201 hop up project

[greg g]

Do a short test trip without the filters and see if your readings change.

Your idle mix should be adjustable via the mixture screws on the carbs opening them up will intorduce a bit more air to lean the mix.

I am willing to bet the over rich on throttle closed after acceleration might be traced back to the intermediate jets in the carb, as they are sharing a split vacuum signal, and that vacuum is pulling against three springs instead of one, the jets may be closing slowly or incompletely. I am refering to the ones you had problems with illustrated in one of your early videos where one was operating properly and the other two were fluttering.

You might try experimenting with lighter springs in those valves. or limiting their travel so they do not pull out so far.

[Booker T]

Can't give any good input on your current situation but just wanted to say I really like your car and what you've done with it. Really enjoyed reading this entire thread!!!

[Cpt.Fred]

Thank you, Booker T.

Greg, i will.

As soon as i cleaned up the ignition mess with a good distributor

i will take a spin without air cleaners. I'd be really surprised, because those filter inserts really should be the sporty type and let lots of air in there,

but we will see.

Before measuring the lambda value, i had all three idle mixture screws completely screwded in until dead stop. then i turned them out one and a half rotation, adjusted idle speed and let the engine sit in idle until the lambda

sensor had reached temperature. then i adjusted the idle mixture to 0.85,

wich equals about 1 1/8 turns of the mixture screw.

afterwards we performed the driving tests.

although i solved the problem with the fluttering step up valves (they all stay down now nice and easy) you might still be right about them having to strong spring pressure for the vaccuum signal, BUT:

one question to make sure i completely understand this!

the step up valve is supposed to open shortly after leaving idle and picking up speed,

the manifold vacuum collapses and lets the jet open up to enrich the mixture.

for rapid acceleration there is the acc pump injecting raw gasoline into the vent tube (they are set all on shortest stroke).

now, if the spring pressure is too high and the step up jet opens too early,

shouldn't my mixture get even richer at the beginning of a slight acceleration?

i don't really understand that part.

what i think i do understand, however, is the part about step up jets closing too late and "flooding" of the engine.

so much to think about!

fun...

thanks for the input, guys!

Fred

edit: i just made this to clear up things even more...

what is that long needle again? i have to find my carter book here... what a mess

Edited April 25, 2012 by Cpt.Fred

[greg g]

Lets start by assuming you are traveling along a 40 mph. You should be a high manifold vacuum, with a partially opend throttle. The step up valves should be closed (due to high vacuum) and the accelerator pump, should be inactive although the linkage may have it at mid stroke.

then you accelerate to get on the Autobahn. You partially or fully open the throttle. The acc pump will move injecting a shot of fuel, enrichining the mix. The airflow will increase which will actually lean the mix until the vacuum drops and the step ups open.

When they open they will enrich the mix hopefully in line with the increase of air flow as the trottle remains open. When you reach your new highway cruise speed, the vacuum will increase, pulling the step ups closed, and going back onto the main jets again.

So there might be a temporary leaning of the mix till the acc pump shot arrives, than another temp lean condition as the step ups open to full stroke. I guess thats what happens in an analog world, and why Electronic Fuel Injection is so much more accurate and efficient. So yes you could see the Lambda signals go all over the place, depending on whether acceleration is from idle to WOT, from cruise with Partial Open Throttle, and again from WOT or POT back to idle. Then throw in whether the spark curve is keeping up and firing the plugs at the right time to give you the most effective burn, and you could have several differnt lambda maps.

Check the longer needle to see if ot is hollow. I would guess it might be an air bleed to help atomize the stream from the step up jets.

Edited April 25, 2012 by greg g

[Cpt.Fred]

thanks, greg.

that gives me even more to think about, actually i didn't know the vaccuum comes back and pulls the jets close even at higher speeds, but it sounds logical.

now i just have to find those carter manuals i got from rich...

did i mention it's chaos here?

i report on my next test run when i get the car back on the road.

fred

[greg g]

This is why modern computer controlled fuel systems use the Mass Air Flow Sensor. It puts the computation of mixture into the system based on air entering the system as opposed trying to adjust as air passes through, which as your readings show is a bit behind the curve.

[Cpt.Fred]

greg, now that you talk about computers,

i guess, when i have this running,

and when i'm done with my harley side project,

i already know where to waste my money next...

a friend here who builds rediculously fast VW beetles

has been trying lately to talk me into building a charged

flattie with programmable mega-squirt injection...

......

enough with that, back to work.

have a nice day everyone!

Fred

[Cpt.Fred]

small update:

i salvaged three springs from old carters and shortened them a few turns

to get less spring pressure for the step up jets.

i have to take some more carbs apart, because i found out the springs are different in later model carters,

and maybe find some other type of spring to replace them with (ball pens? hmmmmm.... bet they can't take the stress...).

also i lowered the float level of all three carbs to 7mm / 0,28"

(taken the distance between the float gauge and the float chamber's upper rim).

i had raised it to factory standart to see how it works then,

but it only made things worse.

still have to take on some ignition issues before i can really go for new test runs.

Fred

[Cpt.Fred]

hope you don't mind i bring this corpse of a thread back to life...

i haven't been here for quite a while, i was (and still am) neck deep

in a motorcycle build, also built a new home for the plymouth last year.

but today i though i should look what you guys are doing

 

 

the car is running well now. i'm still rich in idle and coasting,

but i found that you just need to go for a while and the problems stop...

so i just drove the wheels off of it and enjoyed.

this coming season i will try to swap the plugs and move up in the heat range,

i'm pretty sure that might help.

 

here's some pics from 2012:

 

 

 

 

hope you're all doing fine,

 

Fred

[Frank Elder]

Wonderful to hear from you Fred...don't be a stranger!

[greg g]

Hey Capt.  Some of us have found that the little 4 inch air filters common to multi carb set ups are restrictive enough to cause some engines to run lean.  If yours is running rich, maybe restricting the airflow a bir might also restrict the fuel flow.  Just a thought.  Good to hear from you again.

[Cpt.Fred]

thanks, guys.

maybe i will give it a try and swap the filter inlets from the tripower housings i'm using now

for something less restrictive, and then afterwards for something more restrictive, and then check out

what it does. but, like i said, if i'm not creeping around in idle and low rpms a lot, everything works great

and the mileage is pretty nice for a 4 point something rear end.

there are so many things that i'd have to fix, i think i just finish the harley first and then tear into the plymouth next winter

after driving it as is for one more season...