[Fot] TR6 race engine with 45DCOE triple Webers

[Greg Solow]

    I'll try this again. am having trouble sending to fot. 
   The f-16 emulsion tube is a very lean tube, it is often hard to get a rich enough mixture with this emulsion tube. Try using f-11 or even f-2 emulsion tubes. Start out with 145 main jets and 165 air correction jets. This should get you close. The 36mm chokes should work fine. On my Morgan with a 2187cc full race engine I use 40 mm chokes & every time we went bigger we made more power with no loss on the bottom or an rpm range that is 4,000 to 6800 rpm on the track. 
      The pump jets are probably to large. Try 35 pump jets and install pump inlet valves with a 70 bleed hole in their side.  The pump jets acts as part of the "high speed enrichment" circuit of the carb at high rpm at WOT.  I think that the idle jets are also to large. Try 45 f8 or 45 f6 idle jets. The idle jet size is correct when the best lean idle is achieved with the idle mixture screw between 1/2 and 3/4 turns out from fully seated.  You may even be able to go down to a 40 f6 idle jet. This will help prevent plug fouling around the pits and on the pregrid. 
      Ignition timing should probably end up around 32 degrees total mechanical advance with the engine running at 4,000 rpm and higher. 
     Make sure you have cold enough plugs in the engine. I should probably use the equivelant of Champion C61YC or C59YC racing plugs if the CR is 12.5:1.  C59yc on the dyno, c61yc on the track. 
                                                                          Good Luck, 
                                                                              Greg Solow
  ----- Original Message ----- 
  From: Van Mulders Marcel via Fot 
  To: fot at autox.team.net 
  Sent: Thursday, December 29, 2016 1:45 PM
  Subject: [Fot] TR6 race engine with 45DCOE triple Webers


  The engine for a friend's TR6 racecar is finished at last and it has run a couple of times now.
  I have a problem with the mixture : the air correction jets are 155, I started with 140 main jets but the mixture was much too lean : AFR was 14 at idle and 17 at 5000 rpm. Even with 180  main jets, the AFR  is still 15 at 4000 - 5000 rpm. The engine is 2720 cc and 12.6 volumetric CR.
  The Webers are secondhand, 45DCOE type 152 and they look as new
  The venturis are 36mm, emulsion tubes are F16, idle jets 55F8 and aux. venturis are 4.5. Pump jets are 40 without a bleed hole. The plugs have a correct colour, no sooting, no signs of overheating. The engine is on a dyno but I didn't risk so far to really load the engine, so the plugs doesn't tell much. The lambda sensor is a wide Bosch sensor, about new and with an Innovate controller. I suppose 180 main jets are already too big. I can't find any air leaks and the spark plugs have all the same colour. Is it possible that 36mm chokes are too big? Any idea's why the mixture can be too lean, even with 180 main jets? Should I suspect the lambda sensor/Innovate controller? What venturis should I start with? 
  Another question : I have no experience about the range of total ignition advance a full race TR6 engine does need.
  Marcel 


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