Changing injectors

[lautray]

Could someone list an idiot-proof "how-to" on changing injectors please... my 42lb greentops arrived today & I'd like to have them on the car sooner rather than later. Steps, tools required etc, etc. Any other helpful tips/tricks would be appreciated.

[BOMI]

Look at them for a bit. Work out how to pull them out and what tools you'll need.

Then pull them out Erik :stick: :lmao:

Troy

[lautray]

Look at them for a bit. Work out how to pull them out and what tools you'll need.

Then pull them out Erik :stick: :lmao:

Troy
Hmmm. Funny man, eh? Slaps for you :whip: .

[35R]

Here is the procedure from the Ellerys repair manual (VT~VY LS1):

Note: Thouroughly clean around injectors before removing so as foreigh material does not fall into the cylinders.

1. Fuel pressure in fuel lines should be relieved before work is carried out. Remove fuel pump relay and start engine, allow to IDLE until fuel supply remaining is used, turn off ignition switch.

2. Disconnect battery negative cable

3. Remove engine covers

4. Disconnect throttle cables

5. Disconnect electrical connectors from all injectors

6. Disconnect the fuel rail supply and return hoses

7. Loosen and remove the 4 fuel rail bolts

8. Lift the fuel rail and injectors out

9. Remove the clip that secures each injector in the fuel rail

Replace/upgrade injectors as required. With re-assembly, coat the o-rings/ lightly with lubricant to assist with fitting.


Question: do you need to do point 6, or can you leave it all connected, flip the fuel rails over and just swap the injectors?

[35R]

Erik,

If you are running the 42Lb Green Tops here are the injector flow rates (IFR)


g/sec

6.15625 6.18750 6.22656 6.26563 6.30469 6.34375 6.38281 6.41406 6.45313 6.49219 6.52344 6.56250 6.60156 6.63281 6.67188 6.70313 6.74219

OR

lb/hr

48.86029 49.10831 49.41834 49.72836 50.03839 50.34842 50.65845 50.90647 51.21649 51.52652 51.77454 52.08457 52.39460 52.64262 52.95265 53.20067 53.51070


Courtesy of Luke from a post on HPTuners (thanks Luke!)

http://www.hptuners.com/forum/showthread.php?t=8286

(See post #4)

[NickS]

Could someone list an idiot-proof "how-to" on changing injectors please...

The only real "idiot-proof" guide goes something like;

1. Phone workshop of choice
2. Tell them you need your injectors changed
3. Arrange a time
4. Drop off the car

:D

[SSUte01]

Here is the procedure from the Ellerys repair manual (VT~VY LS1):



Question: do you need to do point 6, or can you leave it all connected, flip the fuel rails over and just swap the injectors?


Pretty sure from memory that you can do exactly as you said, just flip them over and change them - but mine were off the car because we were doing the H/C install at the time so she was in bits anyway.

That guide seems pretty comprehensive and once you do it you will realise that they are quite simple to change. My only advice is be liberal with your choice of lubricant (I used good ol' Vaseline, which works well) on the O-rings as I stuffed one or two O-rings on my install due to not enough lubricant- it will be obvious if you have ruined an O-ring as fuel will piss out the rail. They seem like they are in there quite loose and flimsy but as soon as it is back together it is all good and provided the O-ring is in tact it will be fine.

[lautray]

Cheers for the assistance people :) .

[BOMI]

Glad you got the info you needed mate.

I tend to agree with NickS on this one thought.

Fuel go bang, me no likey car go boom :lmao:

Well that what would probably happen if I changed mine.


Looking forward to the write up mate.

Troy :)

[chrishsv]

Hey just thought i would add this formula for anyone considering upgrading their injectors.

1.Take your target peak horsepower and multiply by
- .5 For Naturally Aspirated
- .6 For Supercharged
- .6.25 For Turbocharged

2. Take that figure and divide by number of cylinders

3. Divide by .9 (For 90% duty cycle)

This will give you the pounds per hour you will need from each injector

Example: Say you have a 520hp Naturally Aspirated v8

Step 1. (520 x .5 = 260) Step 2. (260 % 8 = 32.5) Step 3. (32.5 / .9 = 36)

This amount of horsepower on a N/A engine would require 36 pound per hour injectors

Hope this helps, if its of any use to anyone the hp/kw conversion is 1hp = 0.746kw
and vica versa if you want to work it out in kw, ill give you another example.

To get 500hp in kw multiply .746 x 500 = 373kw
To get 373kw in hp divide 373 / .746 = 500hp

[cosmo vyss]

The only real "idiot-proof" guide goes something like;

1. Phone workshop of choice
2. Tell them you need your injectors changed
3. Arrange a time
4. Drop off the car

:D

Yep this would be my choice. :up2sum:

[BOMI]

Hey just thought i would add this formula for anyone considering upgrading their injectors.

1.Take your target peak horsepower and multiply by
- .5 For Naturally Aspirated
- .6 For Supercharged
- .6.25 For Turbocharged

2. Take that figure and divide by number of cylinders

3. Divide by .9 (For 90% duty cycle)

This will give you the pounds per hour you will need from each injector

Example: Say you have a 520hp Naturally Aspirated v8

Step 1. (520 x .5 = 260) Step 2. (260 % 8 = 32.5) Step 3. (32.5 / .9 = 36)

This amount of horsepower on a N/A engine would require 36 pound per hour injectors

Hope this helps, if its of any use to anyone the hp/kw conversion is 1hp = 0.746kw
and vica versa if you want to work it out in kw, ill give you another example.

To get 500hp in kw multiply .746 x 500 = 373kw
To get 373kw in hp divide 373 / .746 = 500hp


Excellant post Chris :thumbs: :thumbs: Just wondering, does that apply for 6 and for 4 cylinder cars?

Thanks for that lil formula mate.

Troy :)

[veewhytu]

Good formula Chris,thanks :)

I have one question though, wouldnt fuel pressure have an effect on this ?

Most injected cars run 42psi pressure (so ive been told, feel free to correct if im wrong) whereas ls1s run 58 psi.

[RedVYIISS]

they need to flow the lb/hr at the fuel pressure you are running. Also remember that Chris's formula is for fwHp or fwKw (not rwHp/Kw).

[NickS]

Hey just thought i would add this formula for anyone considering upgrading their injectors.

1.Take your target peak horsepower and multiply by
- .5 For Naturally Aspirated
- .6 For Supercharged
- .6.25 For Turbocharged

2. Take that figure and divide by number of cylinders

3. Divide by .9 (For 90% duty cycle)

This will give you the pounds per hour you will need from each injector

Example: Say you have a 520hp Naturally Aspirated v8

Step 1. (520 x .5 = 260) Step 2. (260 % 8 = 32.5) Step 3. (32.5 / .9 = 36)

This amount of horsepower on a N/A engine would require 36 pound per hour injectors

Hope this helps, if its of any use to anyone the hp/kw conversion is 1hp = 0.746kw
and vica versa if you want to work it out in kw, ill give you another example.

To get 500hp in kw multiply .746 x 500 = 373kw
To get 373kw in hp divide 373 / .746 = 500hp

Top stuff Chris ... very informative post

:thumbs: :bravo:

[veewhytu]

they need to flow the lb/hr at the fuel pressure you are running. Also remember that Chris's formula is for fwHp or fwKw (not rwHp/Kw).

Thanks Allan, this means i suppse if buying injectors at an advertised 36 lb/hr @ 42 psi then @58psi they will flow more than this if im thinking correctly.

Ive seen my injector d/c as high as 120% when logged but afrs remain stable, im thinking about changing them anyway to give me a bigger saety margin if pressure drops or a filter gets clogged etc.

[RedVYIISS]

at 4 Bar (58 PSI) they flow about 15% more than the manufacturers nominal designation (which is at 3 Bar or 43.5 PSI).

The Racetronix web site http://www.racetronix.com/ lists a range of injectors and (normally) provides flow rates at both 3 Bar and 4 Bar.

I hope you don't see 120% d/c for very long!!!

[chrishsv]

Excellant post Chris :thumbs: :thumbs: Just wondering, does that apply for 6 and for 4 cylinder cars?

Thanks for that lil formula mate.

Troy :)

Troy, it does apply for all cylinder cars you just get the target horsepower and divide it by the number of cylinders

Allan, out of curiosity if the injectors in veewhytu' car were running as high as 120% duty cycle, what would be the dangers in this? Im guessing just under 100% would be ideal? but anything over would it shorten the life of them or cause any other problems?

[RedVYIISS]

The problem is an injector can't flow more than 100%!!!

If the engine management system is calling for 120% duty cycle, the engine is running lean.

Ideal injector maximum duty cycle is about 70 to 80%.

[35R]

Agreed.

Everything I've read suggests Injector Duty Cycle (IDC) should be 80% or less (as a guide) & over 80% (and certainly more than 100%) you run the danger of maxing out the injector, inviting injector float, losing control of precise fuel delivery, not realising maximum power and running lean. As Allan says, injector duty cycle is merely a calculated value (not actual) - you can't physically have greater than 100%. Large IDC (100%+) serves to highlight how far away we might be from the ideal injector. There are heaps of articles on hptuners, ls1-australia, etc and a million posts/questions too. I'm not speaking from real-world experience (beyond some home tooning) hey perhaps the factory injectors can cope with around 100% IDC with little issues. Personally, I would stick with <80%

A question i would have though, can your injectors be too big? For example, if you calcuate your ideal injector at say 42lb, but are planing on FI down the track, can you run say 60lb injectors on the NA setup in the interim with nil issues?

[RedVYIISS]

From what I've read (no practical experience), it depends on the actual injector involved.

Some good ones are 60# Siemens, 42# Bosch, and the Holden 'Super Six' 36# injectors (not sure who makes these for GM). Again, stuff I've read, no practical experience.

[veewhytu]

Same as Allan, no actual experience but ive heard from those who know that if the injectors are to big they dont atomize the fuel properly and tend to "dribble" out.

My injectors have seen 120% but its not common though i see over 100% on every pass down the 1/4, but afrs have always remained correct....how can this be?
The only thing i can think of is that the injector values in the scan tool im using are incorrect....its nothing more than a guess, does anyone else have any idea ?

[RedVYIISS]

Rick,

What power are you making and what size injectors are you running?

Dunc,

All the GenT1000 guys run 60# Siemens, many on stock cubes and cam. Idling is the issue when injectors are too big yet I've not heard of anyone running the 60# Siemens having any problems.

[veewhytu]

[QUOTE=RedVYIISS;4385]Rick,

What power are you making and what size injectors are you running?

Injectors are stock vy ss, 28 lb IIRC.

It runs 115-116 mph, only been on a dyno once, 365 rwhp at CHE.

[SSUte01]

Injectors being too big can be an issue if the injector has small pulse width issues or if it is pintile or disc or whatever and the engine managment system is not setup to reflect this. The only reason I know this is because I changed my stock injectors in prep for FI setup that never eventuated and I had several small pulsewidth issues that I have since rectified through 'correct' settings in the PCM. Point is with modern engine management with correct inj flow rates, voltage offsets and various other settings they should be fine. The only time you will run into issues is when you ask of the injectors what is not capable, they do have a 'real' minimum pulse width and if you need less fuel that this then you 'may' run into issues. This is same principle as asking too much of an injector.

100% or greater DC implies that the injector is permanently open at this DC. AFRs may well stay as commanded or they may not when the DC is this high, the issue is that is can be erratic as there simply isnt physically enough time for the injector to open, fuel, close and repeat for the next cycle. As opposed to simply DC which is calculated as described above, log IPW in msec. Anything appoaching 18-20ms is asking too much of an injector at say 6000rpm, time to upgrade if you are concerned about potential erratic fuelling, it seems 99.99/100 it will be fine.

From memory you have a 222/224 cam and if you still have stock LS6 injectors (28.8lb/hr @ 3 bar vs 26.4lb/hr @ 3 bar for LS1) chances are you will meet your AFR as you will likely only being exceeding 100% for a very small time and essentially the injector just remains open for that time the main issue as I see it is that you lose control as you are asking the injector to open and close in a timeframe greater than what is available.

This I actually dont have any idea form experience but I believe over taxed injectors have a shorter lifespan too. This is not to say all bolt on tuned cars need new injectors as every car I've logged that is tuned to an optimum AFR and spark is at least 90% IDC at max rpm often 100% or more so I am not surprised cammed cars are. Proof is in the pudding, I do not know of a single person getting around who has had injectors fail, it would just be pretty bad if they did, but they seem quite reliable.

Unless you measured AFR is suffering you 'should' be fine - only time will tell

[lautray]

Did the injector upgrade yesterday... took a little more than an hour. Thanks to Dale for the technical support, my friend Enrique for giving me a hand, & Duncan for his supervisory skills.

Not too difficult a job at all. Even I could do it :) .

IDC now ~65% at ~7000rpm.

[veewhytu]

:) Injectors being too big can be an issue if the injector has small pulse width issues or if it is pintile or disc or whatever and the engine managment system is not setup to reflect this. The only reason I know this is because I changed my stock injectors in prep for FI setup that never eventuated and I had several small pulsewidth issues that I have since rectified through 'correct' settings in the PCM. Point is with modern engine management with correct inj flow rates, voltage offsets and various other settings they should be fine. The only time you will run into issues is when you ask of the injectors what is not capable, they do have a 'real' minimum pulse width and if you need less fuel that this then you 'may' run into issues. This is same principle as asking too much of an injector.

100% or greater DC implies that the injector is permanently open at this DC. AFRs may well stay as commanded or they may not when the DC is this high, the issue is that is can be erratic as there simply isnt physically enough time for the injector to open, fuel, close and repeat for the next cycle. As opposed to simply DC which is calculated as described above, log IPW in msec. Anything appoaching 18-20ms is asking too much of an injector at say 6000rpm, time to upgrade if you are concerned about potential erratic fuelling, it seems 99.99/100 it will be fine.

From memory you have a 222/224 cam and if you still have stock LS6 injectors (28.8lb/hr @ 3 bar vs 26.4lb/hr @ 3 bar for LS1) chances are you will meet your AFR as you will likely only being exceeding 100% for a very small time and essentially the injector just remains open for that time the main issue as I see it is that you lose control as you are asking the injector to open and close in a timeframe greater than what is available.

This I actually dont have any idea form experience but I believe over taxed injectors have a shorter lifespan too. This is not to say all bolt on tuned cars need new injectors as every car I've logged that is tuned to an optimum AFR and spark is at least 90% IDC at max rpm often 100% or more so I am not surprised cammed cars are. Proof is in the pudding, I do not know of a single person getting around who has had injectors fail, it would just be pretty bad if they did, but they seem quite reliable.

Unless you measured AFR is suffering you 'should' be fine - only time will tell

Correct, 100% dc is only being exceeded for a very short period of time.
Awesome post btw, thanks. :)