depends on the rpm the higher it revs the less time u have, at 7000rpm a 18ms IPW basically uses all 720 deg
depends on the rpm the higher it revs the less time u have, at 7000rpm a 18ms IPW basically uses all 720 deg
You're missing when that injector fires. If it's firing with the exhaust valve open, then much of that fuel is going out the exhaust. That stinks, especially for those without cats.
Also your message is a little hard to understand, and your math while correct is wrong. The amount of time is dependant on RPM.
There are 60,000 milliseconds per minute. If you're idling at 1000rpm there are 360,000 degrees per minute. That's 6 degrees/ms and 120ms/combustion event.
If your cam has 20 degrees of overlap and 240 degrees of .05 intake duration you only have ~220 degrees/36.667ms with which to inject fuel into the cylinder without a large portion of it exciting the tailpipes. You want your 4.6ms injection event to take place inside that window.
done some testing today in the 2000rpm and below area and my engine dosnt like too much retardation in the inj window, must be a sweet spot where the valve events allow the fuel to mix in with the air and into the chamber better, even ending injection around half way down on the intake stroke just didn't feel right and the instant litres/100 went up a little so i went back to previous settings, also noticed higher rpm seems to need more advance so i kept the factory 95 deg in the rpm table and tapered down to zero at 2000rpm
Actually, when the exhaust valve is open and you're at low load, the back pressure in your exhaust is higher than your manifold pressure, so you get natural EGR which is where bucking comes from. You won't blow fuel straight through the engine. I wish I could go back and delete any reference I ever made that said something like that.
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Apologies 07GTS and Eaglegoat. Thanks for your replies I hadn't seen them before I edited my reply....yes you are right I was off track. thanks.
2010 Avalanche 4WD; AES 390; Mast LS3 heads; VVT Cam; ported TVS2300; Overdrive 8 rib pulleys; 2.7 snout pulley; ID1000; LS3 TB; WB 450; Twin MM cans; built 6L80; CircleD Triple Disk, CSR flexplate; Trucool 40K; Aeroforce Dual; AFX
My current VVT cam card and stock injection settings that had been used attached. At .050 my exhaust valve closes 357 and intake opens 360. The stock settings I have used for 20k miles has been putting the fuel half way into the exhaust valve open event at higher speeds...meaning fuel pissed out the exhaust. I arbitrarily raised my boundary by 22 (542 at low rpm) the past couple of weeks based on reading others success and it made a significant difference, but I think I need to make some major changes based on this thread. Should I go back to boundaries (less than 540) to stay on the suction side of the piston even though my intake valve doesn't close until 582? And if so I would need to chop my ETC numbers greatly.
CamCard.jpgInjectionBoundary.jpg
2010 Avalanche 4WD; AES 390; Mast LS3 heads; VVT Cam; ported TVS2300; Overdrive 8 rib pulleys; 2.7 snout pulley; ID1000; LS3 TB; WB 450; Twin MM cans; built 6L80; CircleD Triple Disk, CSR flexplate; Trucool 40K; Aeroforce Dual; AFX
That's going to be vehicle dependant. It's also going to be greatest at the end of the exhaust phase, after the initial opening vacuum and subsequent pressure equalization. Just another reason to avoid injection at that time.Originally Posted by DSteck
There's really five stages of a four stroke IC engine... the fifth being the scavenging stage. But that is rpm and valve overlap dependent, so it isn't called a "stage"..
I'm still wondering what GM considers to be optimum injection timing with the direct injected engines. I have heard many references to cylinder wash, if injection is too late. How is this managed with direct injection? I have yet to handle one of these cylinder heads.
When arguing with an idiot, make sure he isn't doing the same thing....
Set it to where you see the least amount of fuel being used. Driveability will take care of itself with this simple conclusion and how you look at it to tune it. Whether it's advanced or retarded... You might even need to mix it up a bit and advance it in the lower cruising rpms to put back on a closed intake valve, then retard it again in the higher and idle areas. All your trying to achieve is best fuel atomization and to keep as much of it in the combustion chamber as possible.
Every setup is different due to cam specs and whether or not it's FI or NA... Then if it's FI, whether or not it's turbocharged or supercharged makes a pretty significant difference too. This will effect spoil time of the turbos...
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
Cylinder wash on DI only happens if it injects too early... It injects straight into a "combustion chamber" built into the piston. Ever wonder why gm had to replace so many of the earlier 4 cyls? Then they came out with a recal to fix it? DI engines are a completely different animal... Then because DI engines are so dependant on correct fuel air swirl for atomization, all it takes is a slight carbon build up on the pistons or valves to really hurt them. Again on the gen 4's or any for that fact your only looking for peak fuel burn and atomization. Build to build is different and calls for different settings.
Last edited by GHuggins; 07-18-2015 at 12:17 PM.
2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80
~Greg Huggins~
Remote Tuning Available at gh[email protected]
Mobile Tuning Available for North Georgia and WNC
what i found out is mine especially above 4k dosnt like too much delay in eoit maby about 20-30 deg delayed from stock is enough but much more and it just feels like it looses power, and the lower rpm like 2k and below i went back to close to stock and just took out 5 deg at a time and gained better fuel average then having too much delay in it, i found the best way is to look at the instant fuel usage and just set cruise and adjust eoit for that rpm until the instant fuel starts to go lower, i think what was happening was if it is delayed too much the fuel dosnt mix properly and even tho u are after the EVC its not a good burn which is why i used the instant fuel usage because it takes into account the tps/ipw ect, i took of about 2L/100 in my cruise areas just with eoit and because it was adjusted too far delayed before, still have some more adjusting to do in the following weeks see where i end up cruising at 1500 and below is really good now just have to make the 1500-2000 better
Can you adjust eoit tables on the fly with vcm scanner? I haven't checked and im away from my tuning laptop. That would really simplify the tuning.
From my testing 800-1400rpm likes advanced injection values. Ie i added to the rpm tables...
Good idea on instant mpg
No you can't. That would be awesome. So best thing I can think of is to set up a histogram to plot instant MPG against the RPM EOIT table. Then you'd need to go for a drive and record those values, make a change and see what it did. Lather rinse repeat. Pretty labor intensive.
Bill Winters
Former owner/builder/tuner of the FarmVette
Out of the LSx tuning game
Even better suggestion. I'll give that a whirl. Otherwise it's hard to judge whether these changes are improving fueling. Quantifiable data ftw
Last time I was screwing around with this, I had MAF disabled, was set up for open loop VE cal, and was monitoring my wide band. Seemed to work fine.
I know this an old thread but I have a tool I would like to share. I use Core-tuning on Ford stuff. One of the partners in Core tuning is Clint Garrity. He has a tool he sells that saves a lot of time for doing work such as this.
EEC_Analyzer.png
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