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Metering Unit Timing CP vs CR


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Does anyone know why the method for setting the timing changed between CP and CR models? I know the camshaft is different and the metering is as well, although I dont know what is changed in the metering unit between CP & CR (apart from the green top:mellow:)

The CR method would seem to delay the actuation of the injectors a little.

Just curious.

Thanks.

 

Simon.

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13 hours ago, kiwican said:

Does anyone know why the method for setting the timing changed between CP and CR models? I know the camshaft is different and the metering is as well, although I dont know what is changed in the metering unit between CP & CR (apart from the green top:mellow:)

The CR method would seem to delay the actuation of the injectors a little.

Just curious.

Thanks.

 

Simon.

I was told it was an emissions thing.  That was from an aging Triumph engineer. That does not make it correct.  

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The change was brought about in order for the 6 throttle PI arrangement to meet the 1972 ECE emission standards. Triumph in conjunction with Lucas had been developing a single throttle PI solution from 1969 onwards in an attempt to reduce production cost and improve the emission performance of the existing arrangement however it couldn't be made to work satisfactorily. 

Derek 

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12 minutes ago, saffrontr said:

The change was brought about in order for the 6 throttle PI arrangement to meet the 1972 ECE emission standards. Triumph in conjunction with Lucas had been developing a single throttle PI solution from 1969 onwards in an attempt to reduce production cost and improve the emission performance of the existing arrangement however it couldn't be made to work satisfactorily. 

Derek 

I've touched one of the single throttle PI inlet manifolds.  It has TRIUMPH cast in the top.

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Peter, It does seem a shame that they spent so long developing it for it to fail at the final hurdle, they even had hopes of it being used in the USA TR6 at one time. It would be good to see an image of it, someone, somewhere must have some photos.

Derek

 

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Thank you Peter and Derek.

I had only ever seen the instructions for the CP cars and was unaware of the change.

A follow up question is did it work? Presumably improved emissions means improved efficiency and so better fuel economy? I know there were changes to the cam and metering unit so it might not be possible to answer this.

Derek, my TR6 is also Saffron. I am not sure it is colour i would have chosen if I had bought it new but if I were to restore the car and had a choice of colors I would go back as saffron.

 

Thanks again for the replies.

 

Simon

 

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Hi Simon,

It was recorded in the General Managers Report for the Triumph Motor Company Board meetning of the 7th July 1972 that the 1973 PI vehicles had satisfactorily passed the compliance tests at the Dutch Testing Station and had received approval relative to Emission Standard E15 which was due to be adopted iin Europe for all cars built after 1st  April 1973. From this it appears therefore that the changes made did indeed work.

Good to hear that Saffron has grown on you. I've had mine since 1978 and whilst it wasn't my favourite colour at the time it is now. 

cheers

Derek

 

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On 12/9/2021 at 11:06 PM, kiwican said:

Does anyone know why the method for setting the timing changed between CP and CR models? I know the camshaft is different and the metering is as well, although I dont know what is changed in the metering unit between CP & CR (apart from the green top:mellow:)

The CR method would seem to delay the actuation of the injectors a little.

Just curious.

Thanks.

 

Simon.

The extra delay may have been useful in minimising manifold "wall wetting" and hence the fuel octane fractionation that causes the brief pinking upon flooring the throttle. 

Peter

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