Hi All. 1981 US GTSi After having my injectors cleaned and tested I was feeling pretty good about how my car was running. Drove about 40 min south on Saturday to a meetup for 3x8 owners. (great meet, I think it was 10 308's a 328 and a Mondial.) While poking around everyone's engine bay I noticed something I hadn't noticed in 2 years of ownership. My vacuum line from my Diverter Valve went straight to the lone port on the left of the plenum and my line from the digiplex (so that's what that hose is!!!) went to the electro switch on the left side of the engine nearest the firewall. Seems like they were reversed. I had to get a new hose for the diverter valve as the one on there fit the lone vacuum port but was way too big around to fit on the electro valve. Starting the car I find that it idles at least 200 rpm lower. Previously it seemed happiest around 1000. I adjusted it up to about 900 now. I have not checked anything else or driven the car yet. Cold fast Idle has been disabled (or doesn't work?) Assuming my electro switch was functioning properly what was happening before with it hooked up this way? Anything else I should check before I give her a drive with the new (correct?) setup? Thanks Jay
This would be normal if no vacuum was reaching the Digiplex ECUs before and now it is because different ignition maps are used for different applied vacuum levels. See page D5 in the Mondial 8/QV 281/83 WSM for the ignition maps/data for your MED801A Digiplex ECUs. They mangled the Fig 6 graph (because it already includes the -5 deg of ignition timing for cold-running), but the table in the upper right corner is OK: When at 1000 RPM idle with no vacuum applied (i.e., curve 1 is used), ignition timing: warm = +6 deg BTDC, and cold = +1 deg BTDC When at 1000 RPM idle with vacuum applied (i.e., something in the curve 5-7 range is used), ignition timing: warm = -3 deg ATDC, and cold = -8 deg ATDC Now that you've applied the vacuum at idle to the Digiplexes, the timing has been retarded by something like 9 degrees (whether at warm or cold idle) = reduces the engine RPM from whatever it was before. Bottom line is that you should set the warm idle speed to 1000 RPM when vacuum is being applied to the Digiplexes. I wouldn't assume that your electrovalve (or anything else) was hooked up correctly . Have you compared your electrovalve plumbing to what's shown in Section 3 of your OM?
I had not compared to the diagram in the OM but now that I have, it doesn’t match. It does however match the diagram on the sticker on the left side of the engine bay. The sticker shows the line from the diverter valve to the switch then to the plenum port. (This is also how the other similar cars were plumbed that I looked at on Saturday.) The manual shows the diverter valve to the switch then the switch going to a “depression line” which looks like it disappears in the diagram on the other side of the engine. In another thread I read that this switch should open at 4000 rpm? Or? thanks.
Here's the SPC for your model -- see TAV. 9 (which does seem different than that OM figure -- with the vacuum hoses connected to different ports on the electrovalve which inverts the logic): https://www.dropbox.com/s/6trvn000tscatc8/Spare Parts Catalogue 81-82 US version 308i 222_81.pdf?st=prokgvzv&dl=0 On the US carb 308, there is a system to disable the air injection at high RPM during cold-running, but I don't know if your model is the same, or not.
Hmmm... Yes, that is how its hooked up on mine now except for reversal of the 2 vacuum lines going into the electro valve (though the shape of the valve is different in the diagram.) Grabbing a vacuum gauge today to test... previously I had vacuum to the diverter valve 100% of the time (and its passed smog 2x like that). Assuming the electro valve is working should I have vacuum to it up until 4400 rpm or only after 4400 rpm?
You should always have vacuum going to one of the ports on the electrovalve. The state of the electrovalve (energized or de-energized) then determines if that vacuum source is connected to another port of the electrovalve (and goes somewhere else) or is blocked. Read Chapter N of the Mondial8/QV 281/83 WSM: https://www.dropbox.com/s/z99soo68ny9n2qa/Mondial8qv_workshop_281-83.pdf?st=26nhr8i8&dl=0 It covers the air injection system and the EGR system used on 1980-83 US version 308 and Mondial.
OK. So here's where I stand today. Everything was wrong. Thanks for that link Steve! Though I confess I don't understand all of it I believe I got the important parts of what should be getting vacuum and when... at least enough to test vacuum at different connections. The diverter was originally connected straight to the plenum getting Vacuum all the time (wrong), the digiplex was hooked to the middle port of the electro valve getting nothing (wrong) while the vacuum line from the plenum was open through the switch (at least while cold?) meaning I had a big vacuum leak (extremely wrong!) Swapped hoses around on the electrovalve so I have confirmed that (at least when cold) I am getting 10in of vacuum to the diverter valve. Based on connecing the digiplex straight to the plenum I had to adjust the idle up a lot to get back to 1000 RPM. With no more (hopefully) vacuum leaks it was running very rich. Smelled and I could hear low popping noises from the exhaust. I lowered the AFR set screw until it was definitely lean and using the "just barely touch the Air flow meter plate" method richened it until it stopped speeding up when lightly depressed. Tomorrow we'll see how well it starts when cold (it was awesome cold starting before with all that wrong...) and I'll test some more and hopefully take it out for a flog. Thanks Jay
Glad to hear that you are making progress with getting it sorted out -- these cars seem to often get wrongly modified/"fixed". You should pick up some decent mid-RPM to high-RPM performance as curve 1 (no vacuum to the Digiplexes) gives some more low RPM advance (so the low end picks up), but it limits the mid-RPM to high-RPM advance because getting a true no vacuum condition only occurs a very heavy engine load (and big advance with big engine load at high RPM = trouble, so manufactures don't let that combination happen).
OK. So here's my update: Fairly certain that all the vacuum routing is correct now. Cold start = same (good). Hot start = a tiny improvement (didn't expect this to cure it but you never know...). Seat of the pants: Wow, what a difference!. 2 years and I had no idea what it should have felt like. Power delivery was VERY linear before. This is definitely more of what I expected of a Ferrari. Feel a definite kick around 3500-4000 rpm and the revs climb much faster at the high end than they did before. Not like its much faster, but definitely much more fun!
