TR6 PI ignition timing

[rogcar]

I need to adjust the timing on my TR6 PI and have read so much about settings I have confused myself totally.  I have ordered a strobe and will be using this, it seems the setting for this should be 4 ATDC (vs 11 BTDC static). Have I got this correct? Also, I have heard that it can be useful to adjust timing slightly to cater for modern unleaded fuel but not sure if this is correct or if so what adjustment should be made. Thanks.

[John McCormack]

28 minutes ago, rogcar said:

I need to adjust the timing on my TR6 PI and have read so much about settings I have confused myself totally.  I have ordered a strobe and will be using this, it seems the setting for this should be 4 ATDC (vs 11 BTDC static). Have I got this correct? Also, I have heard that it can be useful to adjust timing slightly to cater for modern unleaded fuel but not sure if this is correct or if so what adjustment should be made. Thanks.

I set mine at idle with the pulley mark about 1cm advanced from the pointer. I'm not sure what that equates to in degrees but probably 5-10. I then adjust on the road advancing until it starts pinging. I then back it off until it doesn't ping.

Bear in mind that other factors can cause pinging such as carbon build up in the combustion chamber, leaner mixture, lower octane fuel. By tuning it so that it doesn't ping you are accommodating other variables but clearly you should look out for other problems as necessary.

[JohnC]

39 minutes ago, rogcar said:

4 ATDC (vs 11 BTDC static)

Nope. 11 BTDC static, and more advance if the engine is running. The actual amount more depends on your distributor. If you post here with the type number, one of us with a manual will tell you where it should be set. And many more will post with different opinions! But in my manual, the most *additional* advance is +5 degrees at 4000 RPM. At idle it's around +4, or 15 BTDC.

[Mike C]

I set mine at 11 deg BTDC at idle with the strobe for starters, then advance it slowly on test runs until the engine just starts pinging at WOT top gear.

Edited December 17, 2020 by Mike C

[DRD]

56 minutes ago, Mike C said:

I set mine at 11 deg BTDC at idle with the strobe for starters, then advance it slowly on test runs until the engine just starts pinging at WOT top gear.

Same here although 11 deg BTDC is about as far as I can go with 99 RON fuel before it pinks, although I'm running a slightly higher CR than standard.

[barkerwilliams]

As above set 11' BTDC. If you get an adjustable strobe then get someone else in the driving seat and get them to rev the engine slowly. You will see the timing jump when the bob weights throw out, hold the revs there and adjust the timing strobe until the crankshaft timing  marks are aligned and read off the advance on the strobe and get your helper to read of the engine revs from the rev counter. You can then check that the bob weights are working correctly. - easier done than described, takes less than a minute!

Incidentally the rubber in the crankshaft pully can break down and the timing marks move so they are not necessarily accurate. So as with all things set the timing to 11 BTDC then take the car for a drive onto a steep'ish hill and ensure that the car does not "pink". As well as timing the fuel octane affects the timing required.

What you are aiming for is the most advanced timing possible without pinking, but 11'ish suits most of us.

Alan

[CK's TR6]

Theoretically, ignition timing should be advanced to the point of achieving maximum brake torque. For a given operating condition (rpm & load), if you plot MBT vs timing advance it is a curve that peaks, more advance beyond that point reduces MBT and therefore, efficiency. Depending on a lot of factors, you may have quite a bit of advance past the point of max MBT before you get ping. Additionally, you already have ping by the time you can actually hear it in the car. Here is where you can utilize a set of “detonation cans”. Which are no more than a stethoscope up against the block. A modern version is easily constructed from a electronic hearing amplifier off of Amazon. Desolder the microphone, solder it to a ten foot lead then glue it to a clamp. Clamp it to the web on the side if the block where the motor mount is. Plug in a set of headphones and turn it on.  Read up on “spark hook tests” for more information. 

[Andy Moltu]

Static time as per manual and used knurled adjuster to advance until it just pinks and the retard slightly until it doesn't.

Another option is to strobe time so that you get around 32 btc at 4000 rpm and make minor adjustments until it doesn't pink on the fuel you use.

[Mike C]

On 12/17/2020 at 10:48 PM, DRD said:

Same here although 11 deg BTDC is about as far as I can go with 99 RON fuel before it pinks, although I'm running a slightly higher CR than standard.

I'm just a bit more than 11 degrees, on Australian 98 octane and a slightly raised CR in a '69 CP with a TR5 cam. I try to  advance the timing as far forward as possible but I won't risk  pinking and detonation. 

[rogcar]

Thanks everyone, very helpful. Strobe has arrived so I will experiment.

[Steves_TR6]

Before swapping over to 123ignition i actually measured the advance that the original distributor was giving, to serve as a baseline for the new 123 distrib.

this showed that the timing marks had slipped on the crank damper.

with the aid of a tdc tool i was able to get a correct set of readings, and i replaced the crank damper.

steve

[Jules TR6]

Going back to the OP's 'confusion', I have been led to understand that 11 BTDC is measured at idle, but looking at the Haynes manual that's static timing.

So when running, at -

900 rpm : 0 - 4 BTDC

1600 rpm : 5 - 9 BTDC

2600 rpm : 12 - 16 BTDC

4000 rpm : 12 - 16 BTDC

The 11 degree mark we've added to the flywheel would therefore only apply at approx 2400 rpm??

...so at idle timing should be 4 degrees advanced max - not 11 degrees??

Edited October 6, 2023 by Jules TR6

[RobH]

No  - it's 4 degrees static and there will be no centrifugal advance at 900rpm so it is still 4 degrees. 

[Jules TR6]

2 minutes ago, RobH said:

No  - it's 4 degrees static and there will be no centrifugal advance at 900rpm so it is still 4 degrees. 

ok many thanks for quick response, I'll be rechecking this tomorrow morning!!

This is another revelation for me, though as it's in the manual shouldn't be! - but the video as below is therefore VERY misleading.

Many people I believe have been referring to this video, where at 1min 25sec (the link below should start there) 11 degrees BTDC is offered at the timing degrees to be checked with the engine running at *idle*, skip to 3min 20secs...

if one sets the advance to 11 degrees at idle (800-850 rpm) is that bad?

When on points (previous owner) the engine pinked, and I think it was set to 11 degrees idle (maybe because of above video), on electronic ignition the engine doesn't pink at 11 degrees idle, suggesting EI needs (or can take) much more advance?

EI might need very different timing than as stated in the manual - but points should have the max 4 degrees (at idle) as sated in the manual...?

[RobH]

26 minutes ago, Jules TR6 said:

if one sets the advance to 11 degrees at idle (800-850 rpm) is that bad?

Aargh  - I've told you wrong again - I forgot we were talking about a PI engine - 4 BDC  is for the 4 cylinder.  11 degrees static is correct for the PI engine.  Sorry. 

It will be 11 degrees also at 800-900 rpm after that the centrifugal advance kicks in and the numbers you quote are added to the static advance.  e.g.  at idle 0 to 4 +11 = 11 to 15 overall, at max advance you get 13-16 degrees dynamic plus 11 degrees static = 25 to 27 degrees overall. 

 

 

Edited October 6, 2023 by RobH

[Jules TR6]

16 minutes ago, RobH said:

Aargh  - I've told you wrong again - I forgot we were talking about a PI engine - 4 BDC  is for the 4 cylinder.  11 degrees static is correct for the PI engine.  Sorry. 

It will be 11 degrees also at 800-900 rpm after that the centrifugal advance kicks in and the numbers you quote are added to the static advance.  e.g.  at idle 0 to 4 +11 = 11 to 15 overall, at max advance you get 13-16 degrees dynamic plus 11 degrees static = 25 to 27 degrees overall. 

 

 

...all this should be in a new manual for the TR6 !!

I get it, 11 degree static + the various advance amounts at increasing rpm

massive penny dropped again!

11 + 0 to 4 (-at idle) = 11 to 15.

Crystal clear, a million thanks, this is gold.

[Mike C]

I personally start at 11 degrees @ 900 rpm then creep it forward - as per my post of 19 Dec 2020 above.

[FatJon]

on my EFI where I can see the advance very accurately I have 12BTDC at idle rising to 32BTDC at a 3000rpm cruise. It only goes over 32 on a high vacuum overrun.

The 4Atdc was a bodge to meet US emissions. Don’t do that to a PI, it won’t like it at all.