Craig or anyone? Injector firing order with sequential FAST

[Dave King]

My FAST installer didn't put any of the injector plugs on any of specific cylinder. He just plugged them in randomly. When I said shouldnt it matter which one goes where, he said with the FAST sequential it doesnt matter and will drive and perform the same.

Upon thinking about it more, shouldnt the injector firing order make a difference? I would think the timing of the firing of an injector would matter. I'm using a Small block Ford with 96 pound injectors and soon going to 160 pound injectors.

The cars runs good at the track 8.6@160 and the streetibility is good. Does this really mean it doesnt matter? Can power and better drivibility be picked up with better timing fire of the injector?

What about EGT temp for each cylinder? Can injector timing affect EGT to a cylinder? Currently I have one cylinder that runs 120 degrees hotter than the rest.

If it does matter. According to the FAST instructions it says that my firing order is 13726548. The injector harness (FAST side) goes A is black, B brown, c Yellow, D green, E orange, F blue, G gray, H is purple. However the injector side of the harness is A is brown, b is yellow, C is Green, D is purple, E is Black, F is Gray, G is orange, and H is blue. To make this even more confusing is that Green is plugged into 1 at the injector, 2 is Gray, 3 is Blue, 4 is black, 5 is purple, 6 is orange, 7 is brown, and 8 is yellow.

Should I just match the wires at the harness and match the injectors according to the chart, or should I just plug the injectors to match the mismatch of the connector. Another thing that was bothering me was that I didnt like how the pins were in the connectors. I would rather solder both sides of the connector together for a more secure connection.

Can anyone help?

 

[bobc455]

I'm kinda surprised by the dealer's comments. Although I suspect it will run well with the injectors plugged in "randomly", it kinda defeats the purpose of upgrading to a sequential unit.

You would also lose the ability for individual cylinder enrichment, etc., since the ECM would enrich the wrong cylinder!

A bank-to-bank system essentially fires "randomly" with respect to intake valve opening, and this is how you're running now. The whole idea behind a sequential unit is that each injection is timed relative to the intake valve opening for each cylinder.

I would take the time to un-randomize the wiring.

I won't guarantee that this will solve your EGT issues, but it might help. At least once you straighten the wiring out, you can give that cylinder some individual enrichment...

(As a band-aid for the high EGT, you might also be able to figure out which injector the ECM thinks is firing on that cylinder, and fake it out.)

-Bob Cunningham

 

[Dave King]

Hi Bob

Yeah I was kind of thinking the same way. To be honest I was surprised too. I can fix all the wiring problems but because I run the FAST EDIS/Ford Coil packs I do not have the option for individual cylinder control.

As you said maybe if change the timing of the fuel to that cylinder by trying different firing order to that injector it might help. I was also interested to see if it picks up any power as well.

Thanks

Originally posted by bobc455
I'm kinda surprised by the dealer's comments. Although I suspect it will run well with the injectors plugged in "randomly", it kinda defeats the purpose of upgrading to a sequential unit.

You would also lose the ability for individual cylinder enrichment, etc., since the ECM would enrich the wrong cylinder!

A bank-to-bank system essentially fires "randomly" with respect to intake valve opening, and this is how you're running now. The whole idea behind a sequential unit is that each injection is timed relative to the intake valve opening for each cylinder.

I would take the time to un-randomize the wiring.

I won't guarantee that this will solve your EGT issues, but it might help. At least once you straighten the wiring out, you can give that cylinder some individual enrichment...

(As a band-aid for the high EGT, you might also be able to figure out which injector the ECM thinks is firing on that cylinder, and fake it out.)

-Bob Cunningham

 

[Chuck Leeper]

??????????????

A sequential box relies on the firing order to fire the injectors when they are called for... Doing it "randomly" is, like Bob said.. is not sequential as it should be., It's now a "controlled leak".. w/ fuel puddling on the valves, awaitng their opening, etc... Should be wired correctly, as once you get to the 160's, you could see an overfueled mess......

As for the installer.. Is he going to do the tuneup too???

 

[bobc455]

Originally posted by Dave King
because I run the FAST EDIS/Ford Coil packs I do not have the option for individual cylinder control.

I'm a bit out of my league here, but regardless of ignition I would think you could still use the individual cylinder enrichment (even if you can't change the timing of that cylinder).

Let us know if you get any performance or drivability increase. I bet you do!

-Bob C.

 

[bobc455]

One more thing. Is it possible that the one thermocouple is inaccurate? It is probably fine (therefore indicating some sort of distribution issue), but it's just one thing to think about as you are tuning.

-Bob C.

 

[Chuck Leeper]

?????????????

Originally posted by bobc455
One more thing. Is it possible that the one thermocouple is inaccurate? It is probably fine (therefore indicating some sort of distribution issue), but it's just one thing to think about as you are tuning.

-Bob C.

try swapping the probe to another cyl and see if that cyl now reads low...

 

[JDB]

Very interesting topic. I've been given several different answers as to when the fast system actually fires the injectors. I'm lead to believe that it fires them in order (per firing order) but the actual timing (relative to valve opening) might change each time the engine is started.

I was also told by Lance W. that the injector timing really does not matter in terms of performance.

One thing is certain, the FAST system works really well, but injector timing is one thing we have no control over.

Motec and AEM certainly argue the need for control of the timing.

I wonder if it's a patent issue?

JDB

 

[Dave King]

Yeap my installer said the same thing, but logically I can't image how injector timing isn't important especially with 160 pound injectors.

Any FAST reps around that would like to comment?

 

[Chuck Leeper]

Some info....

Injector
This plug will be connected to the supplied fuel injector harness. If specified at the time of order, the harness can be configured for your specific firing order. Otherwise, injector harnesses are shipped for a standard GM V8 firing order (18436572).

If you need to reconfigure your injector harness, refer to the following chart. The 10-pin connector on the end of the injector harness can easily be reconfigured to work with many different engine types. Terminals A through H on the connector are designated for each of the eight injector connectors on the harness and can be reconfigured as per the following chart. Terminals J and K should not be changed under any circumstances.

The configurations in this chart are set up with the injector harness plug on the opposite side of the motor as the distributor to minimize interference from ignition noise. The harness is also configured to operate the injectors in a fashion that minimizes fuel pressure loss in the rails.

Injector Harness A B C D E F G H
Most GM V8 (18436572)
S.B. Chrysler (18436572) Black
6 Brown
5 Yellow
7 Green
2 Orange
1 Blue
8 Gray
4 Purple
3
GM LT-1 V8 (18436572)
B.B. Chrysler (18436572) Purple
6 Gray
5 Green
7 Yellow
2 Black
1 Orange
8 Brown
4 Blue
3
GM LS-1 V8 (18726543) Gray
6 Purple
5 Blue
4 Brown
3 Yellow
1 Green
8 Orange
7 Black
2
B.B. Ford (15426378) Black
6 Orange
3 Gray
7 Green
8 Brown
1 Blue
5 Purple
4 Yellow
2
S.B. Ford (13726548) Black
6 Blue
5 Purple
4 Gray
8 Yellow
1 Orange
3 Green
7 Brown
2
Buick V6 (165432) Gray
4 Purple
3 Green
2 Orange
1 Black
6 Brown
5 Blue
n/c Yellow
n/c

A conversation w/ Craig confirmed the need to wire the injectors as per the info in order to have the system sequential. He also said as the injectors got bigger, the driveability and low speed performance would not be good....

 

[HighPSI]

I am only guessing here, but I ASSume you don't have a cam signal input into the FAST. This would make sense why the injectors are firing in the correct order (out of sinc) and why you can't have individual cylinder correction (at least on fuel). I would think that the larger the injector (less duty cycle) the more of a fueling problem you could have. With a smaller injector, reaching closer to 100% d/c it may not be as critical at WOT.

 

[Dave King]

Originally posted by HighPSI
I am only guessing here, but I ASSume you don't have a cam signal input into the FAST. This would make sense why the injectors are firing in the correct order (out of sinc) and why you can't have individual cylinder correction (at least on fuel). I would think that the larger the injector (less duty cycle) the more of a fueling problem you could have. With a smaller injector, reaching closer to 100% d/c it may not be as critical at WOT.

Yes I am using the cam sensor. The cam sensor is needed when you run the FAST EDIS.

 

[Craig Smith]

Here's the deal.

The FAST will fire the injectors in order, ABCDEFGH, over and over again. (ABCDEF for 6 cylinders, etc.) The FAST will have no idea where the engine is when it shuts down and is subsequently restarted. Therefore, you may be coming up on cylinder #4 when the engine first cranks, but is output A wired to this cylinder? You have a 1 in 8 chance of achieving proper injector timing, and trust me, with a set of 160s it CAN make a difference in how the car runs. The higher the duty cycle, the less of a problem it will be, but cars on 160s generally run at very low duty cycles for anything other than WOT.

Here is where a cam sync AND proper injector wiring become important. The order in which the injectors fire is not determined by the firing order that you program into the FAST. It is determined solely by the order in which you wire them, and there is a way that we consider optimal.

The injector event is triggered by the incoming crank sensor pulses to the FAST. However, these pulses occur a little before TDC of the compression stroke - a lousy time in many people's opinions to start spraying fuel. Fortunately, somewhere else in the engine, another cylinder is approaching TDC of the intake stroke, where the intake valve is dangling open - a great time to stuff some fuel in! Since TDC events for the compression and intake strokes are separated by 360 degrees of crank rotation, you can "offset" the wiring of the injectors to accomodate this. We'll use the SB Ford that the question was raised about - 13726548. If you wire the injectors so that the crank pulse for the #1 cylinder triggers the injector for the #6 cylinder (which is nearing TDC of the intake stroke while #1 is nearing TDC of the compression stroke) then the #1 crank pulse will simultaneously initiate the ignition process for #1 AND the injector event for #6.

So the pulses serve these puposes:

#1 ignition pulse, #6 injector event (injector output A)
#3 ignition pulse, #5 injector event (injector output B)
#7 ignition pulse, #4 injector event (injector output C)
#2 ignition pulse, #8 injector event (injector output D)
#6 ignition pulse, #1 injector event (injector output E)
#5 ignition pulse, #3 injector event (injector output F)
#4 ignition pulse, #7 injector event (injector output G)
#8 ignition pulse, #2 injector event (injector output H)

In a nutshell, begin the injector wiring on output A halfway through the firing order, and then follow the firing order from that point to optimize injector timing.

The last problem is, how the heck does the ECU know which crank pulse is for what cylinder? That's what the cam sync does. It simply tells the ECU that the next crank pulse should trigger injector output A. So, to follow these instructions properly, the cam sync should occur somewhere prior to the crank pulse for the #1 cylinder. There is a very big window in which the cam sync can be set to trigger - about all you don't want to do is get it too close to either the crank pulse itself, or anywhere in the range where the actual spark signal is sent out. If these events happen too close to each other, the ECU won't like it and the proper timing of these events will be compromised.

If you run a sequential system without a cam sync, it will simply fire injector A on the first crank pulse it sees and continue on ABCDEFGH, ABCDEFGH, etc. regardless of which cylinder actually has an open intake valve at that time. It will continue to fire the injectors sequentially even without a cam sync, just not necessarily at the best time, and there are 8 different ways it could happen. A FAST sequential system NEVER reverts to a bank to bank mode or batch fire mode for any reason, despite what you may have heard.

Hmm, let's see, what else...

Any FAST system with the individual cylinder control option installed CAN change fuel settings per cylinder without a cam sync. It doesn't need a cam sync to determine which injector is on what cylinder - there is a piece of wire connecting the two. What the FAST does need to know is the firing order, and this is where the firing order you enter in C-Com is important. It relates a cylinder number to a particular injector output. The order you enter will be associated with the injector outputs in the manner described above - if you enter 12345678 as your order, output A will be mated to 5, B to 6, C to 7, D to 8, E to 1, F to 2, G, to 3, and H to 4.

JDB, what Lance told you about injector timing is largely true, provided that you reach a reasonably high duty cycle at WOT. If you have a 600 hp engine with 160 lb/hr injectors and only see maybe 30% duty cycle at the highest, the effects of injector timing on hp levels will be more pronounced that running that same engine with a set of 36 lb/hr injectors approaching 100% DC. After all, if it's open all the time, who cares when it starts? Or does it ever really start and stop at all? The closer you are to this point, the less it matters.

Last for this post (I think) is that waste-spark ignitions such as the Ford EDIS and Buick DIS do not eliminate the option of individual cylinder timing control. Although two cylinders will actually be affected at once, one of them doesn't matter at all.

 

[Dave King]

Craig

So that I understand this correctly. Heres what I"m getting out of this.

For a Small Block Ford (which I have)

Black wire (Female connector side) goes to Black (injector side) and the fuel injector connector goes to cylinder #6

Brown wire (Female Connector side) goes to Blue (injector side) and the blue injector connector goes to Cylinder #5

Yellow wire (Female Connector side) goes to Purple (injector side) and the blue injector connector goes to Cylinder #4

Green wire (Female Connector side) goes to Gray (injector side) and the blue injector connector goes to Cylinder #8

Orange wire (Female Connector side) goes to Yellow (injector side) and the blue injector connector goes to Cylinder #1

Blue wire (Female Connector side) goes to Orange (injector side) and the blue injector connector goes to Cylinder #3

Gray wire (Female Connector side) goes to Green (injector side) and the blue injector connector goes to Cylinder #7

Purple wire (Female Connector side) goes to Brown (injector side) and the blue injector connector goes to Cylinder #2

Correct?

 

[JrTuner]

Very, very well stated Craig.