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Magneti Marelli MED 801A or 802A

Discussion in '308/328' started by Jbryant, Jan 31, 2008.

  1. Jbryant

    Jbryant Karting

    Sep 23, 2006
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    Jeff Bryant
    Does anyone know the difference between the Magneti Marelli MED 801A ECU and the 802A unit.

    I have two brand new 802A units and I want to use them in my 1981 GTSi. The parts book calls for the 802A units but I have 801A’s installed in the car. The ones in the car are working but are very old and look like they have been wet before in the past.

    I cannot seem to find any information about either unit. I think the 801A units were to meet California Smog requirements by retarding the ignition more, not really sure.

    Any help??

    Jeff
     
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  3. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    pit bull
    Off the top of my head I think the 801A's are euro units which have more advance . .. think you will see a performance decrease going to the 802A's. Advance curves are in the WSM.

    edit: Just checked WSM . .. had it backwards . .. 801A's are U.S. . . 802A's have more agressive advance and I think more total advance but there's confilting info in WSM. Put them in and I'm confident you'll see a performance increase.

    Sean
     
  4. miketuason

    miketuason F1 World Champ
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    Try installing the 802A and see how it performs.
     
  5. Jbryant

    Jbryant Karting

    Sep 23, 2006
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    Jeff Bryant
    WOW WOW WOW WOW WOW

    Either my 801's were about to give up the ghost or these 802's are WOW WOW WOW

    Have not driven the car yet because I am doing other things to get it ready for spring, but in the garage, Wow Wow............

    Starts right up, Idle is never misses a beat, after warm up jumps right to 1,000 rpm, stomp on the throttle and she jumps to 6,000 rpm WAY FASTER than before and when I let off, she comes right back down to 1,000 instantly and never pops, or stutters. Never backfires or smokes. Then engine is sounding like a fresh overhaul. This has to be attributed to the new advance curve and advance system.

    I need to measure the dwell. Can this be done? If I hook my meter to one of the coils, and set it for 4 cylinder, I can see the TACH setting but how do I check the advance? Do I just set the meter to Dwell or do I have to hook up to some other connector to the coil's to measure? Or is this even possible?

    Anyway, It sure sounds better and there is no missing or stuttering. I would have to say that if you loose an 801 Digiplex, I would replace them with two new 802's.

    Once I get this out on the road again, I will report back....

    Until next time
    WATCH THIS SPACE..............

    Jeff
     
  6. miketuason

    miketuason F1 World Champ
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    Congrats Jeff, sounds like a winner to me:) Anyway please don't discard the old 801A, I think there's a company that repairs them but not sure the name of the Co.
    Glad it all work out and sounds like the 802A perform better than the 801A. Keep us inform, thanks.
     
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  8. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    I really think the 801's advance curve has a lot to do with the 2vi's sluggish personality. 2 deg retarded at idle vs. 6 deg advance with the 802 at idle (from memory) . .. that right there will help throttle response.

    I just pulled the CAT's off the stocker I'm tinkering with expecting to see them plugged . . . they've already been hollowed out.

    Once I get it smogged the advance curve is the first thing I'm going to play with.

    That's great you had those boxes sitting around like that and even better you noticed an improvement.

    Sean
     
  9. Jbryant

    Jbryant Karting

    Sep 23, 2006
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    Jeff Bryant
    Just checked my AFR. Was around 14.6:1 at idle with the old 801's. Now its 15.8:1 at idle. When I throttle it up the AFR jumps to around 13.5:1 and the car is running like a raped ape. Can't understand why the AFR would change like that unless it is burning cleaner. I think that the 801's were on their last leggs and most of what I am seeing is due to new parts and better advance.

    Not really sure what the AFR is really supposed to be at so I might have the car put on a Dyno this year and see what setting really works best. With the Hyper-Flow CATS, its hard to tell what setting to use for best performance. If you need to install CATS, go with the Hyper-Flows. My CATS were SHOT. Eugenio installed the Hyper-Flows and that made a MAJOR difference in the way the car ran and sounded.

    STAY TUNED.......

    Jeff
     
  10. dave80gtsi

    dave80gtsi Formula 3
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    This is exactly the sort of info that I've been wondering about for quite some time!

    If there's a significant seat-o-the-pants difference to be found between the 801 vs. the 802, then there's also now a ready market out there for folks who would want to simply replace one for the other.

    Analogous to "chipping" a car of modern vintage.

    Similarly, seems like a fellow who is clever with electronics ought to be able to look at one of these old units and "upgrade" it to higher performance specs.

    Or, better yet, build up a new "black box" that could be simply replaced for the OEM unit, yielding a 10 minute upgrade to better power and performance!

    Cheers - DM
     
  11. bocaspyder360

    bocaspyder360 Karting

    Jan 18, 2008
    128
    sorry new here what are these boxes 801 & 802? have a photo?
     
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  13. miketuason

    miketuason F1 World Champ
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    #10 miketuason, Feb 1, 2008
    Last edited by a moderator: Sep 7, 2017
  14. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,341
    JEFF ---

    Not to rain on your parade, but the MED802A was for the Euro version, and the MED801A was for the US version. And, they are not interchangeable.

    There are other differences in these cars (Euro v. US) besides the ignition maps in the digiplex unit. The valve timing is different, the fuel pressure regulation is different, the location of the flywheel pins for TDC sensing is different. The 802 is matched for the Euro specs and the 801 is matched for the US specs.

    Running 802's on a US car (without making other appropriate mods) may cause excessively lean / rich combustion, and excessively advanced / retarded ignition firing points at certain RPM and load conditions ---- this may lead to serious engine damage.

    I wouldn't recommend it...
     
  15. bocaspyder360

    bocaspyder360 Karting

    Jan 18, 2008
    128
    OK now I know the part..... what do they cost ? They are the computer's that control the ignition electrical componets?
     
  16. Jbryant

    Jbryant Karting

    Sep 23, 2006
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    Jeff Bryant
    I am in the process of testing these units to their full extent. I believe we have a winner here as a performance boost for the US 81-82 308 2V cars. The real test will be how it performs during a Smog Test. Right now my mixtures are well below the California Limit but I do not have access to a 5 gas analyzer to be 100% sure. My test equipment only check for Air/Fuel ratios at the tail pipe.

    If I remember correctly, a reading of 14.11 AFR = 1% CO and a reading of 14.25 = .5%. I have no way of checking NOx or anything else. So this is very important here in the Peoples Republic of California. My Car right now is producing 14.2 at the tail pipe which is below the California Standard if I am correct so using this as a starting point, everything is going well.

    As far as performance, Static in the garage she is performing better then ever. I cannot hear any popping sounds, no backfires, things that might indicate that there is a problem. The water temps are normal, no unusual smoke or fumes from the exhaust.

    When I have everything ready, I plan to both Dyno the car and verify that the Smog Nazi’s in California are happy by using a 5 gas analyzer. Then I will put about 1,000 miles on the car. I will continually report back to either the success or failures of these tests.

    Jeff
     
  17. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    Confirm your base timing at 1000 rpm. With 801's it's 2 ATDC . .. 802's 6 BTDC . . .. that's 8 deg more advance at idle . . . just about any engine will run better i.e. have better throttle response from idle just changing that.

    There's even more potential performance gains IMO by installing a unit like the Haltech units I've used or Nick's Electromotive where you can customize the advance curve. I've had all the way to 42 deg total advance with the stock low compression motor with no pinging. On a side note, I just put colder plugs in my high compression motor and I think it's eliminated any pinging on pump gas at 36 deg total advance.

    Sean
     
  18. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,341
    Remember, it's nearly impossible to detect pre-detonation in an engine running at 6000 RPM...(until after you've eaten holes in the pistons, that is).

    Even if you confirm the 802's will work properly in that car, I don't see it as a good alternative for most owners. All the various Digiplex units ever produced (801, 802, 803 & 805) are in finite supply and becoming extremely scarce to find new. And, the last price I saw for a new 801 or 802 unit was about $1600US / each --- so that's $3200 bucks for a pair.

    A good aftermarket unit (such as Haltech or Electromotive) is superior and costs less money ---- you can even put in a MoTec system for about $4000. These units are far better as they are programmable, utilize better electronics, and some allow the ability to add EFI later if desired. Plus, there are many tuners out there that have already worked out the correct maps for these systems to maximize the potential and reliability of the 308 engines.

    Furthermore, the electronics in the Digiplexes are crap by modern standards --- the circuitry and components are nearly 30 years old. They are prone to failure as well, so why spend 3200 dollars on something that will probably burn out in the end and give only mildly increased performance?

    Don't get me wrong, more power to you with your experiment --- you've already got the 802's so check 'em out --- I hope they work well for you. I just don't see it as a very marketable upgrade for the masses...

    Cheers
     
  19. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    I'm about to start my second Haltech conversion on 308 #2. I'm probably going to do just the ignition and then swap the motor out of 308 #1 to see how much difference the EFI is making over the K jet.

    The only thing I'd do different is the connection to the factory wiring harness . .. if people are interested, I'd consider making some custom plug and wiring schematic. When I converted car #1 over I ran the stock dizzy's and coils with the Haltech reading the stock triggers . .. you could not tell anything had been modified unless you removed the plate in the trunk area where it's mounted (same place as digiplex). I've seen the E6x which runs my fuel injection and igntion for as cheap as $700 brand new from an authorized dealer.

    Sean
     
  20. Jbryant

    Jbryant Karting

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    #17 Jbryant, Feb 5, 2008
    Last edited by a moderator: Sep 7, 2017
    Here is the different model 308’s and the different MED ECU’s. It looks like the largest difference between the MED 801A and the 802A is when the exhaust opens and closes. Only one degree difference in the total advance.

    So far, my 308 is running like a dream. I have to believe that my 801A’s were just old and giving up the ghost. I do not think that the 802A’s are really making that much of a difference in overall performance as having new components firing the spark. The car is running great and so far I have seen no negative effect.
    Image Unavailable, Please Login
     
  21. miketuason

    miketuason F1 World Champ
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    Jeff, this is a good piece of information, thanks for posting.
     
  22. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    The thing is the data in the table is different than what the curves show at 5000 rpm . .. maybe I'm interpreting the curve wrong. Anyone care to look at the curve?

    edit: the curves are way different . . . period. The euro's have 3 curves at different vacum point . .. the U.S. way more . .. look at the WSM
    BTW exhaust valve timing is nothing to do with 'em
     
  23. Jbryant

    Jbryant Karting

    Sep 23, 2006
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    I agree. The exhaust timing and the ECU are not connected. I do not have the WSM. Are you referring to the Work Shop Manual? The manual I have has no curve data in it. The only curve graph I have seen so far is for the Mondial in the owners manual. It has a graph and shows the 3 different curves. I believe that this data is showing the advance at idle to max power, but not under a load, next would be from cruise to max power then under a full load. I am not sure that this is a correct guess but it looks like that.

    There is a solenoid inside the ECU attached to the vacuum line. It has three connections attached to it. These three wires do produce different voltages at different vacuum loads. Maybe that’s how it works?
     
  24. luckydynes

    luckydynes F1 Rookie

    Jan 25, 2004
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    The WSM (yeah Work Shop Manual . .. Mondial 2V/4v) has the 3 different curves you are referring to for the 802's .. . and 6-8 for the 801's. The solenoid you're referring to is really a map sensor . .. the digiplex uses the advance curve based on the engine load/vacum reading by this sensor. The units in the WSM are mm hg for the different curves. A couple years ago I converted them to more familiar units and put them in an excel spreadsheet for other opinions before I programmed the curves into the Haltech ECU. I ended up putting the curves in backwards . .. had 42 deg advance at full throttle instead of full vacum. Had no pinging though with the stock compression but that's another topic.

    Not sure if the digiplex does this . .. the Haltech and E-motive sytems interpolate between the curves when the engine is "in between" the pre-programmed curves.

    Let me know if you want more info like a pic of the curves out of the manual (is it legal to post copies?).

    Sean
     
  25. Jimincov

    Jimincov Karting

    Jun 9, 2012
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    HI everyone - ive been having trouble with my 82 euro 2VI for a while and just removing the digiplexes I noticed that I have one 801 unit and one 802 unit fitted! from reading this thread it seems that that scenario is undesirable... the car seems to run ok for about 30 mins of driving (more or less sometimes - fairly random) but then seems to loose a bank and barely run - usually cutting out until left to cool for afew hours / over night.... what do you guys think? could I have found the culprit???

    thanks for any advice!
    james
     
  26. tinterow

    tinterow Formula 3

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    The two units aren't compatible. Can only be used in pairs...not mixed. Has this symptom been going on for a while or new?
     
  27. Jimincov

    Jimincov Karting

    Jun 9, 2012
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    ive been having problems with the car since Ive owned it - 4 years now! I had never completely removed the digiplexes before - I focused on usual suspects of ignition and FI parts.

    the 801 has a spare parts label on the back indicating it was probably fitted during my cars life in the states...
    quite relieved to have discovered this - I rarely used the car because of this problem and im hoping no damage has occurred to the engine.
     
  28. Badman

    Badman Formula 3

    Mar 4, 2007
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    FYI, Ferrari Service of Bedford in New Hampshire can rebuild your Digiplex boxes with all new components. They can rebuild to any spec, so they could take your two mismatched boxes and make them both 802A boxes, complete with new labels.
     

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