8V71 Injectors

[Fredward]

Don't want to Hi-jack someone else's thread here so I'll post this question:
In my MCI 5A my 8V71 has N65 injectors with a four speed. The engine is pretty fresh (no leaks no smoke) It sounds like this combination of injectors, engine and tranny is not optimal. She's got lots of power at governed speed and throws very little black smoke. But elsewhere on this board I saw reference to the N60 being better for the manual tranny becuase the torque curve starts at 1200 whereas the N65 starts at 1600 rpm? Did I understand that correctly? Aside from slightly higher fuel consumption, does the extra 25 horse and additonal torque really benefit me?
Fred

[Utahclaimjumper]

Fred, you understood wrong, the injector size wont change torque much, the cam timing will (standard vs. 'A' timing) My 8V71 is 'A' timed with N65 injectors which moves the torque curve up for an automatic trans.>>>Dan

[TomC]

Fred- this is directly from the spec sheets at Detroit-so you decide.  N65 injector (300hp and 800lb/ft torque) produces its' max torque at 1600rpm-this is not to say that you can't take it lower-it'll probably produce more smoke and less than optimum fuel economy. The N65 was called a high performance injector, the N60 (275hp and 740lb/ft torque) a balanced, and the N55 (253hp and 680lb/ft torque) was  a high economy injector-both the N60 and N55 produce their max torque at 1200rpm-perfect for a 4 speed manual.  My bus had N55's in it when I bought it.  Since I have an automatic, I changed to the N65's.  Now that it is turbo'd, I have 9G75's in it for 375hp and 1125lb/ft of torque.
You can change to A timing and get a bit more performance out of your N65's-but that involves pulling the rear cover off (removing the trans from the engine).  With A timing you can go to N70's for a true 318hp and 860lb/ft torque.  Injector size is directly proportional to the horsepower and torque the engine produces.
Turbo and naturally aspirated engines have two different horsepower settings. For instance a N65 natural engine will produce 300hp and 800lb/ft torque.  Turbo the engine and re time the injectors for turboing and you get 325hp and 975lb/ft torque.  Deminstrates the higher efficiency of turbo engines. Good Luck, TomC

[Fredward]

Thanks guys. I don't plan on changing it; just wondered what I have here. It seems pretty doggy until its winding out. I'm used to driving four stroke diesels which have lots of low end torque and lug like crazy. This DD is a different animal. I can definitely tell when it gets its power and its about 1500 or 1600 RPM by the sounds of it. (No Tach). I've learned to just wind it out and let the governor handle it. I'd love to stick a 6V92T in it. A friend of mine has one (painted silver whatever that means) and it wouldn't cost me much. But I think that I'll be just fine with my 871. I'm not in a huge hurry and it doesn't leak and it doesn't use much oil so I think I'll just stick with it.
Fred

[Dreamscape]

Good Thinking,

If it ani't broke don't fix it.

I just have to remember that when driving our Eagle with an 8V71 and weighing in at several ton, it doesn't like the hills either. So I sit back and enjoy the ride up knowing I will get there eventually. We all can't have a Corvette, some of us are stuck with toads.

There is one thing I have learned on this board, if you want more power it costs BIG BUCKS. Some of us with little bucks just let 'em go by and smile.

Happy Trails,

Paul

Dreamscape

[Ncbob]

Like you Fred, I have an MC5A with the 4 speed Spicer...no Advanced Timing and N65 injectors. We, like you don't smoke, overheat or set speed records.  What we do is run comfortably at what I refer to as "Economy Cruise" at about 1800-1850 down the road....that gives me about 65 MPH and just under 9 MPG hauling a total of 27,940 lbs gross + a 2300 lb toad.

Sure, the big boys go whizzing by like their butts were on fire but we just smile and wave.  I gave up drag racing over 50 years ago. Some of the big gas jobs do gas well...that really makes me smile!

These Detroits really prefer lower gear pulls of between 1500 and 2000...but we don't (unfortunately) have enough holes in our gearbox to keep them totally happy.  I don't run up against the governor when upshifting...I drive the tach and try to keep the low RPM's above the 1400 mark.

"They're green, they scream, they fly in little pieces"...but only if you abuse them.

NCbob