Newbie question on bigger injectors

Hi all,
I'm new to the TDI world. When I bought my 98 bug the previous owner said he had bigger injectors installed. The injector pump is leaking so I have to put a seal kit in. My question is, it's running fine at 5.8-6.0 fuel quantity (when warm- cold it's more like 9.5) but I know people are aiming for 3-4... My question is, is mine set for more because of the bigger injectors? What happens if it's setting is too high? And what's the point of bigger injectors?

A bigger number actually means less fuel. You might want to ask a moderator to move this to the power enhancement forum where you'll probably get more attention. Good luck.

When going to a bigger nozzle (Injectors are all the same, you just swap nozzles), depending on the nozzle, QA is lowered (higher number) to control EGT's and retain most of the MPG. Its mostly to moderate the amount of fuel injected as your nozzles are larger. I would keep it where it is. if you Raise the QA (lower number), depending on the nozzles installed, you could easily exceed EGT limits and damage your turbo.
Can you get some information from the PO on what size they are and who did them and if they were pop tested and or tuned?
I run 764's at 1.4 to 1.8 QA but i have a massive turbo to reduce EGT's and still can easily get to 1800, if i try. The day i put in my 764's i was on my stock AHU turbo and i saw 2200F on the first pull and melted the turbo on the 2nd run!
Just keep it where it is.

Mongler98 said:

When going to a bigger nozzle (Injectors are all the same, you just swap nozzles), depending on the nozzle, QA is lowered (higher number) to control EGT's and retain most of the MPG. Its mostly to moderate the amount of fuel injected as your nozzles are larger. I would keep it where it is. if you Raise the QA (lower number), depending on the nozzles installed, you could easily exceed EGT limits and damage your turbo.
Can you get some information from the PO on what size they are and who did them and if they were pop tested and or tuned?
I run 764's at 1.4 to 1.8 QA but i have a massive turbo to reduce EGT's and still can easily get to 1800, if i try. The day i put in my 764's i was on my stock AHU turbo and i saw 2200F on the first pull and melted the turbo on the 2nd run!
Just keep it where it is.

Click to expand...

Thanks for the info... All I have is a sheet saying they are power pro 764. Initial stroke of 244 and main stroke of 333 ( all about the same on the four injectors)... If I could post a pic of the paper I would but I don't know how... So you'd say when I rebuild the injector pump to keep it at the 5.8-6.0 which gives less fuel because bigger injectors require less fuel? Just want to make sure I understand what you wrote.... Also, what does 1800 and 2200f mean?

Ray299 said:

...Also, what does 1800 and 2200f mean?

Click to expand...

EGT, Exhaust Gas Temperature.

Your turbo can handle a sustained temp of low 1500s anything more than 1550 is a short burst max otherwise the turbo will melt down. I highly suggest you install a EGT gauge. 764's are huge and a blast to drive but be easy on it until you get a gauge. I suggest auber gauges.

Mongler98 said:

Your turbo can handle a sustained temp of low 1500s anything more than 1550 is a short burst max otherwise the turbo will melt down. I highly suggest you install a EGT gauge. 764's are huge and a blast to drive but be easy on it until you get a gauge. I suggest auber gauges.

Click to expand...

Ok that makes sense... Thanks!

Is there a plug and play egt gauge or is this something I'd have to have fitted? Any links to threats about installation it where to buy?

No plug and play.
The probe needs to be tapped into the exhaust manifold and the gauge needs to get
mounted somewhere you can see it. Then wired into 12V. and lighting if you desire.

If the EGR valve has been deleted, you can drill and tap the block off plate.

There are EGR blockoff plates that are drilled and tapped at the best angle to insert a long probe into the exhaust stream, IIRC.

If you're taking apart the injection pump, I'm gonna guess the IQ will be different. No harm if it runs good at 6 or wherever, the ECU is expecting 2.2 to 9, you will tweak it to get the best performance.

"it's running fine at 5.8-6.0 fuel quantity"

Do the seals on the pump, and then check it. But if the car's running
good, leave well enough alone. "If it ain't broke, don't fix it"
You probably have a bigger turbo as well with that setup, be cautious
about "improvements", at least until you learn more about the motor
and what you got.


My $.02.

Putting in an EGT probe is actually fairly easy.
A few tools and you can do this within about 2 hours max
You will need a 1/4 NPT tap and the apropriate drillbit that goes with it
2 ring magnets with a 3/8 to 1/2 inch ID (inner Diameter)
a pice of cardboard, drill, socket that fits on the taps back square end, and the tools to take off the intake manifold.
You cant just add a probe to the blockoff plate unless the end of the probe is directly over the TURBO input, not just one of the exhaust ports. you can easily have a 500*F temp difference from not having it close enough.
Auber gauges are epic as they have a relay in it and you can set limits and easily add a defuel setup with just a few wires so you cant ever go too hot and you can hide it if you dont want to see the digital meter.
https://www.auberins.com/index.php?main_page=index&cPath=5
Take off the intake
Place a pice of cardboard over the intake ports but not so that its sealed, about 1/2" gap so it can still suck air in but keep debris from flying in
Mark the spot you will drill
Put the ring magnets over the hole
start the engine and leave it running
Drill the hole, and tap it as it idles
Turn off engine and remove magnet
Congradulationgs on not letting any metal bits into the turbo or into the intake
Worked VERY well for me. here is a picture.