Do bigger nozzles = worse emissions?

I'm having trouble finding much info on this. First of all, I'm interested in emissions from an environmental perspective rather a legal perspective. I live in California, so no smog testing for me. I'd like to upgrade my nozzles but I know that requires EGR recalibration. And, I'm worried about the line in the FAQ that says EGR recalibration can increase NOx emissions by 40%.

So, in general, do bigger nozzles create worse emissions from our TDIs?

Now, in specific, I have a 2002 Jetta, 5 spd, B100, no other mods. What will going to Sprint 520s do to my emissions?

Hi, as you are going to increase power, it is supposed that you are going to drive at least sometimes faster. Bigger nozzles increase power and decrease milleage. If you don't change anything else, like doing a remapping or change boost on the turbo, you will get more smoke....and that is one of the things that makes you think in environment and global warming.

First up.. Bio doesn't smoke.
Second, your MPG will only go down if you drive it to its potential all the time.
I have a 100 mile commute every day. Since my nozzles (PP520) i have seen a gain in MPG while maintaining the same driving habits. As far as emissions, the more fuel burned, the greater the emissions.

Nozzles are the only "mod" for me thus far. I am experiencing NO smoke, getting better mileage, and the car is a heck of a lot more fun to drive.

kyllc said:

First up.. Bio doesn't smoke.

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I wish this was true. My car smokes significantly more on cold starts using bio than it did with D2, but that's besides the point. I'm not worried too much about smoke. If it smokes too much, I'll just replace the OEM nozzles. I'm more worried about other emissions that I won't be able to see with the naked eye.

kyllc said:

Nozzles are the only "mod" for me thus far. I am experiencing NO smoke, getting better mileage, and the car is a heck of a lot more fun to drive.

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Did you make any changes with VAG-COM when you installed your new nozzles? I don't doubt that the car would be more fun to drive. I'm just trying to figure out the downsides. I mean there has to be some, right? The VW engineers aren't dumb. There has to be some reason for the bigger nozzle sizes not to be stock.

I believe that VW reduced nozzle sizes when they tuned the Euro TDI engines to pass USA smog tests. I recall reading that it was a soot issue (smaller nozzle --> better atomization --> less soot).

I've also read, though cannot cite at the moment, that they retarded timing to reduce NOx for the USA. Other things being equal, this would tend to increase soot. It seems likely that the smaller nozzles were part of a multi-variable adjustment to the engine, to tailor it specifically for the way the USA smog regs are written and tested.

Eddy

If driven normally - to a point - larger nozzles within reason should improve economy and emissions.

A larger nozzle is going to inject the same amount of fuel in a shorter injection window allowing for a more efficient burn.

However certain "pollutants" (Nox?) will increase.

With just nozzles installed I had more smoke under all conditions, but with a re-map and the availability of ULSD, I have very little smoke.