[Fot] TR6 race engine with 45DCOE triple Webers

Sun Jan 1 05:03:50 MST 2017

Plugging the balance pipes (1/2" diameter and between every inlet tract of
the manifold) did solve the problem : at WOT and 5000 rpm the AFR went down
from some 16 with open balance tubes to 10.2 with plugged tubes, both with
180 main jets wich have now prooved to be too big. The cold engine does
start easily know. With the open balance pipes, I had to crank the engine a
lot :  the engine was running a second and stopped. (accelerator pump).
Probably every single cylinder did suck mixture from the other inlet tracts
too, via the balance pipes, thus weakening the signal at its own Weber
tract?
Are we in 2017 now?
Marcel

  _____  

Van: Greg Solow [mailto:Gregmogdoc at surfnetusa.com] 
Verzonden: zaterdag 31 december 2016 01:48
Aan: Van Mulders Marcel; fot at autox.team.net
Onderwerp: Re: [Fot] TR6 race engine with 45DCOE triple Webers

The F-16 emulsion tube are very lean throughout the rev range. try either
f-2 or f-11 emulsion tubes.  begin with 145 main jets, and  165 air
correction jets. the larger the air corrector, the leaner the mixture. I
think that the pump jets are to large. Try 35 pump jets and pump inlet
valves with a 70 bleed hole. The pump jets acts as part of the "high speed
enrichment system" but you need the bleed or else the pump squirts in to
much gas and can make the car bog or resitate coming out of corners. The
idle jets are to large the the cylinder size. Try 45 f-8 or 40 f-6 idle
jets. you may be able to go down to a 40 f-6 idle jet. This will help keep
the engine from fouling plugs around the pits. 
       Part throttle mixuture reading do not mean much to me. Most of my
experience has been WOT on the dyno where you want a "brake specific fuel
consumption" figure of around .50 lbs of fuel per horsepower per hour.  Part
throttle operation has to do withj "drivability" and not fouling plugs. You
would generally want the engine to run as lean at part throttle as it can
run without constant backfiring in the intake manifold. 
       Make sure you have spark plugs in the engine that are cold enough to
work with the compression ratio of the engine.  An engine with 12.1:1 will
need a Campion Racing plug with a heat range number like  C 61YC. On the
dyno you might start with an even colder plug like  C59YC. just to make
extra sure that you stay away from detonation. After getting things more
dialed in, you can probably go to the warmer plug. 
                                                                   Good
Luck, 

Greg Solow      

----- Original Message ----- 
From: Van Mulders  <mailto:fot at autox.team.net> 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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