injector choice - IDI Engine - VWDiesel.net The IDI, TDI, and mTDI source.

injector choice by steel-jaw-sasha on 15 Mar, 2005 13:56
Hi I have just got myself a 1989 1.6 td jetta and I am going to start by reconditioning the injectors, can anyone point me in the right direction as regards to the best injectors to use, nozzels, pressures etc.
#1 by Mark(The Miser)UK on 17 Mar, 2005 14:36
Quote from: "steel-jaw-sasha"
Hi I have just got myself a 1989 1.6 td jetta and I am going to start by reconditioning the injectors, can anyone point me in the right direction as regards to the best injectors to use, nozzels, pressures etc.

Eurocarparts sell nozzles for less than £15 IIRC. TD pressures are 155bar n/a 130 bar. Not really sure if nozzles are different. Probably just a thicker shim (got one next to me [out of view but I was looking at it earlier 8O)] and it looks like a 10mm dia 1mm thick 3mm hole in middle washer)

This brings me on to my question:

:evil: I'm considering upping
my injector break pressures from 155bar.
Will this lead to better efficiency due to a finer spray?
What happens to the life of a pump when it has to hit the
fuel with that extra force. Camplate wear increase? Shaft
bearing wear increase. Timing belt strain?

Or does everything operate well within limits? :twisted:

Mark-The-Miser-UK
#2 by fspGTD on 18 Mar, 2005 14:29
Quote from: "Mark(The Miser)UK"
:evil: I'm considering upping
my injector break pressures from 155bar.
Will this lead to better efficiency due to a finer spray?
What happens to the life of a pump when it has to hit the
fuel with that extra force. Camplate wear increase? Shaft
bearing wear increase. Timing belt strain?

Or does everything operate well within limits? :twisted:

Yes, it will put more stress on your pump and timing belt. However, it works fine for a turbo-diesel, so... I wouldn't say it is overly-abusive on any of these components. You can actually figure out how much more pressure it puts on the camplate:

155bar-130bar = 25bar extra hydraulic pressure = 370 extra psi hydraulic pressure

plunger surface area = (9mm diameter / 2) ^ 2 * PI
= .0986 square inches

added force on camplate from changing to 155bar injectors
= 36 extra pounds pressure on camplate during injection stroke

And to put it in perspective, the pressure on camplate required to develop 130 bar hydraulic pressure would be 187 pounds.

You can imagine how that extra 36 pounds camplate pressure causes more force to turn the injection pump, causing more dynamic loading on the timing belt, etc. But the thing is, it seems to work fine on turbo-diesels, so there is no reason it wouldn't work OK on a naturally aspirated diesel. I've tried running 155bar injectors on a naturally aspirated application and it works fine but really didn't seem to give any benefits as far as I could tell. Power and fuel economy didn't seem to be effected by upping the breaking pressure. So whatever efficiency was gained by improve atomization of the spray was apparently offset by the extra power sapped of the crank to push the extra fuel pressure. The extra breaking pressure did noticeably seem to make the idle more shakey though. I think naturally aspirated diesels have a slightly smoother idle as of result of their lower fuel injection pressure.

Replacing an old worn out injector(s) that squirts a stream of fuel with a fresh one that shoots a nice finely atomized "cone" of fuel spray (regardless of breaking pressure), is effective in improving combustion efficiency, resulting in less idle "roughness", idle speed being higher, speed of RPM drop when off-throttle not being as abrupt as before, less smoking, improved fuel economy and torque.

A general rule of thumb I've noticed seem to apply after installing new injectors is: if the idle speed increases, then either the fuel quantity rate or the combustion efficiency has increased.
#3 by Mark(The Miser)UK on 19 Mar, 2005 16:17
Quote from: "fspGTD"
Quote from: "Mark(The Miser)UK"
:evil: I'm considering upping
my injector break pressures from 155bar.
Will this lead to better efficiency due to a finer spray?
What happens to the life of a pump when it has to hit the
fuel with that extra force. Camplate wear increase? Shaft
bearing wear increase. Timing belt strain?

Or does everything operate well within limits? :twisted:

Yes, it will put more stress on your pump and timing belt. However, it works fine for a turbo-diesel, so... I wouldn't say it is overly-abusive on any of these components. You can actually figure out how much more pressure it puts on the camplate:

155bar-130bar = 25bar extra hydraulic pressure = 370 extra psi hydraulic pressure

plunger surface area = (9mm diameter / 2) ^ 2 * PI
= .0986 square inches

added force on camplate from changing to 155bar injectors
= 36 extra pounds pressure on camplate during injection stroke

And to put it in perspective, the pressure on camplate required to develop 130 bar hydraulic pressure would be 187 pounds.

You can imagine how that extra 36 pounds camplate pressure causes more force to turn the injection pump, causing more dynamic loading on the timing belt, etc. But the thing is, it seems to work fine on turbo-diesels, so there is no reason it wouldn't work OK on a naturally aspirated diesel. I've tried running 155bar injectors on a naturally aspirated application and it works fine but really didn't seem to give any benefits as far as I could tell. Power and fuel economy didn't seem to be effected by upping the breaking pressure. So whatever efficiency was gained by improve atomization of the spray was apparently offset by the extra power sapped of the crank to push the extra fuel pressure. The extra breaking pressure did noticeably seem to make the idle more shakey though. I think naturally aspirated diesels have a slightly smoother idle as of result of their lower fuel injection pressure.

Replacing an old worn out injector(s) that squirts a stream of fuel with a fresh one that shoots a nice finely atomized "cone" of fuel spray (regardless of breaking pressure), is effective in improving combustion efficiency, resulting in less idle "roughness", idle speed being higher, speed of RPM drop when off-throttle not being as abrupt as before, less smoking, improved fuel economy and torque.

A general rule of thumb I've noticed seem to apply after installing new injectors is: if the idle speed increases, then either the fuel quantity rate or the combustion efficiency has increased.

:idea: That's a very good rule of thumb Jake...
what do you have written on your other thumb? :idea:

As I get 36 to 50 mpg [US] already in my 'Q' I guess my injectors are giving a reasonable spray pattern. I had been toying with the idea of going up from 155bar to 175bar as I thought I'd heard of people doing that.
Looking at the specs of different engines (sizes and makes); there seems to be no real rules on breaking pressures...
Except for any given engine Bosh seems to run 20% higher than Lucas, and larger engines of the same make often :? but not always :? operate at higher pressures and the same with Turboed v N/A
Maybe there is a correlation with compression ratios... hmm not with the 1.6 VW though :evil:
#4 by Mark(The Miser)UK on 23 Mar, 2005 16:54
:
Quote
Yes, it will put more stress on your pump and timing belt. However, it works fine for a turbo-diesel, so... I wouldn't say it is overly-abusive on any of these components. You can actually figure out how much more pressure it puts on the camplate:

155bar-130bar = 25bar extra hydraulic pressure =... 36 pounds camplate pressure causes more force to turn the injection pump, causing more dynamic loading on the timing belt, etc. But the thing is, it seems to work fine on turbo-diesels, so there is no reason it wouldn't work OK on a naturally aspirated diesel. I've tried running 155bar injectors on a naturally aspirated application and it works fine but really didn't seem to give any benefits as far as I could tell. Power and fuel economy didn't seem to be effected by upping the breaking pressure. So whatever efficiency was gained by improve atomization of the spray was apparently offset by the extra power sapped of the crank to push the extra fuel pressure. The extra breaking pressure did noticeably seem to make the idle more shakey though. I think naturally aspirated diesels have a slightly smoother idle as of result of their lower fuel injection pressure.

Replacing an old worn out injector(s) that squirts a stream of fuel with a fresh one that shoots a nice finely atomized "cone" of fuel spray (regardless of breaking pressure), is effective in improving combustion efficiency, resulting in less idle "roughness", idle speed being higher, speed of RPM drop when off-throttle not being as abrupt as before, less smoking, improved fuel economy and torque.
.

:twisted: A learned fried from another site said that he ran 175bar on one of his vehicles; but then reminded himself that eventually the 'overdue' cambelt 'failed' with a loss of some teeth which may or may not have been significant.
What if instead of upping pressures we went for n/a pressures on a TD.
Could we get idling improvement?
In the case of your 'racer' wouldn't this give you that extra bit of torque to your wheels equivalent to ripping out a few seats? speed wise? :twisted:
#5 by foxracer1 on 27 Mar, 2005 10:25
Where can you find these injectors in the us?(155bar)
#6 by Mark(The Miser)UK on 27 Mar, 2005 10:45
Quote from: "foxracer1"
Where can you find these injectors in the us?(155bar)

:idea: Is it possible to use your existing injectors with new n/a nozzles AND the TD shims? Seeing as the TD versions are as common as hens teeth. :idea: I'll ask this on another site where a Danish sage has played around a lot with injectors...
#7 by foxracer1 on 27 Mar, 2005 11:05
ok Well i'm sure my nozzels are in need of replacement. can you just order the shims from the dealer?
#8 by Mark(The Miser)UK on 28 Mar, 2005 01:04
Quote from: "foxracer1"
ok Well i'm sure my nozzels are in need of replacement. can you just order the shims from the dealer?

Research from my peers has informed me that all nozzles are now the same except GTD nozzles. You dont need new shims (those you have will already be TD thickness) Just by new nozzles with their needles.
#9 by vwmike on 28 Mar, 2005 01:30
What engines came with the GTD nozzles?
#10 by Mark(The Miser)UK on 28 Mar, 2005 11:27
Quote from: "vwmike"
What engines came with the GTD nozzles?

RA and SB....At least in the UK :?: from late '88
#11 by Mikeyworks on 28 Mar, 2005 19:55
Ok, maybe you guys can help fill me in...I have a few sets of injectors laying around.

I have full sets of the following:
- 1.6 TD injectors
- 1.9 NA injectors
- 1.6 NA injectors (I think I still have these)

What is the difference btwn these injectors? Will the nozzles from the 1.9NA help in the performance of the 1.6TD? In other words, can I switch the nozzles of the 1.9 NA injectors into the cores of the 1.6TD nozzles and get better output into the engine?

Thanks,
Mikey