est injectors for a 617.952 engine - PeachParts Mercedes-Benz Forum

bro frank · #1 09-09-2009, 11:44 AM

found that i need to change several injectors on my 84 300td. what would you say are the best injectors for this engine and why?

pawoSD · #2 09-09-2009, 11:57 AM

It is the nozzles, not the injectors themselves. I have used both Bosio (Italian) and Monark (German) nozzles with good results. The Bosio nozzles are more performance/low end torque oriented, while the Monarks are more smooth running and fuel efficient....in my experience. I like both of them, but run Bosio's in my car....I love the power!

oldsinner111 · #3 09-09-2009, 11:59 AM

I've never tried the Bozo nozzles,But my Monark are deadly fast.

Diesel911 · #4 09-09-2009, 12:41 PM

In my opinion the reasonable choices if you put in nozzles made for your Engine:

Bosch: Made in India and cost $27 or more depending on who you buy them from (I think this is what you will get if you buy an exchange set from internet venders).

Monark: Made in Germany cost around $23 each depending on who you buy them from.

Fratelli Bosio: Made in Italy cost $43 or more depending on who you buy them from.

If you are in Europe or another country just about every company that makes Injector Nozzles makes their version.

What ever you use I think it is better to have some local shop do the rebuild as they will do a better job balancing them. Meaning that all the Injector Opening/Pop Pressures will be within a max 5 bar of each other. Most tech try to keep that variation lower if they can do so within in a reasonable time frame.

If you buy them from someplace where they are pulled randomly from some Bin with 100s of Injectors in it I think there is little chance they are going to be balanced.

Other things to consider is that at first having work done at a local shop seems more expensive.
But, when you order by mail you pay a core charge (you can get that back but you have to pay to ship the cores $5-$7 per set). Depending on who you buy them from you may also have to pay the shipping to you.
If you have a warranty on the mail ordered one there is going to be a time lag to get the problem fixed; this is assuming the company you ordered from is cooperative.

bro frank · #5 09-23-2009, 02:27 PM

i posted this question on the mbca forum just to see what responses i'd get. this was by far the best.

Re: best injectors for a 617.952 engine
Having worked for an renowned injector and injection pump rebuilder during my salad days in the industry I'll chime in here...

What makes an injector better than another? Sure there are the obvious things like performance and durability. But what do these really mean with injectors? Let's get technical...

Durability: A good set of injectors should last about 100-150k miles. Sure you can get more than that out of them, but the truth is they are likely no longer operating at optimal conditions.

Onto performance...

Injectors are judged by two criteria for the most part. Pop pressure and spray pattern.

What is pop pressure? It is the pressure that the injector begins to release fuel at. For example, an OM617a (turbo) has injectors with a pop pressure of 135 bar (1958 psi!). Per the factory, injectors may have some variance in the actual pop pressure. If memory serves correctly, the allowable variance is 10%. That is quite a window of variance. Regardless, even if it is 5%, it is still quite a significant margin. Some injectors are at the higher end of that spectrum, some lower. Ideally, you will use injectors that are a "matched set." This means that all injectors will be in the same range, either lower, middle, or higher. Pop pressure is set by the injector builder with shims.

When I worked for the injector shop, we sold sets that were matched within 2% of one another. If you have a motor with injectors that are all across that spectrum, performance and economy will suffer.

As a sub-set of pop pressure we have chatter. When testing an injector the nozzle should open and close as pressure approaches the pop pressure and is released by the opening nozzle. On a tester this is called chatter. It makes a unique sound. If the injector gets stuck open, there will be no chatter and pressure will be unable to build, the injector will release fuel until the pressure reaches 0. One should see and hear pulses when slowly applying pressure on the tester.

Next, we have spray pattern. What is the purpose of the injector? It is designed to inject fuel in very fine atomized droplets. When looking at the spray pattern, it should appear like a conical mist of vapor. A nozzle that streams is not acceptable and is often the result of a defective, worn, or dirty nozzle and pintle. Motors are more sensitive to spray pattern than pop pressure in the grand scheme of things.

A badly streaming injector can cause serious motor damage! Worn injectors will often stream, meaning there is minimal atomization and most of the fluid is concentrated in one or a few streams. This will cause many issues over time including poor economy, pre-ignition (nailing), excessive knocking on par with bad rod bearings in volume, mis-firings, ring cracking, and even holed pistons!

So back to the question at hand..."What are the best injectors?"

In short a matched set with proper spray patterns, verified on an injector tester.

What about brand names?

The old Bosch, Germany nozzles were excellent. These are hard to find and are all NOS (new old stock), to my knowledge. The French and Irish manufactured nozzles are not bad either. Bosios are OK, not my first choice. Monarch Diesels work well. The nozzle is what controls spray pattern. Any company may produce a nozzle with excellent or poor spray patterns. Quality control on these is not what it used to be.

What about real world observations and suppliers?

The injectors sold by the dealer (MB genuine) can generally be trusted. Their pop pressures are within variance and the spray patterns are acceptable, but not always ideal. Typically, these injectors are rebuilt in the US or Europe by Bosch. If in doubt these are the best way to go.

Bosch OEM... I'll put it this way... this week I had a client without funds to purchase genuine MB injectors, so they opted for Bosch OEMs at lesser cost to them. The initial order of five injectors yielded two that were within specification. One of them exhibited no chatter and simply streamed its fuel. This is unacceptable, but is and has been the norm for a number of years. I would not install any Bosch OEM injector without testing it first. They can not be trusted without testing, in my opinion. These are typically rebuilt in third world countries, hence the decreased cost and poor quality control.

Local rebuilder? If you have a local outfit that is skilled with these injectors and is using a quality nozzle, there should be no problem withe them. However, you want to know the pop pressures and to witness the spray patterns first hand. I would not trust someone's word on the matter. Fact is, it takes some time to dial in an injector for optimal performance. It is quite easy to throw one together and to get mediocre performance.

As with anything you can take injectors to marginally acceptable all the way to ideal. Without testing them firsthand, it is impossible to know what you are getting regardless of where the injector came from. I do not install any injector, gas or diesel, without testing it first.

In closing, my teacher in this field is the same fellow who builds the injection pumps for Paul Russell in Massachusetts. If they are good enough for him, they should be good enough for most folks.
__________________
Best regards,

Mathieu J. Cama

Old World Automotive (Vintage MBs are our specialty!)
Lawrenceville, GA
www.oldworldauto.com
404-550-8000
9:30 AM - 5:30 PM Mon-Fri EST

Peachtree Section
MBCA Concours Judge

really good answer thought i'd share it.

Diesel911 · #6 09-23-2009, 03:33 PM

Quote:

Originally Posted by bro frank

i posted this question on the mbca forum just to see what responses i'd get. this was by far the best.

Re: best injectors for a 617.952 engine
Having worked for an renowned injector and injection pump rebuilder during my salad days in the industry I'll chime in here...

What makes an injector better than another? Sure there are the obvious things like performance and durability. But what do these really mean with injectors? Let's get technical...

Durability: A good set of injectors should last about 100-150k miles. Sure you can get more than that out of them, but the truth is they are likely no longer operating at optimal conditions.

Onto performance...

Injectors are judged by two criteria for the most part. Pop pressure and spray pattern.

What is pop pressure? It is the pressure that the injector begins to release fuel at. For example, an OM617a (turbo) has injectors with a pop pressure of 135 bar (1958 psi!). Per the factory, injectors may have some variance in the actual pop pressure. If memory serves correctly, the allowable variance is 10%. That is quite a window of variance. Regardless, even if it is 5%, it is still quite a significant margin. Some injectors are at the higher end of that spectrum, some lower. Ideally, you will use injectors that are a "matched set." This means that all injectors will be in the same range, either lower, middle, or higher. Pop pressure is set by the injector builder with shims.

When I worked for the injector shop, we sold sets that were matched within 2% of one another. If you have a motor with injectors that are all across that spectrum, performance and economy will suffer.

As a sub-set of pop pressure we have chatter. When testing an injector the nozzle should open and close as pressure approaches the pop pressure and is released by the opening nozzle. On a tester this is called chatter. It makes a unique sound. If the injector gets stuck open, there will be no chatter and pressure will be unable to build, the injector will release fuel until the pressure reaches 0. One should see and hear pulses when slowly applying pressure on the tester.

Next, we have spray pattern. What is the purpose of the injector? It is designed to inject fuel in very fine atomized droplets. When looking at the spray pattern, it should appear like a conical mist of vapor. A nozzle that streams is not acceptable and is often the result of a defective, worn, or dirty nozzle and pintle. Motors are more sensitive to spray pattern than pop pressure in the grand scheme of things.

A badly streaming injector can cause serious motor damage! Worn injectors will often stream, meaning there is minimal atomization and most of the fluid is concentrated in one or a few streams. This will cause many issues over time including poor economy, pre-ignition (nailing), excessive knocking on par with bad rod bearings in volume, mis-firings, ring cracking, and even holed pistons!

So back to the question at hand..."What are the best injectors?"

In short a matched set with proper spray patterns, verified on an injector tester.

What about brand names?

The old Bosch, Germany nozzles were excellent. These are hard to find and are all NOS (new old stock), to my knowledge. The French and Irish manufactured nozzles are not bad either. Bosios are OK, not my first choice. Monarch Diesels work well. The nozzle is what controls spray pattern. Any company may produce a nozzle with excellent or poor spray patterns. Quality control on these is not what it used to be.

What about real world observations and suppliers?

The injectors sold by the dealer (MB genuine) can generally be trusted. Their pop pressures are within variance and the spray patterns are acceptable, but not always ideal. Typically, these injectors are rebuilt in the US or Europe by Bosch. If in doubt these are the best way to go.

Bosch OEM... I'll put it this way... this week I had a client without funds to purchase genuine MB injectors, so they opted for Bosch OEMs at lesser cost to them. The initial order of five injectors yielded two that were within specification. One of them exhibited no chatter and simply streamed its fuel. This is unacceptable, but is and has been the norm for a number of years. I would not install any Bosch OEM injector without testing it first. They can not be trusted without testing, in my opinion. These are typically rebuilt in third world countries, hence the decreased cost and poor quality control.

Local rebuilder? If you have a local outfit that is skilled with these injectors and is using a quality nozzle, there should be no problem withe them. However, you want to know the pop pressures and to witness the spray patterns first hand. I would not trust someone's word on the matter. Fact is, it takes some time to dial in an injector for optimal performance. It is quite easy to throw one together and to get mediocre performance.

As with anything you can take injectors to marginally acceptable all the way to ideal. Without testing them firsthand, it is impossible to know what you are getting regardless of where the injector came from. I do not install any injector, gas or diesel, without testing it first.

In closing, my teacher in this field is the same fellow who builds the injection pumps for Paul Russell in Massachusetts. If they are good enough for him, they should be good enough for most folks.
__________________
Best regards,

Mathieu J. Cama

Old World Automotive (Vintage MBs are our specialty!)
Lawrenceville, GA
www.oldworldauto.com
404-550-8000
9:30 AM - 5:30 PM Mon-Fri EST

Peachtree Section
MBCA Concours Judge

really good answer thought i'd share it.

Yes!!!!!