Batch firing basics (?)

[fireguy12117]

I understand that to some degree when a person says batch firing in relation to a 4.0 they are talking about the fact that there are 3 coils for 6 plugs and that its set to where one plug is firing on the compression while the other on the exhaust, but my question is how do the injectors factor in?

i see by a wiring diagram that there are 2 signals from the PCM firing either one set of 3 or the other. so is it just in the ordering of the cylinders that only the clyinder on compression is going to ignite while the others do not, but still get fuel shot into them?

 

[MAKG]

Batch firing refers to the injectors, not the coils.

The coils use waste spark ignition. There are THREE of them (not six), and they fire at a few tens of degrees BTDC on all rotations (not just compression stroke). The exhaust stroke firing has very, very little effect, and means half as much control circuitry and only three coils.

Each coil is hooked up to two cylinders exactly halfway around the firing order from each other.

Batch fired injectors just means that you fire three (or perhaps all) injectors at once. It is COMPLETELY independent of ignition -- this happens on 2.9Ls as well and they have conventional electronic distributor ignition (one coil). The first bank is the front half of the firing order (1,2,4), and the second bank is the other half (3,5,6). That way, no cylinder has to wait more than one crank rotation after spraying, for a spark.

 

[fireguy12117]

i guess i am still missing some bits of knowledge, forgive my ignorance...

are there 3 cylinders firing together? all on the compression stroke, all igniting together, all 3 getting air/fuel shot in together by 3 injectors that are tied together at the PCM?

if so, i for whatever reason, didnt understand that there were 3 cylinders actually generating power at the same time, and if thats not the case, wouldnt you be wasting fuel?

 

[Wicked_Sludge]

cylinders fire one at a time. on cylinders that arent on the intake stroke, the fuel hangs out in the intake runner, behind the closed intake valve waiting for the valve to open. when it does the fuel is sucked in.

it seems like your imagining the injectors IN the cylinder. they are not, they are in the intake manifold behind the intake valves...

do any RBV engines use sequential injection? i thought they were all batch..

 

[MAKG]

There was a switch to SEFI in the 4.0L somewhere around 1995 (give or take a few years).

 

[turbo cat]

Most OBDII vehicles switched to Sequential after 96 as it became sort of an emmissions/fuel economy requirment. As far as wasting fuel yes most batch fired efi systems use a little more fuel than sefi. The difference is at lower rpms.however the economy diff is little

 

[fireguy12117]

ok, that clears it up a lot then. i think your right, i wasnt picturing where the injectors were but since i did dress a long block i can picture it.

totally a curiosity question, but is there any ill affect on that air/fuel thats been injected before actually going into the cylinder? like do any fuel particals actually fall out from the mixture, end up on the intake surfaces and reduce the ratio, or does that not factor in- negligable losses perhaps?

errrr....just missed that last post....but i guess the wasted fuel question before was more from not understanding...

 

[Wicked_Sludge]

sequential fuel injection produces a little better economy and power than a batch-fired injection engine due to the SEFI engines better atomization properties.

 

[fireguy12117]

copy that!

the more i get into this stuff, the more i seem to enjoy it...weird...you all have been a great help, thanks!

 

[UrbanRedneckKid]

There was a switch to SEFI in the 4.0L somewhere around 1995 (give or take a few years).

Actually started in 94 but only on models with California emissions, then in 95 they all were.

 

[AllanD]

sequential fuel injection produces a little better economy and power than a batch-fired injection engine due to the SEFI engines better atomization properties.

Actually that would be wrong.

The SEFI 4.0 offers NO advantage in either power or economy over the "batch fire" injected 4.0.
Infact from experience the Non-SEFI '93's typically get better mileage than the SEFI 1994's.

And EEC5 '95-up 4.0's just plain SUCK HARD at that fuel supply hose...

The Switch to SEFI was PLANNED for 1993 (it happened mid-year for Cali)
the full model run for 1994 explorers and slightly later into the 1994 model run for Rangers.

1995 were ALL EEC5 and ALL SEFI

"Better atomization" that would be interesting considering ALL
1993-94 non-Sefi engines used THE SAME disc pintle injectors
as the SEFI engines.

THEORETICALLY there is some difference because the fuel being injected
at a closed intake valve might "puddle" but the fact is that
the intake port and intake valve are WAY too hot for that to happen so the fuel actually gets more time to vaporize, which might be the factor
that explains why the batch fire engines (counter-intuatively) get better mileage....

"atomized fuel" should burn, vaporized fuel WILL burn.

I average better mileage (19mpg) with my 1993 non-SEFI 4.0 than most people have ever gotten with ANY 4.0
and my Best mileage (22mpg) makes 2.9 people jealous

and considering that I've got a 4x4 supercab with 4.10's....

AD

 

[rickcdewitt]

my whooped, high mileage, low compression 4.0 gets between 17-18 mpg in a lifted pile on 33's( i'm sure in a little 2wd with 14" rims and 3.27's i could get into the 20's,and be pretty damn fast too)