Author Topic: WHAT CONTROLS TIMING ADVANCE? (Read 4254 times)

Tony2ltr · « **on:** April 04, 2009, 09:03:04 pm »

Hey folks, I am considering some really aggressive water/methanol upgrades for my 1.6 rebuilt TD in my 92 jetta ( formerly ecodiesel). I have been running about 25 PSI regularly on my engine since I put it in in December, and it seems to be holding up well, but it is getting warmer, and I have no intercooler, except for the water injection cooling effect.

In the past I noticed that when I use straight methanol injection, I can accelerate the car slightly without increasing pedal angle.
Here is my question:
What controls timing advance within the Injection pump, is it RPM, or accelerator pedal/lever angle? I want to really push the envelope with the water injection, and am considering methane injection (I used to convert Gasoline cars to CNG)
I know that you can methan and/or water/methanol misting. I may end up completely disconnecting the Throttle cable, but if advance is accelerator pedal controlled, It won't advance the pilot squirt, which really needs to advance according to ENGINE RPM, not pedal input.

Does my question make any sense? I know there is a lot of information to wrap your head around, but really, I just need to know what mechanism is responsible for the timing advance inside the Injection pump on a NA pump.

Thanks
Tony

Tony2ltr · « **Reply #1 on:** April 05, 2009, 04:15:45 am »

That is the best answer ever!
Thanks a billion BTU's
-Tony

CoolAirVw · « **Reply #2 on:** April 07, 2009, 01:52:08 am »

The following came from the link below.

Quote from: "libbybapa"

Why is internal pump pressure important?

It is important because it controls the dynamic timing advance and if the dynamic timing advance is incorrect then fuel economy and performance will suffer. The dynamic timing advance piston is moved according to the pressure difference between the pump inlet and the internal pressure after the vane pump and internal pressure regulator. The "out" banjo bolt has a specifically sized orifice as part of the internal pressure regulating system as well. So basically you have a specifically sized hole slowing the flow of fuel from the pump, you have a vane pump pushing the fuel in there and you have the timing piston moved according to the amount of pressure built up in the pump.

Andrew

Heres a link regarding subject matter.....

http://www.vwdieselparts.com/forum/viewtopic.php?t=5936

Tony2ltr · « **Reply #3 on:** April 07, 2009, 12:03:10 pm »

I know that internal pump pressure is important, I thought it was a functionof rpm though. I know the banjo bolt affects internal pressure, but does the accelerator lever affect pump internal pressure at all direclty, or does it affect the governor, which affects pressure. I will read more....
-Thanks
Tony

Tony2ltr · « **Reply #4 on:** April 07, 2009, 12:23:44 pm »

I don't know why, but I could not get your link to work...

let me try this...please correct me if I don't have this right:

advance is a function of rise in pump internal pressure.

Internal pressure is a measure of pressure rise created by pressure pump minus controlled outlet (banjo) relief pressure drop.

IP pump accelerator assembly increases pump rpm by adding fuel to the engine through moving the slide collar so more fuel is delivered to the injectors. When necessary the governor restricts this movement.

as a result of reducing the fuel delivered to the engine through the injection pump, as I plan to do, there may be a resulting increase in advance, because from the factory, the pressure drop created by increasing fuel delivery(factory set)is taken into account when setting accel pump spring rate as per expected increase in pump internal pressure by the pump minus expected loss through the banjo and fueling...---right?

maybe a little more wordy than necessary, I hope you can follow...

-Tony

Vincent Waldon · « **Reply #5 on:** April 07, 2009, 02:07:28 pm »

A simpler way to look at this is perhaps:

- advance is controlled by internal pump pressure
- internal pump pressure is a function of the low-pressure vane pump, which provides more pressure the faster it spins
- pump RPM is directly related to engine RPM via the timing belt
- thus, advance is controlled by engine RPM

jtanguay · « **Reply #6 on:** April 07, 2009, 03:14:25 pm »

if the pump is setup to give a lot of fuel (and i mean a LOT!!), this could alter the timing advance. this is why the pump should be calibrated on a test bench, otherwise you'll be going for a drive, take off the timing piston cover, shim it or remove shims, etc. or even mess with the internal pressure regulator if the pressure drops too low.

i don't think underfueling will increase the timing though, as the pumps internal pressure is regulated anyways. and the timing curve is very linear as stated above it is matched to engine RPM.

now if you notice a drop in internal pressure when hard accelerating, then your vane pump is probably bad. this will give black smoke and lack of power. switching to a softer timing advance spring (and shimming as necessary) will help, but 'mask' the underlying problem.

Hey · « **Reply #7 on:** April 07, 2009, 06:21:54 pm »

There IS also a sleeve on the governor axis that will give more advance with throttle.

Vincent Waldon · « **Reply #8 on:** April 07, 2009, 06:49:01 pm »

Quote from: "Hey"

There IS also a sleeve on the governor axis that will give more advance with throttle.

Yup... good catch.. and iirc some pumps do a limited amount of load sensing as well with a tie-back to advance.

So, should probably say "advance is *primarily* a function of engine RPM".

Tony2ltr · « **Reply #9 on:** April 07, 2009, 07:23:33 pm »

Man, great stuff. I knew you guys knew what the hell you were talking about!
so it looks like I may have to keep the accelerator cable attached, but I could probably get away with turning the fuel wayyyyyy down, I have the fuel screw cranked about 1-1/4 turns in now for about 25 psi boost. I will probably turn it back about 2 turns and re-adjust idle, crank up the water injection with methanol and take it for a ride, see how it does. If I can match factory performance with a leap in FE, I would be psyched. If I could match the 25 psi boost and performance that I have now without the cropduster exhaust, it would be even better!
By the way, does anyone know where I could get a vane pump? how about injectors?

-Tony

Hey · « **Reply #10 on:** April 08, 2009, 07:00:28 am »

Ok... if you want the timing to ONLY vary with RPM.. here is want you can do:

Use a 1.9td AAZ pump (the one with the selenoid in from of the pump) put 12V on the front selenoid and the timing advance will always be maximum with throttle position.

Adjust the timing with the 12V selenoid ON and timing will ONLY vary with RPM. In fact, and unmoded AAZ pump will work well with 12V on the selenoid.

tadaaaaa!!

CoolAirVw · « **Reply #11 on:** April 08, 2009, 08:41:03 am »

Quote from: "Hey"

There IS also a sleeve on the governor axis that will give more advance with throttle.

Can you elaborate on that some? Bosch training manual that I have doesn't explain this.

Tony2ltr · « **Reply #12 on:** April 08, 2009, 06:22:05 pm »

Awesome. This is probably the best discussion on the pump that I have heard yet. Thanks everybody. Please continue...
-tony