808 test bench - sensor values

[bldnut]

I'm geussing the dizzy youve got is from an old big cap blue motor, if so you use the VN cap with a XD-XE ford V8 rotor, this combo works well

[Holden202T]

yeah thats what i believe it to be, it didn't have a rotor button or cap so i'm only guessing the top of it looked the same as the VN one though with the slot etc for the cap to locate.

[bldnut]

I've used that combo heaps on the old carby engines and it works a treat, on my 253 VH i also used the VN leads so they were hidden down the back of the rocker covers insted of going over the rockers

[Dylan]

What's the go with the xd rotor button?

[Holden202T]

its probably just the right dimensions to suit the combo.

[bldnut]

XD/XE V8 bosch dizzy rotor is the right size, hight and pin location to suit the early blue bosch dizzy when using the vn cap, i think from memory the early dizzy shafts are imperial were as the vn on is metric (its been over 15 years since i worked it out)

[Circlotron]

All this talk of using a magnetic reluctor type distributor in place of the Hall effect one is good. Just watch out though - in my experience a reluctor setup is VERY fussy about what kind of load it is presented with. They have inductance + resistance in the pulse generator coil and that spells =phase shift= that varies depending on the exact load. Phase shift = an unknown amount of retard. If you feed a module from a reluctor and the two are not specifically made for each other then you may get unexpected results. You really need to bite the bullet and put your new combination on a distributor machine to check that it behaves as you expect. Major pain in the butt, but so is pulling the distributor out of a VN, especially several times.

[antus]

how many degrees out would you expect due to phase shift? 10 degrees spark at cranking speeds has a lot of room for error and once the ecu goes in to bypass mode above 400 rpm you can adjust the reference angle to compensate and get the timing dead on.

[Holden202T]

well its basically what the JE Camira had and i've successfully used it on 202's and theres really no difference on the v8 other than the amount of pulses per rev .... but yeah i know it all works fine, as far as spark shift i have never tested that side of it and i doubt it would be a major issue otherwise the camira wouldn't have used that setup ?

i guess you could fairly easily test it, even in a car, set timing to 10 degrees or any number across the entire spark table and see what happens as you rev it and see if a timing light shows the spark moving on the balancer!

even going from 1000 -> 3000rpm .... if you can do that with 1 degree or less of timing movement then you will get a fair idea where its at.

as for testing, i have a 304 on the engine stand so i have no issues with dizzy access to prove the concept works

[Circlotron]

I think I still have a mag trigger MSD distributor laying around somewhere to try unless I gave it back... I also have the luxury of of a distributor machine and the liability of an in-situ 304. Anyhoo, several years ago I was messing with this home-brew circuit that the MSD dissy fed trigger pulses to, and with a 47K load (100K across terminals, then 100K feeding back to back 1N4148's, 4n7 cap across first 100K, 1n5 cap across second 100K it was about right. Dead on to 10,000 rpm. Drop the first 100K to 10K and there was about 1 or 2 deg retard per 1000. Can't remember the exact figure now. You just have to trial and error it and when you get it right for one kind of distributor doesn't mean it's right for another different sort. This is why I like Hall effects.