Bumping the IP timing one tooth

[8v-of-fury]

It's more accurate. Even with a dial your still guessing. but with a light you can set it exactly at 12* btdc. Every pump varies a bit.. your pumps being set at 12* btdc may yield a dial reading of 1.15mm but mine may yield a dial reading of 1.08mm at least thats how andrew explained it to me when we used his on my engine. I also think it can change as things wear in/out. If you have the cash its a worthy investment as I'm sure you will have to take something on your engine apart again where you may have to remove the belt or ip.

Correctly said sir, the number of where your timing means nothing really except for where it runs best on your exact setup. It is not definitive to say all will run best at 0.96mm, they probably all would run perfectly at 12* btdc ignition.. but for that to happen your actual injecton timing would need to be way different than another trying to hit the same timing.

[TylerDurden]

Yep yep yep...

Start of combustion has a few factors: fuel quality, air temperature, engine temperature, compression, residual line pressure, break pressure, spray pattern... and injection pump timing.

[745 turbogreasel]

I've wondered for a long time how much the rubber  rectangles in the  pump drive play in to it too.

[8v-of-fury]

Those do not run the injection part of the pump, they are merely to interface the toothed ring that drives the governor weight assembly to the pumps main shaft.

The main shaft, and cam disk are locked together with a tight machined fitting cross dealio. I wouldn't suspect much loss of accuracy there.

[Gizmoman]

So, from what I've been reading here and on other diesel sites, 12 degrees BTDC is about right for an IDI at idle - correct?
Reason I ask is that 12 BTDC would be tough to find with a dial indicator stuck into the backside of my pump and may possibly warrant the expense of a light.

That said, I can't find a decent light on the web. I did find one but I need to purchase an adapter for an additional 130 bucks to fit the lines on the VW engine. Sorry but that really put me off as the one that comes with it is useless (but I still get to pay for it).

[8v-of-fury]

If you could rotate the crank to roughly 12*..

Then set the pump to be near its highest cam lift ...

I don't think it works so easily as I had just thought.. lol

[CRSMP5]

dont worry i was thinking protractor on pump gear... then nahh wont work.. then trig to mark flywheel from tdc..

but how do you figure out tdc of the pump together?

[vanbcguy]

What does any of that have to do with when sufficient pressure builds up in the line to pop the injector though? The dial indicator is about the best you can do (besides using a timing light) as it is measuring the volume of the injection head by way of its position, and someone has already done the math / experimentation to build the relationship between plunger position and injectors popping. And that relationship changes if the pump head is worn, if the injectors are worn or really even if you change the injector lines...

[vanbcguy]

Don't forget, the control collar in the pump cuts off the injection before it gets to the top of the cam plate under anything other than WOT...

[Mark(The Miser)UK]

dont worry i was thinking protractor on pump gear... then nahh wont work.. then trig to mark flywheel from tdc..

but how do you figure out tdc of the pump together?

Not sure what you are looking for, but here is some data for a standard 1.6 pump...

Around the operating point of the pump ie 1mm or 39thou, each flywheel tooth is 5 thou on the dial gauge, or 2.73 degrees crank...

[Gizmoman]

The more I think about it (uh-oh, here it comes), the great thing about the light is that it's measuring when the injector actually pulses which is what really counts.
The dial indicator is only telling you when the pump is at full lift (on a non running engine).

I'm going hunting for a decent light - again. . .

[CRSMP5]

well what i mean is there is no true pump shaft to pump body exterior marking for tdc.. there is one on the gear with pointer to bracket.. but pump body turns.. so what is true 100% tdc of the pump to see where 12"* is...

when the dial caliper stops turning and you turn the dial to 0 is that tdc?

i guess i am just not undertanding the whole issue here..

you put it on tdc.. insert dial gauge.. turn ccw till it stops.. set to 0.. when tdc on flywhell hits tdc you look at pointer... so thats in theory a degree that pre tdc.. so is that not like - 12* then?

he/this has me so mixed up..

i cannot see any way someone would install a pump at 1 end of travel.. honestly if you tried it would turn as you inserted lock pin.. would have had enough cam plate spring loaded to do so..

unless the pump is hitting the head.. it should move both directions a good tooth.. take lines off to see..

now moving the pump by ear.. sure why not.. just make sure to use a dial caliper before, then after.. so if you decide to change it again you have some referance points recorded.. and only change 1 thing at a time...

to mod intake and timming you will not know which of the 2 did the change..

[CRSMP5]

one more giz.. which is better? line style or fiber optic... fiber optic is off when it literally ignites vs pressure drop..

if a injector streamed vs sprayed fuel.. those 2 effects i bet would cause a differance too in timming light designs..

[TylerDurden]

^^ Hence the value of hillbilly timing... you hear the light-off.

The pulse can tell you... when the pump strokes?... or when the injector opens? Neither of which represent start of combustion.

[8v-of-fury]

^^ Hence the value of hillbilly timing... you hear the light-off.

The pulse can tell you... when the pump strokes?... or when the injector opens? Neither of which represent start of combustion.

This. What I have been saying for a long, long time. Nobody listened though.