I have a 2V-FI 81 GTSi with US configuration. Is the ignition curve controlled by the RPM sensor input, the vacuum input, or both? My understanding is that the advance is controlled by the RPM input, and the retard is controlled by the vacuum sensor. When the rpm is low, but the throttle is closed creating vacuum, the ignition is retarded. This would be starting and warm idle. Is this about right?
The MED801a has eight programmed curve settings based on RPM and Vacuum. At higher (3500+) RPM with a closed throttle, the graph shows the timing actually advances more. The timing curves of the MED801a box is horrible with emmission being the major driver in the design of the curves.
You say that there are eight curves. Is the vacuum sensor just an on/off switch, or does it give an analog signal indicating the exact amount of vacuum, and the processor used that to select which curve to run? Also, what about the temperature switch? If there is no signal from the temp switch, does it just run one cold start curve until there is a signal, and then it selects from the other seven, or does it select from the eight curves based on coolant temp/rpm/vacuum? Thanks for your help. I just want to cover all the bases.
The ECU recognizes variable inputs of vacuum and is not an on off switch. Coolant temp is not a Factor in the timing curves. The cold start high idle is affected by coolant temp but temp does not effect the ECU in any manor and provides timing based on the RPM and Vacuum like normal. There are Three thermo temp switches on our cars; radiator for the fans, cold start switch in the coolant resivour, and a thermo time switch which sends the signal to the auxillary fuel injector for added fuel in cold situations.
I've never come across an exact description of just exactly how the coolant thermoswitch affects the ignition timing on the US DigiPlex 801A equipped cars (whether it's just a fixed offest from the warm-running US maps or some other more complicated scheme), but both the description of the coolant thermoswitch, item 73, on page 104 of the 216/81 OM, and the text description on page 70 of the same OM regarding what items affect the ignition advance behavior say that the coolant thermoswitch does have a role for "cold" vs "warm" (and it is connected to pin 6 of the DigiPlex ECUs). Agree completely that for warm-running on the US cars, only the RPM and intake vacuum are used.
I have seen that too and I agree that the explination is poor but after reading the bosch K-Jet manual I have come to the conclusion that the opening of the cold start valve changes the manifold vacuum and RPM and that is temp related event affects the timing curve. My manual shows pin 6 goes to the on off switch (ignition) There is chance I am incorrect in my assesment but I can find anything that suggests other wise.
In the ignition-only schematic (page 71) in Section 3 of the 186/80 OM (1980 US/NA 308i-2V), they made a mistake and left pin 6 of the DigiPlexes not connected to anything, but if you refer to the complete schematic in Section 5 you will see that pin 6 is connected to the coolant thermoswitch 73. In the ignition-only schematic (page 71) in section 3 of the of the 216/81 OM (1981-2 US 308i-2V), they drew in the coolant thermoswitch by hand (but didn't label it) and show it connected to pin 6 of the DigiPlexes. Again, if you refer to the complete schematic in Section 5 you will see that pin 6 is connected to the coolant thermoswitch 73. What "manual" is your reference for "pin 6 goes to the on off switch (ignition)"?
What "manual" is your reference for "pin 6 goes to the on off switch (ignition)"? The Ferrari Mondial 8 (2Vi 308 use for injection and ignition) sevice manual. Image Unavailable, Please Login
Why do you think that item 12 is the ignition switch in that diagram? Item 7 is the ignition switch. Item 12 "ON-OFF switch" is the coolant thermoswitch.
read 12 in the notes "on off switch US 2Vi" perhaps I am wrong but feel to free to explain where coolant temp comes into play. You claimed the 6 pin was the driving circuit for coolant input.
No, I claim that the signal from the coolant thermoswitch is an input signal (in addition to RPM and intake vacuum signals) to the DigiPlex ECU via pin 6 that affects the ignition advance mapping. Please see the complete schematic in either of the US 308i-2V OMs -- they have much better labeling of the K-Jet without Lambda USA components. The coolant thermoswitch IS an "ON-OFF switch", but using "ON-OFF switch" for its description here is an example of the poor English translations for technical items that permeates F documentation (and, stictly speaking, the ignition switch is not just an ON-OFF switch). Also, the "USA" notation for item 12 and the dashed wire lines are meant to convey that this item is only used on the US version -- the euro version doesn't have a coolant thermoswitch, but it does still have an ignition switch.
I forgot to include the most obvious, and conclusive, point that proves item 12 in the Mondial 8/QV WSM schematic that you posted is not the ignition switch -- note that item 12 is connected to ground, not to the +12V battery terminal.
As I indicated in post #5, I believe the ignition maps given in the Mondial 8/QV WSM are for the warm-running condition (water thermoswitch closed) only, and have not come across any description of the "cold" (water thermoswitch open) US map, or if it's just a fixed offset from the warm map, or some sort of scaling, etc.. PS You can download a lot of the F documentation, like those other OM, from www.ferraridatabase.com
If I understand what you are saying, a 308 GTSi with all the fast idle equipment removed and the cold start injector disconnected would run the same ignition curve whether the coolant thermoswitch is open or closed? I know that the warm up regulator will still richen the fuel mixture for a few minutes after starting, but the ignition timing would not be retarded? I just want to make sure I have this right because previously I thought the opposite was true.
No, I'm saying the opposite (if when you typed "cold start injector", you actually meant the cold start air valve). If the coolant thermoswitch is still in place, and wired in the stock fashion, then, when cold (coolant thermoswitch open), the system would use the "cold" map -- whatever that is -- even if the cold start air valve has been physically removed so that the cold idle is not very high. After the coolant thermoswitch closes, then the DigiPlex ECUs detect this, and the "warm" map is used. However, if the cold start air valve system has been disabled by connecting the two wires going to the coolant thermoswitch together (always simulating a warm, closed coolant thermoswitch) then the "warm" map would always be used.
I meant the cold start injector. My 81 actually has two fast idle controls: the Auxiliary Air Valve and another vacuum controlled valve. I'm not sure how they are controlled. The cold start injector is on the right side of the plenum and goes to the center of the fuel distributor and richens the intake while the plenum is cold. I think it is on a different system because it only runs briefly on a cold start. The AAV gets current once the engine is running, so it starts to close immediately and if fully closed in 1 to 2 minutes regardless of the engine temp. The second vacuum controlled valve closes when the thermo switch closes. This provides a very fast idle to quickly warm up the cats, but I use a plug to reduce the fast idle to a reasonable level. MNExotic states that there are eight different ignition curves. My question is whether only one of the eight is used when the temp switch is open, or if four are for when the engine is cold and four are used when the engine is warm. I found that it takes about ten minutes for the switch to close on a cold day, so is the engine running off only one map that whole time? He also states that the thermo switch does not effect the timing curve selection, but I have always heard that it does.
Thats confirmed by the wiring diagram, which calls that switch "temperature switch for electrovalves" and controls two valves (in adition to pin 6), "air injection electrovalve" and "fuel injection electrovalve". One of those must be the one you are referring to. Whats the other one?
