Ignition tables and tuning

[Penner]

This is torque graph in Nm (250 is about 185 ftlb) with different ignition advances. (10-30 degrees BTDC). It was done at WOT with a Rocket Roadster that had high compression pistons, cams and open intake and exhaust. If you got something similar, you should not only take care of fueling but also retard ignition tables at higher revs to avoid detonation and heat.
But even if you got a stock Rocket with secondaries set to 100, load at higher revs is improved and you should be careful with adding ignition advance.
Prost

 

[barbagris]

Ulf - Where exactly in Germany are you? - I think maybe one or two of the EU guys here might like to know. I think you're going to be a bit far for me - but you never know. I have a lot of accumulated holiday to take in 2018.

 

[Penner]

It is Bremen in the northern part. I have made a few Rockets from Austria though. Quite some way to travel. But i think it is because they speak some kind of german.

 

[barbagris]

Wow - yup!. Bremen is a haul from Madrid. Still, only about 20 hours in the saddle. 2000 clicks.

Shame I don't still live in Neuss.
But then the weather is better here.

 

[ThingKing]

Penner clearly on the way to the Rocket hall of fame... we do need some help on the continent, so this is just perfect.
Traveling there will be a long haul, but the way back will feel a lot quicker.

 

[Kenneth67]

This is torque graph in Nm (250 is about 185 ftlb) with different ignition advances. (10-30 degrees BTDC). It was done at WOT with a Rocket Roadster that had high compression pistons, cams and open intake and exhaust. If you got something similar, you should not only take care of fueling but also retard ignition tables at higher revs to avoid detonation and heat.
But even if you got a stock Rocket with secondaries set to 100, load at higher revs is improved and you should be careful with adding ignition advance.
Prost

Hey Prost/@Penner, I'm not sure I follow you, perhaps you can clarify?

Is the 10 degree line (about 227NM max torque) the stock WOT ignition timing, or advancing 10 degrees on all WOT stock ignition values, or changing all stock WOT ignition values to 10° BTDC regardless of original value?

I'm also confused by the insinuation that we should advance ignition to 30° BTDC @WOT (presumably a lot more advance than stock), followed by the instruction to retard ignition at higher revs (again presumably from stock timing) to avoid detonation & heat.
Can you help me?

Thanks

 

[Penner]

It is the tables at full throttle set over all revs to 10 degrees (and so on) btdc in Tune-Ecu.
Up to 2000 10 does the job.
From 2000 to 3000 it is 15.
From 3000 to rev limit 20 is enough. (Stock is about 30 there)
In the midrange area there is some signs that 25 may be a little better. (Turbulences are not that strong yet and gas burns a little slower.)
I make a map from that and then start again with smaller 2 degree changes up and down. After a few runs the job is done.
Choosing the lowest advance that gives you full power, will keep heat from the head and it reduces peak pressure.
The stock Roadster does not have issuses with detonation and load at higher revs is pretty low. It can easily handle up to 30 degrees.
But with high compression and bigger cams you should have a look at ignition advance.
Bigger cams also reduce load at lower revs. So that it will ask for more advance than with stock cams. On the other hand, there is a compression ratio of 10.5 - or even higher - instead of 8.7. You will have to try.
Anyway. My advice is: It is all about air and fuel. But don´t neglect ignition timing.
Prost.

 

[Grumpy Ole Codger]

Oooerr...all I feel is this whistling noise as all this info passes over the top of my head!

 

[Claviger]

Thanks for the info, confirms what I’ve been doing in my tunes, raising midrange and leaving top end mostly stock. The old butt dyno told me mid 20s felt right, score one for the butt dyno!!

Triumphs mid range timing on roadsters is all wrong in the stock tables!!

Penner, just a data point for you.

My bikes at almost 14:1 comp, Carpenters biggest cam, and I’ve backed off timing up top 2 degrees from stock, made bang on exactly what it should have on 92 (US) octane pump gas.

My head is decked though so the quench area and chamber size will be smaller than most bikes. Not sure if the reduced chamber size is why it likes the timing or if it’s the cam cutting dynamic compression down, but 27-28 at WOT works perfect for my motor.

 

[Penner]

A main point regarding ignition timing is turbulence.
It is the reason why you don´t have to do something like 60 degrees advance at high revs.
Compression is mainly a matter, when it comes to avoid knocking. It also accelerates combustion, but just a little.
So if you got really good flowing heads and high lift cams, turbulence will be reduced and you will need more advance though dynamic compression is higher.