Injection Timing Assistance Requested

[J-CUE]

Question,
If the normal RPM is used, does the ECM use the 4096 RPM cell in the equation for RPMs above 4096, or is normal RPM dropped out of the equation above 4096 and the ECM is left with just, boundary - ECT - make up?

[liquidforce917]

try to inject as the EVC is happening so it also gets good vaporizing going on, leaving it so it only has 52 deg before the IVC is too late if u stab the throttle it may not have enough time to get the first crack of fuel in, i have my idle injection ending around PPV or just before depends on your PW, if u crack the throttle it should stay nice and responsive

I have a stock cam with tons of negative overlap so there is no chance of fuel making its way out of in open exhaust valve (also know as short circuiting) if thats why you suggest targeting SOI when EVC event happens. I am also basing my IVO and IVC numbers on 0.050" lift which is conservative.

I think you do have a point that 527* for EOI is a little late. After looking at a piston velocity graph, and being reminded where most of the "meat" under the curve was I am going to do some trials with EOI somewhere between 450-490. Those EOI values are a little later than the PPV EOI of 433* you suggested. I am doing this in an attempt to account for the delay between piston velocity and intake air velocity (not travel time to cylinder as calculated in the excel tool).

Let me know what you guys think.

[07GTS]

Question,
If the normal RPM is used, does the ECM use the 4096 RPM cell in the equation for RPMs above 4096, or is normal RPM dropped out of the equation above 4096 and the ECM is left with just, boundary - ECT - make up?

what ever is in the 4096 cell is used above that, thats where its good to use the boundary instead because u have the full rpm range

[07GTS]

I have a stock cam with tons of negative overlap so there is no chance of fuel making its way out of in open exhaust valve (also know as short circuiting) if thats why you suggest targeting SOI when EVC event happens. I am also basing my IVO and IVC numbers on 0.050" lift which is conservative.

I think you do have a point that 527* for EOI is a little late. After looking at a piston velocity graph, and being reminded where most of the "meat" under the curve was I am going to do some trials with EOI somewhere between 450-490. Those EOI values are a little later than the PPV EOI of 433* you suggested. I am doing this in an attempt to account for the delay between piston velocity and intake air velocity (not travel time to cylinder as calculated in the excel tool).

Let me know what you guys think.

ok yea with a cam and no overlap just aim for the intake valve like stock but just not as advanced, it can help having it sit on the closed valve so just see what it likes, for cruise just see what your PW is like and adjust the cruise rpm areas to see if it helps, i dont think there are as big gains for stock cam but still some if u play around with it

[steve-0]

ok yea with a cam and no overlap just aim for the intake valve like stock but just not as advanced, it can help having it sit on the closed valve so just see what it likes, for cruise just see what your PW is like and adjust the cruise rpm areas to see if it helps, i dont think there are as big gains for stock cam but still some if u play around with it

hello i have 15 degree overlap cam ls3 camaro ss , i had lot of back fire when im hit the paddle from 800 to 2000 rpm , i add 10 degree to boundary the back fire is gone , but when the engine temp. hit 203f it start back firing from the intake when im hit the gas paddle at low rpm only ?? any help please ?

[07GTS]

hello i have 15 degree overlap cam ls3 camaro ss , i had lot of back fire when im hit the paddle from 800 to 2000 rpm , i add 10 degree to boundary the back fire is gone , but when the engine temp. hit 203f it start back firing from the intake when im hit the gas paddle at low rpm only ?? any help please ?

is your ECT table all the same or still changes with temp..? if it changes with temp and u have overlap just make it all the same can even help with cold start, does it hesitate at same time..?

[GHuggins]

I have a stock cam with tons of negative overlap so there is no chance of fuel making its way out of in open exhaust valve (also know as short circuiting) if thats why you suggest targeting SOI when EVC event happens. I am also basing my IVO and IVC numbers on 0.050" lift which is conservative.

I think you do have a point that 527* for EOI is a little late. After looking at a piston velocity graph, and being reminded where most of the "meat" under the curve was I am going to do some trials with EOI somewhere between 450-490. Those EOI values are a little later than the PPV EOI of 433* you suggested. I am doing this in an attempt to account for the delay between piston velocity and intake air velocity (not travel time to cylinder as calculated in the excel tool).

Let me know what you guys think.

Do what you want, but your going to want to retard it in the higher rpms much later than this... I did a big write up on all of this a long while back - keep it centered around ppv and don't go above 600 with a factory cam...

[GHuggins]

When I said you wouldn't like it that retarded - I was referring to the lower rpms... It needs to transition gradually into the more retarded levels in the higher rpms...

[steve-0]

is your ECT table all the same or still changes with temp..? if it changes with temp and u have overlap just make it all the same can even help with cold start, does it hesitate at same time..?

thank you , do i need to zero the Normal RPM ? it still backfire from the intake when im hit the gas at low rpm ,

[07GTS]

yea if u zero the RPM then just use the boundary to do RPM cos it has much better scale, what's the spark like there maby a bit more could help the backfire if it's missing ?

[steve-0]

yea if u zero the RPM then just use the boundary to do RPM cos it has much better scale, what's the spark like there maby a bit more could help the backfire if it's missing ?

if i increasing the boundary the backfire come from intake , if i decreasing it the backfire come from exhaust,

[07GTS]

something is going on if it's getting backfires either way, how's the fueling sounds like a lean tip in ?

[steve-0]

something is going on if it's getting backfires either way, how's the fueling sounds like a lean tip in ?

i have afr gauge , fuel is ok , im running ported heads ported intake manifold , using MAF only ,

[07GTS]

is your VVE dialled in also it does get used for transients still ?

[steve-0]

is your VVE dialled in also it does get used for transients still ?

i disabled the LTFT , im ruining MAf only ,

[Niemer]

What is the theory for modifying EOIT for a cold engine? It seems like the factory calibrations have it advanced when ECT is low then retard as it warms up.

[GHuggins]

What is the theory for modifying EOIT for a cold engine? It seems like the factory calibrations have it advanced when ECT is low then retard as it warms up.

Depends on cam and setup... A lot of overlap with a blower for example will probably want it to be all the same number or a touch advanced when colder - it won't like the traditional full advancement like the OE settings at all however whereas a less overlap cam will like it... If you really want to dial it in - use fuel trims and do multiple cold starts to dial it in for the different temps...

[Niemer]

Couple things I noticed when playing with this Scott - First off the injector pulse width cells below 2400 rpms are protected even though they shouldn't be and then even though the regular chart shows the injection timing "soi" coming back around before the 720 degree mark - the black graphs don't correspond simply because the rpms on them don't go high enough? I know realistically most LS engines won't see anything above 7000 rpms, but is it possible to add a couple more black charts Please and Thank You


I'm also attaching a demonstration sheet of a cam and blower setup running 16psi I know is working very well even though I honestly know the injection timing could be a touch more advanced by redline... This is solely pulse width information during a dyno pull which will include transients, so honestly you might want to just look above 2500 rpms for this reason...

Would this be a fair statement?
- Below 1536 rpms, keep SOIT after EVC to reduce fuel smell at idle
- Above 4500 rpms, aim for EOIT-FRC right before IVC

Anything to aim for between 1500 and 4500 for this case? Or revert back to the other notes?

[GHuggins]

Best and most straight forward advice I can give - aim to keep ppv right in the middle of eoi and soi except for high rpms where you will keep eoi after fuel to port time is included at around 15 to 20 degrees before ivc... Especially where your running a PD blower The eoi is about 15 to 20 hp sensitive - you can loose that much with it being off that little and then more if it's off more...

[Niemer]

Thanks, I've updated the DOCs tab with some more notes as well as a few definitions