Idle jetting help

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advinnie
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Idle jetting help

Post by advinnie » Wed Jan 03, 2018 8:23 am

Hi all some of you may of read my other posts about my 1600 draw through turbo bug and the problems I’ve had. Anyway the engine is back together and running and the timing is now sorted but I’m having massive issues with the idle jetting. The problem is that when I use a set of .55 idles the car starts great drives great and the mixture screws are one turn out from seat ( Weber 40 dcoe carb) but leave the engine idling any more than one minute she starts going rich and then floods and stalls, it still dose it with the mixture screws just half turn out as well. So I’ve now installed a pair of .45 idle jets and now the mixture screws need to be two turns out from seated to get best lean setting and she now still starts great but she can idle all day long without going rich and stalling but I’m going lean at around 2500rpm and the Engine wants to stall. Any advice on what to try next?
Cheers and happy new year

Clonebug
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Re: Idle jetting help

Post by Clonebug » Wed Jan 03, 2018 9:25 am

Try smaller vents for a little better air velocity at idle. It's probably puddling in the intake when you let it sit and idle that long.
Either that or you need heat in the intake.........But I'm just guessing since I have no experience with drawthroughs.
Stripped66 wrote:The point wasn't to argue air temps with the current world record holder, but to dispel the claim that the K03 is wrapped up at 150 HP. It's not.

advinnie
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Re: Idle jetting help

Post by advinnie » Wed Jan 03, 2018 10:11 am

Thanks for the reply mate. I’m running 28 vents at the moment and I think you may be right about the adding heat into the manifold

advinnie
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Re: Idle jetting help

Post by advinnie » Wed Jan 03, 2018 1:57 pm

Been thinking and want to know if you think I’m on the right track. Right on a stock carb the idle jet should be between a .50 to .60 jet so all four cylinders take turns in sharing that jet, on twin dual choke carbs each cylinder has its own idle jet that should be between a .50 to .60 idle jet so each cylinder should be getting the same amount of fuel as the stock set up.
With me so far?
Now I have a singal twin choke carb so it has two idle jets that feed each cylinder in turn and each one of them jets is a .55 so in theory each cylinder is seeing a shot of fuel witch is equal to a 1.10 jet?
Does that make sense?
If I’m right that may be why my engine is running mega rich and flooding at idle?

Clonebug
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Re: Idle jetting help

Post by Clonebug » Wed Jan 03, 2018 10:26 pm

That's not how it works. Only one cylinder pulls air through that venturi at a time so it is plenty for your 2 cylinders.

I would guess that you have too slow of airspeed through that intake and it is loading up with fuel.
Try increasing the idle speed to about 1100-1200 rpm and see how it works.
Stripped66 wrote:The point wasn't to argue air temps with the current world record holder, but to dispel the claim that the K03 is wrapped up at 150 HP. It's not.

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buguy
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Re: Idle jetting help

Post by buguy » Wed Jan 03, 2018 10:42 pm

How big are the venturi on those carbs?

advinnie
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Re: Idle jetting help

Post by advinnie » Thu Jan 04, 2018 1:56 am

The vents are 28mm’s

advinnie
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Re: Idle jetting help

Post by advinnie » Thu Jan 04, 2018 2:09 am

Here’s another little question witch I’ve been thinking about. They say that you should only have the idle screw on a Weber 40 DCOE carb 1/2 to 3/4 turns in from when it first touches and the the idle timing should be 8 degrees BTDC, now if I do that the Engine will not idle. If i set the idle timing to 8 degrees BTDC the idle screw has to be around the 1 3/4 turns in from when it first touches witch then has started to open the butterflies to much but if I set the idle screw to open the butterflies to 1/2 turn in I need my idle timing to be around 15 degrees BTDC.
So my question is witch one should I go with and how much timing can you actually run at idle before you end up breaking something?
I’ve also read that you can set the idle timing by continuously advancing the timing to gain the highest manifold vacuum as well?
I’m running a CB performance black box with a manifold pressure sensor to control my ignition

madmike
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Re: Idle jetting help

Post by madmike » Thu Jan 04, 2018 9:11 am

Mine's locked @ 24* all the time :shock: so they can take quite a bit at Idle :wink:

Clonebug
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Re: Idle jetting help

Post by Clonebug » Thu Jan 04, 2018 9:19 am

I have run timing that high at idle before. I have my timing set at 11-14 degrees at idle right now.

With the Black Box you can set your timing anywhere it runs good. Just be careful on boost and listen for detonation.

You don't have a stock engine anymore so don't be setting the timing like a stock engine.............You are the engineer.
Stripped66 wrote:The point wasn't to argue air temps with the current world record holder, but to dispel the claim that the K03 is wrapped up at 150 HP. It's not.

advinnie
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Re: Idle jetting help

Post by advinnie » Thu Jan 04, 2018 10:25 am

Can’t wait till the new pistons bed in then I can wind up the boost again 5psi is boring 😂

madmike
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Re: Idle jetting help

Post by madmike » Fri Jan 05, 2018 7:19 am

What size is the waste gate? I have 38's on both mine,one is a good Tial the other is just an e-bay Knockoff :roll:

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buguy
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Re: Idle jetting help

Post by buguy » Fri Jan 05, 2018 8:31 am

madmike wrote:
Thu Jan 04, 2018 9:11 am
Mine's locked @ 24* all the time :shock: so they can take quite a bit at Idle :wink:
Do you have any hot start issues with that much timing?

advinnie
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Re: Idle jetting help

Post by advinnie » Fri Jan 05, 2018 8:44 am

I have no idea what size the wastegate is the turbo is a aireserch with a .36 hot side and a .42 cold.

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buguy
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Re: Idle jetting help

Post by buguy » Fri Jan 05, 2018 8:50 am

That should work really well!

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