Hmmn, interesting that mine would be the one more "closely tuned to optimum" of the two. I basically haven't done any tweaking on mine yet. Just swapped my pump & injectors a few months ago (after the other one died) and setting the timing by ear (after only having heard two IDIs that were running right). I even advanced the fuel screw one flat on this pump before I ever even installed it. Must've got lucky I guess. I'm kinda' a little puzzled tho. My truck is only getting about 14.5 mpg (mixed driving around town & getting a little "throttle happy") to 16.5 mpg (running a consistent 65-70 mph on the freeway using the cruise control). Shouldn't it be a little better than that? Is it likely it is going to improve much with some tweaks? As in enough to be worth the effort?

Well, maybe not QUITE that "obvious" to some of us.....
Well, I just flushed the radiator (3 times), put new antifreeze in it, and replaced my radiator cap, but don't have any equipment to pressure test the cooling system. I'll be happy try blocking part of the radiator and see what effect that has though.....

 

thebeastof1980......tune it to begin with...no break in required.......does the 45°= 3 o'clock?

as for the 1850-1950 turbo injector speck...........I am basing this speck on the very complete information that I have compiled on the Isuzu 2.2 engine and then plugged this information into my software.............to understand this comparision..............the Isuzu has about 450 PSI cranking compression and the turbo engines run about 7-8 PSI boost.......of which would (on a well tuned engine) produce a peak cylinder pressure of 955 PSI during combustion.....on a street engine the "desired limit" is 1000 PSI peak pressure..................as a comparision, the same engine N/A would have a peak pressure of 689 PSI.....................simply said, with higher cylinder pressures, the injection pressure has to be higher for the fuel charge to "get thru the pressure/turbulence" to reach the "hot plate" for proper ignition.............

So, with the information that I have now.......lets just say that the 1850-1950 PSI pop off speck for turbo is a minimum speck.....................increasing the pop off pressure has a "retarding effect" on injection timing, so the timing should be adjusted for the increase in pop off pressure............

A N/A IP in reasonably good condition should not have problem with a increase in injection pop off of 500-700 PSI on the high side of the IP..............it's the low side that usually has the problems......(just make sure you have a positive pressure between the fuel filter and the IP.....Put a Electric Pump (15 PSI) at the Tank....................)

CheaperJeeper....are you turbo?......what brand and part number are the injectors?.........man, 16.5 mpg at 65-70 mph ............at that speed the wind resistance is most likely decreasing fuel mileage 10-25% ........leave the engine "tweaking" alone for now..................."tweak rolling and wind resistance" and a straight thru muffler...................(see earlier posts about exhaust)..........do not put the tail gate down or use a "web gate".........put a cover on the bed...........

crossbones

 

Note: I will be away until Monday.......sorry that I have not provided more exact information on my glow plug readings.......I have had a new set of injectors for two weeks.......no time to test them or install them...
crossbones

 

Nope - this is the NA truck in my sig - my DD right now.

Dunno - they are the stock used injectors & pump that came off the "spare" motor that I got when I bought the truck
Yeah, probably. If I ran 55 or 60 I imagine it would come up 1-2 mpg. I figured 16.5 was pretty respectable for a 20 year old 3/4 ton truck with no OD doing 70 mph, but hey, more is always better, right?

Already got the straight thru muffler - a 3" system - along with my custom Y-pipe I built (see my gallery). I've thought about the idea of a tonneau cover, but wondered whether it could possibly help enough in fuel savings to be worth the cost.....

 

Will a 94 DI injector fill the requirements or do I have to have my injectors rebuilt to the 1850-1950 PSI pop off?

 

CB2, I remember reading a while ago that stanadyne has "recently" (don't know exactly when) recomended that the pop off specs be set to 2200 psi. Do you know anything about this?

 

What I decided to do is new BB code injectors and have the pop off set to 1950 psi and make sure their balanced [all pop off the same] because it's known new injectors can vary 2-500 psi..

The 2200 spec. david85 quotes makes sense. CB said 1850-1950 for 8 lbs. boost and the newer add on turbo's are supposedly good for 12-14 lbs. boost.

Dennis

 

Wo-hoo- won bid on e-bay for a new Kent-Moore tach-n-time, with magnetic pick up and pulse adapter, so us mid BC coast guy's will soon no longer be timing by ear! I am very curious to see how my timing checks out using the glow plug method, and will be sure to post the results when I get some, and figure out how to run timing equipment etc.

 

Hello. The very major problem with tuning the 6.9-7.3 engines is what "speck to tune it to"..........the information available is all over the board...........the first is at what rpm to set the timing........the second is injector pop off.............now, at what rpm to set the timing at is a simple math problem (this applies to any and all diesels using #2 diesel fuel..........8.5°at 2000 is Not correct period ************* mathematically, 8.5° BTDC is for 700 RPMs)................now, for injector pop off speck.........it is not wise to exceed the "rule of thumb" of 1000 PSI peak cylinder pressure (on a street diesel engine )..............peak cylinder pressure is a direct mathematical relationship of cranking compression in PSI, polytropic exponent of compression (air), and boost in PSI........................that being said, my "personal rule of thumb on a IDI on injector pop speck is to double the peak cylinder pressure plus a "little good measure"..................

So, with 450 PSI cranking compression.............
0 PSI boost=656 PSI peak pressure X 2=1312 PSI = about 1425 used in a lot of Ford speck information( the Isuzu 2.2 is 441 PSI compression and 1493 PSI pop off)

8 PSI boost=975 PSI peak pressure X 2=1950 PSI = about 1950 used in a lot of Ford speck information(the Isuzu2.2 turbo(typical 7-8 PSI factory boost) is 441 PSI compression and 1920 PSI pop off)

12 PSI boost=1131 PSI peak pressure X 2=2262 PSI

14 PSI boost=1208 PSI peak pressure X 2=2416 PSI

just as a comparison with 350 PSI cranking compression
14 PSI boost=960 PSI peak pressure X 2=1920 PSI

so, if peak cylinder pressure is a direct relationship to torque, then what is the advantage of decreasing cranking compression (shaved pistons and such) so you can run 14 PSI boost....................

not what you have been lead to believe is it...........................

crossbones

 

"for injector pop off speck.........it is not wise to exceed the "rule of thumb" of 1000 PSI peak cylinder pressure (on a street diesel engine )..............peak cylinder pressure is a direct mathematical relationship of cranking compression in PSI, polytropic exponent of compression (air), and boost in PSI........................that being said, my "personal rule of thumb on a IDI on injector pop speck is to double the peak cylinder pressure plus a "little good measure".................."



CB---If we're setting the pop off pressure to what our max boost is what effect [if any] do we have under normal driving when we have little or no boost ?

Dennis

 

the added benefit (IMVHO) is in the proper control of the injection period cut off (injection dwell)................cutting the injection off correctly in relationship to crank rotation is a huge "key" to fuel mileage and in the case of using VO a very huge factor in Not getting "ring coking"............

crossbones

 

I'll try to not give a dumb answer to a not so dumb question. Everyone has a different knowledge base...and I may need your help some day

What kind of meter do you have?

If it's digital, it will probably just have a DC volts setting (often a big "V" with a straight bar over it). In that case, it will auto-scale. Just set it to volts and go.

If your meter is analog (has a moving needle), you will want one of the lower settings, if not the lowest. 1000 mV = 1 V. With this type of meter, it is important to not have it hooked to a glow plug that will be used for starting while on the low scale. You could burn it the meter out while starting (unless you switch to a higher scale, or unplug a lead until the glow plug cycle is completely finished).

Hope this helps.

Now I have a question. Are you guys just unhooking one glow plug, or all of them? Has anyone been burning out GPs with just one unhooked?

 

I only confirm good glow plugs, one at a time at idle. My driving checks have all glow plugs connected to the system as normal, I have run a 2 wire lead into the cab, directly off the controller-glow plug terminal, the other to a valve cover stud for ground. (make sure the GP wire iswell protected from ground, as it is basically non-fused wire, would make losts of smoke and fire quick with glow plug current if shorted out)

 

j tate..........there are no dumb questions my friend............once the "balance test" of checking each glow plug is done, reconnect all glow plugs back to the system and connect the volt meter to the system............this gives a measure of protection when advancing/retarding the timing as the meter will pick up the highest reading glow plug of all cylinders....

crossbones

 

thanks tbone and crossbones for the info, i have a digital and a analog meter but im going to use the digital one to do my tests. since i bought the digital one i hardley ever use the analog one lol. i use them for checking ac and dc current, and continuity test but didnt know to much about milivolts. thanks for the help.