[Fot] TR6 race engine with 45DCOE triple Webers

Mon Jan 2 23:12:05 MST 2017

Marcel,
The balance tubes were probably there to try and
equalize the vacuum pluses  to the brake vacuum
booster.  connecting the throats with a 1/16" tube is
sometimes done to run vacuum advance on the street
for better fuel economy. As you have already found,
in a race application, Weber carbs are designed to be
used as one independent throat or choke for each
cylinder and they should not be connected together in
any way. 
     The cam ini this engine is what I would call a
VERY radical design in terms of total duration. I
would expect the engine to feel like it "comes on the
cam" at nearly 5,000 rpm and will have very little
torque at much below 4500 rpm.  The power band should
extend well beyond 7,000 RPM.  The problem is likely
to be keeping the engine together in the high and RPM
range.
      Your friend might be better off with a cam
having duration closer to the 298 to 302 degree range. 
                                                 Greg
Solow

Greg Solow
The Engine Room
Sports Car Specialists
Santa Cruz, CA 95060
831 429-1800

------- Original Message -------
>From    : Marcel Van
Mulders[mailto:van.mulders.marcel at telenet.be]
Sent    : 12/31/2016 6:22:38 AM
To      : Gregmogdoc at surfnetusa.com
Cc      : fot at autox.team.net
Subject : RE: [Fot] TR6 race engine with 45DCOE
triple Webers

Maybe I have to add something about the inlet manifold 
: it has a 1/2" diameter balance pipe connecting the
six inlet tracts : can this 
lean out the mixture, regarding the  320° (at 0.016")
camshaft? At 0.050" 
lift, it is 268°.
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 
  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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