[Diy_efi] Air/Fuel meter now working! And L-jetronic
espresso_doppio at yahoo.com
Thu Jun 16 16:10:16 CDT 2005
--- Astrona <amdcpu at hot.ee> wrote:
> What about 80's Saab, Volvo turbos?
Ah, those were the LH-Jetronic, which used a hot wire
> AFM's act when pressure-differential is present.
That's one way of looking at it, but it doesn't really
capture the point of what it is doing. It's measuring
the speed with which air flows past the plate.
However, the only way the ECU can know how much air
mass is getting past is to know the density of said
air. If you were using a flapper-type VAF sensor
(which you call an AFM, confusing since many people
refer to a WBO2 as an "AFM"), you'd have to measure
the temperature and pressure of the air that was
passing the VAF; this would require taking these
measurements inside the plenum.
> So in constant 2bar they are shut.
ITYM "open", but that is not the case unless the
engine is flowing more volume (not more mass!) than
the VAF is designed for.
> Maybe they have AFM at the atmosphere-side and are
> "reading" air volume at 1 atm.
Since pressure varies greatly in the plenum, and not
in direct relation to either throttle position or
engine speed, you'd be getting an imprecise at best
measure with which to compute ingested air mass.
You'd have the same problem with a MAF located
pre-turbo. A MAF between plenum and throttle body
would be better, although it seems to me that it would
be less and less precise as the boost rose.
| 82 Honda CX500 Turbo (Cassandra) 90 Kwak Zephyr 550 (Daphne) |
| "It was like an emergency ward after a great catastrophe; it |
| didn't matter what race or class the victims belonged to. |
| They were all given the same miracle drug, which was coffee. |
| The catastrophe in this case, of course, was that the sun |
| had come up again." -Kurt Vonnegut |
| M/C Fuel Inj. Hndbk. @ Amazon.com - http://tinyurl.com/6o3ze |
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
More information about the Diy_efi