Twin Weber carb setup advice.....
- Thread starter petex19
- Start date
carl
True Classic
O2 sensor and volt meter
Get yourself an 02 sensor and a digital volt meter as a temporary fuel/air ratio meter. I have done very successful jetting on my dual IDFed spider and dual IDFed 128/1500 using this simple setup. Just be careful driving the car as you can get target fixation staring at the thing and drive off the road. You should not be fouling plugs and this just tells me you are too rich but of course you don't know if that's at idle, part throttle or full throttle without an air/fuel meter. Webers are very forgiving and will run with wildly wrong jetting so the fact the car runs and fuctions is no indication of proper jetting.
Get yourself an 02 sensor and a digital volt meter as a temporary fuel/air ratio meter. I have done very successful jetting on my dual IDFed spider and dual IDFed 128/1500 using this simple setup. Just be careful driving the car as you can get target fixation staring at the thing and drive off the road. You should not be fouling plugs and this just tells me you are too rich but of course you don't know if that's at idle, part throttle or full throttle without an air/fuel meter. Webers are very forgiving and will run with wildly wrong jetting so the fact the car runs and fuctions is no indication of proper jetting.
petex19
True Classic
I'm confused....
When you say choosing a resistor you mean if you're coil requires a resistor? So do you pick a resistor plug is you are using a resistor and a non-resistor plug if you are using a coil that does not require an external resistor or am I completely misunderstanding this thread?
'PeteX1/9
When you say choosing a resistor you mean if you're coil requires a resistor? So do you pick a resistor plug is you are using a resistor and a non-resistor plug if you are using a coil that does not require an external resistor or am I completely misunderstanding this thread?
'PeteX1/9
petex19
True Classic
I'm interested in trying this....
Could you please give me a little more information of getting setup for this setup. I have the digital voltmeter and have the O2 bung on my header so what type of O2 sensor do I purchase and how do I connect the O2 sensor to the voltmeter?
'PeteX1/9
Could you please give me a little more information of getting setup for this setup. I have the digital voltmeter and have the O2 bung on my header so what type of O2 sensor do I purchase and how do I connect the O2 sensor to the voltmeter?
'PeteX1/9
carl
True Classic
Sensor set up.
I always use the stock Bosch 02 sensor for the injected Fiats. The wire from the sensor goes to the + wire on the voltmeter and the ground wire on the volt meter goes to a ground on the car body.
I'll have to check when I get home as to my chart that relates voltage reading to various ratios but I think you want around 0.900 volts for max power and 0.200 for best economy.
I was attending a track day last year in my 128 sedan and the volt meter was indicating around 0.700 flat out down the main straight. I kept jetting up, the volt meter kept getting closer to 0.900v and top speed kept going up.
Doesn't work too well for idle but I think I had my sensor too far downstream to be accurate for slight exhaust flow.
Simple, cheap and effective, can't do better than that.
carl....cheap
I always use the stock Bosch 02 sensor for the injected Fiats. The wire from the sensor goes to the + wire on the voltmeter and the ground wire on the volt meter goes to a ground on the car body.
I'll have to check when I get home as to my chart that relates voltage reading to various ratios but I think you want around 0.900 volts for max power and 0.200 for best economy.
I was attending a track day last year in my 128 sedan and the volt meter was indicating around 0.700 flat out down the main straight. I kept jetting up, the volt meter kept getting closer to 0.900v and top speed kept going up.
Doesn't work too well for idle but I think I had my sensor too far downstream to be accurate for slight exhaust flow.
Simple, cheap and effective, can't do better than that.
carl....cheap
Rupunzell
Bernice Loui
0.028" gap is designed for points based ignition systems that cannot produce very high spark energy at the spark plug. If there is a proper MSD system in your car, it should have enough spark energy to fire a spark plug gap of more than 0.040" or 1mm. Larger spark gap area & higher spark energy, better fuel/air mixture burn.
This will not correct or fix an excessively rich mixture.
Know that your idle circuit and aux ventrui in the DCOE is what you're running at idle and slow driving around town.
When running 45 DCOE's any ventrui size of less than 34mm is not optimum. Typically, 45 DCOE's are used with a 36mm ventrui (choke) and that is a huge amount of carb for a 1500cc engine which would be useful at no less than 8,000 RPM or very serious race engine.
As suggested, a set of 40 DCOEs with 28mm or 30mm Ventrui (chokes) with the proper jetting might work much better for your current engine set-up.
Bernice
This will not correct or fix an excessively rich mixture.
Know that your idle circuit and aux ventrui in the DCOE is what you're running at idle and slow driving around town.
When running 45 DCOE's any ventrui size of less than 34mm is not optimum. Typically, 45 DCOE's are used with a 36mm ventrui (choke) and that is a huge amount of carb for a 1500cc engine which would be useful at no less than 8,000 RPM or very serious race engine.
As suggested, a set of 40 DCOEs with 28mm or 30mm Ventrui (chokes) with the proper jetting might work much better for your current engine set-up.
Bernice
SuperCrap muffler...
...is pretty rowdy sounding.
Assuredly too rowdy for steet use.
Yet, many folks have commented
about nice Italian music.
At 8000 rpm.
Some of whom are here at Xweb.
Many of whom drive other racecars.
When turbo muffler that came on my DarkBlueX failed,
all I had on hand for quick fix prior to a trackday
was old SuperCrap and coupla mandrel bends.
Incredible improvement was gained at upper rpm range!
Setup with a passle of diffuser rings,
which are also spaced out with washers,
and mounted with long SS bolts.
Upside is significant weight loss aft of rear wheels.
Which is a good place to lose weight.
Especially on this X...which has nothing aft of rear wheels
except the outer skin.
Notice dashboard visible through taillight opening...
I have no doubt the official word on SuperCrap muff shortcomings is gospel.
But for simplicity of construction, light weight, and virtually no cost,
it works for this un-schooled ol' country boy.
Pic shows current setup utilizing a short can version.
Picked up a long can version for one dollar,
which will accept more of replaceable fiberglass packing
and hopefully quiet it down some.
...is pretty rowdy sounding.
Assuredly too rowdy for steet use.
Yet, many folks have commented
about nice Italian music.
At 8000 rpm.
Some of whom are here at Xweb.
Many of whom drive other racecars.
When turbo muffler that came on my DarkBlueX failed,
all I had on hand for quick fix prior to a trackday
was old SuperCrap and coupla mandrel bends.
Incredible improvement was gained at upper rpm range!
Setup with a passle of diffuser rings,
which are also spaced out with washers,
and mounted with long SS bolts.
Upside is significant weight loss aft of rear wheels.
Which is a good place to lose weight.
Especially on this X...which has nothing aft of rear wheels
except the outer skin.
Notice dashboard visible through taillight opening...
I have no doubt the official word on SuperCrap muff shortcomings is gospel.
But for simplicity of construction, light weight, and virtually no cost,
it works for this un-schooled ol' country boy.
Pic shows current setup utilizing a short can version.
Picked up a long can version for one dollar,
which will accept more of replaceable fiberglass packing
and hopefully quiet it down some.
petex19
True Classic
Could you take a photo....
If it isn't to much trouble could you take a photo of your voltmeter with the positive and negative connected to it and where you have the voltmeter set at.
The Fiat Bosch O2 sensor obviously doesn't have wiring long enough to go into the car so do I just connect a 14 gauge wire to the sensor's wire and that is the positive and then connect the wire from the DVM to a body ground in the car? A photo would be nice to see
'PeteX1/9
If it isn't to much trouble could you take a photo of your voltmeter with the positive and negative connected to it and where you have the voltmeter set at.
The Fiat Bosch O2 sensor obviously doesn't have wiring long enough to go into the car so do I just connect a 14 gauge wire to the sensor's wire and that is the positive and then connect the wire from the DVM to a body ground in the car? A photo would be nice to see
'PeteX1/9
Lafayette Bruce
Daily Driver
Clarification
You said "If the car increases rpms, you are too lean. If it boggs down, you are too lean."
Did you mean?
If the car increases rpms, you are too lean. If it boggs down, you are too rich.
Thanks
Lafayette Bruce
You said "If the car increases rpms, you are too lean. If it boggs down, you are too lean."
Did you mean?
If the car increases rpms, you are too lean. If it boggs down, you are too rich.
Thanks
Lafayette Bruce
carl
True Classic
Wire arrangement
I don't have the volt meter hooked up on any car at the moment. Last car I had it on was my 128 SL. If I had it on the X I would have to add a wire to the sensor wire and somehow run it into the cabin. This wire is connected to the plus wire on the voltmeter and the negative wire on the volt meter is hooked to any ground. This was all temporary so making a pretty job of the wiring was not an issue.
I don't have the volt meter hooked up on any car at the moment. Last car I had it on was my 128 SL. If I had it on the X I would have to add a wire to the sensor wire and somehow run it into the cabin. This wire is connected to the plus wire on the voltmeter and the negative wire on the volt meter is hooked to any ground. This was all temporary so making a pretty job of the wiring was not an issue.