Weber DCOM's go lean on hard right, rich on hard left

[Stevenola]

Hello, I have a BMW M30 with triple DCOM's.  I have an issue where if coasting along in neutral and I either turn left or right at speed the carbs go rich or lean respectively.  If I turn hard enough right, it will go so lean that it can stall (18:1 ish), or at least enough to trigger the idiot lights.  Turning left goes rich but not a stall issue.  I have:

-proper float height at 26mm below the deck
-Carter 4070 high volume pump regulated at 2.8psi
-the proper DCOM jets (55F17 idle, F47 emulsion, 140 mains etc)
-throttle plates set correctly just covering the first progression hole
-50mm trumpets with foam filters

I've tried richening up the idle jets/mix screws which helps a little but obviously the engine then runs like crap otherwise, and will go even richer on the left turns.

If the car is in gear on throttle the issue is not noticable other than a slight change in AFR either way, it only happens when the throttle plates are closed at idle rpm.  It would appear that the g-forces in these turns are either forcing or starving fuel in the idle circuit somehow.

Otherwise the engine runs great.  Is this a DCOM thing?  Any ideas?

Thanks much.

[Nick Jones]

Not my specialist subject….. but you appear to have covered all of the things I would have suggested (and more), especially the float height.

So I’m thinking it maybe a feature (albeit an irritating one) rather than a fault - most likely due to fuel surge in the float chambers. Any effect from braking?

[Stevenola]

5 minutes ago, Nick Jones said:

Not my specialist subject….. but you appear to have covered all of the things I would have suggested (and more), especially the float height.

So I’m thinking it maybe a feature (albeit an irritating one) rather than a fault - most likely due to fuel surge in the float chambers. Any effect from braking?

Braking is fine.  I've also enlarged the main stack fuel take-up area in the bowls (since the idle circuit draws from the stack in DCOM's) and also put in a baffle to keep fuel around the stack intake in turns, no luck.  I also have the top cover gaskets without float cut-outs to minimize splashing, no luck.  Thanks.

[Nick Jones]

I take it this is you?

https://www.alfabb.com/threads/weber-dcom-and-hard-turns-question-for-the-experts.720327/

[Stevenola]

1 minute ago, Nick Jones said:

I take it this is you?

https://www.alfabb.com/threads/weber-dcom-and-hard-turns-question-for-the-experts.720327/

Yep that's me, the only one in the world with this problem

[Nick Jones]

8 minutes ago, Stevenola said:

Yep that's me, the only one in the world with this problem

Frustrating. I see you did try raising the float level (25mm vs 28mm) and it led to fuel escape under some conditions, but you don’t say whether it helped the “going lean”problem? If it did, have you ever tried anything between those float heights?

You also mentioned that the manifold tilts the carbs to miss other parts, does that mean they are not horizontal across the car?

[Stevenola]

1 minute ago, Nick Jones said:

Frustrating. I see you did try raising the float level (25mm vs 28mm) and it led to fuel escape under some conditions, but you don’t say whether it helped the “going lean”problem? If it did, have you ever tried anything between those float heights?

You also mentioned that the manifold tilts the carbs to miss other parts, does that mean they are not horizontal across the car?

Float level adjustments didn't affect the issue.  Yes my manifold tilts the carbs up a little, but doesn't appear to be more than the tilt recommended by Weber (5 degrees??) but since nothing else has worked that is still a possibility.  I would think that with the rear of the carbs tilted toward the manifold that this would reduce the effect of fuel being thrown away from the idle circuit (having to travel uphill) but I am definitely not a fluid dynamics scholar!