Again: Weber Jetting

ASeries · 05:27 AM

Hi,

I have a 2.0E engine with 40IDAs but as I had them available I put in 33mm venturis instead of the recommended 30mm ones to see if I can get more power this way. I have the carbs running quite nicely by now with F3 tubes, 60 idle, 145 main and 180 air jets. As the engine feels like it got 20 extra hp from this carb setup I had it on the dyno on monday and the mixture was perfect up to about 6000 where it started becoming way too rich.
Therefore the engine produces its max power at 6090 instead of 6500 (good thing is that it produced already there 155hp instead of the official max 140hp with the MFI).
Any suggestions on how to fix this? E.g. use bigger air jets/smaller main jets to get a leaner mixture at this rpm level and try to compensate the lack of gas for lower rpm with bigger main jets/smaller air jets (what's the better combination for high rpm)....?

Or could it be the air filter (stock air box with K&N filter)? But this works for the 2.4S with 190hp at 6900 or something in that area, right...?

Thanks, Peter

john walker's workshop · 09-30-2009, 04:26 AM

try one size bigger on the air correctors.

ASeries · 09-30-2009, 05:25 AM

Quote:

Originally Posted by john walker's workshop

try one size bigger on the air correctors.

one size would be 190?
I tried 200s (only have 180s and 200s here) and that seemed already too lean for full throttle at middle rpms. I did not do a CO check yet, it just felt less powerfull/aggressive at 4-5000 (that's why I asked above if I may have to compensate via bigger main jets).
But will get a set of 190s and try again - maybe one size smaller (than the 200s) already does the trick...

Thanks!

john walker's workshop · 10:02 AM

air correctors fine tune main jets, at higher rpms. like a hole in a drinking straw, they adjust the air/fuel ratio. the bigger the hole, less fluid and more air at a certain vacuum.

ASeries · 09-30-2009, 10:22 AM

Quote:

Originally Posted by john walker's workshop

air correctors fine tune main jets, at higher rpms. like a hole in a drinking straw, they adjust the air/fuel ratio. the bigger the hole, less fluid and more air at a certain vacuum.

yep - but it seems that my 200s add too much air already at lower rpms (=lower vacuum). I guess trying to avoid that with 190s or to compensate for that with bigger mains is a question of trial and error, right...?

john walker's workshop · 10:57 AM

they really don't do much at lower rpm. you could also step down on the mains just a bit. try 140 mains if the 190 airs don't quite get it. 60 idles are also rather large for a 2.0. i had a real good running 2.0 in here that had 130 mains, 180 air, 55 idle, F3 tubes, 30 vent. seemed fine, but didn't dyno it. cams had good bottom end so must have been E or solex.

ASeries · 09-30-2009, 12:22 PM

with the 30 venturis it's all a lot easier and it worked basically quite well with 52 idle and 125 mains. But the greed for more power made me move to the bigger venturis and with those the air flow is so slow at lower rpm that I had to put in quite huge jets - and these are killing me now at high rpm where the venturis actually should improve things.
Without the dyno I'd never thought of modifying my setup as the engine turns very willingly up to 7000 and doesn't feel like losing power - but now that I know that it could be even better...
So I'll keep playing around