Weber settings, almost stock 2.2

[mskala]

Thanks for the help Paul. I understand your idle circuit comment and
will be sure to deal with that later.

For now I'm sticking to full throttle in range of >3000 to 7100. I took a
lot more samples today and probably will be putting up data slowly, to
put things into graphs that make sense.

Since the car was not any faster with 32 venturis I am only using 30
now as I assume the signal will be better.

I won't show the data, but I also proved to myself that the idle jet
size (55 or 50) has no effect at full throttle at these speeds.

And finally, there seems to be no way to avoid leaning between 6000
and redline, it's just possible to change the slope a little. Maybe
that's why IDS carbs have the extra nozzle my IDTP's don't.

Also, I proved to myself that the graphs are almost as good in 2nd gear
as opposed to 3rd gear, just not as many points. This is good as it will
help avoid arrest.

Real data to come.

[mskala]

EDIT: used to say F3, but due to my error I actually made
what I'll call F26A, which is F26 with 4 holes at each level.

First graph attempts to show the effect of only emulsion tube
change. F1, F26, F26A. These all have holes in the same
vertical locations, but F1 has fewest in lower positions, F26
more in lower positions, F26A the most.

Sorry some lower speed data of F26A not captured properly, and note
that F1 was taken on a different day.

I don't think that emulsion tube has a very big effect under full
throttle high rpm conditions. F26A basically looks the same as F26,
but maybe a slight leaning at the very high end.

Can't edit pic, the legend of F3 should say F26A

[mskala]

Effect of changing only main jet. Two graphs. As expected,
one jet size means about 0.5 change in AFR over whole range
of interest.



EDIT: pic says F3, but due to my error I actually made
what I'll call F26A, which is F26 with 4 holes at each level.
Not a big deal for this graph as it's showing change in main jet only

[1QuickS]

Weird; it seems as though E-tubes have no effect.

Did you balance air flows at 3k RPM with helper activating throttle pedal? This keeps the force of your hand on the cross bar from upsetting how the carbs are actually actuated while driving.

Are all four the float levels set correctly and checked with the engine running?

Is the fuel supply pressure 3.5 psi and measured near the fuel inlets to the carbs; again while the engine is running?

I assume the bung for the oxygen sensor is on one exhaust header and before the flange with the muffler.

The 125 main is a bit big for 30mm venturis; something more like a 110 or 115 would be in order. This would lean out your mixture. Also, I believe your cams are falling off the power curve somewhat before the 7300 rev limit you are using which is a "S" specification rev limit. If you kept your revs limited to 7k then your AFR curve looks a bit better. So...smaller mains, smaller air corrector, F3 E-tubes and limit revs to 7k.

[mskala]

Effect of changing the air corrector jet. Two different
scenarios.



EDIT: pic says F3, but due to my error I actually made what I'll call F26A, which is F26 with
4 holes at each level. Not a big deal for this graph as it's showing change in main jet only.


It does affect the high RPM range more, but not as
much as I was expecting. Still significant effect over
whole range.

[mskala]

Originally Posted by 1QuickS

Weird; it seems as though E-tubes have no effect.

Did you balance air flows at 3k RPM with helper activating throttle pedal? This keeps the force of your hand on the cross bar from upsetting how the carbs are actually actuated while driving.

Are all four the float levels set correctly and checked with the engine running?

Is the fuel supply pressure 3.5 psi and measured near the fuel inlets to the carbs; again while the engine is running?

I assume the bung for the oxygen sensor is on one exhaust header and before the flange with the muffler.

The 125 main is a bit big for 30mm venturis; something more like a 110 or 115 would be in order. This would lean out your mixture. Also, I believe your cams are falling off the power curve somewhat before the 7300 rev limit you are using which is a "S" specification rev limit. If you kept your revs limited to 7k then your AFR curve looks a bit better. So...smaller mains, smaller air corrector, F3 E-tubes and limit revs to 7k.

Hi Paul,
I've set and checked the floats and they are good. I've never checked the
fuel pressure, just using the stock pump. I haven't check the airflow at 3K.
Can the synchrometer handle this?

The O2 sensor is in the right header (a 914's right) in the collector near the
muffler.

I have a 7100 limit rotor, so either it is a bit generous or the RPM capture
for the innovate system is off, the thing needs a pot to tone done the tach
signal. I use the car for autocross, and I am not expecting power up so
high but it is great to be able to avoid shifting sometimes.

Basically right now I've decided to stay with 30 Venturi, 125 Main, F3, and
170 Air. I would be going in the direction you suggested, but I have
problems in cruising on the highway with anything smaller. Between 3200
and 3800 is highway speed, and at low throttle with slight incline is the
leanest. Don't want to go above 14.5. This is with 55 idle jet, which is
always too rich at low rpm around town already (~2000, AFR in the 12's).

Thanks for the help. I'm going to try to get a pressure gauge.

[1QuickS]

Hi Mark,

VERY important to set air flow balance at 3k. I'm guessing you have one carb advanced from the other which would affect the other's fuel delivery but you can't see both sides with the LM-1 setup you have. So, when driving you have one carb opened up more than the other and the sum of fuel delivery provides the power but one side is more open and "dragging" the other set which would be rich as a result. If I'm correct then you may want to revisit the 32mm venturis; otherwise 115 mains for the 30mm ones...if I'm right.

I provide a procedure for performing this on my site which includes some little known tips regarding the adjustment of the cross bar and drop links to help avoid other mechanical timing issues. You may be surprised at what you find.

Here's the link: Weber Carbs Technical

By the way, idle adjustments should be accomplished with drop links disconnected and STE readings will be around 4.5 when "Lean Best" idle mixture adjustment has been achieved.

Also, slightly lean at small throttle openings probably won't cause issues but lean at high power demands surely will.

[mskala]

Well some things are easier said than done on old mechanicals.
Without making the throttle linkage bracket holes bigger, there's
no way to have both drop links the same length. Although I
think I'm only 1 turn off. Without working too hard on it, I have
the one side reading 10 on synchrometer and the other side 11
while at 3K.

What's preventing me from going down in main jet size is that
even though 3-4K is rich at full throttle it will be too lean at low
throttle. It doesn't look good on the graph and it has a noticeable
flat spot in the throttle.

I'm not opposed to making mods to the emulsion tubes if they
will have an effect there. I had to make the F3's from new F26's.
Not too bad once you make a little jig.

[911pcars]

Originally Posted by mskala

Well some things are easier said than done on old mechanicals.
Without making the throttle linkage bracket holes bigger, there's
no way to have both drop links the same length. Although I
think I'm only 1 turn off. Without working too hard on it, I have
the one side reading 10 on synchrometer and the other side 11
while at 3K.

What's preventing me from going down in main jet size is that
even though 3-4K is rich at full throttle it will be too lean at low
throttle. It doesn't look good on the graph and it has a noticeable
flat spot in the throttle.

I'm not opposed to making mods to the emulsion tubes if they
will have an effect there. I had to make the F3's from new F26's.
Not too bad once you make a little jig.

Not sure I understand nor where you're starting from (I should review the entire thread). Both links don't necessary have to be the same length, but they should be unless a part was replaced (links different length?). If so, can you shorten the longer one by threading into the link body to match the shorter link?

Are the individual throttle plates on each carb centered in their respective throttle bores and in synch (all closed with idle screw backed out)? Did you start with all throttles closed first before setting the idle speed screws to zero (just touching)? The throttle shaft is a two-piece affair. Adjust if needed.

Sherwood

[Brant]

The emulsion tubes should make more difference than that.

here is a 2.0 with IDS carbs. (the enrichment tubes help a ton also)
the focus was to stabilize the AFR at the top end.

I think this run was with 36mm venturi's, 175 mains, 230 airs, and the auxillary enrichment tubes intact. (F26's I believe)

[1QuickS]

F3's are shorter than F26s, have closed ends and the location and length of the larger diameter in the body is different; easier to buy F3s I would think.

Did you check the cross bar to be sure the 8mm ball studs are coplanar with the main axis of the cross tube; especially the axis of the cross tube as established by the 13mm ball studs? Typically they are not and once this issue has been addressed the drop links can be made the same length and the side-to-side balance can be achieved by using the clearance in the end plate mounting holes.

[mskala]

Oops, you're right about the F3 dimensions. I was looking at a
drawing where the part numbers got cut off. So what I've
accidentally done up to now is really F26 with more holes added
down low. I'll work on getting the real thing.

And I'll work on arm geometry.


Thanks,
Mark S.

[mskala]

It took a while, but I have F3 emulsion tubes now and made a test run.
This doesn't seem to have improved any of the high speed full throttle
leaning.


Also, I edited the earlier posts where I talked about F3 but was really using
a modified F26.

[1QuickS]

Classical answer to high RPM leaning is to decrease air correction jet size.

[mskala]

Yeah, I did that to a degree by going from 180 to 170 to 150. At
full throttle it seemed to affect a lot more than just the high rpm.

So tonight I did a crazy experiment. Soldered up some air
correctors and drilled to 100 (1mm). Went back down to 120 mains
also.

Still looking fairly similar with respect to high rpm leaning.
Here is the graph (sorry RPM was flaky, also the stumble at 4.2
seconds is probably real, ignition related):


I don't know what part of the system can go wrong where the
emulsion tube and air corrector circuit can be so ineffective.

[ratpiper71T]

Well, it's just a pot-shot but, maybe the shafts are leaking-Paul probably could tell from your graph though.

[1QuickS]

Throttle shaft air leakage is an issue during part throttle operation.

Are your auxiliary venturis installed correctly? Do the keeper springs in the wings keep the aux venturis in close contact with the throttle body at the fuel transfer port? Maybe the higher air flow through the aux venturi leaks more air at this interface instead of sucking the heavier fuel up the emulsion tube well???? One of the procedures I perform during my service is to resurface the flat end of the aux venturi where it mates with the throttle body. If this interface is loose or if there is corrosion then the fuel may not efficiently get drawn into the aux venturi and may instead leak down the wall of the carb or draw in false air.

Another possibility is the aux venturis can be installed upside down which would really foul up the main fuel delivery, possibly like what you are experiencing. Just to be sure; the top edge of the aux venturis is the rounded edge and the bottom edge is the knife edge...sorry, I had to put this one on the table just to be sure.

The tall aux venturis are particularly bad for becoming loose but this is another type of problem.

Grasping for straws here

[mskala]

Yeah, no offense taken, there would have been a time when I would not
know which way these things go together. I'm using the normal aux
venturis, and they cannot be wiggled at all. I took one out just to
look, this is probably the only piece on the entire car that has no oil,
grease, rust, or corrosion on it.

It seems that there are very few pieces involved in full-throttle short
duration running. I have never looked at throttle shafts but can't
imagine that being enough of an effect. So tomorrow I think I'll have
a good look down the emulsion tube wells. If the natural order of
things for mains is to richen as RPM goes up, then there must be
something blocking it. The interface to the aux venturi was a
good guess but it 'looks' fine and would take a pretty elaborate
setup to test.

Is there any way the anti-percolation drilling could be done wrong
that could create a problem? I know I did this, but it was over 10
years ago and don't even remember the instructions. Sold the
fixture too.

Thanks,
Mark S.

[1QuickS]

No on the anti-perc drilling. The holes vent to atmosphere via the chamber above the idle air bleeds and then through a notch in the wall of the top cover and into the throttle bore. Atmospheric air enters float chamber from the vent pipes...maybe there is an air restriction to the float bowls which caused fuel level to drop on higher fuel demand??? Are your air filters clean? Could the vacuum in the air filter housing be larger than expected due to filter cleanliness?

Perhaps you should check to see there isn't any vent pipe blockage issues. Also, check fuel delivery and pressure. Perhaps pull a drain bolt and put a nipple of some sort into it and monitor fuel flow out of the bowls. Fuel pressure is to be 3.56 psi per factory specifications.

Perhaps there is a partial fuel filter clogging (in-tank filter or supplemental in-line filter) that is adequate for low speed operation but can't keep up at higher demands...Check also the fuel screens around the banjo bolts.

If you have the tops off it would be good to check for freedom of movement of the floats. Otherwise you could stick a wire down the vent pipe and touch the tops of the floats to assure they are floating freely.



I keep grasping a the straws hoping one will help you out. Something isn't right! Anxious for the answer too!

[mskala]

I saw no issues with the floats or vents. Decided instead of finding
a decent pressure gauge, to get new pump and pmo adjustable
regulator. Also new filter as I will have to mount everything
differently. It will take a bit of time to get everything installed.

Also I should describe a symptom, which may or may not have
anything to do with this problem. That is, when I've got the engine
hot and park for some time, like 30 minutes or 1 hour, occasionally
it will for a couple minutes be almost impossible to avoid stalling
when leaving a stop sign using the 'normal' amount of gas/clutch.
Seems to idle the same, but need to goose it to over 2K before
thinking about declutching. The reason I thought of this is because
if for some reason the pump is weak when hot but runs okay when
cold, I wouldn't see the problem with float gauge or pressure gauge.