engine and drivetrain engine stumble at 5500 rpm resolved

[philv]

after the ignition checked out ok I thought that I might not be getting

enough fuel at higher rpm. maybe the floats were set to low? I checked the float setting and they were actually set to high or to much fuel in the bowl.

I spend about 30 minutes adjust/checking the level on both DCOE's and then

took her for a spin. car pulled strong all the way to redline and could have gone more. Anyone able to explain to me why my car would not want to

go about 5500 rpm with to much fuel in the bowls? The setting was not off

by a lot and it's not like fuel was running out of the carbs at anytime.

pv.

[Guest Anonymous]

Wild guess: Engine is more sensitive to float levels than you think. Can it be that float/s set too high, permit transitory "flooding"? In other words, as demand is increased and flow is increased, bowl level increases so that you have an overly rich situation. How is the extra fuel getting to intake? Spillage? Emulsion tubes are flooded and thus negated.

[c.d.iesel]

-=" AIR / FUEL MIXTURE RATIO "=-

TO much (rich-FAT) is bad

TOO little (lean) is bad

....keep tweeking till your pulling power is the strongest.

'when in doubt - Lean it out'

Go back to ignition timing WITH A TIMING LIGHT

Then return to your jetting.

Then when the outside temp changes by say 50degrees

from your present setting -Re-Jet all over again.

That's why fuel injection is 'better' than carbs - self compensating\for coolent temp, outside ambient temp, air mass, altitude,.......

[philv]

I think I'll tweak some more and see if I can improve on what I have.

Yep, FI is way better but I like dicking around with my old school webers.

[gone002]

That's why fuel injection is 'better' than carbs - self compensating\for coolent temp, outside ambient temp, air mass, altitude,.......

i would have to strongly disagree with you on that one.

i am fighting with a 318i and cursing the fuel injection the whole way

how could they take something as simple and pure as the m10,

and fuck it up with a bunch of dumb ass sensors and tubing, that is as hot and cold as my old lady!

fuel injection may have its benefits but user friendleness is NOT one of them

g

[satsuma]

I'm not familiar with webbers, I found this site its not BMW but it has a lot of info:

http://www.tjwakeman.net/TR/WeberDCOEinfo.htm

Second paragraph sounds similar? (1/3 way down the page, with diagrams)

By the time the engine has passed about 2800 RPM, the top edge of the throttle plate has passed all the progression holes and is opening wide enough to cause the vacuum to drop to where it is drawing progressively less fuel out of the progression holes. This is when the main cruise circuit needs to start kicking in so that the increasing level of fuel delivered by the main jets supplement the decreasing level of fuel supplied by the progression holes. The size of the auxiliary choke determines when the main jets will start delivering fuel.

If it kicks in too early (too small of a auxiliary choke) you get an over rich condition and the engine bogs or stumbles in the progression (or just wastes fuel with no noticeable symptoms). If the auxiliary choke is too large there can be a lean area where the progression openings are not delivering enough fuel and the main cruise circuit has not yet kicked in.

Ben