How to set ignition timing?

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12-07-2014, 14:54
Aterro

What jets? For my carb?

Hi,

I know the best way is to use a wideband sensor and measure afr table then match jets to suit.

But I'm hoping someone on here has fitted different jets to the carb with a similar spec
So I can fit same jets then match fueling to suit.

Standard turbo ( t2)
Aftermarket Exhaust
Different cooler
Hoping for 15 psi of boost by using a manual controller via actuator ( not set yet)

What jets have you used?

Regards
13-07-2014, 12:59
Markey Mark (BD)

Re: How to set ignition timing?

For that set up I find you only need to enlarge the 2nd jet a very small amount, prob 1.1mm will do to give it enough fuel
13-07-2014, 15:48
Alex

Re: How to set ignition timing?

All engines seem different. Some you can get away without changing the jets at that boost some might need the 2nd stage drilling out. I run 15psi and I run a 1.00 a/c jet and the 2nd stage is drilled to 1.4. That fuels 12/1.
13-07-2014, 16:30
GTphil

Re: How to set ignition timing?

Quote:

Originally Posted by Alex

All engines seem different. Some you can get away without changing the jets at that boost some might need the 2nd stage drilling out. I run 15psi and I run a 1.00 a/c jet and the 2nd stage is drilled to 1.4. That fuels 12/1.

Definatly correct Alex, every time i read your afr/carb specs i always think how well your engine must breath with that CTM head of yours....:agree: for 15psi on my car with a T28 and a 1.4 second stage i would be high 10's low 11's
13-07-2014, 20:09
Aterro

Re: How to set ignition timing?

New poster! (less than 10 posts)

I'm using this as a guide
https://www.rtoc.org/boards/showthread.php?t=460

Don't touch 1st jet ( main jet I presume)

2nd jet drill to 1.30 from standard 1.0

Ac change to a smaller one 1.0 from standard 1.25

For drilling use a Silverline Archimedes Drill ? ( any brand) haha

I don't think I'll be using a wideband now, so is it still advisable to be drilling?
Or just change main jet ??

My friend local advised me to try a

130 /135 Main Jet.
90 Air Correcting Jet.
13-07-2014, 20:45
Markey Mark (BD)

Re: How to set ignition timing?

For a standard T2 you don't want to be touching the main jet or ac jet at all, it can be fuelled on the 2nd stage
Even at 230bhp on one of my old engines I was still using standard 1.2mm main jet if you get the rest if the carb right
13-07-2014, 21:03
Aterro

Re: carb jets

New poster! (less than 10 posts)

So just drill the second jet from a standard 1.0 to 1.1??

Leave the rest?
13-07-2014, 21:54
Aterro

Carb jets??

New poster! (less than 10 posts)

So just drill the second jet from a standard 1.0 to 1.1??

Leave the rest?
13-07-2014, 22:55
Alex

Re: How to set ignition timing?

Yes. Just take it 0.1 at a time up to no more than 1.4 if you need it.