18 replies to this topic

[babsbrown]

Hi guys

My rebuilt 1130 is getting run in at the minute. It's had its cam bedded in.

It's currently running an AAU needle. At 1k-2500 rpm it will show 14.6AFR.

Once under load driving different rev ranges ots shooting to around 18 AFR.

Its at around 10 deg btdc static. I haven't properly dynamically timed it yet.

Am I right in thinking it will need a richer needle?. If I enrichen it, the car would sit at 10-12 AFR at idle, but be about right when driving.

I've had a look at the minty lamb comparisons and are thinking I might try my AAA needle again.

Are there any other needle suggestions?


Thanks, kind regards LUKE

[babsbrown]

 20250417_190406.jpg   18.09K   7 downloads

 

The plugs look like this. 

[timmy850]

If you have another needle and your afr gauge, then swap it, set the idle mixture and see how it goes. It’ll then tell you if it’s too rich or lean and where to go next

Your spring and damper oil also need to be selected to match the engine spec and needle

Your options are:
Make some guesses and try more needles
Modify a lean needle to add more fuel

[babsbrown]

If you have another needle and your afr gauge, then swap it, set the idle mixture and see how it goes. It’ll then tell you if it’s too rich or lean and where to go next

Your spring and damper oil also need to be selected to match the engine spec and needle

Your options are:
Make some guesses and try more needles
Modify a lean needle to add more fuel

Thanks Timmy,

I'll have to have a search of alternatives, although all I seem to find are AAA or AAM.
It's funny you should mention the damper oil because its 20/50 at the moment and I find the throttle response a bit soft. I'd prefer it a bit sharper. I may try a thinner oil or 3 in 1.

[timmy850]

Thinner oil will make the piston rise quicker, which leans out the mix under acceleration

Thicker oil will make the piston rise slower, which richens the mix under acceleration

 

You can measure this with your gauge, by quickly opening the throttle and seeing what the effect is on the mixture. 

 

If it's too lean it'll bog/gasp and not drive nicely. If it's too rich it can it can also cause misfires and foul the plugs

[babsbrown]

Thinner oil will make the piston rise quicker, which leans out the mix under acceleration
Thicker oil will make the piston rise slower, which richens the mix under acceleration

You can measure this with your gauge, by quickly opening the throttle and seeing what the effect is on the mixture.

If it's too lean it'll bog/gasp and not drive nicely. If it's too rich it can it can also cause misfires and foul the plugs

Ahh thank you, I honestly didn't really appreciate the importance of the oil. I thought it was all about how quickly the revs picked up. I guess building the engine was the easy bit. 😂

[timmy850]

At least with your gauge you can check, measure and adjust accordingly. Better than guessing or "using your ear" to tune

[babsbrown]

At least with your gauge you can check, measure and adjust accordingly. Better than guessing or "using your ear" to tune

Cheers mate, I had a good go this morning and I seem to have sorted it to some extent. Although I had to adjust it as it got to temperature. Those afr gauges are a godsend aren't they! I can't imagine trying to tune the engine without one.

What sort of values do you expect with your 1100? I remember you had a similar set up.

Ie cruising, decelerating etc...?

That would be handy to check I'm in the right ball park

[timmy850]

I’ve got a fairly highly tuned 1100 and currently have a HIF44

Idle is around 14.0 and should be fairly stable, and should come back to the same reading after revving and driving
Cruising is around 13.5 to 14.5
When go from cruising to full throttle it drops down to 12.5 and stays there until you ease up on the pedal
Coasting in gear with the throttle closed it goes 15.0 to 20.0 which is perfectly fine

You want it to be at full operating temp before you fine tune it, otherwise it’ll change when you drive

[babsbrown]

I’ve got a fairly highly tuned 1100 and currently have a HIF44

Idle is around 14.0 and should be fairly stable, and should come back to the same reading after revving and driving
Cruising is around 13.5 to 14.5
When go from cruising to full throttle it drops down to 12.5 and stays there until you ease up on the pedal
Coasting in gear with the throttle closed it goes 15.0 to 20.0 which is perfectly fine

You want it to be at full operating temp before you fine tune it, otherwise it’ll change when you drive

Excellent thanks mate, I'm pretty sure I've seen yours on YouTube if it's the same one I'm thinking of. Looks and sounds mint

[68+86auto]

You need to adjust the timing before touching the fuel mixture.

[babsbrown]

You need to adjust the timing before touching the fuel mixture.

Thanks

I've got the timing now to about 30 deg BTDc at 3700 rpm. It was a bit of backwards and forwards. Going in and out the car monitoring all the dials then popping out again with the timing light.

[crock]

If your timing is 10 degrees at idle and 30 degrees total at 3700 rpm then you are pretty close with the timing. You would need a rolling road tune to do much better.

[babsbrown]

Thanks Crock,

A little update, I swapped to the AAA but even on the weakest setting it ran borewash rich.

Swapping back to the AAU I have it at a more sensible ratio.

[babsbrown]

Duplicate post sorry

Edited by babsbrown, 21 April 2025 - 02:52 PM.