Bumping this back up. I'm having a terrible time with this setup still. Still a bit of injector rattle, it wants to smoke all the time and egts are always high even when the turbos are lit
EFILive Tuning for Larger % Injectors
- Thread starter SIKDMAX
- Start date
Just for laughs, try dropping the pressure in problem areas.
Here's what's happening:
You have a bunch of hot air trapped in the cyl, and it's getting hotter as a function of crank rotation.
You spray high-pressure liquid fuel into the air. As it vaporizes, it cools the air down around the fuel. Only fuel that is a "gas" can burn, liquids can't burn. There is no way for air molecules get past the surface of a fuel droplet.
Fuel will vaporize faster at higher pressures, because the droplet size is smaller, hence more surface area per mm3 of liquid fuel. However, the faster it vaporizes, the more the air gets cooled, AND the rate that the fuel is coming in at increases as well. Lower fuel pressure might make bigger droplets, but it also keeps the air temp up to allow for more combustion.
When you vaporize the fuel too fast, it can slow down the combustion. If it slows down to the point the liquid fuel hits the walls of the cylinders before it becomes a gas, it REALLY slows down combustion, and this is where most black smoke comes from. Fuel can barely burn when it's stuck on a surface, so it only burns partially.
Bumping the pressure up can either help the situation, or hurt the situation, depending on whether it's retarding combustion. Think about this for a second - Why does GM reduce fuel pressure at lower RPM's? Especially if higher pressure can yield better vaporization? Reason - They have to. They have no choice but wait for higher air temps in the cylinder before they can increase the pressure.
Now at WOT/Max Boost, get as much fuel pressure as possible. The air is brutally hot when you get a lot of boost going. But when you DON'T have boost, you probably can't run high pressure without spraying the walls with most of your fuel.
Large injectors aggravate the situation because by their nature, they make larger droplets.
Here's what's happening:
You have a bunch of hot air trapped in the cyl, and it's getting hotter as a function of crank rotation.
You spray high-pressure liquid fuel into the air. As it vaporizes, it cools the air down around the fuel. Only fuel that is a "gas" can burn, liquids can't burn. There is no way for air molecules get past the surface of a fuel droplet.
Fuel will vaporize faster at higher pressures, because the droplet size is smaller, hence more surface area per mm3 of liquid fuel. However, the faster it vaporizes, the more the air gets cooled, AND the rate that the fuel is coming in at increases as well. Lower fuel pressure might make bigger droplets, but it also keeps the air temp up to allow for more combustion.
When you vaporize the fuel too fast, it can slow down the combustion. If it slows down to the point the liquid fuel hits the walls of the cylinders before it becomes a gas, it REALLY slows down combustion, and this is where most black smoke comes from. Fuel can barely burn when it's stuck on a surface, so it only burns partially.
Bumping the pressure up can either help the situation, or hurt the situation, depending on whether it's retarding combustion. Think about this for a second - Why does GM reduce fuel pressure at lower RPM's? Especially if higher pressure can yield better vaporization? Reason - They have to. They have no choice but wait for higher air temps in the cylinder before they can increase the pressure.
Now at WOT/Max Boost, get as much fuel pressure as possible. The air is brutally hot when you get a lot of boost going. But when you DON'T have boost, you probably can't run high pressure without spraying the walls with most of your fuel.
Large injectors aggravate the situation because by their nature, they make larger droplets.
Broken Record - I'm sure many folk already know this, but years ago I pushed stock injectors (LLY OEM sticks, these are the smallest injectors) up to ~800rwhp uncorrected on pump fuel. Corrected would have be about 850'ish. We weren't at the limits of the injectors yet. Injector overlap and piston melting became an issue though. We were running 2 modified CP3's with a GT42 Mag.
The fantasy setup would be an injector that always ran at high pressure, but had the ability to control the rate of flow so you wouldn't drop the air temp as quickly at first. Multiple injection events are a way of doing this. It would be uber-cool to have 2 injectors per cylinder with different controllers. A 25% injector circuit, and a 75% injector circuit. Most the time cruising, you'd be using the baby injectors at high pressure. But as the boost kicks in, the big dogs come on line.
The fantasy setup would be an injector that always ran at high pressure, but had the ability to control the rate of flow so you wouldn't drop the air temp as quickly at first. Multiple injection events are a way of doing this. It would be uber-cool to have 2 injectors per cylinder with different controllers. A 25% injector circuit, and a 75% injector circuit. Most the time cruising, you'd be using the baby injectors at high pressure. But as the boost kicks in, the big dogs come on line.
Righteyeblind and I had a truck up here that was being a real pain, no matter what he tried he couldn't get the rattle, smoke, & slow spool out. Ended up being a corrupt OS, new OS and she runs like a scalded cat now, no rattle, smoke is normal, & spools very fast. Just a thought....
your cam suggests that you are looking for performance in the higher rpms. when you do that you sacrifice low rpm performance. try raising your shift points two or three hundred rpm if you are still having trouble.
Shifts have very little to do with this issue I held 3rd at 2500+ and maintained speed. Still smoking still high egts
I did bump them up some just to see a while back
I just think these nozzles are way to much for a dd at this elevation
I did bump them up some just to see a while back
I just think these nozzles are way to much for a dd at this elevation
i believe it was just a combination of things, first being the ported heads. long story but i believe the ports were enlarged too much and velocity was lost.
as of now the only thing that has changed is the heads and the issue is pretty much nonexistant. im not sure how it would do now with bigger nozzles. my high pressure is a 71 and the atmo is a 94 and the truck lives at 5800'
let me know if you have any other questions about this, i have tried a ton of things.
