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Message
Maybe you’re comparing apples and cherimoyas.
After a brief Google search, I now know what a
cherimoya is.
Measuring MAP at the downstream end of the TB “runners” is
different than measuring out in the air plenum before any losses. It is
difficult to believe there is 4” drop, but until we have some other
measurements, we don’t know for sure. On my dyno runs I also measured 26”
at 6200 WOT.
As I understand it, the
ideal situation would be to have a TB, that feeds into an air plenum, then
individual runners from there to the engine. It sounds like the only place
you can get a true, overall MAP reading is in the air plenum itself. I'm
guessing that it's difficult to get a good reading in the TB bore, due to the
speed the air is moving. Trying to sense the MAP after a restriction
(downwind end of the runners) will be a different, but still interesting MAP
reading.
It seems to me that the
gold standard of MAP readings almost requires a reading to be taken in the
plenum, and only then will it conform to the expected 30" at WOT. My
theory is that our TWM readings are perfectly usable for tuning, and as a
reference number, but will never see 30" at WOT due to the construction of the
port, and velocity of the air inside the TB. I could certainly be
wrong, and I'd love to pick up an extra 4" MAP, but I can't see that
happening.
What is the orientation of your TB – MAP line coming off the top of the TB or
off the bottom?
Port off the top.
Cheers,
Rusty
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