Ignition timing

[petegardner_901]

Evening all... and Happy Halloween...

I have always worked by the rule that the best way to set your ignition timing is to slacken off the distributor and turn it until the engine speeds up, then keep turning until it just goes over and starts to hunt a bit - then turn it back a touch.

I have now done the job properly using a strobe and dabs of white paint etc on the Spitfire 1500 and have set the timing dead on 10 deg. BTDC.

Thing is, it was way out from my "by ear" method (too advanced) and the engine revs dropped as I set it properly.

Runs well and now ticks over beautifully at 750 rpm.  

Just wondering if anyone has any thoughts on all this!

Cheers

P

[Pete Lewis]

Its quite easy to over advance when using the Ears method  you do need to back it off a fair bit from best .

Pete

[dougbgt6]

Peter,

Yes, sounds like you're going too far with  "starts to hunt a bit". Turn till maximum revs then back off, go for a run, if it's not right back off a bit more.

I have a vacuum gauge, satisfyingly, at maximum revs by ear the vacuum will also have reached maximum and backing off will drop it one bar.

The problem with strobes and paint is the mechanical wear in the system can lead to a false setting.

Doug

[johny]

I think the pinking method is useful as I think it's impossible on today's fuels to advance it too much and not suffer from the old excessive rattle....

[Nigel Clark]

I usually find that advancing just for the fastest tick over leaves the ignition too far advanced.

My method (for what it's worth) is to advance for fastest tick over, back off slightly, then drive and listen for pinking when flooring the throttle at 1500-2000 revs. Back off a bit more if it pinks.

Most Triumph engines run well using this method, and seem to end up with 1-2 degrees more static advance than going by the book.

Nigel

[dougbgt6]

Nigel,

 I think we all agree and the 1-2 degrees is down to lower octane fuel and mechanical wear. 

Doug

[Nigel Clark]

35 minutes ago, dougbgt6 said:

Nigel,

 I think we all agree and the 1-2 degrees is down to lower octane fuel and mechanical wear. 

Doug

Mechanical wear will normally cause the centrifugal advance to come in more quickly than expected. Lower octane  of modern fuel will need less, not more advance. However, it's possible that with bio ethanol the speed of flame spread on combustion is slower, which would require more advance.

I try to use 99 octane Tesco Momentum (not too expensive) or Shell V-Power, so same octane rating as the old 4 star our cars were designed for. I still find 1-2 degrees more static advance than the workshop manual usually works best. Of course the high octane fuels are still zero to 5% bio ethanol, not E10.

Confusing isn't it? I've merely found what seems to work with my classics.

Nigel

[johny]

As I understand it ethanol does increase octane rating but the companies adjust the base fuel octane to compensate so even if there's no knocking I would'nt go beyond the ignition timing that Triumph recommended.

[Clive]

I have always used the tune by ear method. OK, for the last 20 years or so since leaded fuel disappeared.

As in advance the timing and drive it until I get pinking, then back a smidge so it doesn't quite pink under load. One of my cars went on the rolling road twice, a year apart. And my timing, amazingly, could not be improved on. Just shows that the old human senses are a good way of setting things.

[johny]

What timing did they find Clive? Was it more advance than the Triumph setting?

[Pete Lewis]

lots of thing can affect optimum timing , like   compression. fuel ron, timing chain wear , incorrect cam timing,  dizzy advance weights, vac unit spec.  and so on

i say timing chain as often ignored as the  sprocket teeth and link pivots wear the cam timing becomes later and later as the drive side of the chain effectively becomes longer 

then throw in the 4  x 1/4 tooth  gear indexing that many get wrong can make big differences 

Pete

[Clive]

2 hours ago, johny said:

What timing did they find Clive? Was it more advance than the Triumph setting?

I have no idea. Haven't used a timing light on a Triumph for years! (exception below)

Probably the "best" process is to set the timing up without vac advance to give 32degrees at 3000rpm. Then see what happens at idle. And alter springs/weights so you get a good idle and again, just avoid pinking over the rev range. In practice, very few people do that (I did on my Toledo.....but reckon I need to alter the baseplate a little)

[dougbgt6]

Same as Clive, I've no idea, well a vague idea, but the ears work, so it's not a problem.

Doug

[Nigel Clark]

20 hours ago, johny said:

As I understand it ethanol does increase octane rating but the companies adjust the base fuel octane to compensate so even if there's no knocking I would'nt go beyond the ignition timing that Triumph recommended.

Indeed, ethanol may increase octane rating, but that is really just a measure of how soon the fuel in question will pre-ignite, or knock/pink. Rate of flame spread is different. Slower flame spread needs more ignition advance.

In the final analysis, with worn distributors possibly and modern fuel, trial and error to find what timing works best is the answer. These is no exact answer to what the ignition timing should be for a particular classic engine.

So advance until it pinks slightly then back off a bit remained good advice. And this usually results (in my experience) in a degree or two more advance than the workshop manual states.

Only a rolling road can give a better result.

Nigel

[alan.gilbert_6384]

Hi All,

Hope everyone is well.  Lots of time to play with my spitfire 1500 but nowhere to go

Im after a bit of advice.  I bought as timing lamp and checked the timing on my car, but before this I set both the needles correctly and adjusted the mixture (checked again with my very old colour tune), and balanced the carbs.  The ignition leads are accu sparks and new the points have been replaced by PO with the contactless type as in Accu spark ones, the plugs are NGKs and also relatively new.  The engine was running OK, I checked the timing and it was about 6 BTDC, so I adjusted this to 10 BTDC as per book etc.  The engine idle speed increased as i did this, so then compensated it back to 800 rpm.  

So now here's my issue, the engine starts well, revs well, and at a constant speed nothing untoward is apparent.  But if I accelerate under load it starts to get very hesitant and accelerates slowly.  Ive taken it back to 6 BTDC and appears to be better, but not had much chance to test it again.

Has anyone any ideas why it might be like this ?

Thanks very much.

 

 

[Pete Lewis]

have you bypassed the  6v ballast feed to the accuspark    some are very finicky and run better with a 12v ecu feed you can leave the ballast feed to the 1.5ohm coil 

 

and try richen up ,      half a turn  see if that helps 

Pete

[alan.gilbert_6384]

Cheers Pete, Its got a 12v coil (sorry forgot to mention that bit) so the units connected to the + side of the coil.  Will try the richen her up a bit see what happens, thanks.

[alan.gilbert_6384]

So here’s the thing, went for a run today and at 6 degrees she was sputtering and missfireing, then that stopped.  I adjustered back to 10 BTDC. And all was now fine.  Then when running longer the ignition intermittently stopped twice and the tach went to zero each time and then straight back up again.  Then it stalled when pulling off but started ok and ran ok.  I have now taken the switch in the dizzy off ( red part in the pictures, it’s a Brit part not an accu spark one) and cleaned all the heat grease off and replaced it with some I had left over from building a computer CPU cooling system.  I will play again tomorrow, I have not tried the mixture thing yet.

any ideas anyone ?

P.S. could it be coil ? I have a spare Bosch one made in brazil 

[NonMember]

1 hour ago, alan.gilbert_6384 said:

So here’s the thing, went for a run today and at 6 degrees she was sputtering and missfireing, then that stopped.  I adjustered back to 10 BTDC. And all was now fine.

Years ago - 1999, in fact, when leaded petrol was about to disappear - I had a VW Passat which ran lovely. I took it for a service and, given the impending petrol situation, the garage helpfully retarded the ignition to suit unleaded. It then ran very poorly, sputtering and missing when I tried to use 4th gear at 30, or otherwise pull from low revs. I put the ignition back to the 4* setting and it was fine. Some time later it broke down due to, in essence, every single part of the ignition system being really rather tired.

So, yes, it could be the coil, but it could also be the electronic ignition thing, or a combination of both. The tacho going to zero suggests a low-side fault - probably the EI unit - rather than the coil or rotor arm or cap or leads.

[Pete Lewis]

agree the tacho loosing its impulse + stall   is pointing to the 12v and lecy unit having some intermittent break 

{Pete

[blubayou]

I had this a while ago on my Spitfire, occasionally misfiring under load or cutting out. Checked all sorts & got nowhere.

Whilst fiddling with the key it suddenly showed up.

Changed the ignition switch and all has been fine since.

[alan.gilbert_6384]

Hi All,

Latest update, I had the same thoughts as some of you and thought low tension side might be the issue, so brought a new power spark ignition module (which is exactly the same as the Brit part as currently fitted, probably made in the same Chinese factory ;).  Also read this article http://classicmechanic.blogspot.com/2011/05/testing-and-ignition-coil.html

Now what got me thinking was this web site also says that you should replace the heat grease under the module every 1000 miles or so, which was my thinking also.  I also read the instructions (a novel idea according to wifey) which came with the new power spark unit and manufactured the additional you can see in the picture below.  It all now works fine, pulls well and no pinking, but here the thing, i checked the BTDC again and it is 13 degrees ?????  Any body got any ideas ??

P.S. filled her with Sainsbury's super unleaded.

 

[alan.gilbert_6384]

Sorry forgot to say, its still the original Brit part fitted, the new unit is in the boot just incase 🙏

[NonMember]

12 minutes ago, alan.gilbert_6384 said:

 I also read the instructions (a novel idea according to wifey) which came with the new power spark unit and manufactured the additional you can see in the picture below.

The additional....? If you mean the earth wire from the BritPart unit to the disi body then it'll certainly help reduce misfires. Check that the lead isn't restricting the vacuum advance at all - it looks like it might get caught - but otherwise that's a good result.