Hi Mark,
I can tell you what I run in my MGA and Lotus super 7.
I have found that a good lean goal is 12.5. that is 1250 deg Farenhieght. I try
to keep 13 as a top end goal as I use alluminum pistons and 14 as the max.
Beyond that the pistons risk getting fried and will pitt and actualy melt
leaving holes in the pistons. As you can imagine the holes do not help the
compresion ratio. The thing to remember is that temperature, humidity and air
pressue all efect the fuel air ratio and therfore the exhaust temperature. I
can tell you that I was running the 7 at 13 spot on all summer and then went to
VIR for the fall finaly with SVRA. I love the track and SVRA is a great group
so I really like the event. However when the mist comes off the track at 8:00
in the morning and it is about 46deg (as it was last fall); when I take the 7
out for her morning dance on the tarmac I practicaly get cross eyed from
watching the egt's at the end of the straights since they will bang right up to
14.0. However after the engine suffiently warms up the air thins into the carbs
and the EGT;s fall back to about 13.5, if not I have to stay off the juice (or
stop and re-jet the carbs) . The only place to take the readings by the way is
at the end of the strainghts as the sensors foul at the low revs and lower
loads, and you are seeking the max temps anyway.
I have also been told by some respected engine builders that teh EGT are not
teribly accurate and that one should trust more on the color of the plugs, the
briliance of the exhaust note etc.. but the engineer in me simply cannot resist
the imediacy of the EGT readinings.
BIll B
PS: I have a question about suppliers: I am rebuilding a GT6+, I ned to buy
just about every moving part. I am currently sorting out the suspension. Who
has the best parts. I have heard taht some of the British parts supliers are
actualy remanufacturig parts in ASIA and they are inferior. Sice the suspension
parts are important to ones health I want to buy the best and do not car to
save $25 to take the risk another front upright might fail. The suppliers I am
curently considering are
1. Victoria British
2. Spit Bits
3. Dave Bean Engineering (Lotus)
I have included Dave Bean since many of the Lotuses used GT6 parts. Does anyone
have any feedback on who has the best parts?
Thanks
Bill B
-----Original Message-----
From: MARK J WEATHERS [mailto:markjwea@email.msn.com]
Sent: Sat 2/1/2003 8:53 PM
To: fot@autox.team.net
Cc:
Subject: EGT
Amigos.
Greetings from sunny Phoenix where it is over 80 degrees today.
Speaking of
temperature, on my last rebuild I installed temperature sensors in each
branch
of my header close to the head for purposes of collecting data on EGT.
With
this accomplished, I realized I have no idea how to optimize mixture
based on
EGT. I have heard higher is better but certainly a lean running engine
is
going to produce a pretty hot exhaust stream. Can anybody point me in
the
right direction? I had an O2 sensor and mixture gage hooked up to the
collector but I never got any readings that made sense relative to plug
appearance. I think it may have been too cool that far down the exhaust
to
work.
Thanks
TR6 Mark
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