EvilWankel

iTrader: (2)

Well I finally got my wideband installed. I set it at idle at about 13.8-14.1, but it idles at about 1200 RPM and I cant lower it by the idle adjust screw - it's all the way out already. When I transition from very light throttle to a medium throttle it will jump up to about 16-17 at medium throttle...at WOT it will be at about 11.8-12.1 Let me know what I'll need to change up

Main Jets - 190
Idle Jets - 60F10
Air Corrector - 140
E-Tube - F11
Pump Jet - 45
Chokes - ??
Aux Venturi - 42 I believe
Needle/Seat - 250
Fuel Pressure @ 3.5 psi


http://www.racetep.com/weber/48DCOSP.pdf

EvilWankel

iTrader: (2)

Forgot to add it's a streetport using pineapple templates, 13b

j9fd3s

iTrader: (3)

just to work backwards...

the main air jet #9 controls the RPM when the main circuit starts operating. for example on my car (12A pp, IDA) a 130 = mains on by 2000rpm = rich bog, the 150's had the mains coming on by 2500rpm = big lean spot. 140 actually worked for me.

the main fuel jet #13 controls the fuel mixture, between when it comes on, and redline. if 190 is too rich, then 185 or 180 might work, its hard to say though as the air and fuel and Etube interact, so for example on mine going from 170 fuel to 175 fuel puts the mixture from 12.8 to 11.5!

the Etube #10. this is where the magic is. air flows like air, and fuel flows like fuel, but when you mix them, like the Etube does, it can be neither or both.... ive seen a chart for Etubes by engine displacement, the 12A gets an F8 (i think) and this is what ive got and its fine. i havent tried anything else, as the F8 seems to be about right.

idle jet. #12 on a DCOE the idle jet has an air hole, so it also creates an emulsion like the main circuit. the idle jet must supply fuel and air up to the point the mains start working. 60F10, 60 is the fuel size, and actually i found 60 worked for me, and it should be really close for you. F10 refers to the air hole size. although if im not mistaken f10 = no hole?

again the fuel size selects the mixture, and the air acts as a bleed, so less air = the idle circuit works for more RPMS.

the idle speed thing. the throttle stop screw #36, is just that, it is meant to set the throttle plates in relation to the 1st transition hole, and not to set the idle speed.

http://www.tjwakeman.net/TR/WeberDCOEinfo.htm#idle

EvilWankel

iTrader: (2)

So, I guess first I'd like to tackle my idle....what should I set a/f at anyhow? I thought it was supposed to be around 14.0 ish, but a friend in town who runs a weber on his 12a says that he feels it performs best at 11.1ish. I ended up adjusting mine to run around 12.5 but it kicked the idle up to 1500rpm. I would like to get my idle to around 800-900RPM.

As far as the main fuel jet...seems I run lean from 1800-2100 where it could get as high as 20 ratio. I should lower it a little to maybe a 180, because near redline it does get down to like 11 a/f ratio.

Thats a good link, thanks for posting it. I'll have to read up on it tonight. Definitely helps me as I really didnt know what anything did.



First thing I would like to do though is get this damn idle under control.

j9fd3s

iTrader: (3)

dont look at the WB for idle, just tune it so it runs the best

your 1800-2000 problem sounds like it might want either a smaller main air, to get the main fuel jet working faster, or an idle jet with a smaller air, so the idle circuit works longer.

but yeah if its running rich up top, its going to need a smaller main fuel jet too

82FanTC

iTrader: (9)

You confused about how the air correction jets control where progressions start. The air correction jet controls only high RPM mixtures. The bigger the air jet the leaner your high RPMs are. The air bleed on the idle jet may control what RPM your main progression starts, however I have never really understood how to balance the fuel hole size with the air hole size on the idle jets. I just found one that works and stuck with it.

Siraniko

iTrader: (13)

try pulling the bellcrank backwards as most of the time, the spring is unable to close it all the way which results to higher RPM @ idle.

As everyone has recommended, tune the car at idle and low RPM first. If the engine starts to buckle around 3K RPM, use a larger idle jet.

Top end wise, just pop a 150 air and 200 main (I usually start at that range with a minimum of 50 difference between main and air jets). this will allow your engine to run rich, instead of lean, at top end.

13x

evil, what fuel pump you running again?

3 1/2 lbs? Is that for the 48's because what my research has found was 1 1/2 to 2 1/2 but higher flow then the original. Saw the evidance today on the way home when I stayed in the same gear and it leaned the crap out

I have the 45's on the SA and installed a spring, like Wacky said the original doesn't seat back well

j9fd3s

iTrader: (3)

have you actually verified that? that's what almost everyone says, but i haven't found it to be true.

think about how it works for a sec, the air going thru the the Venturi pulls the UP and then OVER into the venturi. the air jet is located right in the middle, and acts like a brake. so with the air corrector in there the pull from the venturi has to overcome the leak from the air corrector THEN fuel can flow.

or TRY it. i was lucky enough that i had a couple different ones to try, but you could remove it, or plug it...

the idle seems to be the other way, i played with the fuel, until it was happy. then thinking i had the same lean stumble as everyone else, i took the 120 holder and filled and redrilled it to 100. it did make a difference, you can pull the whole main jet stack out, and drive around. turns out that my stumble is a rich stumble....

so the main circuit is easy, the idle circuit is easy, and the transition is tricky, but there are a bunch of ways to solve it.

wacky puts a bigger idle jet in, so its got more fuel. i put a smaller air corrector in. wacky's way is better on the racetrack, more fuel = more premix...

so that's the other cool part, if you have a WB, start playing with it. pull the main stack out, try different air correctors (you can fill and redrill...)

82FanTC

iTrader: (9)

Absolutely verified! I have over $1000 in jets and have tried every combination tested with a wide band. AC definitely adjusts fuel at WOT/high RPMs.

The auxiliary venturies which no one ever plays with can help with the progression circuit.

Siraniko

iTrader: (13)

+1

j9fd3s

iTrader: (3)

weird, for me it made a HUGE difference down low, teeny effect up high, maybe we're talking about the same thing but backwards?

EvilWankel

iTrader: (2)

Some 100gph carter fuel pump I believe. Ray, I have read on a few threads to use between 3-4psi on the 13b. Unless someone really openly criticizes it I'll be staying at that PSI.

I ran outside and tested the return for the butterflies (if this is what you guys are referring to) by opening it and then letting it close naturally, then pushing it to see if it closed further. I didn't see it move any more than that. I'm really dumbfounded that I cant get my idle lower than that, maybe it's because of the timing??? I know it was advanced, maybe too much.

j9fd3s, from this link you send (and from what i've heard in the past, these mixture flow screws are supposed to be between 7/8 and 1 1/2 turns from closed. Mine are more like 11 turns out. Very large difference in these. I'm not sure how much this affects it, but I'm going to be looking into this stuff. I think my first order of business would be to re-stab my distributor to bring my timing back to normal....I doubt it was advanced so much that it won't idle low, but who knows.

82FanTC

iTrader: (9)

WOW there is your problem! You need to dial them way down. You should never be any more than 2 turns out.

Siraniko

iTrader: (13)

more like this: small venturies requires small idle jets & vice versa while larger venturies = larger idle jet.

My RX-3s are tuned with 48 IDA with 43 venturies for an aggressive street use just in case of you know what. With 130 air/220 main combo, I'm happy with the result on top end/WOT. Also keep in my mind that I use 3.90 gears.

EvilWankel

iTrader: (2)

Yeah, I counted again, it was at about 14 turns out. When I tried to go at about 1 1/2 turns it wouldn't even idle, but when trying to keep it alive it was reading like 20 a/f ratio :o

j9fd3s

iTrader: (3)

its a tapered seat, so the further the screw is out the less its going to do.

i'm also running the carter. 3.5 is good for fuel pressure, IMO.

you also wanna check the float level, too high and it will leak from the boosters @idle, which if you're running @14:1 isn't happening. look in there when its idling and it shouldn't be dripping from the booster.

yeah i'd set the timing to stock, one less variable. i find its easier to tune, when you basically check everything, and almost go down a list.

j9fd3s

iTrader: (3)

i havent played with the venturi's, the 43's are good!

mines all corked up, but on 3.90's i can floor it @1500rpms and it pulls hard until it runs out of breath @6500, with a 140/175! when i take the cork out, my jetting is going to look more like yours i think

i took the FPR off though, so maybe with the engine running its making more than 4psi of fuel pressure....

82FanTC

iTrader: (9)

Go to a 65F9 or 70F9 idle jet and see if you can get her to idle at 1.5 turns. I bet you'll get your idle smoothed out. And just to be clear you are setting both of the idle mixture skrews correct?

EvilWankel

iTrader: (2)

Yes I was adjusting both screws. I actually just picked up 65f9...I was afraid it was gonna be way off but I wanted to try. Thanks.

Siraniko

iTrader: (13)

I can tune it for you but im not sure when I will be coming back to Vegas and wacky loves to partehhhh lol

13x

K evil was just asking, just curious the varibles and try to get the SA running it's best (right now the nikki seemed better lol)

EvilWankel

iTrader: (2)

I need to make an amendment to what I said earlier about the amount of turns out the idle adjust screw was...I was only counting 1/2 turns, so in actuality it was about 7-7/12 turns out. Now, I put in the 65f9's and got it down to about 4 1/2 turns...so I'm going to be ordering 70F9 and 75F9 just in case the 70's don't work.

Since we're on that topic, where does everyone get their stuff from? There's only one place I know of in town, and they are geared toward VW's, and the 65F9 was the largest idle jet they had. Websites I have are:
www.piercemanifolds.com
www.webercarbsdirect.com

Also, I was thinking about getting one of those synchrometers to get everything tuned precisely. Any suggestions/comments on those??

Siraniko

iTrader: (13)

go to harbor freight (i think its on decatur about 2 miles north of 215) and purchase some index and number drill bits (I cant remember which is set is smaller). Go with the next size drill bit and drill away. if needed, go with the next size over.

sychronizer is useless IF You have good ear lol

EvilWankel

iTrader: (2)

So you suggest that I bore the hole wider and save myself money??? I've never really tuned a carb so I think that tool may come in handy. I can tell when the engine doesn't like how I adjusted it but I'm not so confident in minor adjustments.