45DCOE Weber idle circuit jetting

[wagoner]

Hi Gents,

I’ve searched and read and searched some more... but not quite found the answer. 

Issue is around idle jets. I’m running lean on progression - despite having 55F9’s. Next up is 60’s, they seem very large for a 2L. Please read below and tell me if I’ve missed something?

Here is the setup I’m running 
 

Motor is a fresh 2L m10 with 10.5:1 compression, schrick 292, 123ign dizzy, ported E12 head, valve job, new bavaria mech pump, headers and a pair of new 152Gs, AEM wideband also installed

Weber specs: 
5.0 AV

36mm chokes

155 mains

F9 emulsion

55F9 idles

180 air correct 

40 acc pump

70 acc bleed

2.25 needle

Floats set & checked 12mm

Fuel pressure is fine

 

No static timing. Runs 16 degrees at idle on the 123. Timing mark is correct. 
24 degrees at 1600

28 degrees at 2400 then flattens off whilst I’m getting the fuel tune sorted. 

Edited June 7, 2020 by wagoner

[uai]

What Airfilter are you running?
I have jetted my car these days running trumpets and it was ok, then added the filter and it was absolutely impossible to get over the lean transition only WOT or near to no throttle.
I still haven't figured out how to set it up - my next try is testing a couple of alternative Air filter setups to see what best matches...
What helped narrowing it down is the TPS I've added. Because the difference between Pedal feel and throttle position is immense- you think you're at some throttle but in true world you're still in the progression holes.

 

 

 

The built nk airbox with cold air intake snorkel didn't work at all - it had a Ram air effect - I had the fuel bowls connected to the airbox but that doesn't help. With or without filter - no difference. When the snorkel is on the airbox - no transition only lean as hell. Without the snorkel it's driveable it's still far from good.

 

Edited June 7, 2020 by uai

[2002Scoob]

@uai , U A(nd) I ( common, that's a pretty good pun!) should hang out and play carburettors and compare notes. Stuttgart isn't too far from me. 

 

I feel like i'm SOOOO close, but that last little 5-10% of what I want it to be, or should be, is really hard to get to. And when I get close to where I want to be on the progressions, I also get that big lean gap before the mains kick in. 

 

Sorry to Hijack!

-currently running what I previously assumed to be a stupid amount of advance at Idle.... And love it. 

[Hans]

The King of Advance will be amused to hear me say you could use a bit more advance at the high end. I use 33 all in at 3000.

Maybe German premium fuel is better than North America.

How did you connect float vents to airbox?

What is that cone thing?

Freiburg to Stuttgart A5 is unlimited as I recall. You could be there in 30 minutes!

[rcf925]

Wagoner, I just built my motor, Pretty similar to yours.  E12 heavily ported head, .292 cam, about 10:1 CR, I'm running twin Italian Weber .45's   I'm running F9 e-tube, but your mains at 155 seem way big, I'm running 130's and your 36mm choke seems big, I'm using 34mm. I am using 60 air jet, Had stumble with 50 . It's runs great with this set-up. My biggest problem has been crap linkage so I ordered stock Ti type from Hal Boyles which I'm waiting on

[uai]

 

3 hours ago, Hans said:

Maybe German premium fuel is better than North America.

 

98 or 100 Octane available w/o problem

3 hours ago, Hans said:

How did you connect float vents to airbox?

PA tubing 4mm ID
 

Th cone thing is my cold air intake that had the ram air effect

 

 

[TobyB]

My first observation is that you have big chokes and big jets-

if indeed these are both working, you may also need big

transition jets.  Far worse things have happened.

 

One thing to look at is how far the throttle plates 

are opening.  If they are too far closed, then the transition

ports won't be able to 'get suction' to pull fuel, and you'll go lean.

If you have an air bypass screw per barrel, you can use that to tune plate position

pretty easily.

 

UAI, yes yes yesss!!! on airflow into the trumpets.  My latest 'answer'

is just a huge air filter on a fiberglass box to seal it to the carbs.

It is ugly, it is a hot air intake, and it gives far more power under the curve than 

any plenae I could concoct in a reasonable time.

One member here simply made a 'heat fence' to isolate the air

from the radiator and the hot side of the engine, and that's kinda where I'm at, too.

When the DCOE was a race carb, I'm finally seeing why the real racers ran open trumpets....

 

t

 

 

 

[2002Scoob]

It's always been my understanding that DCOE's want a a large volume of still air to pull from, so that makes sense any snorkel or Ram-air would mess with that. 

 

And Toby, big air filters can be beautiful I rather like my setup, haha. 

 

I've never run my car without a filter other than idling and checking sync in a parking lot,  but there's a noticeable difference in AFR with the filter on, and off. Funny enough, I've even noticed that, depending on ambient air temps, having the hood open or closed with mess with AFR at idle, too.

 

I'd still love to run it without the hood, if but for a day...  Maybe even without a filter! Wouldn't that be a glorious sound. But then it would probably muck everything up and I'd have to have a 'hoodless' tune. 

 

Worth it. 

Edited June 8, 2020 by 2002Scoob