• Hi Guest!
    You can help ensure that British Car Forum (BCF) continues to provide a great place to engage in the British car hobby! If you find BCF a beneficial community, please consider supporting our efforts with a subscription.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Marcos GT Weber Emulsion tubes on ethanol/E85 Kent X flow twin 40 DCOE 32

Share this page

K

kistinie

Freshman Member
Country flag
Offline
Hi,

I have already converted a DCD installed on a Davrian (Hillman Imp engine) without difficulties.I only oversized by 1,16 the jets keeping the rest intact.
To check the results i have an AFR meter with a wide band probe.

But getting a good transition is far more difficult than for idle and fast ride. The 1500 3000 band is difficult to balance in order to be stoichiometric at steady speed and accelerations, light and strong. I get a very weak mixture on light acceleration, a rich on strong.

On my Marcos GT Kent 1700, still on premium, same problem, i get 20/1 on light acceleration, 12/1 on steady opening and 14/1 on heavy acceleration.
I bet the emulsion tubes, idle and main are the problem.

As much as possible i want to avoid modification of the butterfly.

I currently have 130 main, 175 air on F16 and 45F8 for idle, Do you have suggestions or experience with other tubes on premium and ethanol.
Some suggest F9 on premium, F7 for E85, for idle F9 or F6 for E85

Thank you !
 
Weber recommends F2, F3, F4, F7, or F17 emulsion tubes for alcohol-based fuels.

They also recommend F7 to richen the mixture at low RPM and slight acceleration. F2 and F3 (and F16) will give a leaner low-end mixture under those conditions. Since you are going lean on light acceleration, I think the F7 is the tube you want.

If you don't already have a copy, hunt down How to Build and Power Tune Weber & Dellorto Carburettors by Des Hammill (Veloce Press, SpeedPro Series). That is the only book I've ever seen that gives good, solid starting points for jetting AND explains how to find the right idle jet F numbers (and explains how the idle jet F numbers actually work).
 
JHaydon said:
Weber recommends F2, F3, F4, F7, or F17 emulsion tubes for alcohol-based fuels.

They also recommend F7 to richen the mixture at low RPM and slight acceleration. F2 and F3 (and F16) will give a leaner low-end mixture under those conditions. Since you are going lean on light acceleration, I think the F7 is the tube you want.

If you don't already have a copy, hunt down How to Build and Power Tune Weber & Dellorto Carburettors by Des Hammill (Veloce Press, SpeedPro Series). That is the only book I've ever seen that gives good, solid starting points for jetting AND explains how to find the right idle jet F numbers (and explains how the idle jet F numbers actually work).
Click to expand...
I have just received F7, 55F6 for idle and 5 different main and air.145 to 185, 175 to 215
Next week with the AFR i start the test. I'm pretty certain to find a good combination with these. I also have a set of drill to do fine adjustments.
 
Back
Top