Split: crank sensors in high revving 16Vs (internal and external)

From: What engine has a trigger wheel as standard?

Do not use the internal trigger wheels, unless you want to run the risk of a ventalated block when it explodes... which they can do.

 

Only affects high revving motors AFAIK.

 

To a point for sure, but theres no knowing how fatigued the wheel is due to age/previous use. It is a bit of a pain mounting them externally (just done one this week), but I'd rather not take a chance.

That'll be good though if VW parts can be used.

Anyway, 8,700 is'nt that high revving!

 

I have run my ABF on track for 2 years and haven`t had any issues with this.

If the engine is run to the standard 7,200 rpm limit, there is no issue with the internal trigger wheels as far as I`m aware.

 

I like that what is the sensor taking its signal from? a hole in the end of the crank?

 

There's a bit more on Brookster's thread, and a link to Vortex.

Looks like a cracking bit of kit, but it seems to "grip" the crank on interference fit via a plastic flange, and the missing tooth is within the seal assembly.

Fine for production (I still pause, but have to assume it's ok), but I'm eyeing the reliabilty of that on a revvier install.

Very tempted if I can convince myself some more.

 

Hmm - just read the vortex stuff - are not convinced this will survive on high revving engines - it is a press fit with a plastic ring between the steel trigger wheel and the crank......nah.......not when internal trigger wheels that are bolted on will come off when a few revs are applied.....

The way to do this is using the flywheel as the trigger ring

 

What set up do you have Rob ?

 

My car has a distributor and no crank sensor presently (quaint I know, but it aint exactly an engine lacking grunt) - I have not found the right system that I am comfortable using as I think front pulley-mounted sensors are asking for stone damage

Now I have a dogbox, I am considering further upgrades which will spin the engine quicker still (8.7K presently, 9.5K under consideration) and perhaps a large diameter toothed wheel on the crank will give more accurate fuel and spark control than a distributor at higher revs - the largest dia wheel that you could fit is the flywheel......it just needs machining appropriately or maybe the ring gear itself could be used.....?

I thought this might be the answer, but after reading the threads, I'm not convinced its robust enough for a race engine - I await evidence to the contrary as it would be a great idea if it worked in this setting

 

how does the dizzy work with after market ecus?

 

The dizzy works just like a crank sensor - it is giving the ECU data on where the engine is in its cycle; crank rotation angle if you like. It turns at half the speed as the crank though (dizzy is on the end of the exhaust cam which is driven by a wheel 2x the circumference as the wheel on the crank) and only has 4 'teeth' (resulting in 8 'pulses' per cycle) - so theoretically it wont be as accurate as a 60 tooth crank wheel (240 'pulses' per cycle). A toothed flywheel could accommodate at least twice this number of teeth so would give you 480 pulses per cycle and 60x greater accuracy of engine position compared with a dizzy.

But seeing as my 2L 16V engine puts out over 240hp - you gotta ask the question.....how much more accuracy does it really need? There has to be a point of diminishing returns but I have no idea where that point is.

Edit - so the 'point' I reach is....what (robust) system can be accommodated for a reasonable outlay? Taking a signal off the ring gear would be mint if that would work. We know internal ABF-style trigger wheels come off so thats out. Machining a custom flywheel with teeth is going to cost a lot. Using oem parts sounds very attractive if possible.

 

Back in the distant past, when I was at Rover, they started to use separate reluctor rings screwed to the flywheel, as sensors for the ECU. I guess something like that could work, but you could well end up the same issue as with OEM crank trigger wheels, where they let go outside of normal rev range.

Interesting idea on the ring gear, Rob. I guess they won't be fitted accurately enough to give a good TDC straight off, but how many teeth are there on a flywheel for the starter ring gear. If you machined one out, to give a reference position, could the starter cope, or would it make it more likely to break more teeth.

For a manufacturer needing a 100-150k mile life from an engine, it's not a good option, but for a custom job that gets rebuilt every year or two.... maybe? If you did break more teeth on the flywheel, then changing the flywheel is a pain, but less of a pain than changing the standard crank sensor wheel.

My other thought on this, is that maybe the need is more for consistency than absolute accuracy. If the trigger is offset from the supposed TDC, then as long as it's giving a consistent (-ly offset) reference point to map from, then does it really matter. When you think you're at 5*BTDC, it might actually be 6 or 7, but as long as it's consistent, you can still optimise the setup.

The argument against dizzy-based triggers, that I've often read, is that they don't provide an accurate reference point, but once the engine is pushing the dizzy, and the slack is taken up, aren't they at least consistent, particularly once they're at fast idle or above, or do they still vary too much?

 

Rob

Me & Bargate were disgussing this yesterday and with your engine spec and Bargates 270BHP is achievable with better timing and injectors.

Paul is running a 4 -1 external trigger on his webcom (Very old & dated but still gets 240BHP) , which is same a using dizzy for trigger and he is having issues at the momemnt loosing signal over 6k it using revs to 9k before it hits the limiter.

 

Mike

my trigger is set at 44deg BTDC for this reason

 

I dont really know how much they vary - thats the problem - I just have this gut feel that as revs rise, the accuracy of the system goes off and power is less than optimal - but I dont have any proof for this, and by how much.

I know of 2L 16V vw engines making over 260hp that are fitted with a dizzy-triggered system and 4 injectors. VW kitcar engines with 8 injectors and sophisticated ecu's (Marelli I seem to recall?) are reported to make 260-280 depending where you read.

How much would the dizzy-triggered system engine make fitted instead with a 200 tooth crank sensor?......thats the question really

 

How do you come to a gain of 30hp? (not a criticism...I am genuinely interested )

Paul's system is potentially twice as good as using the dizzy as the crank turns twice as fast (but again, how good is good enough...). I doubt his loss of signal is due to the use of a 4 tooth crank sensor - mine is fine to 8.7K - but I have had issues with higher revs in the past due to impending coil failure......

 

http://www.motorgeek.com/phpBB2/viewtopic.php?p=364468&sid=8479263c8544e2faa5cc8b64fc041386

audi s4:

http://images.google.co.uk/imgres?i...v=/images?q=flywheel+reluctor&hl=en&sa=N&um=1

 

Similar to the pug 106 gti flywheel

 

I read that vortex thread and could not find anyone who was as hardcore as some the track masters on here, to put this part on a 8000rpm plus engine using that press on pickup. Initally I liked the idea for non crank triggered vehicles. But in hindsight I am weary of this fitment on a forced induction engine spining to 7500rpm plus the integration of the oilseal with this part. It is not nice to be pulling out gearboxes when your pick up is off and you have to reinspect missing tooth position in relation to TDC. Then whats is the benefit behind chasing a more accurate rpm signal over a dizzy on a track/road 16V vehicle. Fuel economy? Misfiring? Poor crank to cam syncronisation causing a OBD fault?
Not many vehicles here revving to post 8000rpm. Anyone willing to do a back to back test switching from Dizzy hall trigger to crank tiggered pickup to crank trigger on damper to see if there are benfits.
I would also like to know what causes VW internal crank pickup to fail. What conditions such as engine speed of failure, type of engine modification, and engine load when failure occured.