Why would Honda ?

[Phil Lamovie]

Hi All,

> Why would Honda put the MAP sensor just behind the throttle
plate?

Good question. I guess from the tone of what you wrote that you
suspected that this could be an issue.

I agree with you it probably is. They could of course have a
table of correction factors for air temp vs non linearity vs
volume.

Next issue is why are they using an ambient sensor ? Doesn't the
engine
know what air pressure it is subject to ?

To help with the lack of load points you can interpolate with a
calculator and save your precious clock ticks for real work.

If zero vacuum at 5,800 or so needs 12.5 ms per intake have a
look at the
advertised torque curve and overlay it on your fuel map.

Absolutely no desire to make fun Sorry. Only bad manners on my
behalf.

> For a race car calculating a new injector value PW every stroke
may be a
> requirement but is that really needed for marine or aircraft
> applications?

Yes. and on second thoughts  Yes.

If the calculations are done per cycle then the sudden throttle
and/or
load change will encounter maximum of 2 bad combustions.

Now that probably sounds excessively picky but if your engine
goes from
250 hp to 125 hp in 1 revolution and then back again the stress
cycles on the crank are enormous. Even bailing wire has a cyclic
strain limit.

Question ? Who blows up all those F1 engines.

1.  CNC machines that can't tell a thou from a foot

2. ECU (read software) that can't keep up with the engine ?

3. Other


Try creating a 4 byte map.

MAX. Vacuum  1000 rpm    Max Load  1000 rpm
Max vacuum    6000 rpm    Max Load 6000  rpm

if you interpolate b/w these 4 points and each on it's own is
correct
then you will be on average spot on. (This doesn't include
camshaft timing alterations) this would require the 6 point map.

By 65,000 points I didn't mean memory locations I meant possible
calculated values from rpm 8 bit X vacuum load 8 bit.

thus 255 x 255 = possible outcomes.

You will at some stage have to get those 4 measurements as they
are the basis for all further corrections.

Full load 6000 rpm is easy just pull the stick all the way and
the prop will do the rest.

Full load 1000 rpm has more air  per cycle than 6000 rpm so give
it 10% more

Light load 1000 needs the rubber band to be removed.

Light load 6000 needs about 10% less.

say   14.0   12.5
            2.2     2.0

This of course brings us to the point of when or if your system
is crossing over from injecting once per revolution at light load
to once every second at full load into focus.

The differential b/w light and full load is on average 350%
i.e. 2.0 - 6.5 ms. You need to investigate this further.

There ! that's  4 bytes of eeprom all used up.

You have only to get rpm from the timer ticks vs a single A/D
Vacuum Load and you are ready to go. Your last air, water and
accel corrections are waiting from the last stored calc. apply
these and squirt.

Given a 1 mHz internal clock and 6000 rpm you have 10 ms or
10,000 clock cycles to get this done. say 2000 instructions
executed
at worst.


 P.S. if this to and fro is boring the pants of others please
chime in and tell me firmly.

TTFN


 Regards

 Phil Lamovie

 injec at ains.net.au

     cogito ergo zoom