Timing Advance

[DVST8R]

Well after an intresting disscusion with my boss's cousin. I learned a few things and I am more confused then when i started. :?

First I don't remeber how much advance our stock 1.6L pumps make but I am guessing it is less then the 15.5 degrees that the stock 1.9TDI's have or about the same.

Then we have the TDI PD150's that have a max of 24 degree's

Then finally we have what klass is into Pulling tractors he own 6 of them, with the 6th currently being built with 3 stages of turbo's meth/water inj between the stages and looking for about 200psi. He was pretty tight lipped about the workings of it put he did give me a few numbers one was RPM 7450 !!!! is what they will max it at (he said some guys turn about 8K). The other is timing advance he said over 50 degrees and probably closer to 60. He was rather vague with most of this stuff as they  are still just building it and have already put 60K+ into it and are estimating at over 100K by the time it sees its first hitch.

So what does this have to do with us? MORE TIMING. Now I know that FSPgtd was working on a cover for more advance and I found the one off of my ranger pump and it is significantly deeper then the VW one. I will mic it tomorrow at work.

I guess the question is how much timming advance do we have stock, and how do we measure it?

What are all of the different things that effect it?

[Patrick]

HOw much advance you need is partially dependant on load, and partially dependant on engine speed. In a typical gas engine, say a 350 chevy, initial advance with the engine idling would be between 6 and 10 degrees depending on year, pollution controls, etc. Max total advance (mechanical in the distributor plus vacuum in the distributor) at high rpm and full load (once again dependant on a lot of other factors) would be more like 30 degrees or more. Too much too soon can cause problems, and so can too little. What the relative numbers are for our diesels I'm not sure, but I'm looking forward to finding out!

[lord_verminaard]

I'm guessing that is going to be the key for having any chance of making the TDI's rev higher as well.  Unless I can find a super deal on a 1.6 or 1.9 IDI, I'll probably be forced to go TDI-M with my project.  Not that it's a bad thing, but it's going in a Scirocco, a true sporty car, and I want it to have a sporty feel with a usable rev limit of around 5500 rpms, wich isnt too far from what it currently is in gasser form.  Right now I'm not sure that too many people have even tried a hot-rodded mechanical TDI pump before so there might be some rpm's gained there, but I'm thinking timing will also play big into the equation.  I'm a long way away from doing this but I'm gathering up as much info as I can before I bite the bullet.  

Brendan
84 Scirocco 8v
00 Camaro L36 M49

[racer_x]

Are you asking about the static advance setting? or the actual total advance under dynamic conditions?

The static advance depends on how you set the pump. Stock, with 0.9mm-1.0mm of plunger movement, it's around 4 to 6 degrees BTDC if my memory is right. To some extent, that varies with wear inside the injection pump.

Dynamic advance depends on engine speed and pump condition. The vane pump/lift pump in the front half of the injection pump pressurizes fuel in the inlet portions of the main distribution pump. That pressure is higher at higher RPM's, and it operates an advance mechanism that works in principle like the centrifugal advance mechanism on the ignition distributor on a gas engine. If the lift pump is weak, the pressure will be lower and the timing will advance less. That's why some pumps seem to deliver a lot more power than other pumps.

And, when you rebuild the pump for performance, in addition to playing with the governor springs and altering the operation of the governor, you can also adjust/modify the advance mechanism and dial in more or less advance at higher RPM's. It's the same concept as re-curving a distributor for a gas engine. What you change is different, but the results are similar.

If you can get a dynamic timing diagnostic meter with the optical sensor that screws into the glow plug hole, you can map out advance vs. RPM's.