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CP PI IGNITION ADVANCE


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I have been a bit underwhelmed with the get up and go of my 1970 CP PI TR6.

The car was idling between 8-900 rpm and was going ok but lacked something. It is a stock engine with Lumenition ignition the only upgrade. The rest of the tune was done recently, tappets, plugs, cap, leads etc but at the time I was unable to adjust the timing, and it seemed ok so I left it.

When I started the process yesterday it was about 6 degrees advanced at 850rpm idle.

I advanced it by rotating the distributor to around 20 degrees advance at idle, the micrometer adjustment was fully advanced so I had plenty of retardation available to me. A test drive revealed pinging so I retarded it about 8 degrees, pinging stopped so I advanced it 5 degrees. Very slight pinging so again retarded it 3 or so degrees. No pinging with it about 13 degrees advanced at now a 750 rpm idle.

The idle is now as smooth as expected with a CP car at 700-750rpm. I feel I've got an extra 5 to maybe 10% more grunt.

Thoughts?

 

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Have you checked that the timing marks actually are aligned with tdc….. as they can slip.

i found mine to be 5 pr so degrees out when i was fitting a new 123 distributor a few years ago.

Steve

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9 hours ago, John McCormack said:

I have been a bit underwhelmed with the get up and go of my 1970 CP PI TR6.

The car was idling between 8-900 rpm and was going ok but lacked something. It is a stock engine with Lumenition ignition the only upgrade. The rest of the tune was done recently, tappets, plugs, cap, leads etc but at the time I was unable to adjust the timing, and it seemed ok so I left it.

When I started the process yesterday it was about 6 degrees advanced at 850rpm idle.

I advanced it by rotating the distributor to around 20 degrees advance at idle, the micrometer adjustment was fully advanced so I had plenty of retardation available to me. A test drive revealed pinging so I retarded it about 8 degrees, pinging stopped so I advanced it 5 degrees. Very slight pinging so again retarded it 3 or so degrees. No pinging with it about 13 degrees advanced at now a 750 rpm idle.

The idle is now as smooth as expected with a CP car at 700-750rpm. I feel I've got an extra 5 to maybe 10% more grunt.

Thoughts?

 

Sounds like its about right now, mine is set to around 12 BTC. I do find that over time the timing gradually gets retarded and I have to readjust again.

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17 hours ago, DRD said:

Sounds like its about right now, mine is set to around 12 BTC. I do find that over time the timing gradually gets retarded and I have to readjust again.

 

20 hours ago, Steves_TR6 said:

Have you checked that the timing marks actually are aligned with tdc….. as they can slip.

i found mine to be 5 pr so degrees out when i was fitting a new 123 distributor a few years ago.

Steve

Yep, the pulley is in the correct position. Interestingly a mate and I have just been through that issue with his TR2.

If 12-13 degrees advanced is about right it would explain the better performance. I'm using BP 98 octane no ethanol.

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On 3/12/2022 at 5:21 PM, John McCormack said:

 

Yep, the pulley is in the correct position. Interestingly a mate and I have just been through that issue with his TR2.

If 12-13 degrees advanced is about right it would explain the better performance. I'm using BP 98 octane no ethanol.

I took the car on a longer run today including a freeway at 110-115 km/h. It is going superbly and there is no pinging at any speed or load.

However, when I got home I put the timing light on her and the timing is a lot more advanced than I thought. Closer to 18 degrees BTDC at 750rpm.

I intend leaving it where it is, the performance is excellent and I cannot detect any pinging even though I am listening hard for it.

Is 18 degrees advanced at idle out of the ordinary?

 

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I've never used a timing strobe because there are so many variables that a 'factory' setting is just nonsense.

I have always done what you did John.

Jerry

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I came across this article (or one similar) a few years ago and found it to be very interesting and very helpful w/regards to guaging the results of tuning my sons 74 TR6 after we put in a higher performance cam and a PI head.   Its been really helpful as I've tinkered with my other cars as well w regards to being able to pull a plug and get a general idea of how well the timing is set.   As our ears and "seat of the pants" arent exactly the most accurate I hope this gives an additional data point on ones engine and state of tune...

How do you “read” a spark plug (c5ignitions.com)

 

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Sorry....the cut paste of the page link didn't work.  

Start here:     http://www.c5ignitions.com/uploads 

click on tuning page tab

then select Spark Plug Reading

Page 3 of the .pdf shows how depending on where  the shadow line from combustion flashes on the spark plug electrode will indicate timing and either retarded or advanced.

I found it to be pretty interesting reading.

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9 hours ago, John McCormack said:

I took the car on a longer run today including a freeway at 110-115 km/h. It is going superbly and there is no pinging at any speed or load.

However, when I got home I put the timing light on her and the timing is a lot more advanced than I thought. Closer to 18 degrees BTDC at 750rpm.

I intend leaving it where it is, the performance is excellent and I cannot detect any pinging even though I am listening hard for it.

Is 18 degrees advanced at idle out of the ordinary?

 

18 BTDC is about right for a low compression head (mine is 8.5:1)

Is your cylinder head standard CP-spec?

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5 hours ago, Peter Cobbold said:

18 BTDC is about right for a low compression head (mine is 8.5:1)

Is your cylinder head standard CP-spec?

As far as I know, and the known history of the car goes back 32 years, it is a stock early CP PI 150bhp engine. 

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18btdc seems a lot to me

how did you check that tdc on the pulley is actually tdc ?

i made a tool out of an old spark plug to check mine, as pictured

post-9473-0-54928800-1514739882_thumb.jpeg

insetred in no 1, gently turn engine to touch the tool, mark pulley, gently turn the engine the other way to touch the tool, mark the pulley

tdc is halfway between the marks.

on my car this was nowhere near to the tdc mark on the pulley !

Steve

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On 3/17/2022 at 7:40 PM, Steves_TR6 said:

18btdc seems a lot to me

how did you check that tdc on the pulley is actually tdc ?

i made a tool out of an old spark plug to check mine, as pictured

post-9473-0-54928800-1514739882_thumb.jpeg

insetred in no 1, gently turn engine to touch the tool, mark pulley, gently turn the engine the other way to touch the tool, mark the pulley

tdc is halfway between the marks.

on my car this was nowhere near to the tdc mark on the pulley !

Steve

I'll do that to check. As the pulley is keyed onto the crankshaft I see no reason why it won't be right.

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14 minutes ago, John McCormack said:

I'll do that to check. As the pulley is keyed onto the crankshaft I see no reason why it won't be right.

The outer that has the markings on can move relative to the inner that is keyed to the crank because of the rubber sandwich between.

Stuart.

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5 hours ago, stuart said:

The outer that has the markings on can move relative to the inner that is keyed to the crank because of the rubber sandwich between.

Stuart.

This is what happened to mine.

I was surprised it slipped only 5 degrees or so, thinking it would continue to slip once it had ‘let go’ , but it didnt.

steve

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I have physically checked the pulley and the TDC mark is spot on to TDC of No 1 piston.

The timing is now set at 18 deg BTDC at 700rpm idle. 

It advances to about 35 deg at revs. It is a bit hard to measure on your own (the markings only go to 24 deg) and it might be a few deg more than 35 at revs .

I set it as described above so there was no pinging under any loads. I then retarded it a couple of deg just to add a margin in case I just couldn't hear the engine pinging. 

The car is performing superbly with very good power and acceleration. Idles nicely with a slight lumpiness at 700rpm, like an early PI should.

The local Triumph mechanic, very experienced and very well regarded, says to leave it as it is if there is no pinging.

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Hi John,
This is a good method. I made some extra markings on the pulley to see where max. advance is.

Off course, when it is running so nice you need to dismantle is to understand why:)

Cheers,

Waldi

 

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Posted (edited)
22 hours ago, Waldi said:

Hi John,
This is a good method. I made some extra markings on the pulley to see where max. advance is.

Off course, when it is running so nice you need to dismantle is to understand why:)

Cheers,

Waldi

 

You are right, it is running very nicely. I just filled it up and I seem to have improved fuel consumption from about 18mpg around town to 23mpg, admittedly with a longer drive in the middle of around town driving.

After some more thought I retarded it a couple of degrees to now 15-16 deg BTDC at 700rpm. I'm going on a longer open road run over the Blue Mountains on Saturday and back Monday. I'll play with it and see where it ends up.

Edited by John McCormack
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The Blue Mountains, that sounds like magic. Enjoy the tour.

Waldi

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2 hours ago, Waldi said:

The Blue Mountains, that sounds like magic. Enjoy the tour.

Waldi

Called the Blue Mountains because when viewed from a distance they appear blue because the eucalypt leaves contain an oil and emit an 'oil' type vapour.

When I was younger and Sydney smaller the mountains could appear a deep blue. You don't see it quite as much now with Sydney growing and more pollution. In a westerly wind it is still a sight.

The eucalypt oil is a major reason our bush fires are so intense, and trees can explode although not touched by the actual fire. 

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The weekend trip went superbly.

It was raining quite heavily on Saturday which revealed very few and only minor leaks in the passenger side of the cockpit. The weather cleared up and I drove home yesterday in the dry, good for drying the water out of the various places it gets trapped.

Exactly 400kms covered with a combination of high speed, 110 or so km/h, and 80 km/h going up the mountain and back down. I detoured into Katoomba on the way back to walk around the abandoned Catalina Park racetrack where my BRG TR2 raced in the 60s.

The car performed very well indeed. It pulled well from above 1500rpm in top and od, I rarely had to disengage the od going up the mountain above 70 km/h, 4th down to 55-60 km/h. It revs freely and powerfully to around 4500rpm (my self-imposed limit) in 2nd and 3rd.

No pinging or knocking. Plugs a nice colour.

Fuel consumption averaged 27mpg, 10.51 lt/100kms. On a less hilly trip it would probably do a bit better.

Timing is on 15 deg BTDC at 700rpm idle.

Very pleased.

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10 hours ago, John McCormack said:

The weekend trip went superbly.

It was raining quite heavily on Saturday which revealed very few and only minor leaks in the passenger side of the cockpit. The weather cleared up and I drove home yesterday in the dry, good for drying the water out of the various places it gets trapped.

Exactly 400kms covered with a combination of high speed, 110 or so km/h, and 80 km/h going up the mountain and back down. I detoured into Katoomba on the way back to walk around the abandoned Catalina Park racetrack where my BRG TR2 raced in the 60s.

The car performed very well indeed. It pulled well from above 1500rpm in top and od, I rarely had to disengage the od going up the mountain above 70 km/h, 4th down to 55-60 km/h. It revs freely and powerfully to around 4500rpm (my self-imposed limit) in 2nd and 3rd.

No pinging or knocking. Plugs a nice colour.

Fuel consumption averaged 27mpg, 10.51 lt/100kms. On a less hilly trip it would probably do a bit better.

Timing is on 15 deg BTDC at 700rpm idle.

Very pleased.

John - any difference with 18 deg BTDC?

Cheers Darren

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10 hours ago, DRD said:

John - any difference with 18 deg BTDC?

Cheers Darren

To be honest not really.

I think it might have dropped a few percent in torque and performance, but I feel a bit more comfortable that it won't ping/knock.

There was no detectable pinging at 18 but, especially at speed under load, you won't always be able to hear it.

The car has a good 10% improvement in performance and nearer 15-20% better fuel consumption than it did before I advanced the timing.

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