Redeasysport

I have been doing some thinkin' and am a little confused. I have done numerous searches on the 92-93 Lt1 EFI and cannot find a source that directly answers this question. Are they Batch fire (all 8) or Bank fire (4 @ a time). I went and looked at my datamaster files it shows different (although not by much) Inj PW for each side based on what the O2's do. It also shows different Inj DC (once again not by much) from time to time. Yes I know they are not SFI but looking at the scans it sure seems they are Bank fire. Anyone got a link to a reputable source that says exactly what EFI system these cars use. I know the l98 with 1 O2 can only be Batch. I have always thought the LT1's were Bank fire but am no longer sure. I am not sure also where Datamaster is getting these left and right PW from to begin with. TIA

joecarter85

It is my understanding that the '92-'93 LT1's are Bank fired. I could not imagine a V8 being Batch fired(all 8) as this would require extremely long FI duty cycle periods at high RPM's. I would imagine that a Batch fired arrangement would lead to alot of fuel hitting the back of closed intake valves and open exhaust valves.
-MikeC4

FICINJECTORS

dave lets make it easy. This is a good question. I put a link to the L98 schematic on the other thread, it shows all the injector grounds wired to the same driver circuit. Find out the ECM # in the 93 and lets get the schematic for it. Once reviewed I think it will show 1 driver or two. I am leaning to bank batch due to the info the scan gives. Lets see

JackDidley

L98s are inded batch fire V8s.

Redeasysport

Well I just found pg 8A-20-6 in the FSM and indeed it does show 2 sets of 4 injectors going to pin 11& 10 in the "D" plug in the ECM with 2 seperate Control switches called Left injector and Right injector that ground them. Both sets of 4 injectors are tied togther on the ECM side and fuse side and seperately fused on the power side. I guess that pretty well sums it up from what I see they are indeed bank fired as I thought. I wish the FSM was easier to find things in but it is what it is.Thanks for making me think about the electrical section. The ECM# is 16159278

I found pg 6E3-A-7 has similar info that page is the ECM wiring. 2 injector drivers. 1 for 1357 1 for 2468.

FICINJECTORS

good work, now we know.. also that ecm fires twice per rev but 4 then 4 not 8 then 8. on the schematic is it 1,3,5,7 and 2,4,6,8 or does it use the firing order?

Redeasysport

1,3,5,7 and 2,4,6,8 side to side as I thought.I have just seen so much conflicting info on batch fire I was beginning to doubt what I thought was true.

FICINJECTORS

thanks for finding the correct answer

Damien89

Correct me if i'm wrong but aren't LT1's sequential fire?

engle1147

1994 was the 1st year for sequential port injection in these cars. Years previous they fired on odd / even banks (bank fire).

Redeasysport

I think l98 was simple batch fire based on the above referenced schematic in another thread. All fire at once ,only LT1 were side to side bank fire.

engle1147

There are two switching solid state relays (in most OBD1 ECM) that open and close each bank (odd or even)....also there is a fuse for each injector bank in the fues panel. These 2 banks may fire at the same time I don't know for sure...or they may fire one bank at a time...if so why the 2 SS relays and fuses (seems redundant if they all fire at once you'd only need one relay to pulse the injectors in this case). I've always called the L98 set up a batch fire (4 in a batch makes 2 batches) system myself but feel the bank fire term fit the description better...not sure if it is correct term or not....maybe not. Maybe someone else with L98 injector knowledge will step up and comment.

I have a FSM for every C4 year model. I'll go through each year this week and see what the differences are and post any documented difference I might turn up.

Redeasysport

Take a look at the schematic Jon posted in the other thread. I believe it shows all 8 tied togther not seperate with 1 driver.

This is a quote from GMHP magazine
"Most early EFI systems were batch-fire systems where the ECM fired all eight injectors simultaneously. Usually batch-fire systems fire the injectors once per engine revolution. This way, the injectors could be sized small enough to be more easily controlled at idle. Later, sequential EFI systems were refined to fire an injector a few degrees before the intake valve opened. Generally, sequential injection offers more precise fuel control at the price of increased complexity. But on production engines, the benefits are more in the area of emissions and driveability than in performance"

Take a look at the FSM and confirm one or the other I have referenced the pages that prove the bank fire on LT1's It would be good to have a reference to the L98 and finally get this straight.

I have found this and indeed it does show 2 sets of 4 but it appears the Driver is tied togther
http://members.shaw.ca/corvette86/En...agram%2086.pdf

Here is a site showing a Datamaster scan of a L98 unlike the LT1 it only has 1 BLM showing
http://www.customefis.com/faqsite.html

In my FSM it clearly show 2 different switches/drivers I do not see that with the L98 post above unfortunately.

engle1147

I do see in the above post/diagam link that there appears to be only one drive for both banks on the '86.

I read the article with the 1 BLM showing also...not sure what they are using to drive the L98 engine they recorded but engine in the pic just above it appears to be of a MAP set up....this could be an aftermarket set up....didn't see specific data.

I hear you I'm very interested too....got a thread link for me for Jon's post? Just to be sure your specifically interested in the '92-'93s and the L98's in general right?

Redeasysport

The Datamaster could have been from a '90. I have read a lot of conflicting info on this topic and nothing with factual back up and think it would be good to have at least 1 thread somewhere on the web that has some factual info on this subject. Yes I have a '93 but it would be good to have references that prove one way or the other what our cars injectors are doing. Thanks for the help. Here is the link it is a little confusing though.

http://www.cruzers.com/~ludis/1227749schematic.html

FICINJECTORS

been thinking about this. I have a schematic for the wiring on the body wire harness for a 86. I can't scan it. But the bat plus side of the injectors have nothing to do with the ECM. the two fuses are confusing. I believe the two fuses are there because the car will run on 1 bank. Do you think the two fuses are for the load, the fuse would have to be almost 30 amps if all 8 were all wired to that 1 source. The ground side of the injectors goes into the ECM and have a common driver on the L98 and 2 drivers on the LT1. Also in the L98 there is a split in the schematic that drives a few injectors in limp mode (i can't read the numbers). The schematic is hard to read but I see the LIMP circuit

engle1147

Jon,
So I've looked up the L98 TPI pulse injection for the '86-'89 C4s so far....they seem to have only one injector driver/switching ground relay for both the odd and even banks. I seem to have missed or am not seeing the "limp" diagram your talking about....what page or section of the '86 FSM PDF/book are you looking at?

FICINJECTORS

http://www.cruzers.com/~ludis/1227749schematic.html
tab to injection look at u13 do you see it or am I seeing something else

engle1147

For those that don’t already know injectors are opened/closed by means of energizing and de-energizing a solenoid within each injector. The energizing and de-energizing occurs by closing the ground side of the injector circuit within the ECM/PCM by means of a solid state switch/driver/control (the term changes by year model ….I’ll just call it a control to avoid confusion). The injector pulse signal is generated as ground connection is open/closed. This signal or lack of signal activates or deactivates an injector’s solenoid open/closed at precise regular intervals/pulses which are measured in terms of milliseconds (MSEC). The amount of fuel delivered may be varied by the length of time injector/s are open/energized as calculated by the ECM/PCM.

So now we know how and injector circuit works…..by opening/closing the ground side of the fuel injector circuit. The ground side of circuit is what I’m concerned from the information from here on out. So now we’ll take a look at 1984-1996 fuel injection diagrams…and I think you’ll see why people get confused by terms like “bank” and “batch.” In the diagrams below you can notice the variation of how the fuel injector circuits are grounded between year models. Some years show only one grounding control for all 8 injectors other years show multiple controls, one for each bank of 4 injectors or one control for each injector.






















Basic Types of Injection
Throttle Body Injection (TBI): the fuel injectors are located at the throttle body (1984 cross fire setup)
Single Port Fuel Injection (SPFI) simply implies that a fuel injector is located within the intake port very close to the valve location (L98, LT1, LT4 & LT5) Port Fuel Injection systems on a C4 Corvettes can also be Batch, Bank or Sequential Firing injector setups.

Batch/Bank Fire Injection includes TBI, TPI & early LT1s (1984 TBI, 1985-1991 L98 & 1990-1992 LT1)

In a batch fire setup the injector pulse signal is actuated by the ignition reference pulses. All 8 injectors are energized at the same time, once per engine revolution. Because and engine makes 2 revolutions per combustion cycle, each port gets 2 injections of fuel during each cycle. With a batch fire computer all 8 of the injectors are fired simultaneously once for each crank rotation.

In a bank fire setup there are a minimum of 2 contollers; one for each bank. Instead of one firing of all 8 injectors are two firings of 4 and 4 (odd 1357 and even 2468) injectors. One firing occurs one after the other. Same as mentioned above, the both batches in each bank are fired once per engine revolution. Because and engine makes 2 revolutions per combustion cycle, each port gets 2 injections of fuel during each cycle. With a bank fire computer all 8 of the injectors are fired one time for each crank rotation.



Timed Sequential Firing Injection (SFI) (1990-1995 ZR1 1994 & up LTX motors)

Injectors are controlled to deliver fuel just before the inlet valve for each cylinder opens sequentially (one after another) and each injector requires its own controller. The delivery control on an SFI system is done using a camshaft position sensor and or crank/ignition reference pulses. The introduction of SFI in the 1994 LT1 is done at the PCM prom logic level.

Conclusion
Cross referencing reputable informaton I've read it seems that the 1984-1987 & 1990-1993 C4's are all bank fire and only 1988-1989 are batch fire....since they appear to have only one injector contoller for both banks.The LT1 was introduced in 1992 but was bank fire unitl 1994 when the sequential fire system was used.

Confusion
In regards to this link:http://members.shaw.ca/corvette86/En...agram%2086.pdf
The diagram is a simplified diagram for illustration purposes only...wire diagrams that are accurate you'll need to look in section 8A...if you flip to section 6E in most other early FSM books you'll see the same misleading diagram.

References:
1984-1996 GM FSMs
GM STG injector service manual (Service Technology Group)16009.10-3
Corvette Tech Q&A 1953- Present by Dave Emanuel
http://www.fuelinjection.com/portinj.html
http://www.speedscenewiring.com/fuelinjection.html

Redeasysport

Ain't it. As I already posted it seemed to me on the 93 (and probably 92) that a Datamaster scan shows different PW and duty cycles for each side and we know since there is only 1 O2 for L98's they cannot have different PW's so I assume all injectors in those fire at the same time (or not?) at the same PW regardless of dual drivers or not. I also assume that the 92-93 balance fuel by banks due to the 2 O2's that allow side to side PW adjustments. As Arte Johnson used to say "Verthy intresting"