Marelli advance curve figures

Discussion in 'Discussion Forum' started by NEG, Sep 23, 2019.

  1. NEG

    NEG True Classic

    Location:
    UK
    Does anybody have a list of advance curves for Marelli distributors, IE: S155AX, LX, S135, S178 etc.

    Many thanks!
     
  2. ghostdancing

    ghostdancing True Classic

    Location:
    italy
    unfortunatelly i dont..BTW: are you working on a particular ignition tuning of your motor? i'm currently playing with advance settings on my 128 and interested on the matter..
     
  3. NEG

    NEG True Classic

    Location:
    UK
    I’m also curious about timing and I'm questioning if my car has the correct distributor fitted (S135). There are some notes on EurosportUK that indicated it should be fitted with an S155 distributor, an AX version. I wanted to compare the advance curves of the two distributors and any other compatible variants. I know the S178 has max advance of 28deg @5500 but that’s probably not steep enough for the 1300 which should be 28@4500
     
  4. I've been playing quite a bit lately with advance curves, and have been doing some reading on the subject. For performance applications, you might choose something quite a bit different than stock. When I got my cam, it was recommended that I go with a static advance of 20 degrees. I thought that was a bit much, but a number of sources confirm that long duration cams may prefer it. Mine seems quite happy with it. The other thing I was told by the cam supplier was to get to full advance by ~3,500 rpm. I was initially targeting in the 30 - 32 degree range total advance but based on some of the information I found, up to 38 to 42 degrees may be advantageous for low compression engines (8.5:1) like the X. Right now, I've got mine set for 20 degrees static (and up to 1,000 rpm) with ~39 degrees above 3,500 rpm. It will quickly wind the tach off scale if I let it with no evidence of pre-ignition on regular gas. If you are running premium, you might go for a few more degrees as it burns slower.

    I've been experimenting with the curve on my Ducelier distributor (1974) and it is not too difficult to adjust the curve other than having to pull the distributor out every time (I've gotten pretty quick at it) since I don't have one of those Sun machines. I plan to replace it with a Bosch distributor out of a 79. Unfortunately, the carb Bosch distributor for the X has way too much advance and too late. The FI cars got a more suitable curve. If anybody has recurved a Bosch I'd be interested in the procedure and the availability of springs, weights, and advance stops for that model.
     
  5. Integrale

    Integrale Daily Driver

    Location:
    Davenport, IA
    This from a 1978 Australian manual.
     

    Attached Files:

  6. ghostdancing

    ghostdancing True Classic

    Location:
    italy
    Don, didnt understood your math: 20° static + 28° full "dynamic" advance = 48°total advance..?
     
  7. NEG

    NEG True Classic

    Location:
    UK
    I think Don has adjusted his centrifugal advance to give less than the normal 28deg

    @Integrale thanks, I have that document but had forgotten about it!
     
    dllubin likes this.
  8. NEG

    NEG True Classic

    Location:
    UK
    My distributor is simple stamped S135 no suffix letters.

    I mapped it today as accurately as I could, so this is approximately within the accuracy of my timing gauge and revs etc.

    Total advance
    Idle 8
    1500. 20
    2000. 25
    2500. 27
    3000. 30
    3500. 33
    4000. 35
    4500. 38
    5000. 41
    5500. 43

    I don’t think this is correct, it’s not that far out up to 4500 but overall it seems a few degrees too much and doesn’t top out until 5500 RPM

    Either it’s the wrong distributor or the springs are tired.
     
    Last edited: Sep 24, 2019
  9. 20 + 19 = 39
     
  10. ghostdancing

    ghostdancing True Classic

    Location:
    italy
    my car (128 coupe 1300) had the OEM S135 fitted, i swapped it with a marelli SE100CX (breakerless), and it works really better (i guess the old dizzy was very tired tough)..now i'm in the process of making some test with the static advance\vacuum..generally i found that more advance= better low rpm oomph, but engine stall\become rough around 4000-5000; less advance=nice fast revving build up (wow: feels like a japan 4 cylinder bike!), but lazy before 4000..would be nice to get both worlds.. but looks like is not so easy
     
  11. Sounds like you may have too much total advance if your optimal low speed advance results in too much high speed advance. That is the issue I had so I needed to keep the centrifugal advance mechanism from moving too far.
     
  12. NEG

    NEG True Classic

    Location:
    UK
    Interesting.

    I pulled the distributor and found some marks on the base which says it’s a S135F. Which is curious because the curve at the top end is different to the one in the Australian service manual.
     
  13. ghostdancing

    ghostdancing True Classic

    Location:
    italy
    so Don how you made this modification?
    @NEG for recording that advance\rpm data you simply used a timing light ? guess the one with advance regulation+ built in rev tacho (i.e. the expensive one)?
     
  14. ghostdancing

    ghostdancing True Classic

    Location:
    italy
    ..another problem: the vacuum..in my dizzy it produce a max advance of 12° (max manifold vacuum should be at idling\throttle closed with the car running?) but i know that the old ducellier (points) had a retarding vacuum..maebe that's why when you disconnected the vacuum it resulted in too much centrifugal advance?
     
  15. NEG

    NEG True Classic

    Location:
    UK
    Yes, one with an advance dial on the back
     
  16. ghostdancing

    ghostdancing True Classic

    Location:
    italy
    NEG, regarding the difference S135- S155, as far as i know the 155 is the newer version: the car that came with the 135 in the first '70s (128, x1\9, 127, later had the 155 fitted from factory (from late'70s)
     
    NEG likes this.
  17. NEG

    NEG True Classic

    Location:
    UK
    Ok, again, that is interesting, mine is from ‘78 so maybe it should have an S155. This would agree with the notes on EurosportUK.
     
  18. Yes, I was using a timing light with an advance knob on the back. The Ducelier distributor has a lot of centrifugal advance to compensate for the vacuum retard. I created an advance stop by using a heavy spring filled with JB Weld that creates a rigid link. The outer hook on the spring is connected to a post. You can bend the post to control how much advance you can get. Seems to work OK.
     
  19. ghostdancing

    ghostdancing True Classic

    Location:
    italy
    @NEG: accordingly to the italia x1\9 forum guys this breakerless marelli dizzy is the one that fit the x with no problems (short body):

    https://www.ebay.it/itm/SPINTEROGEN...hash=item469ae5cdad:m:mnQ0ih_Mfnx2l0DqX0Z7d2Q

    the other option (to go breakerless with new parts) is a remanufactured bosch sold by rockauto, the bosch is known to be very relialable

    another way to play with advance curves (that looks to be an all inportant matter to have the small 1300 perform well): how about programmable electronic advance devices? i guess there are available in the market, correct?
     
    NEG likes this.
  20. NEG

    NEG True Classic

    Location:
    UK
    Many thanks ghostdancing, what else is needed to get that working?
     

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