Injector Timing? Reference Periods? refereencing what?

[Wnts2Go10O]

Maybe I am burning my brain from over thinking, but "300.5º ATDC compression stroke" is the stock value.

I am confusing myself on the "ATDC compression stroke". Can anyone elaborate?

think of where an engine starts its cycle. that point is 0*. every 90* is a reference point for the injector timing (hence 8 reference points). a 5 in the box would be 450* degrees through the cycle

try this... drop all of the formula except normal(90) and it will give you the exact point in the cycle where the injector stops firing.

5.55(90) = 499.5* through the cycle.

the formula is to base it off cam rotation not crank rotation.

[WS6FirebirdTA00]

I want to say all injection is finished at 59.5* BTDC while on the exhaust stroke, which is before the intake valve even starts to open. That would mean that changing the values by .2 or .3 would only delay injection slightly and at low engine speeds should not show a difference, yet people say it is.

So I think it is going to have to be delayed to 380-390* to see some noticeable changes. That would mean that the normal values will need to be 6.5 or so. Right?

[Wnts2Go10O]

I think you lost me even more lol

Where did the 300.5 come from? Is this 300.5 crank degrees after starting the power stroke?

((boundary value +normal value)90)-784 = where in the cam timing the injector is finished firing. if you took the normal value and multiplied it by 90, it would give you exactly where (based on crank rotation) in the total engine cycle it finished. where does a normal 4 cycle engine start? thats the reference point

What is getting me here is that if the injection end is after the inlet valve is already open, changing the values small amounts won't matter as that is the end of the injection. At short pulses for idle it would still keep it injecting when the valve intake valve is open and exhaust is closed.

if you use engineers xls sheet, you will see that you can easily work it to end wherever. chris, i think it was, stated that the end point is simply the point from which the hardware calculates the injector firing point. you say you want it to end there, then the computer determines where it starts. why gm did it this way i dont know. the consesus on the stock settings however is fuel mixture, emissions, and other variables that are based on the cam design.

If the injection ends before the intake valve opens, the small changes that are being made still inject all the fuel before the valve is open. So it would take a big change to get rid of raw fuel going out the exhaust at low engine speeds.
a small change, by a tenth lets say, is still around a few degrees worth of crank rotation

Forgive my ignorance, I thought I had this but read some conflicting posts and it threw me all off.

I want to say all injection is finished at 59.5* BTDC while on the exhaust stroke, which is before the intake valve even starts to open. That would mean that changing the values by .2 or .3 would only delay injection slightly and at low engine speeds should not show a difference, yet people say it is. That makes me think I am totally wrong.

it works because those 2 tenths are delaying fuel injection by ~16* of crank rotation.

the tables allow values from 0-8. each point is 90* up to the 720* cycle. each tenth is 8*.

if you break it down to 720* cycle of the 4 stroke engine, its much clearer

[WS6FirebirdTA00]

I tried to clean it up. I read your other post.

So the end of injection will always be 300.5*, which is 59.5* before the intake stroke (BTDC for my example). When looking at cam values this would be directly related to the IVO. The stock LS6 cam has an IVO of 15* BTDC. So all injection is completed well before the intake valve even opens. Changing it by 16* would make it end by 43.5*, still well before the intake valve even opens. You would need to change it by 15-25% or 1-1.5 in the table to make it late enough where at idle you are spraying some point after the intake valve opens, and late enough to really help at all.

To add, if you are trying to find the ideal injection point it should be the richest value seen for a given fixed fueling table, no? This would mean you have the best burn because you have the best mixing, with minimal loss through scavenging and minimal washing down of the cylinder walls. At least my thoughts. The bad thing here is we can not make changes based on RPM.

In the newer LS stuff it is entered directly in angles right? The end base target is given at 520*, the rest of the values subtract from this? Do you add the ECT and RPM tables? If so, we are looking for ~115-205 off of that (315-405). So the higher the RPM the earlier it finished? Just wanting to compare values.

[Wnts2Go10O]

I want to say all injection is finished at 59.5* BTDC while on the exhaust stroke, which is before the intake valve even starts to open. That would mean that changing the values by .2 or .3 would only delay injection slightly and at low engine speeds should not show a difference, yet people say it is.

So I think it is going to have to be delayed to 380-390* to see some noticeable changes. That would mean that the normal values will need to be 6.5 or so. Right?

somewhere around 6.55 would do it.

[WS6FirebirdTA00]

Just edited the post while you replied lol

So the two tables, makeup and normal, need to be increased by about 1.0.

I am curious to see how this does on a cold motor. With cold intake valves I am sure there is a LOT of pooling and maybe false lean mixtures?

[Wnts2Go10O]

Just edited the post while you replied lol

So the two tables, makeup and normal, need to be increased by about 1.0.

I am curious to see how this does on a cold motor. With cold intake valves I am sure there is a LOT of pooling and maybe false lean mixtures?

if you have a good amount of overlap, youll probably have the gas smell go away as more fuel will be in the chamber. so yea. id think the false lean would go away. the key is to try and take advantage of the scavenging effect of the overlap without losing the fuel through the exhaust

[WS6FirebirdTA00]

I am starting to wonder if the cold values need to be the same as the others. Wish we had an RPM table lol

Then my worry at high RPMs is intake valve temps. How much cooling does the fuel provide and will it add the chance of knock.

[Wnts2Go10O]

I am starting to wonder if the cold values need to be the same as the others. Wish we had an RPM table lol

Then my worry at high RPMs is intake valve temps. How much cooling does the fuel provide and will it add the chance of knock.

the only reason the smarter ones here can figure is that the spraying of the intake valve was for fuel evaporation

i think changing the low temp values ot the same as the high temp ones would make cold starts and such harder. if anything, they should be changed by the same amount as everything else but not made the same.

[MikeGyver]

I'm now wondering if there is no rpm table because maybe at higher than cruise rpm, there is not enough time to squirt past the open valve? Or maybe the only way that timing could be perfect at all rpm would be to have a strobe light and camera looking into the port. (?) How long is the intake valve open at 5000 rpm, and how long does the injector spray at WOT and 5000 rpm? How long does it take for the column of air to travel from the point of injection to going past the valve seat at the same 5000 rpm? Why am I being such a naysayer when I so badly want it to work?

[Wnts2Go10O]

very, very little time. 5k rpm = 83.3 revolutions per second..

[WS6FirebirdTA00]

Well, in my car when cold I can get some missing and am wondering if too much fuel is being pumped out. It will still cause the issues during the overlap period and may be even worse because it sits in there so long. The problem at hot idle is still there even when cold. The question is does that late of an injection when cold pose some other issues. I still think if you inject late enough you can get enough velocity and mixing.

Setting the end of injection at 400* will (for my setup) mean at pulse widths of 4 ms and higher, and 3000 RPM and higher will inject on a closed intake valve, at least anything over those values. So my hope is that at the higher RPMs and higher DCs there will be enough pooling for cooling/vaporization while still injecting up to 40* ATDC (when you have higher air velocities). Hopefully this will still get some good charge. I assume that at higher engine speeds the scavenging will "waste" less of the fuel mixture therefore you don't have to inject as late. But also as stated are things happening fast enough that you actually aren't getting the full charge in the cylinder before the valve closes.

Now if I can make those changes, and at 6000 RPM the AFR does not change much, then I think it may prove it is OK. If it leans out, some fuel is not making it. If it richens up, it is mixing better.

Lots of assumptions, may be poor.

The fix is direct injection I think lol

[WS6FirebirdTA00]

Good discussion though, lots of questions we need to find answers to lol

[MikeGyver]

...
this was just my morning observation... I'll drive the long way home tonight and see how it feels to test more.

Holy crap we're waiting on you, your long way really is the long way.

[Wnts2Go10O]

Good discussion though, lots of questions we need to find answers to lol

i think youre just over thinking the idea of thinking about valve events and the event of injecting fuel thats injected by injectors

[S2H]

never mind it's in your spreadsheet. Duh... Thx Sound...


.006 for LS6?

Intake Valve opens - IVO 15 BTDC
Intake Valve closes - IVC 75 ABDC
Exhaust Valve Opens - EVO 73.5 BBDC
Exhaust Valve Closes - EVC 23.5 ATDC

My spread sheet is 0.050 values

[S2H]

Holy crap we're waiting on you, your long way really is the long way.

My long way home involved a half hour out of the way to a friends house to help him with Wiring on his project Car...3rd gen camaro with an High Boost LT1 engine, running an LS1 PCM.
I made some gauges and stuff work tonight...
then I drove a half hour home

what I noticed is that the Fueling went richer now that I'm not blowing so much out the exhaust...
part throttle definitely feels better.
I actually tried to roll race a buddy of mine in his LS3 GTO, but I blew the tires off my car in 2nd and 3rd gear on the highway at 65mph in 2nd and 75mph in 3rd...
but I dont know if that was my crappy tires or an increase from injector timing... I would guess at shitty tires.. I have problems with this rubber on these rims.

[MikeGyver]

That's all I need to hear, I'm going out and getting some shitty tires!

[S2H]

That's all I need to hear, I'm going out and getting some shitty tires!

Just get some corvette rims
Stock 2008 Corvette Base Model is where mine came from

285/35/19
Goodyear Eagle F1 GS-2 EMT Run Flat
from all the tire reviews..apparently really good for pulling sideways G's.. not so much for straight line power..
but it was free rubber mounted on expensive rims that I bought at a steal of a deal.

[LSxpwrdZ]

Another thing that will play a role in this stuff guy's is the cylinder bore, valve size, chamber design, port flow intake and exhaust at different lifts. All that stuff will play a role in adjusting this table to make the setup perform right.

My values are 6.5 base and 6.383 normal. This calculates into giving me an end of injection point of 375.2* or 15.2* ATDC. This coincidentaly was my exhaust valve closing point at .050".

I am also a little puzzled by going richer means less fuel is going out the exhaust... my mind is telling me that the richer the wideband is reading the more unburnt fuel is in the header... maybe I'm missing something??? However I also see the argument that the engine is more efficient and requires a shorter pulse to make use of the cycle...

As far as determining peak velocity points within the port really changes with RPM I would say. It's really weird that my setup likes the injector timing it does because my injectors are firing with an open intake and exhaust valve, but then again just because it injects it at that point means that it's going to instantly be in the chamber that instant. It does take a small amount of time for the pulse of fuel to make it's way down the intake port of the head and into the chamber. Maybe that is why with my end of pulse being closer to the exhaust closing point it's keeping the fuel from being spent right out the exhaust.

I haven't had the chance to play with the colder regions to see if it potentially cures my issue but I'll update when I do try a few things.

There are so many variables and theory's to truly make a blanket statement on what should be done to this table.