RedWS6 00

From what I understand the injector fires just before the inlet valve openes to help improve the atomisation of the fuel.

What if you have a different cam, obviously with the earlier opening of the valves you would assume that you'd need to move the injector timing. I've had the cam in for some time now, but never touched the injector timing. I know its not going to give much in the way of gains. Just wondered if anyone has played with it and what was your basis for calculation?

Hemi2Slo

That's really interesting. I've never thought of that before but it makes sense. I would think you would need to know, of course, where the intake valve closes in relation to TDC. That's if you are using HPtuners. Also you would need to know what exactly a reference period is, as referred to by the software. If you knew both of those it would probably be easy to calculate the change. I'm gonna have to look into that.

PS, I see what you're saying too Mr. Todd, you must've posted while I was typing lol

Texas_WS6

iTrader: (9)

I have personaly played with this and did not see any power or drivability improvements from it. It actually did nothing for me. I know it will effect your emmissions, and I am sure if you were able to move it 90 degrees it would effect power and drivability. I don't think it moves it that much. Maybe others have more info on this.

voda1

iTrader: (4)

Check here: http://www.hptuners.com/forum/showthread.php?t=32510

Higgs Boson

iTrader: (3)

Yes it makes a huge difference if you know what to do and why you are doing it.

If you understand valve events and understand what the table means and does, you can definitely improves idle quality and smell, low speed driveability and torque and throttle repsonse all by keeping fuel from blowing out the exhaust during overlap.

I worked on mine and made a very nice improvement after airflow and fueling tables could not correct the problem.

It all has to do with the cam, overlap, and valve events and pretty much nothing to do with a huge turbo, lol....

SSpdDmon

iTrader: (10)

So what's the concensus? Raise the values based on valvetrain/cam dynamics and delay the injector firing times so less fuel is passed through the overlap into the exhaust?

Hemi2Slo

From what I understand, it depends on your cam. Say your cam opens the intake valve 16 degrees earlier than stock, as mine does, then you want to make the injector spray 16 degrees earlier than stock. You do this by decreasing the values in both tables by .2. This is all according to the guys in the hptuners forum thread. According to them, each .1 is 8 degrees of rotation of the crankshaft. So therefore the formula is (stock intake open event-new intake open event)/90.

So results, I made the change in my truck and I felt a noticeable difference in torque below 3000 rpms, and a pretty bad cam surge issue below 2000 rpms I was having is now nearly non existant.

SSpdDmon

iTrader: (10)

I thought I read they were increasing the numbers to delay injector timing until after the exhaust valve closes, which means the intake valve is already open. So you're saying we should actually reduce them so that the injector sprays the back of the intake valve once again?

Jim_PA

iTrader: (9)

So, if a stock LS1/LQ4 cam (12561721) intake open event is 22 BTDC (can anyone confirm this?)

And my new one is 31 BTDC (I need to confirm with my cam card at home)

(9*.1)/8 = .1125

I'd want to decrease values in injector timing tables by .1125?

Higgs Boson

iTrader: (3)

bigger cam, bigger eoit number. you want to delay injection. yes the intake opens earlier but the exhaust also closes later. the exhaust closing event is the key. a stock cam intake opens and closes before the exhaust even opens so they can spray a closed intake valve.

my cam has 12 degrees of overlap. mine seems best increases from 5.55 to 6.55 eoit.

GenIV ECUs use real numbers of degrees to adjust, not an interpretation number like GenIIIs.

you would never want to inject sooner, your car will run like crap. you'll blow raw fuel out the exhaust, get terrible combustion, smelly car, dirty bumper, less power, etc.

also, remember that the value is END of injection timing, so it starts SOONER than what you're working with.

you guys need to read the WHOLE HPT thread.

Hemi2Slo

Ok I see what your saying, so I went the wrong way. So in that case should the calculation be done using the exhaust valve? I haven't had time to read the whole thread, I've only got through the first 8 pages or so. But in my case, my cam doesn't have any overlap so should I actually reduce the numbers like I did? I realize my results may be a fluke, I'll try adding .2 to the tables today and see what happens.

Higgs Boson

iTrader: (3)

Just compare your exhaust close event on your cam to the stock cam and think about (and calculate) where the piston is in its travel vs injection vs exhaust valve event and command the injector to spray at a time where the fuel won't be lost out of the exhaust (so the exhaust valve could potentially be open during spray IF the piston is traveling downwards not pushing upwards - which would require delaying injection).

If you don't have any overlap, there is really no point in modifying the table. Spraying earlier onto a closed intake valve may help if you are spraying a larger amount, allowing more atomization, etc than needed with the stock amount of fuel.

With overlap, you want to spray as late as possible compared to exhaust valve closing (so you don't lose fuel out the exhaust) but not so late the piston can't efficiently draw fuel into the bore for combustion (because its too far down the cylinder already).

You just have to calculate it.

SSpdDmon

iTrader: (10)

I'm on another computer right now, can't find a decent VE calculator, and could use a little help here. I've got a 240/244 112lsa cam (I think it's an XER on the intake and an XE on the exhaust)....so I would need to add in roughly how much to the Injector Timing tables to have the injectors firing at the right time?

Also, does the value get added to both tables?

I've got one that is 5.55 flat across the board and one that starts at 2 point something and maxes out at 5.55.

Thanks in advance!!! =)

Jim_PA

iTrader: (9)

Ouch, my head hurts, but I think I get it, at least I hope!

5.55ms is factory timing with a factory cam so it sprays the intake valve

6.5ms is how you would adjust timing a factory cam so it would spray when the exhaust valve is just closed.

Then you calculate what your cam does...

And I come up with

5.83ms is if I wanted to mimic factory settings by injecting when the intake valve is closed

6.49ms if I want to inject at the point that the exhaust valve just closes.

Is that right?

Is 6.49 the final value for my injector timing table, or is that added to what's already there across the board? I might be able to figure that out for myself if I had it in front of me to see what values are in there now.

Seems like at best what they have come up with is a good theory with some positive results, but there's no definitive answer to what is the best for what you have.

I also suffer from gassy exhaust smell, and some erratic idle AFR values, and although it's not a huge issue, it would be nice to clean it up.

Jim_PA

iTrader: (9)

And one last thing... I can only imagine your cam needs to be degreed in perfectly if you are expecting the perfect result. Otherwise you'll be much closer to where it should be, but not as perfect as it looks on paper.

Jim_PA

iTrader: (9)

This is the spreadsheet I used from the HPtuners site (soundengineer's) to get the values I posted above.

Higgs Boson

iTrader: (3)

Well, it makes the biggest difference at idle and low engine speeds. The faster the engine spins, the less it matters because the injectors hardly turn off at all. It just becomes one big spinning happening. It's really pretty cool when you think about all the stuff that happens and the speed at which it happens.

SS and PA, I would recommend starting at about 6.5 or 6.55 and go from there. Keep in mind the formula (in the HPT thread) about how Boundary and Normal work together. You really only need to edit Normal to alter the equation as a whole. Just leave Boundary alone.

I also doubt you will see a difference from 6.49 or 6.55, etc. Those will be small changes in the already correct area. It's correct that you'll only be able to get close.....

SSpdDmon

iTrader: (10)

I think my answer is to either ~.75 to the tables to get the end of injection timing to line up with the EVC. So, I'm assuming that get's added to both tables that I previously mentioned... Hopefully, I'll be able to give it a shot this weekend.

Higgs Boson

iTrader: (3)

This is a good spreadsheet to work with.

I personally feel that when you have overlap, the most important consideration is to "start" spraying just as the piston starts to move back down. Even if the exhaust is open (and maybe beginning to close) the piston should still pull the fuel into the cylinder and not push it out the exhaust.

Notice I said "start" spraying as we are dealing with End of Injection....You want to End Injection, therefore, a little later than TDC, maybe 10-15 degrees into the downward travel of the piston....You will have to experiement with it, but like I said before, close is good enough, IMO.

Higgs Boson

iTrader: (3)

FYI, going from 5.55 to 6.55 is 90 degrees.