External trigger wheel fitment details on ABF?

I need to fit an external trigger wheel on my engine.

I'll be using the standard Vw pickup sensor mounted on a bracket that'll be secured to the block using the rear power steering bolts. I can do that easily.

What I'm unsure about is what's a simple yet robust trigger wheel securing method.

I've seen a couple of them, some welded to the bottom pulley, others bolted using the four m8 cap heads.

I'd prefer something that I can do, without access to a lathe If possible. Adjustment is probably wise to get the timing correct.

Any links / info is welcomed

Oh, and I want to fit it next Tuesday

 

I think you're going to struggle Nige unless someone has a boss to sell you. Do you already have the trigger wheel? I had a local machining company make me a boss to fit mine and I will happily share the drawing if you want to get one made...

 

Sparrows



Nearly ten years sinc it was first built

 

That one didn't fit, it was the wrong pulley for my engine, despite coming with it. lol

This was the final version:


Already been in touch with Nige to see if we can sort something by Tuesday.

 

That's where I'd mount it ^^. If you get the right pulley, there is already a rebate the correct size to take a trigger wheel (once you machine the inner down to size). It could be a push fit and tack welded or four small cap head bolts - there isn't really enough room for M8 and you don't want it any bigger dia than needed. If the machining is right there is no way it can move, the bolts are only there to ensure its fixed. I favoured the drill, tap and bolts method as I could guarantee the weight was equally spaced around the pulley, not so easy to judge with welding and I didn't want to get it balanced.

The block has two redundant bolt holes to take the pick up, plate design is obvious when you look at it.

Mine runs to over 9k with no issues.

There is a lot spoken about the damper in the pulley letting the trigger wheel move and a poor signal et. etc. All crap, it works fine - no offence to any one.

I guess ideally you could mount it behind the pulley but as there is a handy rebate on the front, its much easier that way - and very secure and accurate.

 

On cars like that, I have never heard any issues and I have seen quite a few with external stuff over the years VW and non.

 

That gap seems very small, from my experience of probes and toothed wheels. My first attempt at mounting with 6 off M4's lasted three rallies before it came slack. Result DNF. M5's locktighted and 2 pack metalled over the top worked after. Welded is better. I made a spacer to move the crank damper out 8mm and fitted it around that, so it was bolted to the non rubberised part of the pulley. Think I have a spare whole assembly somewhere, will try and find and photo it. It meant offsetting the waterpump and alt to match, but it was further away from the stones
Jon

 

Gap should be around 20 thou on a 138mm diameter wheel (or 0.5mm to 1mm in new terms), getting bigger as the diameter of the wheel increases, smaller as it decreases.

 

Mine doesn't rev as high as yours, but it's been fine for 9 years, and 3 or 4k miles.

Something like this:

https://store.034motorsport.com/16v-crank-trigger-kit.html

 

The box my spare pulley was empty, only this toothed wheel was in the bottom. Think I machined the centre out of it. Bit hazy as was 15 + years ago
Jon

 

Yeah, I've seen those kits. The pick-up mount looks fine, but the way they mount the trigger wheel is dodgy in my opinion. Lot of stress and leverage going through those bolts with them so close to the middle and that big spacer. I would imagine there could be slippage/deflection at best and a total failure at worse.

 

Thanks for the info! I'm looking at various wheels, the ones that bolt to the crank using the m8 bolts look good, but I'm not so keen on the slotted ones. Seems like an extra place for things to possibly move?

I knew I'd seen a photo of a welded one but couldn't remember on which engine. Thanks Alex.

I believe I can 'align' it electronically in the ecu, so don't need the slots.

The bracket is easy and hearing people have run it on the outside of the harmonic damper without issues give me a lot of confidence

 

This is my setup:





Trigger wheel from http://bamracing.co.uk/products-2/trigger-wheels.html
Slots not really needed in the trigger wheel as like you said aftermarket ECU's can be adjusted to suit but I guess they are there to suit all applications.

Turned the spacer myself to suit ribbed type belt and to give 5mm clearance from the pulley to avoid any pickup interference.

Personally I wouldn't mount the trigger wheel to the outside of the dampened pulley as I'm sure I've read that someone had sync errors due to slight movement at high revs.

 

The spacer is a pain seeing I don't have a large, but I think Tom is sorting me

I don't like the billet ones. The more I think about it, the less I like the idea of removing the damper.

 

I used the press on unit that forms part of the crank seal from a 1400 lupo on my Abf,
A bit pricey as you need to buy the special tool to fit it but it seems to work fine.

 

Harmonic dampers on cranks have a function, dynamically. I wouldn't run a high rpm engine without one.
Maybe I'm being cautious, but I snapped a couple of billet mini cranks in my time.....
Jon

 

^^Wise man.