2001 LS1, batch or sequential injection?

[LS1_Dragster]

I have a weird problem.

I put a 98 7.4 with a ZZ502 cam, ported heads, 01270003 OS, edelbrock intake and Holley throttle body in my 71 firebird. It was a bugger to get it running a few years ago, nothing I did would get it running good and it backfired out the exhaust when you revved it up.

I finally stumbled on the B3702 and B3703 Injection timing and by increasing these numbers quite a bit it actually started to run good.

It's now been a couple of years and there's been one thing that really irritates me and thats the exhaust! It's too loud for no reason. I had a 70 chevelle with a ZZ502, large cam, 3" exhaust and I loved the sound of it, nice and quiet at idle and driving but really woke up at WOT. So i put the same mufflers but with 2.5" exhaust and this thing is so damn loud it ridiculous! Again, it runs good, I feel it has way more power then it should all though it hasn't been on a dyno or at the track.

So I've been thinking about what would cause it to be so loud and the only thing that comes to mind is cam events in relation to fueling. In other words, do I have burning fuel exiting the head when the exhaust valve opens? Then I start thinking about B3702 and why I have to increase the value to get it to run and stop backfiring out the exhaust.

Does anyone have any ideas? This leads me to the title, are these batch fire or sequential? Do I have the injectors wired incorrectly, banks switched, do I have just two crossed etc. I really don't want to pull the computer out of the dash unless it's a possibility they are crossed. And once and for all, does increasing B3702 fire the injectors sooner?

Lee

[LS1_Dragster]

I'm glad I'm not the only one stumped!

[joecar]

The LS1 injectors are fired sequentially.

B3702: I don't remember if this is before or after... there's been another thread on this some time back...

[5.7ute]

I was thinking more around a mechanical issue, valve events, too long a pushrod etc. But more than likely you would have gone through these earlier.
These are sequential injection, so the possibility does exist that your wiring is out between banks.
Cyl Pin
1 36
2 04
3 03
4 44
5 76
6 37
7 43
8 77

[joecar]

Read thru to this thread: showthread.php?11222-Interesting-info-on-B3702-Injection-timing (http://forum.efilive.com/showthread.php?11222-Interesting-info-on-B3702-Injection-timing)

post #37:

OK, it looks like the info here went sideways pretty hard...

Before adjusting injection timing, it's important to understand why it's there. Most OEM applications are timed to inject fuel against a closed intake valve. This does two things; it cools the valve and aids in evaporation. When the engine is cold, fuel takes longer to evaporate, so it must be injected sooner to get enough of the liquid evaporated to enable clean combustion.

Clean combustion is the key here. If you're burning everything you injected and you had decen charge mixing, it shouldn't matter as much when you injected it. On the other hand, if you're either not burning liquid fuel in the chamber or not mixing completely, it can skew what you think got injected into the cylinder. This is why the OE calibration injects earlier on a cold engine to allow time for fuel to evaporate and mix prior to combustion. (Look at the table and you'll see the trend!)

In the aftermarket, we have the nasty habit of plugging huge cams into engines that open the door for a couple problems. One is that the lower port velocity reduces charge mixing at low engine speeds. The other is that having both valve open simultaneously (during overlap) opens the door for "short circuiting" where vaporized fuel may escape out the exhaust valve without ever being burned if there isn't sufficient port velocity to push it down into the cylinder. This can usually be addressed by delaying the injection event slightly so that the vapor isn't there when the exhaust valve is open. The potential downside is that large quantities of liquid fuel being injected into a cylinder at low port velocity may lead to bore wash at extended idle.

If you see a change in AFR resulting from injection timing, it just means that you didn't get a complete burn in one case. The object is to completely evaporate and burn whatever fuel you inject, regardless of what's going on with the aircharge or port velocity. This was one of the exercises we did in my last advanced GM tuning class with a 23x+ camshaft in a GTO. Once you find clean combustion, it's a lot easier to dial in the VE (or VVE) tables, THEN you can address idle airflow targets.

post #42:

It's hard to give you a single formula that will work most of the time since you guys all like to pick snowflakes for cam and head combinations. (No two are alike) To make things worse, different ECUs describe the timing with different units. Some use degrees of crankshaft rotation relative to TDC, others degrees relative to BDC, and many GM ECUs use "cam reference pulses." The cam reference pulse is still a unit of angle (which is time at a fixed RPM), so you're really tuning how much time "lead" you're giving the fuel delivery much like ignition timing. Just like ignition, there's a sweet spot that gives better results and it's possible to go too far. This is one of those grey areas that more experienced calibrators end up building a "feel" for as they do more of them.

[LS1_Dragster]

So, since the factory B3702 has smaller numbers at colder temps and based on eficalibrator's description smaller numbers means it injects sooner.

So in my case where I have to increase the numbers to get it to run right means I'm now injecting later in the cycle, opposite of what I thought.

Since I backfire out the exhaust with stock settings then I can assume that for some reason I'm injecting way too soon. Is there any way to get the injector timing out of sync with the cam shaft? How does the injector timing get synced and to what, crank or cam? Does the crank relearn have anything to do with this timing sequence?

5.7ute - I do have good valve train geometry. I don't think it's mechanical unless for some outrageous reason I'm off a tooth with the timing chain but I just don't thinks that's possible at all!

[joecar]

That's what I got from his description.

We're not sure which event: TDC, BDC, valve events... or, cam x1 transition was mentioned, this coincides with TDC 0° on #1.

No, crank relearn doesn't have to do with timing/sequence... crank relearn is the calibration of the rate of crank deceleration on a misfire.

[swingtan]

Don't forget that injection timing also impacts dynamics. Firing the injectors earlier is a little like increasing the dynamic fuel amounts, as the fuel has longer to evaporate. This only occurs a lower RPM's though, as when the RPM rises, the time the inlet valve is closed is shorter. This is where INDC comes in to play as well. FWIW, you only have around 14ms between valve openings at 6500 rpm, so when your IDC is over 80%, the injector is still firing when the valve is opening and in some cases, may be still injecting fuel as the valve closes.

In the E38, timing is taken from cylinder TDC, but it timed on "crank degrees". The LS1 o the other hand times in mS and I'm assuming it is again TDC. The stock figures seem to match up with firing the injector XmS BTDC, higher figure used when the engine is cold.

Simon.

[LS1_Dragster]

In the E38, timing is taken from cylinder TDC, but it timed on "crank degrees". The LS1 o the other hand times in mS and I'm assuming it is again TDC. The stock figures seem to match up with firing the injector XmS BTDC, higher figure used when the engine is cold.

Simon.

This is why it's so confusing! eficalibrator and you are opposite of each other if I'm reading yours correctly. Your showing it fires BTDC. With the factory numbers being smaller when it's cold 2.55ms BTDC and when hot 5.55ms BTDC. Injecting it sooner with smaller numbers based on BTDC would fire the injector while the exhaust is open (really depends on the cam overlap) and increasing the ms would only make it worse so I don't "think" it's based on BTDC.

So I'm starting to think it's ATDC (or TDC). The smaller number would now inject it closer to TDC (0ms would be TDC) while the larger number would let the piston travel further down as in 5.55ms ATDC. With a lot of cam overlap increasing this number to inject ATDC would eliminate injecting while the exhaust valve is open.

Anyone know how to convert the ms to crank degrees?

[joecar]

Let me restate:

cam x1 step (up or down) coincides with TDC 0° on #1, but more specifically:

cam x1 down step coincides with TDC 0° on #1 with both valves closed (i.e. ignition event just occurred, beginning of power stroke);

[joecar]

...

The LS2 injector timing is directly in degrees... makes visualization easier...:cheers:

The LS1 injector timing is in milliseconds, so I have to convert that to degrees based on rpm:

offset[°BTDC] = 720 * Toffset * RPM/120000

where Toffset is in ms
...

120000/RPM is the time [ms] the crank takes to complete 2 revolutions (720°);

so Toffset*RPM/120000 is the fraction of 2 revolutions.

I'm not sure if it's BTDC or ATDC.

[5.7ute]

Just to confuse matters even more, there appears to be an end of injection trim in the tables, which in different modes denotes where the end of injection occurs.
So is the end of injection the target, and the pcm calculates back from this point? Or are these tables inactive in all but certain conditions.(if at all)
Joe, can you hook your scope up to both the cam sensor & injector pulse on cylinder 6 & find a reference that way? This may help in finding a relationship between these tables & the actual injector timing.

[joecar]

...
Joe, can you hook your scope up to both the cam sensor & injector pulse on cylinder 6 & find a reference that way? This may help in finding a relationship between these tables & the actual injector timing.I want to do this, I have to make extension cables for the CKP and CMP signals to gain access, give me a week or two... the difficult access to CKP and CMP has been holding me back, but I'll just get get on it.

I'll be able to capture 4 waveforms at the same time: CKP, CMP, #1 injector, #1 secondary... or #6 if you want.

[5.7ute]

NO#6 should give us TDC before the intake stroke using the CMP as a reference (Since No#1 will be on TDC compression) & may give a better picture.

[LS1_Dragster]

Just to confuse matters even more, there appears to be an end of injection trim in the tables, which in different modes denotes where the end of injection occurs.
So is the end of injection the target, and the pcm calculates back from this point? Or are these tables inactive in all but certain conditions.(if at all)
Joe, can you hook your scope up to both the cam sensor & injector pulse on cylinder 6 & find a reference that way? This may help in finding a relationship between these tables & the actual injector timing.

Any way to get the cax file with these tables so I can play with them?

[5.7ute]

Any way to get the cax file with these tables so I can play with them?

I will see what I can find in your OS. I will also make one up to suit Joe's OS so if he has time he can play with them with the scope connected. (No sleep for you now Joe.lol)

[joecar]

I have plenty of scope waveforms of injectors/secondary...

the problem with getting CKP/CMP is that the CKP is tucked away above starter and CKP is tucked away under cowl, it's really difficult to stick a backprobe into those connectors...

I don't really want to pierce the CKP/CMP wiring (I have learnt not pierce, very bad), so I need to make/find extensions for CKP and CMP, these I can pierce with no regrets.

[5.7ute]

I have plenty of scope waveforms of injectors/secondary...

the problem with getting CKP/CMP is that the CKP is tucked away above starter and CKP is tucked away under cowl, it's really difficult to stick a backprobe into those connectors...

I don't really want to pierce the CKP/CMP wiring (I have learnt not pierce, very bad), so I need to make/find extensions for CKP and CMP, these I can pierce with no regrets.

I don't blame you. Finding open circuits due to moisture ingress etc is a real PITA.

[joecar]

Yeah, no sleep for me...

I looked thru some of my old waveforms (which lacked CKP/CMP) to see if I could determine anything... see my pics attached (with my TOL notes)...

TOL = thinking out loud.

I didn't arrive at anything... :doh2:

[5.7ute]

If you had the injector & induction lead on cylinder 1 you still have the 90ms offset from when that cylinder is getting ready for the intake stroke. That still leaves 10 ms to account for though. What happens if you calculate from the end of injection time?

[5.7ute]

Lee, I can give you a .cax that will give you the raw values. Scaling will have to wait until we can do some experiments with Joes scope using reference pulses from the CKP. If you want it post your .cax file & I will add it in.

[swingtan]

This is why it's so confusing! eficalibrator and you are opposite of each other if I'm reading yours correctly. Your showing it fires BTDC. With the factory numbers being smaller when it's cold 2.55ms BTDC and when hot 5.55ms BTDC.

My bad... I should have opened an LS1 file rather than relay on memory..... :P

Given 5.7's mention of an "end of injection event" PID, this may be of some use.

Actually, I'm not sure what drugs I was on yesterday........

At 6500 RPM.....


RPM RPS Cycle/S mS/Cycle nS/deg
6500 108.33 54.17 18.46 25.64


Perhaps the "timing" in B3702 is a delay from the previous "end of injection event". This would make sense with having lower numbers when the engine is cold.

simon

[5.7ute]

Here is the .cax with end of injection raw values added Lee. It is set up for Joe's 12212156 but can just be renamed for your OS since the addresses are the same.
.cax file upgraded. This now has the trim pulse end of injection & normal pulse end of injection.

[5.7ute]

BTW Joe, when you get the time to scan those waveforms with the scope, will you be able to do it at a couple of rpm values so we can see if it is based on time or angle?

[joecar]

If you had the injector & induction lead on cylinder 1 you still have the 90ms offset from when that cylinder is getting ready for the intake stroke. That still leaves 10 ms to account for though. What happens if you calculate from the end of injection time?Ah, I was calculating from the end of injection time (injector closing, the big green up spike)... but, the injectors are only open for about 3-4ms (the green down pulse immediately before the spike).

[joecar]

BTW Joe, when you get the time to scan those waveforms with the scope, will you be able to do it at a couple of rpm values so we can see if it is based on time or angle?Yes, that is my plan.

[joecar]

...
At 6500 RPM.....


RPM RPS Cycle/S mS/Cycle nS/deg
6500 108.33 54.17 18.46 25.64
...Simon, I know you meant us/deg as in microseconds/degree. :)

[swingtan]

Simon, I know you meant us/deg as in microseconds/degree. :)

Some days, it pays not to get out of bed...... it should be 51.51 uS as well........

[LS1_Dragster]

Here is the .cax with end of injection raw values added Lee. It is set up for Joe's 12212156 but can just be renamed for your OS since the addresses are the same.
.cax file upgraded. This now has the trim pulse end of injection & normal pulse end of injection.

In the firebird I have 0127003, any way to get the cax file to work with this OS?

[joecar]

Some days, it pays not to get out of bed...... it should be 51.51 uS as well........25.64 us/deg is correct...

I did: 2[rev/cycle]*60[s/min]*1000[ms/s]/6500[rev/min]/720[°/cycle]*1000[us/ms] = 25.64[us/°]

i.e. 2*60*1000/6500/720*1000 = 25.64

[5.7ute]

In the firebird I have 0127003, any way to get the cax file to work with this OS?

Just unzip the .cax file. Rename it 01270003 to match your OS & put it in your calibrations folder.
The physical addresses for the tables are the same as the 12212156 OS that Joe uses which allows you to do this. It is only when the addresses are different that a seperate .cax file needs to be made.
I should add the warning that this .cax file has not been tested.
Cheers Mick

[joecar]

If the addresses in a .cax file are the same across OS's, then you can just rename the .cax file to match your OS like Mick said.

[LS1_Dragster]

My fault, I didnt put enough zero's in the name so it didnt see it, sorry to bother you!

Lee

[LS1_Dragster]

OK, all 3 of my cars have different values! I'm not as smart as you guys so in idiot terms, what would you do, increase these numbers or decrease when you have a larger cam?

[5.7ute]

I would not be in any position to give you any advice on this until we can test them. Especially since we are not certain of which pulse these tables are referencing & which direction a larger value would take.
Best bet IMO is to change the values & watch what happens to your wideband AFR for the same IBPW. The richer the AFR the more fuel available for combustion in the cylinder.

[LS1_Dragster]

I'll mess with it in the morning, curiosity is getting the best of me. At least I'll try one of the tables on the firebird from one of the other cars. I figure I cant go wrong with that.

Lee

[Highlander]

upd???

[Highlander]

I've noticed that on the C6s there are 2 tables that are referenced by degrees instead of ms.

That means that if you do the opposite of the equation posted you can get the ms out that. Now, C6 have 2 tables. One referenced by rpm and another referenced by coolant temp. Do these add to each other to calculate the final timing? It makes sense that they are added.

On the C5s we have two referenced tables by coolant do these add to each other? Doesn't make sense to have 2 tables referenced by the same axis to be added.

Anyways... with the simple math on excel you could loose from 40-50% of your injector duty cycle if you wish to inject at the correct moment (depends on when is the correct moment of course). That is why the ls7 comes with 42lbs when they are clearly not needed for a 440rwhp n/a car.

[swingtan]

I see that at some point, someone will twig about IDC.....

For some time, people have been quoting that 80% IDC is a limit, but others have said that you can still get accurate fueling as long as you are under 99% IDC. If you read the last few posts, you'll stat to realise that that at some point, the injector will completely miss the end of the intake valve opening. That is to say, that a single injection event will still be occurring as the intake valve closes. The fuel that misses the valve close, will sit in the runner and can (some probably will), be carried back up the runner to the plenum, where it can be "stolen" by an adjacent cylinder intake pulse.

I've played a lot with injection timing and thought about what might work and how it might affect driveability. In the end I set up a spreadsheet to show the valve events for open and close, and then show the minimum injection advance to ensure the injector pulse ends just prior to the intake valve. This ensures that any specific injection event will complete before the intake valve closes. So all the intended fuel for a specific induction event will actually make it into the cylinder (minus wall wetting).

Simon.

[joecar]

Hi Simon, can you point us to that spreadsheet...

:)

thx