Weber 48 IDA. Accel pump issue?

Okay so i have mixed many an issue with this car.

-Timing is correct
-Fuel pressure is around 3.5 psi. (gauge gets jumpy between 3 and 4 but stable higher or lower than that. no idea why). its not the pump
-Jetted per what Racing Beat wants for a 13b 6port stock engine. The carb was running on a 12a streetport for years and ran wonderfully.

The car idles odd when i play with the idle adjustment screws. And for the most part its good with medium speed acceleration enrichment. But quick stabs makes it fall flat on its face. That is with no load mind you.

Car runs great wide open above the 2300 mark.

So it seems like i need more acceleration enrichment. But frankly, i have no idea how to do that.

Could it be the needle valve? Im running a 300 that looks like the the first pic, but i do have some 330s like in the second. I frankly have no idea what the change means or does.

---

First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

More flow.
Have you moved timing up or down with same result falling flat?

timing hasnt made a difference. i ordered some idle jets of a larger size. Im running 65f10s. Im guessing that they are a touch too small.

---

First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Has the carb had a thorough service to ensure all jets are clean and the float height is correct?
Unfortunately modern fuel with ethanol in it seems to cause corrosion in carbs which causes a lot of issues if vehicles are left sitting for a while.

300 needle jet is quite large and I suppose would make sense in this single carb application to ensure enough fuel flow at high rpm. The needle jet should not really affect low rpm / acceleration. It needs to be sized correctly to provide enough fuel flow so the fuel level in the float bowl remains consistent at high rpm.

What size pump jets and accelerator pump bleed back valve (aka spill jet) are fitted? If the engine capacity has been increased then the fuel demand may also need to be upped.
Normally IDA and DCOE type carbs are setup with one choke per cylinder, but when a single carb is used the air / fuel flow through the carb can reach a point where things like the progression circuit become out of wack.

---

Disappointingly not yet a Jackass

I would start with the acceleration parts lke you are doing. This type of symptom is often caused by the progression circuits of the carb. The emulsion tubes and air jets play a major part in that. Have you checked those to see if they are per the reccommended types/sizes?

13B Engine (6-Port) setup per racing beat.
Venturi - 40mm • Fuel Jet - No. 195
Air Jet - No. 205 • Emulsion tube - F-4
Needle Valve - 300

the 65F10 idle jets are just what was in there. Above 2500 rpm, she screams just fine. Is all below 2300.

pump exhaust is a .000 closed, or at least should be.

Not sure on the pump jets but no one has the screw in types right now anyway.

---

First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Quote
Gravity Fed
the 65F10 idle jets are just what was in there.

I have not come across F10 idle jets before, nor can I find a listing for their spec. The idle jet's fuel orifice should be 0.65mm, but can you measure the air orifice as this is what the "F" number relates to and it has an affect on whether the progression phase is weak or rich.

---

Disappointingly not yet a Jackass

that side came out as .0735" (my micrometer doesnt do mm)

---

First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023



Edited 1 time(s). Last edit at 01/10/2014 01:43PM by Gravity Fed.

Quote
Gravity Fed
that side came out as .0735" (my micrometer doesnt do mm)

=1.8669mm

We have metric AND SAE typees on here, you should download and install this program:

http://joshmadison.com/convert-for-windows/

---

Parfois, on fait pas semblant!

I am:
I know:
I am from:

Nobody.
Nothing.
Nowhere.

Here is an interesting thread about the IDA progression issues and solutions (3rd progression hole) in a rotary from a bunch of Mazda roatary guys:

http://www.rx7club.com/1st-generation-specific-1979-1985-18/jetting-reccomendations-weber-48-ida-38mm-chokes-685778/page2/

so what does the F10 mean exactly then? And i have noticed that i can only buy the jets based on the .65 or .70 size, no reference for the F# at all.

---

First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Read the thread I posted above; it explains that the F10 is an IDA specific jet, not use for the DCOE's.

yea just read through there and found it. Pretty sure i have the 3rd progession hole. Worked great on the 12a streetport engine, but the same idle jets just arent cutting it for the 13b

---

First Rally: 2010 First RallyX: 2004 (a bunch)
Driver (0), Co-Driver (7)
Organizer (3), Volunteer (3)
Cars Built (2.5), Engines Blown (2) Cages Built (0) # of rotations (3.5)
Last Updated, Apr 9, 2023

Good link by Starion.

Hyper4mance2k wrote:
"I read the haynes weber book and saw that the IDA and DCOE idle circuits are in fact different and so are the jets. kinda... What I said before is true. the jets are the same, but IDA jets are F10. F10 means that there is NO flute hole. You see in a DCOE the flute hole controls how much air is mixed with the fuel in the idle circuit. In an IDA the jet holder controls how much air is mixed with the fuel, that's why there is no flute hole in the IDA idle jet. Now the idle jet holders come in 3 sizes. 100, 110, 120. I'm currently running a 65F9 idle jet and a 120 holder and it runs better than it did with the 65F10 (a.k.a. none flute) I think the flute hole is leaking extra fuel through the carb and that's why it does run better, but it's too rich. I'm going back to the 65F10 tomorrow and I'm going to order the other idle jet holders and report back on how it drives.
FYI I tune with my nose, butt, ear, and a narrow band."


I was wondering why I had not seen F10 idles before. The link and reading through my weber manual explains this. The IDA idle jets comes with a fixed large 1.9mm air orifice which is big in DCOE terms.
The DCOE idle jet F numbers govern the proportional mix of air and fuel, but the IDA idle circuit operates differently from the DCOE as it uses a separate idle jet holder to meter the air to be blended with the fuel in the idle circuit.

I found this link which lists a lot of other useful info.
http://www.webercarburatori.com/?p=handbook&s=2

---

Disappointingly not yet a Jackass

Quote
danster
Good link by Starion.

2 comments:
- Even a blind squirrel finds a nut once in a while.
- Is that the modern 'thumbs up', or the Roman gladiators' "stick it to them"? lol