EspenT

A few months ago i started a tread about building a 928 drift car. Unfortunaly I'm not alowed to link to that tread. The project has come to a point where we are puting things together.

Our engine, that's based on a M28/47 will have to two turboes mounted in front.
It wasn't easy to get someone to fab up the headers for that. And they are not quite finished yet. Wish i was bether with the tig myself.

Tonight I'm doing some wiring for the aftermarket ECU I'm going to use. Insted of starting from scratch I cut open the old engine harnes. Then I discovered that on the injectors it 4 and 4 of them was wired together. It's probably a good explanation for that.. But after a long, long week's work my head does not understand.
If 4 injectors open at once, then only one of them would squirt trought an open inlet valve? And each injector will open 4 times eache cycle?

Another question is about the EGT thats taped into the head at the exhaust port on cyl 4 and 8. Are they special, or would they work with a "of the shelfs" EGT gauge?

Another thing swirling around my head is that cable that conects to the timing belt tensioner.. Gues it's for telling you when to replace the belt. But how is it working?

AO

Yep, they're batch fire injectors. I was surprised to find this as well, but it works.

The EGT you are refering to are becasue of the batch fire injectors. They are used to see if one side is hotter than the other. If so, the stock Bosch LH/EZK brain shuts down the cooler side to prevent raw gas from being dumped down into the cat.

The TB wire is there to tell you if the belt is too loose. That is not to say you tighten it until the light goes off - but rather if the TB light comes on, you need to investigate.

Jim bailey - 928 International

all 8 injectors fire at once...the temp sensors are for the Ignition Control Monitor and a special relay when it senses too great a temperture differential cuts off the + power to 4 injectors two on each bank. The LH brain "fires" all 8 injectors with a ground signal...

AO

Jim, I thought it fired them 4 & 4?

Jim bailey - 928 International

Nope the brain fires all eight at once by switching the ground . Terminal 18 on the LH gets the wires which go to all 8 injectors

Bill Ball

I agree with Jim. You can fooled into thinking the injectors fire 4 and 4 by the ignition monitoring module wiring, but all 8 injectors share the same ground and are taken to ground (firing them) at the same time. This issue was discussed last year when we found that a short in any one of the 8 injector's power leads takes them all out.

AO

Bill,
I remember that discussion. Unfortunately, I eroneously remembered it as one bank going out rather than all of them. Now I know. You never know what your going to learn on rennlist.

EspenT

Hmm... Stranger than I tought. Is it a reason why it its that way? Why not fire one at a time, or maybe two. but firing tham all? I would belive that the fine mist of fuel from the injector would become less fine.
When pulling the engine apart I didn't look very close things. But I belive i saw what I then thought was a hall sensor reading the cam. I was planing to use that and make the injection sequential.

Vilhuer

Much easier to control one firing per crank revolution than trying to do multiple in each revolution.

Passenger side cam has hall sensor at front end. Its used to monitor knock together with two knock sensors. There is also other sensor to monitor flywheel position at rear end of the block.

Jim bailey - 928 International

there is a hall signal generator which is used with the knock sensors ONLY to determine which cylinder is knocking so the ignition can retard the timing ONLY for the cylinder which is knocking, the flywheel toothed ring is used for the ignition timing . Batch firing works fine when gas hits the back of a closed intake valve the heat helps vaporize it.

EspenT

So the injectors fires only once every revolution? Does it fire at the same time every revolution, og does it change.
The injectors themself are only 18.45lbs/hr. I've seen a lot of members here have superchargers on their cars. Is it possible to maintain a stoichiometric combustion without changing injectors.? Do you rise the fuel presure?
I'm hoping that some 34.0lbs/hr that i had laying around would be enough.

Could i wire the EGT probes to a autometer EGT gauge or something simular?

Jim bailey - 928 International

I seem to recall it being twice per revolution but not sure why I think that ?? I never got too excited about it since it is not going to change.

Vilhuer

Its once ot twice per revolution, can't recall any better than Jim. In any case opening time is only important variable.

Almost all SC cars have larger injectors, some up to 42 lbs. There are two ways to make them work, raising rate fuel pressure requlator or custom chips. Chips are easily doable with SharkTuner and better option I think.

davek9

Does this apply to all MY's or only 87' and up as that is when the knock sensors started? I am not sure when the coil or bank monitoring started.

Great info, thank you all,

DaveK9

Jim bailey - 928 International

Knock sensors 87 > the ICM started in 89 ...