# ABA | Weber 45s | Ignition Sytem Questions.



## 01 (Sep 9, 2009)

so ive been reading and reading, just wrapping my head around what ignition system/setup to run. 

first ive read to keep the 1.8 dist with vacuum advance, and buy the TT gear adapter. well after reading a bit im told this shouldn't be done. 




the12for12 said:


> Spark advance is the other problem you are faced with. Most factory carb equipped cars have vacuum advance distributors. This is fine when installing a 32/36 or 38/38 because they have vacuum advance ports int the carb but when installing sidedrafts you do not have this option.
> DO NOT hookup the distributor vacuum advance to the intake Manifold. That does not work and is a common mistake we see. If you do that you will pull full advance at idle then as soon as you open the throttle it loose vacuum and the timing will retard quickly causing a big stumble or flat spot and very bad throttle response.


 
so now im debating what to do. seems there are tons of options, all looking more complicated then i wanted. 

1. Knockbox 
2. MegaJolt 
3. MSD Ignition\Coil And MSD Timing Control 

any input or advice would be appreciated, im trying to keep wiring and stuff to a minimum, shaved bay and such, yet retain performance and reliability.


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## B4S (Apr 16, 2003)

To be honest, the MSD setup is the last choice you should make. It only allows for a 2-D timing curve, so no vacuum advance under cruise (WHICH IS WHERE YOUR FUEL ECONOMY COMES FROM). The Knockbox works ok, but does not allow for timing curve adjustments obviously. Idle timing of 10-12* will make your life easier, but the knockbox sets to 6*. 

Now, I'm really biased here, but Megajolt is simply the best thing you can do for your setup (or any other crank-triggered ignition that offers 3D mapping, like electromotive, etc). It allows for mapping via throttle position or MAP, so that while cruising, you can run advanced timing and make good economy. I was getting 31-32 MPG on my dual carbed 1.8 with the megajolt .


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## 01 (Sep 9, 2009)

im just confused at how many people ive seen running the 1.8 dist, with vacuum advance/retard.. 

i mean this means even TT is telling people to use improper parts/tuning for the carb conversion. can they seriously all be wrong? 


-- 

and as far as megajolt is concerned, wiring looks far to complicated for what im trying to do. unless i have some serious help, wiring is not my strong point.


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## B4S (Apr 16, 2003)

There is no wrong way to do it, really. 

You can use the vac advance dizzy, but since there will be no vacuum source, it will operate only on centrifugal advance. This, in effect, gives a 2D timing curve, like the MSD would offer. The car will run fine, and you will be able to set it up for max power very easily. You will lose access to the maximum fuel economy you could be achieving, that's all. This is usually the point where the carbs go up for sale . The lack of a 3D ignition curve (like having vac advance hooked up) WILL affect your economy, it's proven. 

TT isn't giving the wrong info, they're just sharing what they know. With watercooled VWs and dual carbs, most times this information is lacking in depth IMO. Hell, even the aircooled crowd (the ones that pay attention anyway), make sure to run some sort of advance with their carbs. It's not always the case, but it does happen. 

The fact is, that 90% of the people out there into carbs are stuck in the old ways of tuning them. This means that any info they pass along will be incomplete (going by the available tuning methods of the 21st century anyway  ). I love carbs, but will NEVER run them 'the old way'. When I'm getting amazing mileage and great power (31mpg and 105whp/119tq on a BONE STOCK 10:1 1.8 8v, 1.5" exhaust), it's hard to ignore the advantages of a fully functional ignition system.


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## 01 (Sep 9, 2009)

B4S said:


> There is no wrong way to do it, really.
> 
> You can use the vac advance dizzy, but since there will be no vacuum source, it will operate only on centrifugal advance. This, in effect, gives a 2D timing curve, like the MSD would offer. The car will run fine, and you will be able to set it up for max power very easily. You will lose access to the maximum fuel economy you could be achieving, that's all. This is usually the point where the carbs go up for sale . The lack of a 3D ignition curve (like having vac advance hooked up) WILL affect your economy, it's proven.
> 
> ...


 
wowo, thanks for the insight, guess i need to hire you to build me a megajolt setup :laugh::laugh::laugh: 

or just try to figure it out myself.


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## B4S (Apr 16, 2003)

Oh, side note . 

Most Dellorto sidedrafts out there on the market today are old emissions-based models (since alfa romeo used them on everything they made, basically), and have a vacuum take-off for a vac advance dizzy . Alfa was passing carbed cars through strict emissions standards in the 70s thanks to the emissions mods they made to their Dellorto carbs. This also makes them super easy to tune, and great for fuel economy.


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## B4S (Apr 16, 2003)

01 said:


> wowo, thanks for the insight, guess i need to hire you to build me a megajolt setup :laugh::laugh::laugh:
> 
> or just try to figure it out myself.


 I bought one completely assembled . Then I rigged up a TPS to my carbs (although you can easily use the MAP version by blending all 4 runners together with vacuum line), and drove off into the sunset .


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## antichristonwheels (Jun 14, 2001)

vacuum advance on a distributor requires ported vacuum which most DCOE setups do not provide 

a block mounted distributor will not clear carbs on a 16V and I imagine its the same on an ABA, maybe not 

If a distributor will fit, you can use a plain electronic distributor or points and just not use the vac advance. The distributor has centrifigal advance and you can set the initital timing higher. 

If the distributor will not work you will need a trigger on the crank to drive the ignition


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## 01 (Sep 9, 2009)

antichristonwheels said:


> vacuum advance on a distributor requires ported vacuum which most DCOE setups do not provide
> 
> a block mounted distributor will not clear carbs on a 16V and I imagine its the same on an ABA, maybe not
> 
> ...


 Block mounted dist works just fine on aba/ carb setups. And can actually work on 16v setups if you get a dist cap that has a 90 turn for the plugs.


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## 01 (Sep 9, 2009)

sooooo


couldnt you just tap and create a proper vacuum source on the carb itself?, im not scared


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## 01 (Sep 9, 2009)

01 said:


> sooooo
> 
> 
> couldnt you just tap and create a proper vacuum source on the carb itself?, im not scared


bump



also, do i need to keep the mk1 stock ICM and wiring that runs to the dist?


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## B4S (Apr 16, 2003)

A ported vac source is required, it's a bit tricky to drill through the carb body in order to get the port at exactly the right place close to the throttle plate. Manifold vacuum won't work, the throttle plate has to pass over the port to increase/decrease the signal.

Like I said...Dellortos have this port .


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## 01 (Sep 9, 2009)

B4S said:


> A ported vac source is required, it's a bit tricky to drill through the carb body in order to get the port at exactly the right place close to the throttle plate. Manifold vacuum won't work, the throttle plate has to pass over the port to increase/decrease the signal.
> 
> Like I said...Dellortos have this port .


not all of them, and well i got brand new webers for a super good price so..

if i have to drill and tap the carb body.. i will


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## B4S (Apr 16, 2003)

I guarantee that if you search Ebay.ca, .com, and .co.uk...you won't find any non-emissions Dells on there. I got a set recently, and it had been the first set of universal 40s that I've seen in years. The 45s are all non-emissions, so those are easy to find.

Not disputing that you should stick with the webers, but drilling through them might be a bad idea. Unless you've got an internal map of the channels and passages, you could muck them up pretty badly . Not doubting your ability...but even hardcore carb tuners would think twice before trying that.

Use the vac advance dizzy in non-vac mode, you'll still get an ignition curve...it just won't be optimal for all conditions of driving. All you'd need at that point is the ICM and vac dizzy.

A wise man from this forum once told me "You don't build your carbs around the engine...you build the engine around the carbs". Basically, chose the right tool for the job, or change the job itself.


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## 01 (Sep 9, 2009)

B4S said:


> I guarantee that if you search Ebay.ca, .com, and .co.uk...you won't find any non-emissions Dells on there. I got a set recently, and it had been the first set of universal 40s that I've seen in years. The 45s are all non-emissions, so those are easy to find.
> 
> Not disputing that you should stick with the webers, but drilling through them might be a bad idea. Unless you've got an internal map of the channels and passages, you could muck them up pretty badly . Not doubting your ability...but even hardcore carb tuners would think twice before trying that.
> 
> ...


i didnt plan on doing it myself, there are some carb experts locally that rebuild and modify carbs for custom applications. i sent them an email regarding this issue 

hell i have time to figure this out, only my bottom end is built. and im still trying to work out the details when im sitting here at work doing nothing.


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## YJSAABMAN (Jun 28, 2006)

I plan on running a knock box setup with my bike carbs on my ABA. Makes the most sense with the lack of proper vac port on teh carb setup and the knock box dist doesn't have a vacuum advance to begin with.


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## WolfzGangVR6 (Jan 1, 2002)

yjsaabman... do you have a wiring schematic on how your running your knock box? i have a 87 jetta on cis-e and i believe it has the seperate knock box. i wanna try and retain the factory ignition.


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## Svedka (Jul 4, 2008)

info on knockbox 

http://forums.vwvortex.com/showthread.php?424779


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## YJSAABMAN (Jun 28, 2006)

WolfzGangVR6 said:


> yjsaabman... do you have a wiring schematic on how your running your knock box? i have a 87 jetta on cis-e and i believe it has the seperate knock box. i wanna try and retain the factory ignition.


 I do not have a wiring schematic for my setup. I stripped mine out of a MKII 8V GTI harness and used the Bentley diagrams, but it's not completely installed yet, or up and running. The diagram posted about looks similar to another I've seen posted, but the other did not work out for the poster, and they were back to the non-knock system. I'll have to look at them side-by-side when I get a chance. I'll also only be running the idle switch and a non-vacuum distributor that matches teh rest of the ignition I'll be running. The full throttle switch is really for WOT with the CIS.


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## WolfzGangVR6 (Jan 1, 2002)

yea i'm also running a non vac dizzy currently, and wanna try and use the existing knock box setup. i'm keeping my ecu for now untill i can figure out what controls the a/c , starter and alt charging. then i'm going to eliminate any wiring un-used. i gotta get a mk2 bentley for this ce1 wiring. i'm so used to the ce2 stuff from past mk2's. 

again if all else fails then i always have the vac dizzy and spare icu. i'm anxious to get these things on and hear her start to really sing  

thanks for the link svedka :beer:


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## sw5 (Mar 22, 2006)

01 said:


> DO NOT hookup the distributor vacuum advance to the intake Manifold. That does not work and is a common mistake we see. If you do that you will pull full advance at idle then as soon as you open the throttle it loose vacuum and the timing will retard quickly causing a big stumble or flat spot and very bad throttle response.


The VW's that came carbed from the factory used manifold vacuum. It did work and I don't see why it shouldn't. No big stumbles too. Throttle response is quite normal.


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## squish917 (Apr 29, 2010)

sw5 said:


> The VW's that came carbed from the factory used manifold vacuum. It did work and I don't see why it shouldn't. No big stumbles too. Throttle response is quite normal.


They had a log manifold with a relatively long distance between carb and signal. As well as mild cams.


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