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TR6 PI CP series AFR tuning

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Dear forum

Need some advice on the best way to set up AFR .

Brown book section19.20.05 states that we should use pair 5/6 as reference airflow and set pairs 3/4 2/1 to the same flow rate.

Green book from service and training, states otherwise,  use central pair 3/4 as master then set  the other pairs

Wich way is the best? It makes sense use center pair?

Never got a good spark colour using bb instructions

Thankyou all

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Do you have an air bleed screw on the front inlet manifold?

Are the 3 nylon bushes on the throttle shaft under the throttle bodies new if not renew them first. 

What are the linkages on the 3 throttle bodies like, worn perhaps?

Do you have an air flow meter?

You will need these items to get it set up correctly


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I would just get the engine to idle once warm at around 900 rpm and check the air flow, in 2, 4, 6 bodies with the flow meter and get the flow the same by adjusting the link to the throttle butterfly shaft, if you need to increase/decrease idle speed use the air bleed screw in or out to fine tune the speed.  You may have use some asbestos gloves as the links are close to the manifold!

You are aiming to get all the butterfly shafts to open at the same time.

I choose the 2,4,6 as these are the ones that the butterfly shaft can have the most air if the bodies are a little bit worn, it may mean that 1,3,5 will be slightly less air flow, but you have to put up with that a bit, and finish with an idle speed around 800/900rpm.


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I used the BB just as a guidance on my CP.

I used the 3 idle screws for idle, this is very easy, and then the 3 rods for 1500-1800 rpm. I replaced the original linkages by ball-type linkages (mine came from Moss).
Both speeds should be “sync“, not just idle.
This worked for me.

The basis should be sound first: plugs, timing from Ignition and valves, and engine warm. And as John says, a good linkage system and the TB’s in good condition. If not, it will not be as good as it could be.


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I'll take the midle pair as master,, looks to be consensual and folow the notes for idle setting, air screw and minimum screw

Take the path this weekend, still have to buy the abestos gloves:) it really  gets hot..

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I don’t think “the middle pair” makes much difference, it is an iterative process until you are satisfied (at least, that’s how I did it). 
The car should be able to stall when you close the air idle valve. In other words: do not open the butterfly too much.


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