I am doing my injectors DIY (balancing and such) since a long time.
I have a 603...fine engine... and I was increasing the pop pressure from 140bar( spec) to 145 and now 150bar.... and set timing 1 degree earlier relative to spec.... 14 vs 15 degrees according to the light method.
What do you say how much advance in degrees would be correct in order to offset increase of 10 bar pop pressure?
Best, Martin

Hi,

I remember back when I installed 150 bar pop pressure injectors on my 617a SD the dynamically measured delay was about 2.5 -3 deg compared to the old ones with almost 140 bar.

Worse starting and hard nailing even when warm will tell you that it is too much advanced.
Please report your experience as the 603a engines are more sensitive and I am also playing with timing and pop pressure.

Tom

Thanks Tom,
Higher prop pressure resulted in delay of injection start of fuel delivery (because the pump needs more time in order to increase the pressure level?)
If you say 617 engine (was it a 115bar non turbo injector or a 135bar turbo injector?) then what was the difference in pop pressure relative to the 2.5 - 3 degrees delay? Did you test both situations (both sides pop pressure and timing?)
Did you then advance your timing by the 2.5- 3 degrees in order to offset the greater pressure?

okay I assume you have a turbo and spec pressure id 135bar...if you increase by 15 bar and have 3 degrees of retard...so this makes 0.2degrees per 1 bar pressure differential?



I am using the DN 0 SD 265 nozzles from Monark and the spec of new nozzles for the 603 is at 135-145bar...140bar medium pressure. So let's say I increased by 10 bars. I also turned up the IP a bit (my EGTs are very high if I hit the gas).
I adjusted injection time with RIV method..the 2 lights... at 14 degrees ATDC (vs spec of 15 degrees)...[I don't know what 14 degrees translate to as the 'real' injection timing...should be way before TDC.]
10 bars pressure differential would retard my timing by 2 degrees according your formula?
This means I should advance my timing to 13 degrees ATDC?

Someone also mentioned that : Higher pop pressure will end up injecting just a smudge less fuel, the injection will take place later (retarded timing), and the injection pulse will be shorter (but more intense and better atomization)

if you just boost the pop-off pressure without changing anything else it is gong to hurt things.

however if you are willing to do some work tinkering with the injector pump (timing, turn it up a smudge, etc) you may be able to improve the power and efficiency a bit.

I seem to remember reading that higher pop-off pressures will also result in sharper noise at ignition and therefor a higher overall noise level, but I can't remember details.

Martin

617 a (=Turbo), I went from 140 up to 150 bar pop pressure and could see the 2.5 -3 deg retard. Both tested with clamp and strobe light dynamically.

At that time I advanced the timing to 26 deg with 150 bar and I was happy.
1 bar steps on pop pressure is way too small, think in approx. 5 bar steps.

265 Monark is a good choice. Turning up the IP will compensate for the shorter injection time to get the same amount of fuel.

RIV method 15 deg (after TDC) means 24 deg before TDC physically but only for pop pressure within spec. This is why I use the clamp and strobe light to get real life data independent from pop pressure. I.e. just putting the clamp on the IP side of the hard line (instead of the injector side) will show one full deg "late" (=hydraulic delay of injection). Next: The RIV method follows the notch on the fly weights. The fly weights are fixed on the pump cam just on a cone and it depends how accurate the pump was assembled...
Assuming the RIV method conditions are o.k. and you now have 150 bar pop pressure you can easily go to 11 -12 deg (RIV). During the first 800-1000 miles the injector/nozzles will "loose" some bars in pop pressure, therefore timing will retard and the noise will decrease.

this is why you advance and compensate with more fuel adjusted on the IP.
Why should this hurt??

noise level will be higher but it should not be hard nailing when warmed up.

As long as you are able to balance the injectors within some few bars or even better all this makes sense. But imagine you have a delta of 5 bar on one injector this means injection on this cylinder is different by one deg. Doing so you did not gain anything at the end of the day.

Tom

Thanks Tom, great conversation

I understand what you are saying.
As we have the same pressure increase (10 bar) the retard of start of injection is probably the same: 2.5 – 3 degrees. 15-3bar = 12bar ATDC for the RIV method.

You are touching an interesting point… I never heard of this: Meassuring and adjusting timing in real time and not based on assumptions (with the strobe light)
Assumption 1: IP is well adjusted for the RIV sensor and thus accurate (might be true or not… you’ll not know)
Assumption 1: Pop pressure…well I adjusted it as precisely I could (all 6 within 1or 2 bar) but what the heck…what if the gauge is not correctly calibrated? What if the pop pressure goes down during driving? (well I know from a fact that my last generation of injectors nozzles lost 5-10bar within 30K miles)

Now this interests me: How do you practically use here… do you have a quick manual?
Are you using a gas engine strobe light and put the clamp on the diesel line cylinder 1 [not sure what you mean with IP side..do you mean close to the IP?] and ground on battery minus…like you do on a gas engine? Does the diesel line give the pulse?
At what engine speed are you testing? And what are you testing really?
Can you read start of injection directy (the 24 degrees BTDC real time)? No…you say you are seeing ‘one full degree late’ meaning your diesel line is one degree ‘faster’ than you measure? So your target is seeing 25 degrees BTDC (= 24 degees in reality?)?

Lots of questions…sorry.
Best, Martin

I have seen this strobe and Diesels are mentioned...is this it? seems to be a regular strobe...or what is different?

http://www.clas-equipements.com/en/impression/produit/4238

I use this one:

1x Motor-Tester Diesel von AVL A1 Injection Tester 875 Ex BW Bundeswehr (DTG8) | eBay

make sure to have to correct clamp diameter for the hard line. To buy it separately can be expensive.

the one in your link should also do the job.

Tom

Thanks

Upps...'da muss ich ja meine bescheidenen Deutschkenntnisse einsetzen?'
Quite expensive and they don't ship to the US...I'll see what this testing is about. Is there something available in the US?

Anyway can you shed some light on the questions:

What are your test parameters? engine speed for instance...and associated timing in degrees BTDC.
What exactly is the strobe indicating ...beginning of injection? (beginning of injection...the moment when the injector pops? or when the IP provides the pop pressure?)

You mentioned the 26 degrees BTDC...what is this number?

Best, Martin

Hi Martin,

I missed your other post.

The clamp is a piezo thing that detects the pressure pulse in the hard line=pressure peak just before the injector pops.
The book says that the clamp should be close to the IP, ground is connected on the hard line nut on the delivery valve.
The strobe can be retarded or advanced to spot TDC on the pulley and you can read the timing on the display.
I also have a cable that is plugged into the rpm amplifier of my SD (where the TDC signal is provided) and I see more or less the same deg timing on the display.
I usually test at idle and check the timing device is working at all by increasing the rpm.
Even more accurate is using the signal of needle lift. Some BMWs have a needle lift sensor on cylinder 1 and the upper part of the injector can be used. I have to say that I was not able to adapt the mV signal to my AVL before I swapped the injectors again.
One deg delay shows up when you put the clamp near the IP compared to near the injector. This is hydraulic delay.
BUT, what you really want to "see" is start of combustion.
I am working on a super fast pressure sensor installed where the glow plug of cylinder 1 is and triggered with TDC notch of the pulley.
The deeper you go into this the more complex it gets.

There are cheaper strobe lamps but I had the chance to catch the AVL long time ago.
http://www.ebay.de/itm/Diesel-Zundlichtpistole-Stroboskoplampe-12-24-Volt-dig-/390154979843?pt=Elektroger%C3%A4te&hash=item5ad70c8a03

Tom

Hi Tom,
Interesting it is.
I want to be very pragmatic at this point.
I understand that you can sense the pressure pulse/pressure peak of the fuel right before injector pops.
Assuming having the equipment in place(strobe light and connecting the clamp to cylinder 1 fuel line close to IP) and can measure the pressure peak… what do I do with this information?
How can I get the spec for the 603 for this situation? Who can provide the information to what the setting is….what degrees BTDC should I adjust the IP (rotate it) at idle for pressure peak at IP?
Is this spec the same as for the 617 turbo? Hard to believe.
What do you suggest for the 603 engine?

Best, Martin

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Speaking of pop pressure, I'm about to rebuild my injectors for the second time 18k miles. I suspect my injectors are set too low because the engine is extremely quiet. By the sound you would be hard pressed to guess its a diesel at idle. From what I've read this is a symptom of pop pressure being too low. It also tends to smoke a bit above 3500rpm. I'm guessing I set the pressure too low because the 5800psi gauge on my Bosch pop tester isn't accurate enough. I picked up a $15 Wika 2000psi gauge on Ebay which hopefully should help me set the pressure more accurately. I think I'm going to aim for exactly 2000psi.

Has anybody else run into this problem?
http://i.imgur.com/F3a0OGT.jpg

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it is easier to advance timing a bit and see if the smoke disappears.
What is wrong with a smooth and quiet running engine?

Tom

Nothing unless the pop pressure is below spec and its burning more fuel than it should be. Timing is already advanced.

Some reading to go along with the subject.
I.C. Engines And Combustion - Google Books

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good reading.
To follow this correctly you need to measure combustion pressure over crank angle. Plus the matter Volker mentioned that pop pressure is limited by the injector spring to about 150 bar unless you have custom made nozzles.
Up to 150 bar there is no real need for measuring but you might not see that much of a difference.

Tom

I've been playing around with a spare injector to try to increase the pop pressure from the stock 135 closer to 145 simply by polishing the mating surface where the 2 halves meet using 2000 grit paper (no spare shims). So far I have it popping just a hair under 2000psi. The nozzle is old, worn out and pissy so I put a dab of polishing compound on the tip and spun it by hand inside the nozzle body. It stopped pissing completely and pops repeatedly with a distinct high pitched buzz. I'm going to try to capture some high speed shots of the tip on the pop tester with my GoPro.
http://i.imgur.com/UolXY7E.jpg

I don't think I have balls to try increasing the pressure past 2100psi but I'm interested to see your results.

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