Author Topic: Custom pump calibration  (Read 1231 times)

July 14, 2022, 12:02:19 pm

Bigmick77380

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Custom pump calibration
« on: July 14, 2022, 12:02:19 pm »
Hi everyone,

I made a custom pump for my AAZ (rebuilt the engine, Holset hx27w turbo, and custom pump with a xud9 Citroen engine pump and an 11mm head) and I have some issues with the calibration...

Timing set to 0.91mm, cold start is good, hot start a little bit harder (maybe I have an air leak)

Idle is chaotic,(impossible to set, it goes up and down between 800 rpm and 1200 rpm without touching anything. If I play with the idle screw, I have a "point" where the pump slowly goes from 800 to 1200, impossible to set a 950 rpm.

Off boost, nearly no power. Flat out and wait for it, then the boost comes (at 2500/2800rpm) and the power shows up (Waste Gate spring set to 0.5bar/7PSI for now).

Does anyone have any idea why my idle is so chaotic, and why with no boost I have absolutely no power?

Thanks, and excuse my bad English :)

did some edits for ya.  ORcoaster
« Last Edit: July 15, 2022, 01:09:50 am by ORCoaster »



Reply #1July 15, 2022, 02:54:19 pm

libbydiesel

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Re: Custom pump calibration
« Reply #1 on: July 15, 2022, 02:54:19 pm »
Tough to tune a pump when the timing is completely unknown and subjective.  I would try advancing a bit, testing, retarding a bit, testing, and see where smoke is minimal and power is best.   

Your current idle setting sounds like it is above what the idle spring can handle and getting into the main spring(s).  There are a couple ways to deal with that but from the rest of your description I would proceed as follows.

Looking at it as wholistically as I can, given your symptoms, the first thing I would do is increase your max fuel.  That will increase the fuel off-boost and also increase the idle.  For testing, it might be a good idea to remove the boost line to the aneroid and plug the line (no need to plug the port on the pump).  Check your EGT gauge, boost gauge, and smoke.  Keep adjusting up until you see a bit of smoke or close to max EGT *prior to boost kicking in*.  Testing on some hills can be helpful to gauge that point.  As far as off-boost performance, that's as good as it will get.

That increase of the max fuel will naturally increase idle and may well bring it into the range where the idle screw will work well.  See if you can now set it at 800-850 and have it stay there.  Why do you mention 950?  That's higher than I would want it and likely not going to work.

Now reconnect the line to the boost aneroid.  Report back what happens regarding smoke and EGTs when boost starts to kick in and at max boost at higher rpms. 

Reply #2July 23, 2022, 11:15:30 am

Bigmick77380

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Re: Custom pump calibration
« Reply #2 on: July 23, 2022, 11:15:30 am »
Thanks for answering and sorry for the late answer, no time to work on the car this week...

So today I played a little with the fuel screw, when the engine is cold it runs much better now. It is more stable, starts right away, I don't have too much smoke off boost, and it runs pretty well.

But when the engine is hot, it's really hard to start (like I have no fuel), and the idle drops to 600/650 rpm, and the car starts shaking.

I found that my injectors are not tightening enough on the head (i see some bubbling on the thread between the injector and the head), do you know the torque specs for them? I'm scared of messing up the head thread...

Do you think the injector leak can cause a hard start when the engine is hot and the rpm drops?

Sorry again for my bad English, hope you understand what I'm writing, and thanks again for the help!


Edited for clarity by OrCoaster
« Last Edit: July 24, 2022, 10:39:18 pm by ORCoaster »

Reply #3July 24, 2022, 12:10:45 am

fatmobile

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Re: Custom pump calibration
« Reply #3 on: July 24, 2022, 12:10:45 am »
52 ftlbs on the injector torque.

 The engine is tighter when it's hot.

Often, the hard start when hot problem ends up being a weak starter.
« Last Edit: July 24, 2022, 10:41:25 pm by ORCoaster »
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with a re-ringed, '84 quantum, turbo diesel, MD block

Reply #4July 24, 2022, 11:56:09 pm

libbydiesel

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Re: Custom pump calibration
« Reply #4 on: July 24, 2022, 11:56:09 pm »
Bubbling at the injector threads is almost never from a leak between the injector and the head.  It is caused by fuel leaking down into the threads where it sits until the engine gets hot enough to boil it off.  Fix any fuel leaks at the injectors and run the engine through a couple heat cycles and the bubbles will go away. 

Reply #5July 31, 2022, 06:53:52 am

Bigmick77380

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Re: Custom pump calibration
« Reply #5 on: July 31, 2022, 06:53:52 am »
Well, problems solved

In fact, my 11mm head was worn out, so I change it with a spare one in 10mm from a 1Z.

Now it starts right up when cold or hot, the idle is much stronger (when I go in 1st gear or reverse, the idle barely drops without touching the throttle), and the car is much more drivable than before.

The only little thing that is not really a problem is that when the engine is hot, sometimes the idle increases a little after I rev up (like 200 or 300 rpm), if I restart the engine, the idle goes back to normal.

Maybe it's the idle spring tension?

Thanks again for all the answers!
« Last Edit: July 31, 2022, 09:54:53 pm by ORCoaster »

 

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