How Many Flats??

[79GLIDE]

Looking for advice for turning up the pump on my 1993 7.3 based on these specific conditions:

Banks Sidewinder boost 10psi at 2800 RPM pulling under load with max EGT 750 and no appreciable haze. No real smoke from this truck under any condition, and only light haze under full pedal from standing stop. Thanks in advance.

 

[YJMike92]

I suppose you could do one flat at a time and monitor for a day or two and see how it goes. I would check and adjust your timing first.

 

[79GLIDE]

Timing is dialed in. I was hoping to save some time by getting close initially, but maybe a flat at a time is best.

 

[gnathv]

You know you’re going at least 1 flat. Then you’ll open it again and go 1 flat to see if it’s better. Turn it up 2 flats to begin with. If it’s hot and smoky you’ll open it and turn it down. It’s just one of those things. At 750 EGT you’ve got some room for more fuel. If 2 flats gives you 1200 egt you’re there.

 

[u2slow]

Is your pyro pre or post turbo? Makes a difference... its a couple hundred degrees difference on a cummins usually. (Dunno what's typical on the IDI)

EGTs are largely about load... so if you only do light stuff, you can run more fuel (flats) If you're borderline, its harder to regulate EGTs with an auto than a manual.

My buddy ran 3 flats on his '90 NA 5spd; which I drove extensively. It never did anything heavy, and it wasn't a problem. It was hazy though.

 

[Isaac Ristow]

Mine is a 7.3 studded with a Rajay turbo kit I max at 15psi my pump is turned up at least 4 flats. The only way I can break 1000 pyro is pulling my 9500lb camper up a hill its not scary I really gotta be pushing it to get to 1200 degrees and all I have to do is drop a gear and back out a bit. Empty driving I average 400-600. A big contributer is I have a zf5 and 4.10 gears that helps a lot. I'm using a Isspro gauge probe is in the turbo feed right above the manifold

 

[CBRF3]

When you ask about how many flats alot is at play at what elevation / what Injection pump model & version ( reason being high viscosity or low viscosity version flow much differently on modern diesel) / then condition of your injectors ( aka pop pressure and are they leaky or not along with spray patern ) and are you intercooled and be aware if you think your set with a light load full throttle and peaking 950f your wrong our injection pumps are a bit different ours only add more fuel dependant on load for instance if you have 6000#'s of weight behind you it will only get 3/4 the fueling that the injection pump is set to but when you go to 10,000# you will get 100% fueling our injection pumps feel the resistance to accelerate and will add fuel to try to hold a RPM or to accelerate dependant on said resistance this is what your messing with when you turn it up its the max fueling and this is load dependant so you need to be carefull.

Then you also need to factor in our setups are odd and more setup like a tractor or genset injection pump not really like a truck injection pump so the fuel rack in our injection pump has a internal governing / fueling curve built into them that tries to hold a RPM at a set throttle position and the fueling again is load dependant so as you add more load the injection pump will add more fuel to compensate even if you do not move the throttle at all and have it locked in a position and turning up the pump is just messing with max load fueling and our injection pumps start defueling around 2500-2800 rpm's this is a governing feature built into our injection pumps after market injection pumps are modified to hold max fueling in CC's for longer aka higher up in RPM's stock ones start defueling unless you mess with the governor settings which I don't advise because it will throw off internal pump settings like fueling curves and timing curves and mess with also throttle position fast idle hardware and transmission kickdown and such.


I want to throw a word of caution out there also when you turn up the fuel it becomes risky for other things when was young was coming out of a muddy field road with a 2x4 dually with bald tires spinning and well learned the hard way when it caught traction on the pavement the injection pump responded with heres load give it the fuel and well I scattered rods all over the road and i was not that high in rpm's like 1800 rpm's but found out this is the factory peak of the fueling curve so when it sensed the load it gave it the beans and well the motor was turned to scrap in a few seconds be carefull turning the pump up mine was maxed out and my EGT's were good and was running 13psi boost I learned the hard way hopefully you don't have to and it was expensive.