Boring out injectors. - PeachParts Mercedes-Benz Forum

Cervan · #1 04-22-2008, 07:19 AM

I have a set of injectors on my NA 616 1983 mercedes 240d. Im going to take a drill bit, that is a tiny bit larger than the pintle hole is, and bore it out ever so slightly. Then i will carefully grind it to a flat and deburr it to help it flow better. After this, i will take some valve lapping compound, thin it out as thin as possible and lap the seat of the nozzle. I will also be doing some minor headwork as well. I will be enlarging the precombustion chamber holes as well. Wish me luck.

#2 04-22-2008, 08:18 AM

Good luck. How will you get the air needed to use any more fuel?

bgkast · #3 04-22-2008, 12:24 PM

Your injector is going to pee like a boy writing his name in the snow after that. I am going to send mine to be professionally modified.

KarTek · #4 04-22-2008, 01:46 PM

I like your "out of the box" thinking but the "ever so slightly" you plan to bore out the nozzle probably equates to a 50% increase in area, lower pressure at the nozzle and very poor atomization resulting in lots of black smoke and high temps...

I would turn the pump up first then look at doing something like having the injectors extrude honed. Not so much for increased size but mainly to de-burr and smooth the opening.

Oh yeah, you do have gauges right?

bgkast · #5 04-22-2008, 05:31 PM

Quote:

Originally Posted by KarTek

...then look at doing something like having the injectors extrude honed.

That is what I will be doing to mine. They will be opened up 15 thousandths over stock. AFAIK nobody has enlarged injectors for MB IDI engines, and not many people have done it for ANY IDI engines, so it is not really known what the results will be.

Sorry to come off as rude, but my original point was that these injectors require much more precision than can be obtained with a drill bit.

KarTek · #6 04-22-2008, 09:26 PM

I'd be willing to guess too, that the injector tips are extremely hard and will destroy a drill bit in short order...

Monomer · #7 04-22-2008, 09:51 PM

EDM machining could also work.

"wire burning" can yield a surface finish on par to that of a surface grinder.

Coating might also be worth it. the entire nozzle face could be coated (evaporation method) to be smoother than possible with grinding. TIN coatings and such arnt that expensive anymore

TheDon · #8 04-22-2008, 10:12 PM

what a joke

MTUpower · #9 04-22-2008, 10:26 PM

On a non turbo? You MUST have more air to burn the fuel. This will do nothing if you are able to make the "hole" bigger except billow black smoke.

Diesel911 · #10 04-22-2008, 11:53 PM

Where I used to work they bought a nozzle regrinding setup (for direct injection nozzles) when they lapped the pintels to the new seat they used 1200 grit lapping compound to lap the pintal seats. Filne valve lapping compound is around 220 grit.
Also even with the the machinery they bought they had a low success rate.
Think off your injector spray nozzle as if it was a nozzle on your garden hose. When you make the hole in the nozzle bigger what happens to the stream of water that comes out?

Cervan · #11 04-23-2008, 04:12 AM

guys guys i understand that i need more oxygen to burn lol. Im simply doing this to see what the results will be. i have a spare head and engine so i have nothing to loose. (These will not be going into my good engine) Extrude honing sounds good, but wouldnt that also enlarge the diameter of where the nozzle rides inside the hole? I guess it doesnt matter as long as it seats well.

Cervan · #12 04-23-2008, 04:13 AM

Quote:

Originally Posted by Diesel911

Where I used to work they bought a nozzle regrinding setup (for direct injection nozzles) when they lapped the pintels to the new seat they used 1200 grit lapping compound to lap the pintal seats. Filne valve lapping compound is around 220 grit.
Also even with the the machinery they bought they had a low success rate.
Think off your injector spray nozzle as if it was a nozzle on your garden hose. When you make the hole in the nozzle bigger what happens to the stream of water that comes out?

Sorry for the double post, but isnt this why we have IDI engines? the small "ball" for the lack of a better word, inside the precombustion chamber is suppose to deflect and cause more entropy inside the comubstion chamber correct?

bgkast · #13 04-23-2008, 11:02 AM

Quote:

Originally Posted by Cervan

Sorry for the double post, but isnt this why we have IDI engines? the small "ball" for the lack of a better word, inside the precombustion chamber is suppose to deflect and cause more entropy inside the comubstion chamber correct?

You do still have to have a good spray pattern, but I'm not sure the garden hose analogy is a good one. You can have a good spray pattern that still flows more (in both garden hoses and fuel injectors).

Bio240D · #14 11-22-2008, 12:21 AM

Hey Cerven,
I think the critical insight here is to realize that an injector nozzle is Not like a carb jet. Increasing the area that the fuel flows through will only decrease its velocity. The fuel volume is controlled entirely by the injection pump plunger volume. If you want more fuel, that is where you have to start. My turbo 240D is shooting about 100 cubic mm per shot. The stock setting is 41.5 cubic mm. The IP seems to have no trouble shooting this much fuel through stock injectors set at 135 Bar. Cheers, CHris

#15 11-22-2008, 12:26 AM

Thats because its only now getting close to stock turbo settings. Much more than that and the injectors ARE a restriction.

Increasing the area that the fuel flows through will not just decrease its velocity, it increases the volume the nozzle can flow. If there were no gains then performance injectors for the pickups and TDIs would not exist.