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Engine Specific Info and Questions => IDI Engine => Topic started by: AAZJetta on November 26, 2006, 12:32:16 am
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Hello again, guys,
I have a 1985 Jetta Turbo-diesel Jetta I've installed a 1.9 litre Code AAZ turbo-diesel engine into, and I've got about 3,300 miles on the new engine since I installed it. It was manufactured in 1998 as a replacement engine, and was complete from turbo to injection pump when I installed it.
I noticed the injection timing was much different from most 1.6 litre diesels I've monkeyed with. The Bentley manual lists the timing as anywhere from .90 to 1.00 mm for most 1.6 L D and TD engines, but .80 mm for the 1.9 L TD AAZ code engines. This seems to be retarded too much on my engine. The evidence for this is as follows:
1. When I start the engine after it has reached operating temperatures, the cranking time seems to be excessive, but if I pull the cold-start advance lever out, it starts immediately.
2. My old '83 diesel Rabbit starts immediately when warm without pulling out the cold-start advance mechanism.
3. On a cold day, when starting the engine from a cold start, the engine cranks and starts almost immediately with the cold-start advance lever pulled out, but still runs slightly rough until it warms up a little.
I was wondering if anyone has experimented with timing settings that were more advanced than those listed in the Bentley manual, with good results. Were these settings due to pollution standards, rather than what might make the engine run best? How far might I try advancing the timing without problems?
P.S. The injection pump I have installed on this engine has a retard solenoid on it, which I have wired to a constant 12v when the ignition key is on to prevent the timing from being retarded even more. The car has been getting a consistant 44 mpg on the freeway at 65 mph.
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Im having exactly the same symptoms with my AAZ in a rabbit,my pump is set at 0.85mm and isnt right,i will think about trying 1.0mm when i get it out the garage,im happy with the performance but its lumpy until it warms up,the engine is new vw exchange unit with the tdi crank and the fuel pump is brand new bosch,the only things not shure about is the injectors.
Try 1.0mm and give us a shout if it works for you :wink:
Bert
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You have described EXACTLY how my 1.9AAZ used to run. Even warmed up, it would only idle smoothly if the cold start was pulled out.
The pain on these engines is that they are difficult to time "by ear"... ie you cant adjust the timing with the engine running. Instead of being able to rotate the pump, they have a split pulley you have to loosen & rotate.
To time them "by the book" you're supposed to set it at TDC, lock the cam and the IP. That is supposed to be the right setting, end of story. Well, that doesn't necessarily work so great as the engines age, if we run alternative fuels (vegoil, in my case), or if we like to play around a bit.
What I usually do is set the timing "by the book", and then advance the timing in very small increments, taking it for a quick drive after each adjustment. I have my pulley marked, so I can go back to the "by the book" setting.
When it's set right, it has just the right amount of "clatter" at idle, which is increased when you pull out the cold start.
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My AAZ is a 94 so it has a 1 piece pulley,i just have to slacken the pump and rotate it to adjust timing with the dial guage in the rear of the pump.
Bert
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hi guys
yes pls change your timing to .95mm it will make a big dif.
Giles
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Giles is right,it needs more timing.
You can even go up more,I usually go 1.00 to 1.05mm to get them to run the way I want.
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Giles you have pushed me into adjusting my pump :wink:
Cheers for the information from the guru.
Bert
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I will try .95 mm to begin with next time I get a chance to work on it. Does anybody know how this change from the factory-recommended setting of .80 mm affects other engine parameters such as fuel economy, EGTs, engine operating temperature, and of course, power? My main goal here is the best compromise between power and economy. What are the best indicators to watch for that might give you a clue you've advanced the timing too far?
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I will try .95 mm to begin with next time I get a chance to work on it. Does anybody know how this change from the factory-recommended setting of .80 mm affects other engine parameters such as fuel economy, EGTs, engine operating temperature, and of course, power?
Fuel economy will improve, EGT will be reduced, engine operating temperature will remain the same if the thermostat is working properly and power will improve. Emissions of NOX will increase, NOX reduction is the single reason for the retarded factory timing.
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Fuel economy will improve, EGT will be reduced, engine operating temperature will remain the same if the thermostat is working properly and power will improve.
It will also make your whites whiter, cure gingivitis and alleviate embarassing foot odor. It's amazing!
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It will also make your whites whiter, cure gingivitis and alleviate embarassing foot odor. It's amazing!
Indeed, you would be insane not to do it...
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I live and drive at elevations 5,000 to 8,000 ft. above sea level in hilly/mountainous country, so I may even go for 1.00 mm. I've noticed all of my other engines seem to run better (including diesel tractor engines) in positions advanced farther than the "Book" settings. I wonder if it will still be okay at lower/sea level drives, for holiday/vacation, etc., occasionally. You're right, you'd be stupid not to. :twisted:
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Just thought I'd get back to all who were interested in the AAZ timing question I posted at the first of this thread.
I checked my initial timing, before I attempted any changes or advancements. When I made changes, I did as "addautomotive" above suggested and tried small increments. The results were as follows:
1. Initial timing was found to be .79 mm at TDC. The "book" setting is .80 mm.
2. My first adjustment ended up at .86 mm. I didn't notice much difference in performance, cold start-up, or warm re-start improvement. It was still doggy.
3. The next adjustment went to .95 mm, and what a HUGE improvement that made! Cold-start, warm-start, and performance improved, as well as the general smoothness of the engine. The engine started instantly on warm-restart, and would even run smooth with the cold start advance lever pushed in after a cold start.
4. The next adjustment went to 1.00 mm, which is where I locked it down permanently, and where it seems to run the best of all the adjustments. Starts, runs, and re-starts great. The exhaust even smells better, whereas before it smelled quite strong.
I was getting a consistant 44 (US) mpg at 65 mph on long highway trips with the original factory setting, and using a ACH code trans. with the 3.94 final gears, and basic 90W mineral gear lube. I can't wait to see what the mileage will be with the 1.00 mm setting. I probably won't be able to get a good comparison now that it is colder and the fuel is doped with #1 diesel.
The next thing I plan to do, in my quest for better fuel economy, is to install an ACN trans. with the taller final gears (3.67). I just bought one, and I'll try REDLINE MDL synthetic in it. I then plan to install an intercooler. Thanks to all who helped out!
By the way, does anybody know what the VW part number is for the injection pump lock pin for the AAZ engine with the split pulley, as I have? I have the one for the old 1.6, but was surprized to see this one needed something different.
This engine only has 3,600 miles on it now. I hope to see some further improvements on it as it breaks in more. I'll keep all of you posted.
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Please keep us posted on your new mileage. It may actually inspire me to face the cold and go and advance mine
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so, i have a dumb question...
if you set the timing to 1.00, would the cold start advance be useless? or do you have to advance it too?
is there a lot of risk from going from stock (0.86) to 0.95 or 1.0?
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so, i have a dumb question...
if you set the timing to 1.00, would the cold start advance be useless? or do you have to advance it too?
is there a lot of risk from going from stock (0.86) to 0.95 or 1.0?
from what QuickTD said, it seems that the single reason for retarding the timing was to reduce NOX emissions... so i dont think there would be much risk, but lots of gain :)
if you set timing to 1.00 then the timing advance would increase it to 1.05.
if it was a really cold day, then that could be the difference of your car starting, and not starting... or just starting really rough :)
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Exactly what jtanguay said
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By the way, does anybody know what the VW part number is for the injection pump lock pin for the AAZ engine with the split pulley, as I have? I have the one for the old 1.6, but was surprized to see this one needed something different.
Get a long 6mm bolt, one with about 50-60mm (2 - 2-1/2") of unthreaded shank. Cut off the threaded portion. Done. An allen bolt works well, the knurled head is easy to grip.
Regarding the risks of advanced timing, there are none.
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I spun a locking tool on the lathe, but before that I used a 6mm drill bit and one time I changed my dads TDI T belt in his driveway so I used a 6mm allen key.
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When I pull out the cold start advance cable on a cold morning for a cold start, it seems to help even more, even though I have the pump set for 1.00 mm now. I took great pains to precisely and accurately set the pump timing to 1.00 mm as a final setting. I am using Pentosynth (VW spec 505.00) synthetic oil in the engine. Road performance is excellent.
I will be taking the car on a 400+ mile roundtrip next week through southern Utah/Arizona, all under open highway conditions, and I am anxious to see what the mileage will be at the new pump setting. Although I don't expect to get what the car is capable of since the weather is much colder now, I do expect to see an improvement in mileage. Diesel here is 2.57 USD/US gallon currently.
Then it will be on to the transmission (ACN), intercooler, and synthetic REDLINE MDL in the trans. for maybe more improvement. My goal is great fuel economy with nice performance as well.
By the way, a great addition to this car was an electric cruise control (no vacuum source needed) made by Rostra. I used the magnetic pickup option for the speed signal. Works great. Took me most of a day to install, and I used the stock switches (signal, cruise set, resume, etc, and clutch switch) from an '89 GTI gasser.