Interesting info on B3702 Injection timing

[joecar]

I'm slowly digesting this (I'm drawing myself sketches to relate to valve events).

[PRAY]

Any more on this? I think I have the ECT table figured B1205 (I have to add to it for my larger cam) but my RPM table B1206 is populated with zero's and only goes to 4,096 rpm. Would I subtract from zero to shorten the IPW or just do that with IPW to ensure the injection is complete before the overlap period happens? Do they both need to be adjusted to ensure the SOI and EOI only happen on a closed intake valve after the compression stroke? I am dealing with 10* overlap in a LS2. I want to stop the fuel from going out the exhaust valve at idle and low rpm cruise.

[Gelf VXR]

Is it a stock E40 tune or tuners file? If it was me, I would start by copy and paste the stock values for B1205 and B1206. Leave B1206 as is, calculate the difference between IVO from the stock to your new cam profile, assuming the new cam opens earlier, subtract the difference value from B1205. EOI earlier as the IVO is earlier.

I think the B1206 only goes up to 4096rpm as above that SOI maybe around the start of injection boundary, when that point is reached, the EOI has to happen later when the inlet is still open.

[Gelf VXR]

Sorry, add the difference to B1205 like you said

[PRAY]

Thanks for the reply. I have an E67 ECM. Does that make a difference with the technique. I have been tuning the truck my self so all the IPW, Injector timing and Dynamics are still stock. I have actually tuned about 60 cars from stock to 575rw N/A up to 850rw S/C Vettes but have never delved into the injector timing, injector tables or the Dynamics tables. I have been doing a lot of reading on these topics as of late. Since all of the cars in the past have all run really well I thought through all of the fuel and timing calibrating the rest was taking care of it's self. Boy was I wrong. I have a lot to learn and am doing my best to do so. Unfortunately tuning is solely a part time thing. I have often wondered about pump shot and injection timing but rarely get the time to mess with it. I didn't want to hurt what was working. But now learning all of this has lead me to the belief that if the injector timing is off then all of your fueling calibrations will be off also since you are essentially putting a band aid on the actual problem.

Back on topic. From my summation. I take all the original valve events from the stock cam, compare them to the values of the new cam in crank degrees and come up with the difference of where the new intake valve opens vs where the old intake valve opened. I am assuming that will be in degrees of crank rotation of do I do that off of a percentage. The measurement of cam events also has me a little confused. Am I using at .002", .006" or .050" to derive my math? That will lead me to adjusting B1205 and B1206 in actual degrees or a percentage added to the base numbers. I also have to do that for where the new exhaust valve closes vs. the stock exhaust valve to account for the overlap period. Once I have figured those out, I add the difference to B1205 to open the injector earlier in the crank cycle for the intake valve and subtract from B1206 for the new exhaust closing point to avoid the overlap period. That will account for the injector firing on the intake valve after it is closed on the compression stroke/power stroke to avoid fuel being sucked out of the exhaust valve during overlap. Is that right? I see where B1205 is calculated in degrees and I think B1206 is the same but I will have to go back and look at it. I hope that made sense. I am a soldier by trade, not an engineer. Thanks.

BTW, here are my cam specs at .050". LSL 227/235 .617/.621 110+4.

Also, what table represents injection boundary?

[joecar]

So IVC is the event that injector timing precedes...?

( yes, I'm learning a lot )

It appears that EFILive does not expose a table for injection boundary.

[Gelf VXR]

Hi PRAY,

For example I think I am correct in saying, stock IVO 18ATDC, new IVO 18BTDC, difference is 36 crank degrees, add 36 to all values in B1205. The values are crank degrees advance, before the boundary.

I've not looked that closely at an E67, my laptops under repair so i can't look now, it's strange B1206 is all zeros, I'm sure for all the different PCMs I looked after the Ls1, these two tables were all identical and populated?

Hi joe

IVC event is the boundary, 585 ATDC, confirmed for gen 3, 99% sure it's the same for the E40 gen 4, based on my previous tables posted above.

Gen 4 infector timing calculated before the boundary and gen 3 calculated after the boundary.


Edited to correct valve events IVO, not EVC, too much to drink last night

[Gelf VXR]

0.050" lift events

[PRAY]

Thanks. As I look at the way a four cycle engine works it seems to me to avoid the fuel going out of the exhaust valve during overlap you have to wait to start injecting fuel till after the exhaust valve closes. Using this thought pattern you will have to figure out the new crank degrees for that event and adjust your IPW to match the new time that the exhaust valve is closed before the intake valve opens. That would also lead you to your new injector timing. But, with a cam with overlap, there is no time that the exhaust and intake valve are not open together during the exhaust stroke before the intake stroke starts. So now I am just confused. Mathematically, there is no way to not loose fuel out of the exhaust during the overlap period unless you start the injection timing once the intake valve starts to open. So, do we just adjust for the new intake valve opening period and live with the loss out the exhaust valve or wait a couple degrees and just start spraying fuel down an open intake valve? I though the whole point of this exercise was to clean up idle and part throttle by hitting the back of the intake valve after the exhaust valve closes for best atomization before the intake stroke happens. Kind of looks impossible now.

Here are the events that I came up with last night using the Wallace racing calculators. According to the stock LS2 cam card I am off a couple degrees for the stock cam but if you do the math that is the only way it works out. So I used the calculator for the stock cam and my new cam. I am not sure what is going on here.

Ls2 cam @ .050” 204/211 .525/.525 116-2 -24.5* Overlap
IVO 16* ATDC + 360* = 376*
IVC 40* ABDC + 540* = 580*
EVO 39.5*BBDC - 180* = 140.5*
EVC -8.5* BTDC - 360* = 351.5*

IVC-IVO = 580-376 = 204
EVC-EVO = 351.5-140.5 = 211
(IVO+IVC)/2 = 478 = (478-360 = 106) 118 ICL
(EVO+EVC)/2 = 246 = (360-246= 114) = 114 ECL
118+114 /2 = 116 LSA and the 118ICL makes it -2 retarded


My cam @ .050” 227/235 .617/.621 110+4 11* Overlap
IVO 7.5* BTDC - 360* = 352.5*
IVC 39.5* ABDC + 540* = 579.5*
EVO 51.5* BBDC - 180* = 128.5*
EVC 3.5* ATDC + 360* = 363.5*

IVC-IVO = 579.5-352.5 = 227
EVC-EVO = 363.5-128.5 = 235
(IVO+IVC)/2 = 466 = (466-360 = 106) 106 ICL
(EVO+EVC)/2 = 246 = (360-246= 114) = 114 ECL
106+114 /2 = 110 LSA and the 106ICL makes it +4 advanced

So 16*+7.5*=23.5* rounded up to 24* or 376*-352.5*= 24.5* rounded down to 24* that I have to add to B1205 to get my new IVO table. B1206 is populated with 0 in my stock tune. I will see if I can find out on the TBSS forum what others have populated in their stock tunes. On the other vehicle tunes I have B1206 is populated but with different data. LS1 being inverse scaled of LS2.

[PRAY]

Something just hit me, if the injector timing stays stock then with a new cam with an earlier opening time and closing time (which mine does not have an earlier closing time, WTF) you are essentially spraying fuel on a closed intake valve. That fuel would get trapped in the runner and would be sent out of the exhaust valve when it opened again during the overlap period. That would result in unburnt fuel exiting the exhaust and causing false WB02 readings. Rich or lean I am not sure of. But that could lead to a lean condition in your cylinder on the intake stroke from late injection fueling that would be masked at the WB02 on the exhaust stroke due to the extra unburnt fuel. So you would essentially be running lean and not knowing it. That would lead to shorter IPW sequences making up for the perceived rich condition therefor expounding on your leanness. If the inverse is true that unburnt fuel makes the WB02 read lean then the IPW will increase creating more fuel being injected after the intake valve closes causing a even leaner reading. So, late injector timing is actually very dangerous? To me, best case scenario now is to find the happy medium where you are injecting fuel as early as possible as the intake valve is opening during overlap. Using a little of the exhaust stream to help fill the cylinder with as much fuel as possible with out leaving any left over to sit in the runner before the exhaust valve opens and dumps raw fuel during the overlap period. Am I making any sense?