I'm installing a 12mm pump in my Volvo D24T (6 cylinder version of the 1.6 IDI), and I'm getting my injectors tested (currently Monarch GTD nozzles @163 bar).
If they need work - what nozzles do I go for?
On the D24T forum, the following have been tried?:
Standard 293 @ 155 bar
GTD 273 @ 165 bar
297 @ 170 bar
XUD @ 175 bar
There seems to be no definitive answer of which are best, and why. The XUD is a very recent test, and appears to be successful with the 12mm pump.
As the 1.6 is the same design as the 2.4, I wonder if any testing of different nozzles has been done on this forum? Anyone ran the XUD nozzles for any reasonable time?
There has been a good bit of comparison on the forum. Many to most will disagree with me on this (flame suit zipped and ready) but i have had my best performance with Monark and Elsbett nozzles for a Mercedes. There are a lot of concerns about this since the Mercedes configuration involves injection onto a hot "ball" in the prechamber and the worry that precups on a VW idi will crack or blow out of the head. This hasn't happened to me (yet). The the VW design relies instead on the fuel hitting the side of the precup for more complete atomization. My experience is there is a good deal more power, and smoke at load, in a 1.6l NA with Monark for Merc nozzles (without a pyrometer to get a good sense of how bad this setup could be).
IIRC the consensus is Bosch 273 GTD nozzles for a VW don't provide a lot more power than standard nozzles. Don't know if that is true for Monark GTD. Monark and Elsbett nozzles seem to be quieter in a 1.6 single stage set injectors at ~135 bar with a pump set at 1.00mm. Would imagine a two stage injector with Monark nozzles would be quieter still.
I had read things about the Merc nozzles which supposedly don't suit the VW pre chambers. I will probably stay away from those, although your experience is very interesting!
How does the XUD pre chamber design compare to the VW? Would you say they are suitable?
After reading through more posts, I've seen there is also a "274" GTD nozzle, as well as the "273"?
And, sorry, but how would I know if my injectors are 1 stage or 2 stage? What is the difference?
Whoops, you are right about the 274 being the GTD. i have seen folks say the 293 and 273 nozzles are the same.
Two stage injectors are taller and used in 1.9l AAZ idi engines, maybe others too. If i understand correctly they pop twice during the combustion cycle which reduces their clatter.