M-TDI Audi 80 quattro AHU/LT pump

[8v-of-fury!]

So stock TDI breaking is 195bar? The LT pump must have a steep ramp and high lift cam plate then to require so little advance?

what was the cam like in the pump you built bbbob?

[libbydiesel]

His pump has the stock Cummins 4BT camplate which has higher overall lift but is less abrupt than the stock TDI camplate.  I cannot comment on the LT camplate as I haven't had one but I disagree that it 'must' have a steeper camplate.  I mentioned three variables and even if using stock opening pressure injectors it is illogical to assume you can know what 'must' be WRT either of the remaining variables without knowing the other one.  

[8v-of-fury!]

When someone says "well it must be this then?" instead of "it is this way for sure, I can prove it", it is because they do not know %100 and are implying that by saying that.

So unless you know all of it, most people are just shooting in the dark.. lol.

This pretty much (minimum %78) confirms why timing by ear (or pulse adapter if you have the means), is substantially better then any one timing number for any one engine.

[libbydiesel]

One other variable that I believe affects the static timing is the residual line pressure determined by the delivery valves.

[Toby]

When someone says "well it must be this then?" instead of "it is this way for sure, I can prove it", it is because they do not know %100 and are implying that by saying that.

This pretty much (minimum %78) confirms why timing by ear (or pulse adapter if you have the means), is substantially better then any one timing number for any one engine.

Well, timing by ear is for idiots. I suspect you are using some form of performance testing. The G-Tech, Norwegian Dyno, ets are not part of "timing by ear".

I have known guys that did their timing "by ear". The thing was they were CONSTANTLY timing their cars by ear. With the Norwegian Dyno and an hour or two you will know where the sweet spot is. Lock it down and forget it. I always put the indicator to it so I know where to put is back to.

[rbremiller]

I got hold of a pulse adapter and checked my timing. http://www.vwdiesel.net/forum/index.php?topic=34340.75   It was exactly 12º. I am completely satisfied with all the research and testing I've done that's repeatedly brought me back to this same setting. So: the timing which I set by ear many times and from the recommendations of others with the same pump; it came out at the 12º mark at .83mm lift. I have no reason to continue exploring the pump timing issue with this car.
Rich B

[rbremiller]

Here's an update from my last post. I purchased a TDI spec transmission for the car from Frans in The Netherlands this spring. I finished the install last week and returned the car to DD status. The proper gearing is essential for these engines and am looking forward to better mileage and new found driveability. It still starts and runs well at the .83mm pump setting. I re-installed the eTDI return flow restrictor valve and added a non-return valve just after it inline. I had problems with the eTDI restrictor valve draining back and causing hard starts. I prefer the eTDI valve as it seems to have a smoother idle and starts more quickly (with the non-return valve in place). It has a small piston and spring inside that must compress to open the return port like a pressure valve. The stock Audi diesels of this vintage had the non-return valves originally. The one I'm using came off my old '85 Jetta diesel with 400,000 miles on it. I'm going to drive it for a tankful and then consider if I might adjust the timing a bit. There seems to be a 400 rpm difference(lower) in each gear and is way less clattery at steady driving speeds. I have 20k miles on the motor now; the oil consumption is undetectable and the compression seems a little higher as the break-in continues.

[rbremiller]

I re-evaluated the IP timing with the new trans. It still runs best at the .83mm setting without a doubt. The first tank with the TDI trans. was 820 miles, used 16.7 gals. for 49.1 mpg.

[golftd412000]

it's very to hight static timing

yes .83 it's better

[rbremiller]

it's very to hight static timing

yes .83 it's better

Thanks for the confirmation. i appreciate your interest. I will put the timing at .80 when I have an after-glow circuit for the very cold weather. The car starts good at that setting but it's smoky without further glow plug action.

[golftd412000]

I have no glow on my vehicle.

I have already started in -15 ° c rolling with 15W50 ca jerk a little time this heater

[njdub]

Please post a video of this so we can all hear it!! Great build!

[rbremiller]

Please post a video of this so we can all hear it!! Great build!

http://vid245.photobucket.com/albums/gg45/rbremiller62/file_zps840184cf.mp4

[rbremiller]

  Here's an update that's overdue. I finally installed a circuit to extend the glow period after starting. It uses a 50 amp relay and a re-purposed 5 minute wall switch timer.  The big news is the last two tanks of fuel netted 50.3mpg and 50.0 respectively. 2nd tank included a 580 mile trip to PA with cruise control at 75mph. Boost held steady at 12psi up the steepest hills. The static timing is now at .945mm to take advantage of the proper gearing. The latest fill was at 835 miles for the most miles ever from 1 tank. The car still runs very well and is the best starting diesel or car of any kind for that matter I've ever owned, period.

[libbydiesel]

Nice.  I like the timer.  I do notice that without 'afterglow' mine will miss a bit in really cold temps.  I imagine that helps.