EFI ECU Wiring & Unused circuits

lookforjoe

lookforjoe

True Classic
I was wondering if anyone on here ever bothered to determine what other functionality may have been available through the EFI ECU.

I'm not interested in going standalone at this point, just want to refine what's already there.

I found this ECU Wiring, which is very helpful - but I'm wondering about some of the unused portions.

I want to add a heated 02 sensor, for example - they last much longer & operate sooner than the old single wire jobs. I can of course wire from scratch, but it would be nice to know if there are (+) (-) pins that can be utilized. A real IAC valve would also be nice, and for all I know, there are unused signal points in that ECU that could be also utilized.

Any pointers?
 
Page John Allen and Bob Brown or...

... write them direct.

I know of possibly one other but he has been off the forum now for some time.
 
I haven't looked into it that deeply

I still have the 'plug-in replacement' Megasquirt project sitting in a box here for lack of time.
(I travel all the time) I've noted that our cars use the narrow band O2 sensor to the Bosch ECU.
That alone tells me that a two-wire O2 system is out of the running. (remember, the ECU was designed in the early eighties) Far as I can tell, the O2 sensor acts
more like a logic switch than an analog signal.

Correct me if I'm wrong, but Hussein is looking more toward the analog side than a logic level?

With regard to the other functions (outside of running the fuel pump for a short time prior to starting)
there's the AFM pump switch,
Air Flow Meter (AFM),
Aux. Air Valve,
Fast idle Valve,
Fast Idle Solenoid,
Coolant Temp sensor,
and Throttle position sensor
the Fuel Injectors (to my surprise all run in parallel, not separately!!)

all of which I have yet to address, but I haven't got there yet.
All takes time, and we had a short winter in NH last year. Ha!
Hopefully this fall...
 
O2 sensor

Hussein, the heated sensor creates the exact same signal as the unheated. The only difference is it has a heating element, so that is warms up and is useful to the ECU sooner. Any switched (+) and a good ground can be used.

An example of this system is on my '88 Vanagon, it uses a Bosch Digifant ECU which controls both fuel and ignition, and has a heated O2 sensor. It also uses a troublesome digital idle control valve. Such a system might be the transplant for you if you want it to be a plug-in system. Otherwise the systems are nearly identical. The O2 sensor heat power could be even drawn off of the ignition.

Bob, the O2 sensor is read by the ECU like a resistor, except that it creates a swinging signal rather than a steady one, varying by about 200mv per second. The ECU uses this signal to fine tune the mixture above idle.
 
????

I thought these older ECU designs where all "mapped" 100% of the time. I've always wondered how much input the O2 sensor actually has?

Later ECU's use the hard program "map" until the O2 sensor comes on line, then it goes to live calculations. Did the X get this system?

If so, a really nice addition would be intake air temp sensor.
 
Not 100% mapped...

The ECU has a "map" it uses for cold or idle situations. Once warmed up, the O2 sensor is used to adjust the mixture during all but idle situations. This is why we have an O2 sensor, and why the idle CO% is set at idle.

The AFM contains an air temp sensor.

The early and late ECU's are identical, except that later models like my Bertone also use an altitude sensor, which lives in the spare tire area with the ECU and dual relay.
 
Haven't seen an altitude sensor

Not in my X anyway. I have an 86 but have scrapped (2) 87's.
Do you have a photo of such?
 
a heating element, so that is warms up and is useful to the ECU sooner. Any switched (+) and a good ground can be used.
Click to expand...

Do you really want to have the heating element on whenever the ignition is on? It would seem better to turn the heating element off when the exhaust gets hot enough to keep the sensor at operating temperature.
 
Sensor photo

DSC00155.jpg


bbrown said:
Not in my X anyway. I have an 86 but have scrapped (2) 87's.
Do you have a photo of such?
Click to expand...
 
O2 sensor heater...

On my Vanagon (and I assume other vehicles with heated sensors) the heater is powered all the time that the key is on. The heat generated by a hot engine's exhaust is probably a lot hotter?
 
budgetzagato said:
On my Vanagon (and I assume other vehicles with heated sensors) the heater is powered all the time that the key is on. The heat generated by a hot engine's exhaust is probably a lot hotter?
Click to expand...

...actually heated sensors have a pulsed ground through the ECU for the 1st 30seconds, after that, the thermistor in the O2 governs the heater element - so it always maintains at least 350ºF - to prevent condensate damaging the ceramic.

The pulsed ground would be the issue, but since the system is kinda primitive, there's probably no point providing it with a more refined 02 signal.

I'm wondering if I should just swap it out with a LH2.2 system from a -88 Volvo :grin:
 
!!!!!!!!!!!

I have an idea, why don't you just buy an 88 Volvo and slap a BERTONE emblem on the hood!! Save a lot of time that way!

:p

I'm kidding of course.
 
I worked for Volvo back then....

.... I know all about the Bertone 780 :rolleyes2:

Volvo gave one to the owner of the P1800 that reached 1,000,000 miles.

I'm not trying to turn my X into a Volvo - just improve it with some of the Bosch technology used by Volvo :grin:

Anyway, I pulled the entire LH2.4 EMS from a 1991 240 this afternoon. Now I have to figure out if I can generate a speed signal it finds acceptable, or maybe re-pin it for the LH2.2 ECU & MAF, which doesn't use any crank sensor, etc.
 
budgetzagato said:
The ECU has a "map" it uses for cold or idle situations. Once warmed up, the O2 sensor is used to adjust the mixture during all but idle situations. This is why we have an O2 sensor, and why the idle CO% is set at idle.
Click to expand...

I also believe L-Jetronic systems go open loop at wide-open-throttle... so the system would be using a "mapped" value.
 
Curious what you think the LH system would get you over the stock L?...

If you're going to go through the trouble of reworking the entire FI system, going with Megasquirt might be an easier path... ...and you'd end up with something much more tunable...
 
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