<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class=""><div class="">How far downstream of the exhaust valves is the Lambda sensor installed, and how far from the exhaust system outlet is it? You mentioned having checked for air leaks, but didn’t say whether you checked both intake and exhaust. Is the dyno operator also using a lambda sensor?</div><div class=""><br class=""></div><div class="">This comment is not specific to the TR6 but since it’s leaning out at the high end I would have initially guessed that your air correction jets are too large, but one typically expects the AC jet to have a number about 50 higher than the main jet, whereas your AC jets are nearly the same number as your original main jets and a lot smaller than your second main jets choice.<div class=""><br class=""></div><div class="">According to the Weber choke selection chart the 35mm chokes correspond to a maximum output of 6000 rpm so 36mm seems fine unless the engine’s desired max output is a lot higher than that.</div><div class=""><br class=""></div></div><div class=""><div class="">
<div class="">Duncan Charlton</div><div class="">Elgin, Texas USA</div><div class=""><br class=""></div><br class="Apple-interchange-newline">
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<br class=""><div><blockquote type="cite" class=""><div class="">On Dec 29, 2016, at 3:45 PM, Van Mulders Marcel via Fot <<a href="mailto:fot@autox.team.net" class="">fot@autox.team.net</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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<div class=""><font size="2" face="Arial" class=""><span class="885500321-29122016">The engine for a
friend's TR6 racecar is finished at last and it has run a couple of
times now.</span></font></div>
<div class=""><font size="2" face="Arial" class=""><span class="885500321-29122016">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.</span></font></div>
<div class=""><font size="2" face="Arial" class=""><span class="885500321-29122016">The Webers are
secondhand, 45DCOE type 152 and they look as new</span></font></div>
<div class=""><font size="2" face="Arial" class=""><span class="885500321-29122016">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? </span></font></div>
<div class=""><font size="2" face="Arial" class=""><span class="885500321-29122016">Another question : I
have no experience about the range of total ignition advance a full race TR6
engine does need.</span></font></div>
<div class=""><font size="2" face="Arial" class=""><span class="885500321-29122016">Marcel
</span></font></div></div>
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