[Monsterlover]

How do the fuel injected Ducs maintain a nice a/f ratio? Are they a mass air metered setup, or a speed density with a map sensor? Ive read a lot here, but haven't seen anything about this particular subject. Thanks!

Kevin

 

[Guest]

Duc's work on the throttle-speed theory. basically rpm and throttle position to reference a fuel map.

 

[Speeddog]

What Retro said, plus...

The recent Ducs with the IAW 5.9 ECU use ambient air temperature, ambient air pressure, and either coolant temp on the S4's or oil temp on the air-coolers to tweak the mixture.

On my S4, it seems to work pretty good. If I 'hot soak' it, it seems to run a little off, but that may not be due to the FI, it just may be the way it runs after a 'hot soak'.

 

[Monsterlover]

Duc's work on the throttle-speed theory. basically rpm and throttle position to reference a fuel map.

Hmm, sounds like speed density to me. No MAP sensor though?

Kevin

 

[Guest]

Duc's work on the throttle-speed theory. basically rpm and throttle position to reference a fuel map.

Really? So there is nothing that meters airflow, like a mass air sensor, or a "barn door" or anything like that?

That almost seems too simple. I wonder why all cars have to have some kind of air flow sensing device.

 

[Guest]

There are 16 engine speed points and 16 throttle position points. The computer checks the throttle position-engine speed, evironmental sensors, user trim, battery voltage, ignition, and compares (senses) this against a table to come up with a fuel pulse duration and ignition timing. there is a comparison table for engine speed and throttle, a table for the sensors, and a table for the ignition.
There is also a offset map for the rear cylinder in there somewhere.
for a better explanation check here:
http://www.sigmaperformance.com/weber.html

another intersting blurb.
http://msting.gixxer.com/fi.html

 

[Guest]

Very interesting - thanks for the link!

 

[Speeddog]

To clarify:

No Manifold Air Pressure sensor.
No Mass Air Flow.

AFAIK, most new cars are like our Ducs, throttle position and RPM are the main signals. Much cheaper per car (or bike) to not have a Mass Air Flow sensor.

And it keeps us hot-rodders from messing with the motor ( ;D ), as the MAF systems (like on my Merkur XR4Ti) can compensate for limited improvements in airflow.

 

[krista_k]

actually, most cars now have closed loop efi with O2 sensor monitoring things. current bike efi technology is in the late 1970s, car wise. some ofthe newest stuff is catching up, though.

chris

 

[chaf]

Duc's work on the throttle-speed theory. basically rpm and throttle position to reference a fuel map.

As an aside, the BMW car people refer to this configuration as "alpha-N," don't know how widespread the term is. All I know is, it's my very favorite way to meter air and fuel. Of all the FI vehicles I've ever driven, the two best-behaved ones (no funny glitchy behavior) were my old BMW 2002tii (mechanical alpha-N system) and my M750.

M.

 

[chaf]

AFAIK, most new cars are like our Ducs, throttle position and RPM are the main signals. Much cheaper per car (or bike) to not have a Mass Air Flow sensor.

Speeddog, how sure of that are you? The story I always heard was that using the throttle-position technique ("alpha-N," whatever) was great for driveability and power, but not so fantastic for emissions, since that setup didn't let you run quite as lean as with a MAF. However, I've been out of the loop (Loop! Oxygen sensor! Ha! I kill me) for quite a while on the new stuff; they may have gotten it figured out.

M.

 

[Speeddog]

My info is about 5 years old, but it was from folks who were very tight with Toyota in Japan.

I could be wrong and/or quoting ancient history. It's happened before....

 

[Guest]

Another aside I am guessing not all Duc's have 16 points on throttle and rpm. Some may have more, and some less I suppose. I am guessing Ultimap stuff is again quite different also.