My Bosch rebuilt injectors have a so, so spray pattern... - Page 2 - PeachParts Mercedes-Benz Forum

rwthomas1 · #16 03-06-2008, 09:22 PM

Quote:

Originally Posted by patbob

He's increasing the fuel flow into the piston with his internal polishing of the injectors. You'll get more apparent power, but that's because you'll be putting more fuel in all the time. In other words, won't you just be hitting max load at a different throttle position?

Of course, you'll also get more than stock max load at WOT, so if you then play with the boost, you can get beyond stock HP before needing to diddle around with the max load setting on the IP. Has potential.

Yes and no. The result of the Extrude Hone process is an injector that flows more fuel than stock or a so called "high flow" injector. At a given "throttle" setting the IP is still delivering the same amount of fuel as it was before so the modified injector does not increase fueling by itself. What is does do is inject that same amount of fuel in a shorter period of time, expressed in degrees of crankshaft rotation. Injecting the same amount of fuel in a shorter period of time means that there is more time, again in degrees of crankshaft rotation, for combustion. This CAN increase power simply from a more complete combustion process. Obviously the modified injectors also allow more fuel and help to maintain the injection time period when the IP is turned up. Clear as mud. RT

GREASY_BEAST · #17 03-06-2008, 09:56 PM

I don't think it's quite that simple. Backpressure from restriction in the injector shouldn't affect flow rate too much in this situation, because the IP plunger will just push it through at a higher pressure, maintaining the same flow rate... that is unless you attribute a delay in injection to flexing of the high pressure injector lines...

In short, injection duration should remain pretty much the same.. unless the system actually does flex enough to make this effect occur, in which case this mod, combined with adjusting the pop pressure to a higher setting, should result in significant (measurable) gains in power, and conversely, fuel economy, especially in the high end of the rev range where timely injection duration is of the greatest importance.

EDIT: It is important to remember that the IP really doesn't "care" what pressure it is seeing. It can handle many times the 135 or so bar at which the injectors pop.

Diesel911 · #18 03-07-2008, 12:01 AM

From what I read on Extrude Hone process i got the impression they were talking about direct injection injector spray nozzles that have multiple tiny holes in them. On direct injection nozzles the seat of the injector pintel has a lot of metal around it and is exposed to combustion by way of the tiny holes.
Pintlel type nozzles normally (as in Mercedes) have only 1 hole in them and part of the pintel stick out into the combustion chamber. If you enlarge that hole enough (extreme example: if you enlarge the hole enough the pintel will fall out of the injector) you are going to get more carbon particles under the seat and expose more of the pintel seat to the heat of combustion. For racing this is not a problem but for everyday use you want longevity.

Alberta Luthier · #19 03-07-2008, 12:09 AM

Quote:

Originally Posted by cornblatt

Alberta Luthier, what shop did you use for injector testing?

I just had my injectors tested at GCL Fuel Systems in Calgary, which is a Bosch authorized shop. They quoted $55 to test four of them (and the quote didn't mention the additional $11 in shop supplies and surcharges that showed up on the final bill). However, they did tell me that they all tested OK and had a good spray pattern and pressure, so I appreciate their honesty. The place was really clean and the staff was friendly.

If rebuilding or cleaning was done, they said it would be about 1/2 hour ($55) per injector to disassemble, lap, seal, and balance if necessary. Fortunately I didn't need to do have this done.

Injector heat shields ($0.96 online) were $6.99 each there. I try hard to support local businesses but I can't when the price difference is that big.

I did get mine done at GCL as well. The injectors are VW 2 spring AAZ injectors with new Monarch 265 nozzles. Although I had thoroughly cleaned the injectors and installed the new nozzles, I wanted to be sure they were balanced, (150 bar) and pop tested. So I knew I would have to pay for some time but having spent quite a bit of time cleaning them out ( Boy do they ever get cruddy in there!) I thought I might get billed for actual shop time not 1/2 hour per....
What really counts for me anyway is: Did they do it right? I hope so. I expect so. And I can hardly wait to scrape a couple of hours of free time together so I can get 'em in and find out.

I keep changing my mind which car to put 'em in they both need them!