How does the throttle work on an ALH? (VE)

[she_loves_the_D]

I know its a super old topic but for some reason i never really thought about it. Maybe it could be a fun conversation on the old freds tdi club.
I know there is no throttle body as the fuel is injected directly into the cylinder.
I know the fuel timing is controlled by the timing belt.
I know the boost is controlled by vacuum via the n75 valve.

But i never really thought about what happens when i hit the accelerator pedal.

??????????????????????????????????????????????????
Is there a solenoid in the pump that allows more or less fuel? or is it vacuum controlled or something? I cannot find a breakdown or explanation anywhere for some reason.
???????????????????????????????????????????????????

I am asking because i want to do a swap. Most likely into an older car that does not have to pass emissions. I am just trying to figure everything out. I was looking at so many engines and the ALH is still in a fair price range and seems to be the most simple as there is not much that goes on electronically. Get rid of the egr system. Its either an alh or turbo vr6 (15lbs on stock with just a head spacer).

 

[Mongler98]

pedal goes down, sends signal to ECU, ECU tells IP (injection pump) to increase fuel by moving the lobe in the QA (Quantity adjuster). more fuel is added
its a bit more complicated than this but thats the basics of all the parts involved.

 

[300D]

Although this is for a mechanically actuated version, the principle is the same for ours:


https://www.youtube.com/watch?v=SqBlqdeP3uE

 

[steve6]

You buy, or have the Injection Pump converted to mechanical. Lots of info out there, just gotta search. Sometimes referred to a 'm-tdi' i think

 

[Curious Chris]

And the N75 controls the boost using Pulse Width Modulation based on what the ECU says it needs in the amount of air to support throttle position. The ECU waits for the MAF to confirm the airflow is sufficient for the desired power. The MAP sensor also measures temperature as the hotter the air gets the less dense it is (remember PV= nRT)

 

[KLXD]

To expound a little:

The high pressure plunger moves "up" toward the end of the pump to "compress" the fuel.

I rotates to select which cylinder gets the fuel.

There is a hole in the side of the plunger that opens at the end of injection to determine how much fuel is injected.

There is a ring around the plunger that blocks that hole. The QA moves that ring. At idle it only leaves it blocked a small part of the stroke of the plunger so little fuel is injected. As you depress the accelerator the QA moves the ring farther so it blocks the hole for more of the stroke.

When you shut off the engine the hole is unblocked for the full stroke so no fuel is compressed or injected.

On the old "mechanical" pumps the pedal moves the ring. Since the spill port is always blocked enough for the engine to idle shut off is effected by cutting power to the solenoid valve on the side of the pump head. I then blocks fuel entering the plunger bore.

 

[Jamierara]

So, if I figure out the pin out for the QA, I can slowly apply positive voltage and I can control my throttle that way? I can probably just use any electric pedal within range then, right?
(I got a TDI that I am completely modifying and putting in a truck, so it’s gonna be me and the Haynes)

 

[ts888]

Although this is for a mechanically actuated version, the principle is the same for ours:

"Leave the Full-Load adjustment screw alone!"

 

[burpod]

So, if I figure out the pin out for the QA, I can slowly apply positive voltage and I can control my throttle that way? I can probably just use any electric pedal within range then, right?
(I got a TDI that I am completely modifying and putting in a truck, so it’s gonna be me and the Haynes)

you'd be better off tuning it the right way and that means a lot of things. putting a tdi in a truck, you're going to have different gearing,load, etc requirements. with doing it in the software, you can really optimize timing/boost for your application and get fueling accurate, so boost will work better

 

[KLXD]

So, if I figure out the pin out for the QA, I can slowly apply positive voltage and I can control my throttle that way? I can probably just use any electric pedal within range then, right?
(I got a TDI that I am completely modifying and putting in a truck, so it’s gonna be me and the Haynes)

Idunno but seems you could use a mechanical QA. I think that's what they do when they build a pump for a MTDI.

 

[ts888]

Or just use the VW accelerator pedal.