Technical anyone play with carbs?

[wannabfast]

im trying to figure out if theres a different combination of jets/emulsion tubes i can use in my 32 datra carb... according to my haynes manual says taht its supposed to use teh f30 emulsion tubes and 110 jets, altho the euro spec uses 1 110 and a 115 jet, anyone play around with different jet combinations on the downdrafts?

 

[Whitevanman]

there was once a modification in one of the old x1/9 owners club magazines where you replaced the jets for bigger ones and retarded the timing unfortunately i no longer have the magazine (or the car) but if you can get hold of this mod (if i remember right the owners club used to do a special edition of the mag just containing the mods) it did work for me my car ran as sweet as a nut after it hope this gives you an idea of where to go

 

[wannabfast]

well putting bigger jets in there goes without saying..

 

[x/19castori]

I have a 1500 engine with a 32 datra and have found that emulsion tubes with fewer and smaller holes give better overall "punch". I've tried the f130s of course, but f122s are much better on my otherwise stock X1/9. Let me know what you think if you try this. Good luck!

 

[x/19castori]

My previous post concerning emulsion tubes on a 32 datra carb was incomplete. I should have mentioned that my X is a U.S. model. I've tried quite a few combinations of fuel jets, air correctors,and emulsion tubes. For now (still experimenting) I'm using : primary- 110 fuel, f22 emulsion tube, 175 air corrector; secondary-110 fuel,f22 tube, 245 air. Again, my car is an '80 model with no mods except the earlier model carb. The timing is set @ 13 btdc.

 

[RS Pilot]

Contrary to popular belief, bigger jets do not mean more power! If you overfuel your car you will actually reduce power so don't get sucked in to bigger is better! Running rich is more preferable to running too lean though.

There's a current thread on the owners club website where one guy has changed his jets during a rolling road session however this was done in conjunction with advancing the cam timing by one tooth to raise the power band up the rev range which is a well known mod. Before going to twin 40's I increased both main jets by 5% when running with a pipercross filter and straight through exhaust. Sounded good but made very little noticeable difference to performance. The fuelling was correct when checking against the plug colour.

 

[wannabfast]

My previous post concerning emulsion tubes on a 32 datra carb was incomplete. I should have mentioned that my X is a U.S. model. I've tried quite a few combinations of fuel jets, air correctors,and emulsion tubes. For now (still experimenting) I'm using : primary- 110 fuel, f22 emulsion tube, 175 air corrector; secondary-110 fuel,f22 tube, 245 air. Again, my car is an '80 model with no mods except the earlier model carb. The timing is set @ 13 btdc.

where do you get the air correctors?

 

[fiatfactory]

Where do you get metered parts from....from a carby place...

DMTR/DATR air correctors are like the DCNF series carbs ... lots of air cooled VW places carry parts.

Basic weber part number is 77501. followed by the orifice size, so for example a 1.50mm air corrector will be 77501.150.

A larger air corrector weakens the mixture more at higher than lower RPM.

As a rule of thumb 3 progressions of air corrector (say 1.50 down to 1.35... so 3 x 0.5mm jumps) equals (roughly) one step up in main jet size (say from 1.50 to 1.55)

Increasing the main jet orifice size enriches the mixture uniformly at high and low engine speeds. Weber basic part number for DMTR/DATR main jets is 73405. followed by the orifice size, so for example a 1.50main for a dmtr/datr is 73405.150.

Both these metered parts are linear in their numbering... so a bigger suffix = a larger orifice... however when it comes to emulsion tubes, this goes out the window and you need to consult reference tables to decide what is richer/ leaner... as E tubes doesn't follow a numerical progression... just to make life interesting.

Emulsion tubes have more influence at small throttle angles and during accelerations, significant factors that influence it's operation are the outside and inside diameters of the E-tube, which alters the amount of fuel that is displaced in the jet well, generally a thinner tube is richer as it will leave more fuel in the jet well for the engine to draw on.

The location, size and numbers of holes that it has along its length control how the fuel is emulsified as the fuel is drawn from the jet well thru the primary venturi...

SteveC

 

[sumplug]

Where do you get metered parts from....from a carby place...

DMTR/DATR air correctors are like the DCNF series carbs ... lots of air cooled VW places carry parts.

Basic weber part number is 77501. followed by the orifice size, so for example a 1.50mm air corrector will be 77501.150.

A larger air corrector weakens the mixture more at higher than lower RPM.

As a rule of thumb 3 progressions of air corrector (say 1.50 down to 1.35... so 3 x 0.5mm jumps) equals (roughly) one step up in main jet size (say from 1.50 to 1.55)

Increasing the main jet orifice size enriches the mixture uniformly at high and low engine speeds. Weber basic part number for DMTR/DATR main jets is 73405. followed by the orifice size, so for example a 1.50main for a dmtr/datr is 73405.150.

Both these metered parts are linear in their numbering... so a bigger suffix = a larger orifice... however when it comes to emulsion tubes, this goes out the window and you need to consult reference tables to decide what is richer/ leaner... as E tubes doesn't follow a numerical progression... just to make life interesting.

Emulsion tubes have more influence at small throttle angles and during accelerations, significant factors that influence it's operation are the outside and inside diameters of the E-tube, which alters the amount of fuel that is displaced in the jet well, generally a thinner tube is richer as it will leave more fuel in the jet well for the engine to draw on.

The location, size and numbers of holes that it has along its length control how the fuel is emulsified as the fuel is drawn from the jet well thru the primary venturi...

SteveC

:worship:
seriously, emulsion tubes are a bit of a science.a lot of tuners dont know how to use them.its a case of guess and see.i would stick with the E tube and alter the fuel and air jets as you suggested.good post steve.