injector question

[catmandoo]

will 6.2 injector interchange with the 6.5's is the only difference the length?or are they metered different?i see kennedy lists short body 6.5 but then notes on some 82-88 the longs were used and when body style changed they used shorts.

[britannic]

Early engines used coarse thread injectors and as far as I know, you can only get them calibrated for 6.2L.

The later fine thread 6.2L will interchange with 6.5L. The difference between them is the pop pressure (around 1800psi 6.2L and 2050psi 6.5L).

Van injectors have shorter bodies for "dog house" cover clearance.

Marine injectors have higher flow rates, but unless you fit a marine calibrated pump, and your engine can eat and healthily digest the fuel these can inject, they may not be worth the extra cost.

I'm 6.5LTD injectors in my 6.2L and have been very pleased with them; my pump is calibrated to 4911 specs.

[catmandoo]

pop pressure is what i was after.i think i have weak injectors on my 92 with n/a 6.5 and i have an old 84 with fairly new injectors and was looking tonite and they are the same length.was thinking of trying them but if the pressures are diff so much for that.

[britannic]

The 6.5L will run with 6.2L injectors, but probably won't perform to it's full potential.

[Animal]

Originally posted by britannic:
The 6.5L will run with 6.2L injectors, but probably won't perform to it's full potential. Why would the performance be off if the flow rates of the two injectors are the same and only the pop off pressure is less. The only thing I see different would be the timing may need to be retarded slightly to adjust for the lower pop off pressure, or am I missing something here.

[catmandoo]

well that was kinda my thoughts as lower pressure it would pop sooner and this thing has the timing marks on the pump probably as far as they will go to the drivers side.but the guy i got it from said after the new motor at 260,000 he's never touched the timing it now has 380,000 and i still run 25-26 mpg but its been running a little rough seems to have a little bit of a vibration thru the steering wheel and on a rare occasion it will like miss a cylinder and my surging it was suggested that it could be combustion pressure pushing back thru the inj's creating air in the pump, and the 6.2 inj's have maybe 30,000 on em since i put them in was thinking i'd try them and if they helped my surging then i'd go get some 6.5 inj's .hate to fork out 360.00 for inj's and then have to drop another 850.00 on a pump.why do these 92-93 pumps have bad head and rotors was it a design change or the higher pressures. heck my 6.2 that came out of my pickup had 320,000 and i never touched the pump my sub has 130,000 since i got it and it works great

[britannic]

Originally posted by Animal:
</font><blockquote>quote:</font><hr />Originally posted by britannic:
The 6.5L will run with 6.2L injectors, but probably won't perform to it's full potential. Why would the performance be off if the flow rates of the two injectors are the same and only the pop off pressure is less. The only thing I see different would be the timing may need to be retarded slightly to adjust for the lower pop off pressure, or am I missing something here. </font>[/QUOTE]Higher pop pressures allow more fuel to be injected in less time with better atomization. This is why the latest diesel injection systems employ such high pressures. Faster injection of more fuel allows for higher peak rpms; the optimum injection window is very small in an engine spinning at 3200rpm and the injection time/fuel amount is the limiting factor - this is one reason why older diesels have lower peak rpms as opposed to a gasser.

[catmandoo]

how many more rpms can be gained with the higher pop pressure 500,1000 ,1500?

[britannic]

Originally posted by catmandoo:
how many more rpms can be gained with the higher pop pressure 500,1000 ,1500? The pop pressure is just one part of story, the IP and engine design is the other. Using the higher pop pressure injectors in our 6.2L and 6.5L permits more efficient combustion, with a subsequent improvement in torque and power.

Very high injection pressures are also needed to inject fuel directly into the cylinder of a DI turbo diesel.

[Animal]

Originally posted by catmandoo:
6.2 inj's have maybe 30,000 on em since i put them in was thinking i'd try them and if they helped my surging then i'd go get some 6.5 inj's .hate to fork out 360.00 for inj's and then have to drop another 850.00 on a pump. I'd try the 6.2 inj. and if they worked well enough power wise I'd stay with them, if not you can get new 6.5 inj. on Ebay for $249 all the time.

Read this thread, it should answer some of your questions.

http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=2;t=002168

[painthorsman]

A lot has been said on here reguarding nozzle opening pressures between the old 6.2 injectors and the later 6.5 injectors. It is relativly easy, although time consuming, to adjust the opening pressure of the injector. The pressure opening point of the pintle (needle valve) is controlled by means of a spring and shims in the injector body. The maximum pressure capacity is determined by the condition of the pump ie: how much clearance there is between the plungers and bores in the pump.
I use an injector tester and shims avialable from Bosch to calibrate the opening pressure of the injector. While the factory pressure for 6.2 is set at 1800 to 1850, I set mine at about 1950psi. This allows for better atomization of the fuel at higher fuel settings and less smoke & EGT's for a given fuel setting... allowing for the fuel screw to be turned a little more than normal without "flooding" the engine with raw fuel, that cant be completly burned. As far as the total volume of fuel injected at full throttle, that is controlled primarily by the volume of the pumps plungers & bores... and the condition of the pump..ie: as earlier stated the 29 plungers in the old 6.2 pump and the 31 plungers in the 4911 pump.
If you have the mechanical know how and the tools required, you can set your own injectors to open at whatever pressure requirements you need... keep in mind 1:Too Low Pressure can cause injector "peeing" and piston damage etc. 2:Too High Pressure is harder on pump drive parts and could cause warm start issues with a worn pump.
Above all else: if you do this yourself, do it in a CLEAN environment! I re assemble injectors in a clean pan of diesel fuel to prevent any dirt from my hands from entering the nozzle assy.

[catmandoo]

you say you use an injector testor what does this consist of?

[dieselhumvee]

I have a 93 6.2L with intake and exhaust mods, the injection pump is turned up 1/6th of a turn and I get just a tiny bit of black smoke with full throttle, could my engine benefit from 6.5TD injectors? I have a 4979 pump on a 93 6.2L non EGR Hummer engine. This pump number does not show up on the dieselpage list and I have checked the number several times, if I remember right correctly, it puts out 50.5 MM @ 3600 rpms. So can I gain power with injectors and this pump?will my stock injector lines fit?

[catmandoo]

man if i turned mine up that high the epa would be on my a#* for pollution and we don't have emission laws here in iowa.i turned mine up an 1/8 and it smoked pretty good under load so backed it off just a hair and cut the smoke in half and seems to run better also.

[painthorsman]

Catmandoo, An injector testor consists of mainly a manual pump that mimics the high pressure of an injector pump. There are several manufacturers but the most common are Bacharach, OTC, Snap On, Rotunda (ford) etc. They have a pressure gauge on them that allows you to check the "pop off" pressure of the nozzle as well as hand valves for pressuring up a nozzle just below pop level, locking the line and checking for fuel leakage... they should not have a drip, form at the tip at 100 lbs less than pop off in one minutes time. Also you can check for good nozzle "chatter" and spray pattern with this tool..... Caution! Do Not Ever Get your hand or any part of your body in contact with the spray from an injector... the high pressure fuel WILL penetrate your skin like a knife and can cause serious blood poisoning or even death.