M-TDI Audi 80 quattro AHU/LT pump

[rbremiller]

I have a 1991 Audi quattro with an AHU, a 12mm LT AGK pump, K14 turbo, now with new nozzles. It's been on the road as my DD for a year and a half.
http://www.motorgeek.com/viewtopic.php?f=6&t=45645

 I've been driving the car for over a year with a set of new T4 injectors out of the box. It turns out, they were not .216's as promised but a smaller nozzle with a higher breaking pressure. It caused the engine to run in a very narrow power band and very noisy at all rpms. I changed the pump timing many times looking for the sweet spot.


New Years Day I installed a set of new Titan nozzles I've waited 8 months for and it runs beautifully now.
  
Pump as it arrived from Berlin via Czech Republic.
  
  I sent the pump initially to Giles to calibrate for my application. The pump was already factory rebuilt so all he had to do was adjust it (whatever it is he does). After I installed the pump but before I started it; I noticed that the yellow sealing paint on every screw was undisturbed. I examined and re-examined close-up pictures I took when I first bought it and they were all exactly the same. So I inferred that he never opened the pump and so it must have been OK(?) He changed the mount bracket after I asked him not to, as I have several. As it turns out then, I had no real reason to send it to him. The pump starts and runs well; but still has clatter under part load. I am looking to adjust the axis governor and would like some input on this. Not so much how to adjust it but whether or not this might help. This pump was originally set up for a lower rpm engine and I think the axis shaft should be turned out a half turn (CCW)? I've had no luck finding any pictures of the inside of an LT pump if anyone can point me in that direction as I want to understand how the low smoke governor works as well. I have rebuilt and repaired several IDI VE pumps, and I'm very familiar with them.
 
I've had my project/thread posted on 2 other sites for a few years now. A lot of fluff, K&N filter debates, and dyno queens. I find most who post on this site are more nuts and bolts, grease under the fingernails and most importantly share with me a fierce love for the mTDI. The last reason is what really sets vwdiesel.net apart from any other site. Kudos guys. Thanks in advance.

Rich B.

[libbydiesel]

I think the partial pedal clatter is just the nature of the beast with a 12mm plunger.  The 12mm plunger can inject a lot more fuel in less time and so at partial pedal, the injection event is much shorter and results in more clatter. 

[bbob203]

Yes my 12mm 4bt built by libby has quite a bit of clatter. Infact it sounds like a cummins.   It also has 230bar opening pressure as well as .216 nozzles.

[rbremiller]

My previous setup had a very sharp throttle response which made a difficult transition from on/off throttle. The current nozzles have eliminated that. It's now much smoother; more eTDI, if I may. I now have to reset the pump timing as it smokes too much at .80mm; where it had to be for the previous nozzles. There is such a wide range of adjustment that people are using that it's confusing. I'm going to set it @ 1.15 for now going by one of Andrew's posts about using his piezo timing light to get baseline timing readings from a # of diesels. This is the best explanation I've come across so far. (Thanks Andrew)

I do not know how Westyman (Karl Mullendore) arrived at that recommendation for a timing setting.  I can tell you how I've arrived at mine, tho.  I have a diesel pulse adapter and strobe timing light with rpm and advance functions.  The pulse adapter has a piezo pickup that clamps to the #1 injector line.  When the pressure builds in the line, the steel line gets slightly bigger in diameter.  That enlargement of the line compresses the piezo crystal and stores a charge in it.  When the start of injection occurs, the line relaxes slightly.  That relaxation of the pressure on the crystal causes a discharge and sends a signal to the pulse adapter box.  That box transforms that signal into a typical spark signal that can be read by a typical gasser timing light.  That timing light flashes a strobe light with each pulse.  The advance function of the timing light lets me very quickly and accurately see exactly the #1 injector's start of injection.  I have tested many VE pumps both TDI and IDI with stock nozzles set to stock timing specs.  With calibrated stock injectors and the pump in good condition and set to spec, using my diesel pulse adapter and strobe, the start of injection always falls between 12° BTDC and 14° BTDC.  Personally I find that 14° BTDC is to clacky on the TDIs.  When building a pump I install it, use my pulse adapter and timing light to initially set it to 12° BTDC.  I then adjust the fueling and set the idle.  With the idle set I re-check the pulse adapter timing.  When I have removed the injection lines I use my dial indicator to check the plunger lift @ TDC for each pump.  The delivery valves affect the timing fairly significantly so the plunger lift of each pump will be different, even with a specific set of injectors.  I can say that each mTDI pump that I have tested has had to have a plunger lift between 1.15mm and 1.45mm with the idle set and the pulse timing @ 12° BTDC.  I attribute the differences entirely to differences in the delivery valves and the amount of residual pressure they hold in the metal lines.  Similarly, changing injector opening pressure will change the timing of the start of injection as a higher pop pressure takes more plunger lift to pop.

   

BTW I just had my first gelling experience ever in 30 years of dieseling and I'm not talking about shoe inserts. The good thing is I knew exactly what it was and just kept moving until I got more fuel and 2 cups of PS. It was -15º last night and 0º this AM. Definitely the coldest weather this car has seen. I don't have the thermostatic filter "T" on my filter flange so that probably contributed to it. I am interested in anyone who's changed the axis governor with good results.
Rich

[bbob203]

I went and paid Andrew a visit back in October and we ended up setting my timing to 12* btdc with his nifty pulse adapter. Prior to that (last march on) I was running my timing anywhere between 1.2 and 1.4 and it just never seemed to be at its full potential per what he said to expect. I have never rechecked with the a dial what it is set to now but we had to bump it past 1.4 where it was set when I showed up to his place in order to get it set to the 12* mark.

[rbremiller]

I've been advancing the injection timing in .05mm increments for a few weeks and I'm up to 1.20mm. The useable power is increasing and so is the noise. I'm really understanding now that the "Cummins" rattle is unavoidable with my pump configuration. Got it. The exhaust scent indicates a more complete combustion as well. I'm looking for a piezo pick-up adapter for my timing light ultimately. It's amazing all the different timing specs being used for these 12mm mTDI pumps. Using a light seems to be the only way to put you in the 12º BTDC ballpark. Tuning by ear can be very subjective IMHO.

[8v-of-fury!]

AHU, stock turbo, stock intake, no I/C, LR 300TDI with an AAZ camplate (high lift, steep ramps), about 50psi of idle pump pressure, .216" Veg-Injection nozzles on stock injector bodies with tons'o'miles on them.

I have been as high as 1.40mm and a measured low of 1.14mm. I am at 1.14mm right now, but I was also thinking of creeping up on the timing to see how it felt. 1.40mm was FAR too much, mileage was poor over a long highway trip and it was SOO clacky/rattle. 1.14mm seems a little low but it still doing alright.

[rbremiller]

Thanks, I appreciate the input. I've followed your thread as well. Going up to 1.25mm and will stay there for a tankful to evaluate power and mileage.

[theman53]

FWIW, Giles told me to start with 1.25mm for the 12mm bosch pump. From what I have read Libby has posted that would seem accurate. I think he has been everywhere from where 8v is at to 1.5mm depending on the delivery valve lengths. I am not 100% on that so you would have to ask him or read tons of his posts.

[rbremiller]

I quote one of Andrew's posts earlier in the thread as a basis for what I'm doing. Giles told me to set the pump between .90mm -.95mm. As I mentioned earlier I've been mislead by Giles about a few things. Thanks for the post; I seem to be on the right track.

[8v-of-fury!]

Giles told me to set the pump between .90mm -.95mm. As I mentioned earlier I've been mislead by Giles about a few things. Thanks for the post; I seem to be on the right track.

For a bone stock 12mm Land Rover pump that he didn't touch the insides of?? Interesting..

[rbremiller]

It's an AGK VW LT pump. He told me it was the first one he'd seen. My new pump & new injectors sat in his "core return" pile for 3 1/2 weeks because he forgot that's how he told me to send it. His last advice was time it by ear. I just reread the email. This all just an education. Some have had a great experience with Giles' pumps.

[8v-of-fury!]

Oh so basically.. this was a completely ***ty experience :0  lol.

[rbremiller]

The reason I sent him the pump was to address the low-smoke governor spring issue. When he sent me back the pump; said I might have slight inflexibility at low speed; ie: jerkiness when rolling on the throttle in second gear. I didn't ask him what he did to adjust the pump because it's "impolite." In our arcane little world of VE pump tuning secrets are "golden eggs." I trusted him to do what he said he would do. I've learned a lot more about mTDIs since then. I don't want to impugn anyone's character, just relating my experience.
  I moved the timing to 1.26mm this afternoon; will drive it tomorrow to evaluate.

[rbremiller]

I've been driving the car and it runs excellent. After a full tank to check mileage I'll probably move it to 1.30mm. I've got some sub-zero temps coming in for a few days so we'll see how it starts.