tbh I think I'm gonna have to do this systematically soon and try every combination to be sure which is the best.

MAIN: 125 127

Have you now got good colour spark plugs? I've tried a range of jet sizes, I did think the 125 primary felt good.. but fuel econ?

That's been worrying me too. Plugs looked tan, no obvious carbon, but most other 24mm carbs have less than 120 for 1.3 litre.

So I hand made a 112 main using solder in an old jet and a 1mm drill bit and a needle file and a micrometer.

Engine sounds crisper. Pulls just as well.

I've been doing some more thinking about this recently..

For some while I've been using large main jets (like 115+). When I took it to the rolling road the tuner used something in between a 100 and 105 I beleive and a 125 secondary. So today I swapped back for a 105 and went for a drive. Once you get passed all the leaning out below 2000rpm it really pulls well and plugs come out tan ish. Interestingly If i pull the choke on just a tiny bit all the stalling goes away...

I'm just wondering wether I'd been using over large mains to compensate for idle jets or accelerator pump not being man enough (because the mains do still influence down low I gather). Also I'm now using the 50 pump jet.. and as soon as I tried it I was like... wheres all the power gone?? Thing is the 45 creats a spray of emulsified fuel and although it doesnt get there as soon it must give better lean-out prevention overall.

Anyway, there's some food for thought. Also I tried putting my f-30 emulsion tube in with the primary jets and couldnt pull away at all?? How are you guys pulling away?! (dvdlerm I know you used to drive with 2X f30s....)

Bear in mind I bought the carb brand new so no worries with faults and I'm 100% confident there are no air leaks.

How are you guys pulling away?! (dvdlerm I know you used to drive with 2X f30s....)

The F30s were really smooth, like a BMW automatic, it just kept pulling.

Original specced F22 had more attack, like an angry Audi joining the motorway, but not quite reaching the busy outside lane.

(That was with the 22/22 venturi DMTR. Really like the F33 since I tried them.)

Where does your pump jet spray? - it shouldn't splash off anything.

But actually I'm perfectly happy with the 24/25 venturi DMTLs pump jet. It might even be a 40 not a 45 if donor vehicle is a Landrover.

Don't know how much influence my MAP sensor controlled Bosch Dignition has.

I personally didn't like the F30's, was too progressive for me, tried a 22 and it totally transformed the power deliverey,

Was much peakier, especially when it came on cam!

How are you guys pulling away?! (dvdlerm I know you used to drive with 2X f30s....)

Where does your pump jet spray? - it shouldn't splash off anything.

But actually I'm perfectly happy with the 24/25 venturi DMTLs pump jet. It might even be a 40 not a 45 if donor vehicle is a Landrover.

Mine was a new DMTL from southern. The 45 I have squirts horizontally.. and it hits a surface (have no idea what its called) in the centre of the bore.. Bt I changed for a 50.

I tried the F30 in 1st stage and it was totally unmanageable untill 2200rpm.. is there something I'm missing? Mayb its idle settings..

bt yeh once you got passed all the difficulty it was sweet as!

You guys should move up to the DCD range, far better than the DMTL/R stuff.

hm 28/36?

So a nice smooth primary with a huge secondary in reserve for full chat?

I would say from my experience of the DMTL now, that 30/32 would perhaps be a better size. Can you really get more top end from the 36? seems massive to me. The 34 of the DMTL seemed to be pulling harder and harder when I dared 6000+rpm.

Its a simular size to the GT throttlebody butterfly valves, granted your relying on a decent signal for the venturis to properly pull the fuel out of the "fuel tube" with a carburettor, so the bigger the venturi, the lazyier the signal.

What you want is a nice big ratio between the size of the venturi and throttle valve, this way you have a decent air-flow, and keep the decent signal, fuel atomization.

The great thing about the DCD and simular specification units is the ability to change the choke size, so tuning potential is greater, the idle jet assembly also has an emulsion tube, the choke isn't the flap type, so doesn't restrict/upset flow into the primary choke. It was made in italy opose to spain meaning the quality + finish is much better.

It was made to be a performance carb at the end of the day, not a production scale for a land rover/golf etc.

Also, think about a set of 40's, thats a lot of air-flow potential, but they restrict them with smaller venturis.

Edited 1 August, 201214 yr by MaxGT

Could anyone explain to me whats different about the F-33 emulsion tube for the DMTL?

I've got the F22 and F30 now, how does it compare?

Also is it possible to modify an emulsion tube like you would a jet?

F33 has a hole all the way through... and its only 5mm diameter, while F22 is 6mm diameter and F30 is 6.2mm.

Search for 61450.231 in http://www.webercarburatori.com/?p=handbook&s=2 which has pictures of all the tubes.

Don't confuse it with the F33 part number 61440.502 which is for IDA/IDF carbs.

Also is it possible to modify an emulsion tube like you would a jet?

Yes, you can block up holes with solder, or drill new holes. But you can't change fundamental dimensions.

I haven't tried modding a tube - they appear to be very close tolerance items.

Totally would'nt bother fucking about with emulsion tubes, i know they're costly but it would be so much harder to properly change them like you would a jet.

Have you got the weber tuning book from "Fastroadcars"? It will tell you everything!

Have just fitted a rebuilt weber 28/36 DCD to my 2G engine (In a jetta)

The performance difference between it and the pierburg 2E is amazing, and i'd estimate its easily as quick as my standard polo GT

The jetting;

Idle: 50 70

Main: 100 125

Air: 205 200

Emulsion: F30 F30

hmm thats great. The Weber really is a genius device. There again the pierburg was still a very smooth carb (I preferred it to Bosch Monomotronic).

Quick note, I've really been getting on top of the jetting recently and loving the F30s. I got a best time 0-60 of a little over 10 seconds! If I recall correctly the GT was around 11? So that means I must be producing around 75BHP+ now. I'd expect the GT injection to be a fair bit smoother down low and the weber is till fairly toppy. that said it really starts to go at 2K now which I like.

I'm still perplexed as to how you are managing to use such large air correctors. I've upped to 170 now I'm using a larger primary main. Anything more than that and high rpm performance really suffers.

Have just fitted a rebuilt weber 28/36 DCD to my 2G engine (In a jetta)

The performance difference between it and the pierburg 2E is amazing, and i'd estimate its easily as quick as my standard polo GT

The jetting;

Idle: 50 70

Main: 100 125

Air: 205 200

Emulsion: F30 F30

Jetta, 1.3.

2e2 or 2e3?

What size chokes are you using with the DCD?

Don't know which sorry, its in the shed now.

23/25 IIRC on the DCD

Sounds good. GK Pierburg 2e3 has 22/26.

I'm still perplexed as to how you are managing to use such large air correctors. I've upped to 170 now I'm using a larger primary main. Anything more than that and high rpm performance really suffers.

Does the Jetta has TCI-H ignition?

What heat range spark plugs are you using. Lean burns hotter. You've got to take the heat away and cold spark plugs have more nose to conduct heat away. Try with a Bosch 5 or an NGK 7.

Yes, infurtiatingly the numbers go opposite directions.

Hi guys, I've been reading this thread and gained quite a lot from it. Just wondered if you may be able to help point me in the right direction with my set-up. I've got a standard mk2 polo with a 1.3 2G engine, pipercross ring element is the only 'mod'. I've recently taken the dive into removing my pierberg and replacing it with a weber dmtr. The carb is second hand, only has a few thousand miles on it apparently and cam off the same engine as mine, i know all cabr set-ups regardless of the engine are different.

I am having a few problem with the current set-up which is as follows.

Primary Secondary

Idle Jet 45 70

air jet 155 185

Emulsion f-22 f-30

Main jet 115 120

The problems are similar to some described earlier in the thread. When sat at a junction the car can sometime cut out, but also the other issue is on half throttle the car accelerates great, but on full throttle it seems to bog down and hold back. Any ideas what I could change to try sort this ?

I only really know a little so any help would be greatly appreciated.

Hi guys, I've been reading this thread and gained quite a lot from it. Just wondered if you may be able to help point me in the right direction with my set-up. I've got a standard mk2 polo with a 1.3 2G engine, pipercross ring element is the only 'mod'. I've recently taken the dive into removing my pierberg and replacing it with a weber dmtr. The carb is second hand, only has a few thousand miles on it apparently and cam off the same engine as mine, i know all cabr set-ups regardless of the engine are different.

I am having a few problem with the current set-up which is as follows.

Primary Secondary

Idle Jet 45 70

air jet 155 185

Emulsion f-22 f-30

Main jet 115 120

The problems are similar to some described earlier in the thread. When sat at a junction the car can sometime cut out, but also the other issue is on half throttle the car accelerates great, but on full throttle it seems to bog down and hold back. Any ideas what I could change to try sort this ?

I only really know a little so any help would be greatly appreciated.

I don't know what the cutting out is about.. But the bogging down is probably to do with jetting, I eventually found upping the primary main then fiddling with the idle jet mixture screw was the solution for me. Hopefully Dvdlerm can help you as he owned a DMTR for years. It could just be a blocked idle jet if the two problems are linked. The DMTR should be easy enough to make run smoothly on a 1.3.

By the way I used to have the username 'Breadvan Princess' but for some reason I can't access it.

tbh the jets you are using are large. And 'rule of thumb' (though this is rarely the best jetting) would say that your air correctors are out of proportion with your mains.. ie there should be a larger gap. 115 main with around 180 air for eg. But even this is down to debate.. so basically just experiment!

I seem to remember Dvdlerms jets were 100 120.

I'm using:

(roughly) 112.5 (175 air) 127.5 (195 air) on a DMTL

swifty53's issues dealt with outside the FAQ

http://www.clubpolo.co.uk/forum/index.php?...t&p=2410079

Edited 20 November, 201213 yr by dvderlm