are.

It seems pretty likely that you have a problem with the injector trigger points, or with the wires from the ECU to those.

What JP means by "checking continuity" is to unplug the injector, and pull the plug out of the ECU. Then use the continuity tester (AKA diode tester, AKA beeper) or an ohmmeter. Put one probe on one of the pins in the plug connector, then check the four pins in the ECU connector that are supposed to connect to the injectors. (Look at the wiring diagrams in Haynes or elsewhere on this website for which ones those are. The wires have numbers stamped/painted on them so you can tell which ones are which.) If you don't get the "beeep" from the diode tester, or you don't get ~0 ohms from the ohmmeter, switch to the other pin in the injector connector and try again.

If the injectors are clicking when you open the throttle (do all four click?), it is likely that the wiring to them is OK. The trigger points are then your primary suspect.

Perform a similar test for the trigger points wires. One word of warning: At least one of the wiring diagrams has the numbers for two of the trigger points pins swapped around! I think they swapped 21 and 12. Check the numbers on the plastic receptacle on the trigger points part itself--if you can see them. Those are correctly numbered.

Are you certain that you're not getting any signal at the injector connectors? Could it be that your voltmeter does not respond quickly enough to see the pulses? Or that you have it set on too high a scale for those to register? No offense intended, just trying to come up with things that might be able to explain what you're seeing.

--DD