Ok guys, i'm putting this here cuz you're the ones who know. I'm having trouble thinking of how to describe this question, so bear with me.
Does MAP vary with outside temperature. Meaning, during the summer do you average lower MAP readings then during the winter.
I know, the MAP is a pressure sensor, but i have a funny idea about higher barometers going along with the better air in the cold.
The reason i'm wondering is in relation to my MAT bypass. In case you didn't see my other post, i'm currently using 20k of resistance to the MAT (on a DT switch so as to easily return to stock), mimicking 10' intake temp. Theoretically that would seem to make me run way too rich, but it runs great like this. If i flip the switch during a WOT, i can feel it SOTP. And so far it's worked fine even on the few warmer days we've had here.
So what i'm wondering is if maybe a slightly lower MAP reading would take a little fuel out on a warm day compared to a cold day, to compensate for the extra enrichment of the MAT bypass.
make sense to anyone...ed

ps, i'll be burning proms soon enough, then i can get rid of such kludgy tricks. But for now it seemed like a good idea.

------------------
Ed Maher - Moderator @ The Carb Board
92 Z28 Convertible - Quasar blue / Tan top
LB9 4L60 GU2 G80 - stock, soon to be sleeper

- Definitely prototypes, high powered mutants of some kind. Too weird to live, too cool to die

 

MAP
Manifold Absolute Pressure.
You have two corrections, one fuel one timing, both should vary by MAT. Depends on calibration thou.
No need to Kludge too get things right.
SOTP is guessing.
With no MAT you need more timing in hot weather.
Better to recal the chip, then hammer it, with mechanical *aids*

 

I know i'm a butcher mechanic. I need to resist frankensteining this car and get on with the real projects, get a burning set-up and port the plenum.
And i know SOTP is guessing, but in the meantime it will do. With the stock MAT i am definitely getting some detonation, flip the switch and it dissappears and runs better. Of course this 10' simulated MAT will probably make me run like hell in top-down weather.
Hell, for all i know the fuel filter is cloged and dropping pressure at high rpms, and my kludge resistor is increasing the PW enough to compensate.
You wanna hear something funny...i'm a circuit design engineer for ASICs that fly in all kinds of satelites and the NASA pathfinder mission, and the upcoming X2000 stuff. Scary what they'll let a butcher like me touch...lol. Then again, with all the disorder thats been piling up around here, i fit right in, a sane person would run away.
...ed

 

>With no MAT you need more timing in hot >weather

Is this to start the burn earlier because of a lean or rich condition, or something completely different ? Lean slower burn is my guess. How much closer will the higher inlet temperature put the motor to knock is my other question ? You only talking a degree or two additional timing or more ?

Thanks
Paul

 

depends on the calibration, your using. You can generally cover things with 2-5d of timing, but when ya start geting close, you can see a table of like 10d of timing.
It's just recovering *effective* compression from the already less dense air.