Weber selection and initial jet tuning

[blodi]

F2 and 160/230..... much richer overall...but...flatter too! 

92817 by blodi, on Flickr

Im thinking my next step might be keep the F2's in and swap in 150 mains to lean it back up overall. 

Other things I noticed....F11 and F16 are very similar at highway cruise`mid to high 14's. F2 is a bit leaner...in the 15's....good for mpg. F2 also is much richer when giving partial throttle. 

F11 seemed to bring the power on quicker when at light to moderate acceleration around town. 

 

[240260280]

 

Not as big a difference in the shape as I had hoped. The biggest effect of changing E tube is like changing main jet... i.e. richness.

All curves have the same hump in the middle so this can not be tuned out by e-tube.  It may take fuel level or choke size.  A smaller choke will cause high end richness and too high fuel level will cause low end richness.

 

Your observations seem to match the curves:

The F11 seems to be best near the start of the run (12 to 13) so you will see good power here.

The F2 is the flattest.

I agree with you.  Please try smaller mains with F2.  Hopefully the shape will change too. 

 

[240260280]

Hopefully when the main is reduced, the higher end of the F2 curve will lean more.

 

Below are some general ratings and specs of E Tubes.   The trend from F16 to F11 to F2 above has the tube diameter going from 8.2mm to 8.0mm to 7.5mm. This should enrich the mix as we observe.

 

The drawing also shows F2 has the leanest low end of the 3 tubes tested. This agrees with the shape of the curves above. 

It is interesting to note in the hand drawing below that the F2, F11, and F3 have holes in the middle of the E tube.  I think the F3 could flatten the shape even more by leaning the low rpm area. It seems this leaning also affects cruise (as you noted).  If the cruise is too lean then the idle jet may need to go larger to compensate.

 

So far from the E Tube swap experiments, the effects are subtle, and the defacto F11 and F16 tubes used in most Z's may not be optimal.

 

 

 

Edited September 30, 2017 by 240260280

[blodi]

Threw in the 150 main. Did a pull on the way in this morning...still way rich.  I'll get a log on the way home and post. 

Doing some research I found this thread which makes me think the overall shape I'm getting is basically "normal"...

http://forums.hybridz.org/topic/111194-just-started-playing-with-innovate-lm-2-on-mikuni-44-29l-stroker/?page=3

Might be that I go back to F16's and run either the 155/225 or 160/230 combo. Might be about as good as it gets. Then I can start trying to play with the accel pump stuff.

 

[240260280]

Be wary of Hybrid Z posts...especially the Weber stuff on that site.  The scientific method is usually missing. They did not even recommend changing E Tubes in the thread nor could I see a mention of it?

 

If you look at the range of their curves in the thread you references, it is > 3 A/F Ratio points, your best is less than 1.5 with the F2 and 2.3 with the F16. 

 

For your solution, the F2 will need smaller mains.

 

Fuel height is another tuning parameter but it is labour intensive so we can call it quits for the testing and I can pick it up again when I get my SK's installed. They have external fuel adjustment. to make things easier.

 

 

 

 

 

 

 

 

 

 

[blodi]

F2 150/230......

10217 by blodi, on Flickr

Thinking 140's....gotta order em. 

[240260280]

The curve is a lot flatter in the lower RPM's than the F16. This is very interesting.

 

btw the Weber Tuning Manual recommends F2 emulsion tubes for cylinders whose range covers the L28 displacement.

 

You should also consider 240 airs.

 

 

[blodi]

Ordered 140/240.

[blodi]

While waiting for the 140/240's to show up I was curious and installed the F16's with 155/185 as originally stated on the engine when I bought it. I did this with the 36mm chokes before but, not with the current 35's....

F16 155/185.....

10517-2 by blodi, on Flickr

10517-1 by blodi, on Flickr

 

The 140/240's showed up tonight and I installed them. I'll report back with data. But, also ran into a tapping noise that I am not thrilled about today too.

Edited October 6, 2017 by blodi

[240260280]

It is interesting comparing the 35mm to the 36mm choke.  

 

By Shifting the curves on top of one another and ignoring the a/f offset, the shape is the same except:

- The 36mm is much leaner in the low end.

- In the middle just before the peak the 36mm gets slightly leaner then it gets slightly richer at the peak.

 

 

 

(Below)By aligning each plot to the  AF Scale, 36mm seems to be richer in the mid to high; but this may be due to the variations that seem to be going on with the meter. 

One would expect the opposite: more dilution due to less venturi pressure drop (aka signal) to pull the fuel out of the well with the larger 36mm choke.

 

 

Edited October 6, 2017 by 240260280

[240260280]

Check your valve lash for the tapping. Usually that is the cause and an adjustment will cure it. Also make sure the rockers are getting oil form all holes in the lobes or oil bar.

[blodi]

Yeah, going to try to pull the valve cover and check lash this weekend. I adjusted it all when before i installed the engine (1.5 years ago)...I'll check it again. It's a bit of an unnerving sound.