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I am trying to nut out:

if an old style engine distributor is turned one way or the other to advance or retard - is the timing altered degree for degree in relation to the dizzy and ignition timing as seen on the crankshaft?

Or is it a one for two OR two for one deal ?

We have a two turns of crank to a camshaft revolution so not want to confuse that issue.

I have a dizzy apart and looking at how far the mechanical advance mechanism will advance.

The distance between two spring posts is 50mm giving a circumference at that spot of ~157mm.

The gap at standstill is ~6.5mm drill bit

Divided ~157 by ~6.5 to get about 24. Divide 360 degres by 24 to get 15

The bit I have has 15.5A stamped on it, wondering if that stands for 15.5 degrees advance at flywheel

The specs I have for this Hitachi D4R84-49 dizzy from EA82T has specs of centrifugal advance

nil@500rpm
7.5 deg @ 1800rpm,
11 deg @ 2700rpm

the vac advance has up to 10.5 deg and retard of 4.5 deg


So, looking at it like this. initial of 20*BTDC factory spec, at 2700 when boost is well and truly there add 11* mech and subtract 4.5 for boost retard and I get 20 + 11 = 31 - 4.5 then = 26.5*BTDC and knock sensor can retard up to 10 degrees and slowly release it, I recently set initial to 16* instead of 20, and experiencing what may be the timing slowly being released by knock box it is sort of a weird hesitation - sometimes

I may look at it as the 6.5mm gap the mech advance has gives 11 degrees advance so about every 1mm I reduce that gap I reduce max mech advance by ` 2 degrees.
Hmm, helps to come in here to think things out loud

Feel free to comment

Jonno

explain : Tinkering with LPG, needs to have max timing total kept to 28 degrees as normal aspirated. Thinkng turboed may need even more held back under boost, although some LPG gurus say not always so for turbo and gas - all depends on what I don't know. Ben letting knock sensor sytem take care of things in the past but if this system fails due to age? internal mechanical back up will save engine is my thinking.

if you held the dilithium crystal @ 17 degrees perpendicular to uranus,it just might work scotty,um i mean jonno......um have you considered using a timing light dude?

actually, in your moment of humour there Dan, you and your Baja remind me of a mechanic fiddling with a Porsche engine from a snow plough being fitted to a Baja, twin Delortos , a missfire while his bearded face was too close, fingers snapping open the throttle A change of underpants for a few of us there.

Do you know how hairy it is leaning into an EA82T with timing light in one hand trying to get boost to watch timing changes. I need a dyno , so was resorting to theory for starters. Add compressed LPG vapours ready to unleash if a backfire occurs .....

time to stick my cheeks on the boost gauge to se if I can give its dizzy six pounds

steptoe
is it possile to simplify the question??


if you want more or less advance than you can get with the dizzy pull it out and move the base one point around.
if this doesnt do it its time to get into that computer of yours abnd have a play

Thats sounds like a hairy proposition or no hair with a backfire thanks..

Hey jonno i noticed you mentioned vacuum advance of 10 degrees or so....and retard of 4 degrees or what ever.....
it just jolted my memory,that vortex i just sold had 2 vacuum diaphrams off the dizzy piggybacked.....factory produced without a doubt...

where 2 hoses could go....vacuum and boost i am guessing...but why when it was factory n/a...non of the ea/ts i have seen have more than 1 vacuum advance diaphram hangin off the dizzy.....maybe shuffbag could post a pic if we needed to see it again...
my turbo engine runs better than the average ej20t and only has the stock single diaphram dizzy..(1985-1987.may)

for spike, simplified questin

if an old style engine distributor is turned one way or the other to advance or retard - is the timing altered degree for degree in relation to the dizzy and ignition timing as seen on the crankshaft?

Dan, I think I have seen the two chamber diaphragm on a NA Vortex FWD myself, believe it is pollution style, limiting advance while cold, the other advance when op temp.

The new unit I bought genuine (swapped a testicle) has internal advance and retard in the one chamber. advancediaphragm options can build one for about a third of the price, may see if he can build one with more retard for boost

something on the models using VINs I had a rolling shell 11/85 compliance plate with BROBF in the VIN, the first B means it is an 86 model although built in 85. My current is 3/87 compliance plate date 179 VIN digits younger is also a BROBF regarded as an 86 model too AROBF is 85 'build' or MY likely also a SUPER fuel model. BROBF's were unleaded

My downfall may be LPG octane rating not as high as it used to be or timing is just too advanced for its slow burn rate - does that make sense at 5.00 am ?

I have slipped a 10mm length of rubber vacuum hose over these pins reducing gap from 6.5mm to 4.5 mm so reduced gap 2mm, should reducing max advance by about 4 degrees. For longevity I should source silicone hose.

Tested my knock sensor circuit in less than ten minutes, spent more time thinking about it than the actual test took. Found timing light, multimeter, hooked red end of DMM to test lead near coil - black wire white insulator over 6.5mm female blade terminal, black DMM lead to battery NEG.

Started car to find it read 1.72V which is what we are looking for, found when tap block near sensor with breaker bar end the volts read near 4.5V and watched as timng went from 16* back to about 6 or 8 and slowly back up to 16 after the knocking stopped. According to manuals it is working fine. Possible that the pinging ? I think I hear is just before knock sensor retardation begins.

Often hear cars in traffic pinging like crazy on take off wondering if they have slow or roo ted knock system

Not all EFI cars have knock sensors.

If you want to produce boost without the engine running, a syringe like this

is good for accurately producing positive pressure in diaphrams


What are you doing up so early?

too much caffeine it 180grams of rum n raisin cadbury choccy that I gobbled before bed maybe? syringe ! good one 99 !