Author Topic: carb jets/ pump adjusting  (Read 1438 times)

fordy

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carb jets/ pump adjusting
« on: 21:24, Fri 04 March 2011 »
whislt the engine is apart again thought i'd double check the carb so i dont have a repeat of my engine blowing up

This is what i've got writen on the jets and it looks likea standard carb
120main
100ac
1st stage has been soldered and drill possibly 1mm -1.2mm checked by eye
2nd stage untouch again checked by eye
1.7mm needle

Do these jets sound right for a car boosting over 1bar?


Also when setting the accel pump,
Am i right in thinking its 5mm drill bit held flush on the body, then adjust the pump nut untill it first starts to compress?

markey mark (bd)

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Re: carb jets/ pump adjusting
« Reply #1 on: 18:15, Sat 05 March 2011 »
You need to check jet size acurately and not by eye, they all vary from 0.1mm at a time.

That looks roughly standard, ac jet is normally 1.2mm so thats been reduced if its 1mm.

How much boost you running on the car?
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fordy

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Re: carb jets/ pump adjusting
« Reply #2 on: 21:39, Mon 07 March 2011 »
only checked by eye atm as the engine is in bits and i dont have a micro drill bit set

Am i right in thinking the 1mm ac will make it fuel more than standard on boost?

I'm going to be running a new standard t2 at actuator pressure, i have got a aem uego i use for sniffing cars whislt checking for det.

I'm more a efi tuning guy not got much experience with carb tuning, still trying to get around what jet changes fueling under what condition  :lol:

James5

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Re: carb jets/ pump adjusting
« Reply #3 on: 22:49, Mon 07 March 2011 »
Yes the air corrector does'nt make a huge difference at normal driving rpm's, it has more effect on boost and higher up the range.

The 2nd stage is were you want to adjust for on boost driving it only comes alive after a few psi of positive boost.

fordy

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Re: carb jets/ pump adjusting
« Reply #4 on: 22:32, Mon 21 March 2011 »
just to bump this up again

I found a spare carb in the garage whilst looking for an old ht lead

Now the spare carb is untouched jet wise
120 main
125 ac
100 1st stage
untouched 2nd stage

So i swapped the 1st stage jet over into the running carb
so i've got now in the running carb these jets

120main
100ac
100 1st stage
untouched 2nd

When does the ac jet alter fueling? coming on boost? if so i'll probably leave the 100ac in so its a bit more safer

markey mark (bd)

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Re: carb jets/ pump adjusting
« Reply #5 on: 16:34, Tue 22 March 2011 »
The ac jet will richen or lean the fueling out top end of the revs depending on the size of it mate.
I would not adjust the 1st stage at all, leave that standard.

Are you running 1bar of boost at carb top or inlet?
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fordy

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Re: carb jets/ pump adjusting
« Reply #6 on: 21:40, Tue 22 March 2011 »
Quote from: "markey mark (bd)"
The ac jet will richen or lean the fueling out top end of the revs depending on the size of it mate.
I would not adjust the 1st stage at all, leave that standard.

Are you running 1bar of boost at carb top or inlet?

I've currently got the 100 ac jet fitted so i'm assuming it'll be richer?

my spare carb has a good 125 ac jet

All my pipe work is standard and i've got a new std t2 from turbo technics so i hope its been set for running standard boost on the actuator.

out of interest what is standard boost pressure on these?

I'll make sure i've got my decent standalone boost gauge and wideband hooked up when its on the road

markey mark (bd)

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Re: carb jets/ pump adjusting
« Reply #7 on: 21:45, Tue 22 March 2011 »
If your going 15psi at inlet manifold then the carb will only need slight adjustment, having smaller ac may do the job but you'll only tell once you have an AFR gauge on there.

its 12psi at carb top which is standard from memory, been long time since i played with standard boost!  :lol:
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fordy

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Re: carb jets/ pump adjusting
« Reply #8 on: 21:50, Tue 22 March 2011 »
sweet well i'll leave the 100ac jet in then and double check on the wideband

I like less boost and more timing on my cars as it keeps the turbos thrust bearings healthy

Ash-Lee

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Re: carb jets/ pump adjusting
« Reply #9 on: 22:51, Tue 22 March 2011 »
Standard boost is 10PSI measured at the carb top.

I think.......  :lol: