IDA Jetting

[Brother Lovedub]

Looking for some advice on jetting a pair of IDAs I'm fitting,  they were jetted when I bought them for a far larger motor and I need some help as a starting point.

Is there a decent website or can someone make an educated estimate on idles and mains as a starting point..

Motor is a 1904 (74X90.5)
Heads are reworked 044s with 42 X 37.5 valves
1:25 rockers
Runing a shade over 9:1 compression.
 
the jetting on the carbs  are currently 190 correctors and 135 mains
65F10 idles

Any help appreciated :-)

[colin jardine]

PM sent steve 

[Jim Ratto]

need to know vent size you have in them

[Brother Lovedub]

sorry, going to be running 37mm.

[Jim Ratto]

60F10 idle, the stock 120 holder may work, you will have to experiment and test.
135 main
F2 emulsion tube
your 190 air should work

[Felix/DFL]

60F10 idle, the stock 120 holder may work, you will have to experiment and test.
135 main
F2 emulsion tube
your 190 air should work

Hi,

what`s the deal with the F2 emulsion tubes?
Since now I only played around with F7 & F11 with my old 1776cc but didn`t feel any major differences.

Mine engine is a 2,2l; 42x37,5; CR 10,6:1; FK10, 1 5/8 header

I only did a few miles with the new combo and tryed 60-65 Idle, 150-160 main, 160 correction, stock 120 idle holders and F7 emulsion
With the 60`s idle and 150 main I got a too lean transition
Any ideas what the engine would like ?
A Lambdameter is installed.

Best greetings,
Felix

[Brother Lovedub]

I'm interested to hear opinions on emulsons tubes as well, I was planning on using F7s (only because that's what the carbs came with)...!

Mine have the 3rd progresson done so I was thinking the followng to get me started

F7 with 145 main and 190 correctors
keeping the 65 idles

[Jim Ratto]

all I can say is to compare by driving the two, back to back. I did and that is why I run F2's.

[Felix/DFL]

all I can say is to compare by driving the two, back to back. I did and that is why I run F2's.

Ok thank`s, I will try the F2 tubes.

At the moment I drive F11 with 145 main, 65 idle, 160 correction, 120 idle holder
But I have a loosy transition between idle/main around 2500rpm. The engine leans out
.
With the F2`s I will even get me a set of smaller jet holders and see what happens.

One other problem is that the engine gets too rich (lambda 0,75-0,8) when driving a steady speed of 110-130 km/h.
I had the SAME problem (a bit heavier) with my 1776cc.
The problem was more present with the F7`s. Fuel pressure is set at 3,2 psi.

Is that a common problem with IDA`s ?

[lawrence]

Felix, in theory, your air corrector is too small. The textbook rule of thumb is main jet + 30-50= air corrector, so experiment between 175 and 195. You should not be rich with the F 11 since they lean out the upper mixture and your problem would be more present with the F 7 because the richen mixture at partial throttle opening and at high rpms.

My car was running rich at freeway cruising speeds, about 70 mph at 3,500rpm, with 135 main, 160 air corrector and F 11 tubes. So I switched to 140 main and 185 air corrector. The engine ran much better on the freeway but ran rich around town due to rich transition with 60 idle and 140 main. So I went back to the 135 which worked great and sized the air corrector accordingly. My final jetting is 60 idle, 109 holder, 135 main, F 11 tube and 178 air corrector. I still plan on changing the air corrector slightly (170-175) because the engine is running a little hotter than normal. Hope this helps.

Oh, 1914, 8.3:1 compression, IDAs, 40x35.5 valves etc.