<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="">There has been discussion on this lately on one of the DCOE tuning discussion groups ("sidedraft_central" Yahoo group) and I learned a couple of things: If the sensor is too close to the exhaust valve, the sensor can overheat, give faulty readings and perhaps damage the sensor, so in that regard, too far away is better than too close. Most sensors have a heating element to keep them operating properly if they are far enough downstream that the exhaust gases are below the optimum level, so I don’t think distance from the exhaust valve is necessarily wrong. <div class=""><br class=""></div><div class="">The sensor has to be far enough from the outlet that the exhaust gases are not diluted by fresh air cycling back in. I don’t know what that minimum distance would be but my local dyno operator attaches a copper pipe to his sensor which he then inserts perhaps 18-20 inches into the exhaust pipe.<div class=""><br class=""></div><div class=""><div class="">I assume you already know that the sensor can get out of calibration of you disconnect the sensor from the gauge and then power it up, power it down, and then reconnect the sensor.</div><div class=""><br 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 30, 2016, at 11:25 AM, Marcel Van Mulders <<a href="mailto:van.mulders.marcel@telenet.be" class="">van.mulders.marcel@telenet.be</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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<div dir="ltr" align="left" class=""><font color="#0000ff" size="2" face="Arial" class=""><span class="384441017-30122016">Duncan wrote :".... how far downstream of the exhaust
valves is the Lambda sensor installed..." : this may well be the culprit. It is
installed at 130cm/4ft of the exhaust valves because of the long primaries and
secondaries of the exhaust. The Lambda sensor is part of the dyno. Exposed on
the open air it is reading 22.37 so I suppose it is working correctly. I can't
find any leaks on inlet and exhaust side. The engine is running sweetly and
crispy, so I wonder if I get a false ARF reading. Can the distance to the
exhaust valves have such an influence on the ARF reading?</span></font></div>
<div dir="ltr" align="left" class=""><font color="#0000ff" size="2" face="Arial" class=""><span class="384441017-30122016">In fact, also at lower RPM the ARF is much too
lean, but that can be corrected by turning out the idle screws way too far
(4 complete turns or more!), so I was misleading you by speaking of "leaning out
at the higher RPM."</span></font></div>
<div dir="ltr" align="left" class=""><font color="#0000ff" size="2" face="Arial" class=""><span class="384441017-30122016">Should I install the Lambda sensor in one of the
primary or secondary exhaust pipes (and check the spark plugs if they all get
the same mixture strength)?</span></font></div>
<div dir="ltr" align="left" class=""><font color="#0000ff" size="2" face="Arial" class=""><span class="384441017-30122016">Marcel</span></font></div>
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<font size="2" face="Tahoma" class=""><b class="">Van:</b> Duncan Charlton
[<a href="mailto:duncan.charlton54@gmail.com" class="">mailto:duncan.charlton54@gmail.com</a>] <br class=""><b class="">Verzonden:</b> vrijdag 30 december
2016 13:53<br class=""><b class="">Aan:</b> Van Mulders Marcel<br class=""><b class="">CC:</b> Duncan Charlton via
Fot<br class=""><b class="">Onderwerp:</b> Re: [Fot] TR6 race engine with 45DCOE triple
Webers<br class=""></font><br class=""></div>
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<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>
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<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.
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<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>
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<div class="">
<div class="">Duncan Charlton</div>
<div class="">Elgin, Texas USA</div>
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<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">
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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
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