turbocharged798
Veteran Member
Disclaimer: this how to is intended for reference only. Do this at your own risk. I may be sharing bad information. Injectors and nozzles are critical for the proper running of your TDI and will result in engine damage if done incorrect. This may not be the correct way to do things.
Also swapping nozzles and pop testing requires a decent skill level. I would say its a 7 out of 10 difficulty.
Now that's out of the way, lets get started. There is information out there how to swap VE nozzles but very little information on how to pop test and set the pop pressures. This is unfortunate because I believe swapping nozzles and not setting the pop pressures is really a bad thing to do. As the injectors wear so do the springs and the pop pressures drop. Lower pop is bad for the nozzle, bad for the balance, and bad for the engine. It also ruins the ability to fuel heavier without smoke.
So the VE TDI injector is shown below. Looks complicated but is really not. There are two springs of interest, the primary and the secondary. These injectors are two stage meaning that it starts with a small pilot injection and then drops the main after a certain amount of pilot fuel is dropped. The tricky part here is that after setting the pilot, you still need to set the main and its nearly impossible when the pilot drops first. However, there is a way around this which I will explain shortly.
So item 2 is your pilot shim and item 9 is your main shim. Bosch varies the thickness this shim to set the prop pressures. Keep in mind that due to the design of the injector the pilot shim also effects the main event.
Other part is interest is item 11 which is called the stop sleeve. This is the key that allows the needle to lift slightly before main is triggered.
The idea to set pop pressures is by changing the thickness of item 2 and item 9, one can alter the pressure at which the injector fires. Seems easy? Well its not that easy. The first task is the shims themselves. Bosch for whatever reason only shares these shims to certain businesses. After a lot of searching I have pretty much came to the conclusion that these are not obtainable by the average person. To get around this, we can do two things, to decrease pop pressure is easy, lap the shim down. We are talking thousandths here. I believe the formula is 1 thou is about 5 bar. The difficult part is adding shims to increase pressure. I tried some cummins 7.5mm shims that are 10 thou thick and they could work but just not enough graduations. 10 thou will give you a 50 bar increase which is HUGE. I suppose you could lap the factory shim down and then stack the cummins shim on top. Its just becomes a ton a work. I acquired some shims from an undisclosed aerospace company that I work for that ended up working good enough and they are in 5 thou increments which works out pretty good. Please do not ask me for them, I cannot provide them to you.
The second task is locking out the primary stage to set the main injection event. This is done by reducing the height of "h1" shown in the picture so its flat on the bottom and does not allow the primary injection. This can be done by taking an extra part and modifying it by lapping the lip down so its flat. Shown below is a modified part which we now use a tool and the factory part which has the lip. There are two problem with this. First, you will need a sacrifice an injector for this part. Lucky I had a dead #3 injector that had a failed needle lift sensor laying round that I stole the part from. The second problem is that its slightly shorter which will reduce the main pop pressure. I believe its around 10 bar if you just take the lip off and nothing more. To get around this I simply target a second pop pressure around 10 bar less. The important thing here is that the injectors will be matched and all be popping around the same pressure.
Now you will need a pop tester. I bought a cheap one off ebay from India. Its cheap, leaks, and does the job. Seems to be accurate which is good. Leaks like crazy which is not so good.
Finally, you need to be absolutely CLEAN when doing this. Very important.
With all that nonsense out of the way, lets get started.
Remove nozzle retainer nut. These can be TIGHT sometimes. Scary tight.
Remove nozzle and retainer. Sometimes nozzle sticks in retainer from the carbon buildup, just tap it out. These nozzles were complete junk so I didn't care about damaging them.
Clean out the retainer from carbon:
Install new nozzle:
Install retainer nut snug but not super tight as we will be taking it back off shortly to shim the pressures.
Get it on the pop tester and start popping it. This requires a bit of feel and skill. You have to bring the pressure up really slowly or you will get inaccurate readings. You should be able to use the knob on the side to get a more precise reading but mine was leaking so badly that is pretty much useless. This nozzle had a primary at 185 bar. Way too low and very typical. Now time to shim. Dump out the guts, add a shim shown below and reassemble.
Pop it again and now its at 215 bar. Wanted it closer to factory spec of 220 bar when I tried a 10 thou shim it ended up way over close to 240. I ended up settling for the 215 bar shim.
Now take the nozzle back off, and put the special lockout hat on. Re-assemble and pop test. Ended up at about 305-310 bar which is high, especially since we have the lockout hat on now which is likely making read about 10 bar low. I like closer to 280-290 bar. Factory spec is 300 bar.
Remove nozzle but no need to dump out guts this time. Secondary shim is just under the lockout hat and easy to get to. Measured secondary shim is micrometer.
Lapped the shim down a stone and removed about 3 thou of material. Re-assemble with lockout hat and we are now at 290 bar. Good enough.
Remove nozzle, and lockout hat. Install factory hat and re-check the primary. Should not move. Hold pressure on the nozzle and make sure it doesn't drip. Finally do a couple spray pattern checks to make sure all the holes are evenly making a good pattern. Remove injector from tester and torque the nozzle holder now.
That's pretty much it. #3 injector is similar with just an extra sleeve. Everything works the same way.
Good way to check your work is to put the injectors in the car and check group 13. Should be less than 1.00 on any cylinder.
Hope this helps someone out there.
Also swapping nozzles and pop testing requires a decent skill level. I would say its a 7 out of 10 difficulty.
Now that's out of the way, lets get started. There is information out there how to swap VE nozzles but very little information on how to pop test and set the pop pressures. This is unfortunate because I believe swapping nozzles and not setting the pop pressures is really a bad thing to do. As the injectors wear so do the springs and the pop pressures drop. Lower pop is bad for the nozzle, bad for the balance, and bad for the engine. It also ruins the ability to fuel heavier without smoke.
So the VE TDI injector is shown below. Looks complicated but is really not. There are two springs of interest, the primary and the secondary. These injectors are two stage meaning that it starts with a small pilot injection and then drops the main after a certain amount of pilot fuel is dropped. The tricky part here is that after setting the pilot, you still need to set the main and its nearly impossible when the pilot drops first. However, there is a way around this which I will explain shortly.
So item 2 is your pilot shim and item 9 is your main shim. Bosch varies the thickness this shim to set the prop pressures. Keep in mind that due to the design of the injector the pilot shim also effects the main event.
Other part is interest is item 11 which is called the stop sleeve. This is the key that allows the needle to lift slightly before main is triggered.
The idea to set pop pressures is by changing the thickness of item 2 and item 9, one can alter the pressure at which the injector fires. Seems easy? Well its not that easy. The first task is the shims themselves. Bosch for whatever reason only shares these shims to certain businesses. After a lot of searching I have pretty much came to the conclusion that these are not obtainable by the average person. To get around this, we can do two things, to decrease pop pressure is easy, lap the shim down. We are talking thousandths here. I believe the formula is 1 thou is about 5 bar. The difficult part is adding shims to increase pressure. I tried some cummins 7.5mm shims that are 10 thou thick and they could work but just not enough graduations. 10 thou will give you a 50 bar increase which is HUGE. I suppose you could lap the factory shim down and then stack the cummins shim on top. Its just becomes a ton a work. I acquired some shims from an undisclosed aerospace company that I work for that ended up working good enough and they are in 5 thou increments which works out pretty good. Please do not ask me for them, I cannot provide them to you.
The second task is locking out the primary stage to set the main injection event. This is done by reducing the height of "h1" shown in the picture so its flat on the bottom and does not allow the primary injection. This can be done by taking an extra part and modifying it by lapping the lip down so its flat. Shown below is a modified part which we now use a tool and the factory part which has the lip. There are two problem with this. First, you will need a sacrifice an injector for this part. Lucky I had a dead #3 injector that had a failed needle lift sensor laying round that I stole the part from. The second problem is that its slightly shorter which will reduce the main pop pressure. I believe its around 10 bar if you just take the lip off and nothing more. To get around this I simply target a second pop pressure around 10 bar less. The important thing here is that the injectors will be matched and all be popping around the same pressure.
Now you will need a pop tester. I bought a cheap one off ebay from India. Its cheap, leaks, and does the job. Seems to be accurate which is good. Leaks like crazy which is not so good.
Finally, you need to be absolutely CLEAN when doing this. Very important.
With all that nonsense out of the way, lets get started.
Remove nozzle retainer nut. These can be TIGHT sometimes. Scary tight.
Remove nozzle and retainer. Sometimes nozzle sticks in retainer from the carbon buildup, just tap it out. These nozzles were complete junk so I didn't care about damaging them.
Clean out the retainer from carbon:
Install new nozzle:
Get it on the pop tester and start popping it. This requires a bit of feel and skill. You have to bring the pressure up really slowly or you will get inaccurate readings. You should be able to use the knob on the side to get a more precise reading but mine was leaking so badly that is pretty much useless. This nozzle had a primary at 185 bar. Way too low and very typical. Now time to shim. Dump out the guts, add a shim shown below and reassemble.
Pop it again and now its at 215 bar. Wanted it closer to factory spec of 220 bar when I tried a 10 thou shim it ended up way over close to 240. I ended up settling for the 215 bar shim.
Now take the nozzle back off, and put the special lockout hat on. Re-assemble and pop test. Ended up at about 305-310 bar which is high, especially since we have the lockout hat on now which is likely making read about 10 bar low. I like closer to 280-290 bar. Factory spec is 300 bar.
Remove nozzle but no need to dump out guts this time. Secondary shim is just under the lockout hat and easy to get to. Measured secondary shim is micrometer.
Lapped the shim down a stone and removed about 3 thou of material. Re-assemble with lockout hat and we are now at 290 bar. Good enough.
Remove nozzle, and lockout hat. Install factory hat and re-check the primary. Should not move. Hold pressure on the nozzle and make sure it doesn't drip. Finally do a couple spray pattern checks to make sure all the holes are evenly making a good pattern. Remove injector from tester and torque the nozzle holder now.
That's pretty much it. #3 injector is similar with just an extra sleeve. Everything works the same way.
Good way to check your work is to put the injectors in the car and check group 13. Should be less than 1.00 on any cylinder.
Hope this helps someone out there.
