300SD injector theoretical Q's - PeachParts Mercedes-Benz Forum

cho · #1 02-07-2013, 01:22 PM

hi guys

what is the loss/gain if the injector (all 5) is set to wrong pop pressure...say 115 bar instead 135 as it should be in turbo engine?

in case of weakened elements in IP is playing with injectors pop pressure
advised..?

and no,..I did not play with my IP or the injectors....lately

TX

cheers
ChO

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Simpler=Better · #2 02-07-2013, 02:18 PM

A lower pop pressure will make the injectors pop sooner, and may not flow as much fuel due to the lower pressure.

Don't know about adjusting pop pressure to accommodate a worn IP.

greazzer · #3 02-07-2013, 02:28 PM

The key to a smoother running engine is having the injectors balanced, preferably at 25 PSI +/-. If you have all 5 well balanced, then having them set at 1,900 PSI for example in a turbo engine with worn nozzles that don't pee, then you should be OK. However, the spec's are the spec's. The FSM is 50+/- PSI so you should be good if you balance them at 1,900 since you are still within nominal spec. A BAR is 14.5038 PSI, so 135 x14.5038 = 1,958.013 or a nominal 1,950.

cho · #4 02-07-2013, 03:21 PM

.

thanks guys

over here we use 3 bar +/- max.diff. formula fwiw

so sooner pop-ing means less power or more fuel wasted in
case of 115 bar adjustment?... just trying to find some corelation...

.

eatont9999 · #5 02-07-2013, 03:30 PM

Lower pop pressure will advance your timing. Your turbo engine most likely won't like the lower pop pressure and too far advanced timing can cause problems and even engine damage.

Can you tell us why you think your IP is weak? If you have verifiable IP issues, the cheapest option is usually to source a good used one at a junk yard, etc. Still, it's not common for an IP to fail on a 617.

Diesel911 · #6 02-07-2013, 04:15 PM

In theory when the Turbo is Boosting the Air in the Cylinders is compressed that Air Should be denser than a non-turbo Engine.

Having to spray against a higher density (thicker) of Air is the reason I think the Turbo Injectors have higher Pop/Opening pressure

eatont9999 · #7 02-07-2013, 09:29 PM

Quote:

Originally Posted by Diesel911

In theory when the Turbo is Boosting the Air in the Cylinders is compressed that Air Should be denser than a non-turbo Engine.

Having to spray against a higher density (thicker) of Air is the reason I think the Turbo Injectors have higher Pop/Opening pressure

I have done lots of research on this and you are exactly correct. Some people will dispute that slightly retarded timing allows for exhaust gasses to continue burning when exhausted and thus spool the turbo in less time. I tend to disagree with this theory, though. I can't see how incomplete combustion could create more exhaust gas pressure/volume than complete combustion and maintain efficiency and low-end power.

cho · #8 02-08-2013, 04:38 AM

Quote:

Originally Posted by eatont9999

Can you tell us why you think your IP is weak?

worn elements verified by bosch guys,I m in the process of building a new one
with 5.5 elements supplied by Tomnik..... no junk yards over here

it will be resolved soon, but I wanted to learn a bit more about
"logic" behind IP, opening pressure and injector corelation....

I will cry
about my IP and cost of building new one later

thanks

.

Simpler=Better · #9 02-08-2013, 08:07 AM

Quote:

Originally Posted by cho

worn elements verified by bosch guys,I m in the process of building a new one
with 5.5 elements supplied by Tomnik..... no junk yards over here

it will be resolved soon, but I wanted to learn a bit more about
"logic" behind IP, opening pressure and injector corelation....

I will cry
about my IP and cost of building new one later

thanks

.

If Tomnik is building you pump, is there any reason you aren't going with 7.5mm or 10mm elements?

cho · #10 02-08-2013, 08:29 AM

Quote:

Originally Posted by Simpler=Better

If Tomnik is building you pump, is there any reason you aren't going with 7.5mm or 10mm elements?

nope, Tomnik is only supplier of the elements

7.5 or 10 mm will be project when I acquire proper turbo (2014?)

for the 2013 5 stick from 300N/A is scheduled

cheers

.

eatont9999 · #11 02-08-2013, 10:56 AM

Quote:

Originally Posted by cho

worn elements verified by bosch guys,I m in the process of building a new one
with 5.5 elements supplied by Tomnik..... no junk yards over here

it will be resolved soon, but I wanted to learn a bit more about
"logic" behind IP, opening pressure and injector corelation....

I will cry
about my IP and cost of building new one later

thanks

.

I'm guessing it would be cost-prohibitive to have one shipped to you with customs/taxes, correct?

cho · #12 02-08-2013, 01:34 PM

Quote:

Originally Posted by eatont9999

I'm guessing it would be cost-prohibitive to have one shipped to you with customs/taxes, correct?

Correct.

over here we have loads of M pumps desired by US folks,over there
you have loads of MW pumps desired by Euro guys.... crazy

sadly,..same goes for transmissions.

.

Diesel911 · #13 02-08-2013, 09:03 PM

Quote:

Originally Posted by eatont9999

I have done lots of research on this and you are exactly correct. Some people will dispute that slightly retarded timing allows for exhaust gasses to continue burning when exhausted and thus spool the turbo in less time. I tend to disagree with this theory, though. I can't see how incomplete combustion could create more exhaust gas pressure/volume than complete combustion and maintain efficiency and low-end power.

One of our Members Dr. Bert and likely more of our Members advance the timing as much as 28 degrees BTDC and claim it gets better performance.

I did 27 degrees BTDC and it was slightly peppier when you applied the Pedal but mine was too noisy for Me at idle (using Diesel Fuel). But, I think that puts to rest the retarded timing being needed to spool the Trubo better.

cho · #14 02-09-2013, 03:04 PM

Quote:

Originally Posted by Diesel911

One of our Members Dr. Bert and likely more of our Members advance the timing as much as 28 degrees BTDC and claim it gets better performance.

I did 27 degrees BTDC and it was slightly peppier when you applied the Pedal but mine was too noisy for Me at idle (using Diesel Fuel). But, I think that puts to rest the retarded timing being needed to spool the Trubo better.

I went through that post recently.

as for better spooling only thing that I established with STD guys is
narrower exhaust pipe (with default turbo) but that will lead to another set
of problems... heat,no top speed...etc....

cheers
chO

.

eatont9999 · #15 02-10-2013, 11:21 AM

Quote:

Originally Posted by cho

I went through that post recently.

as for better spooling only thing that I established with STD guys is
narrower exhaust pipe (with default turbo) but that will lead to another set
of problems... heat,no top speed...etc....

cheers
chO

.

I would not put a smaller exhaust on the car for better spooling. You want the exhaust post-turbo to be as free flowing as possible. Unless you make modifications to the IP to deliver more fuel, the standard 2.5" pipe is fine. You may see a small performance benefit and lower EGTs if you cut out the resonators and muffler and run a straight pipe. Obviously the sound will be greater if that is a concern. The other thing that can be done is to make the intake air cooler and more open. The stock OM617 turbo air filter is designed to do that. Again, no need to mess with air intake unless you make fuel modifications to the IP. You should also adjust the wastegate for more boost and install an intercooler if you are delivering more fuel. More fuel needs more air to be efficient.