Effects of ignition timing on power characteristics.....

[drunkmunkey6969]

Thought this may be of interest to some. It is a graph which shows a TS1 that i was working on, and was trying to find the best ign timing setting on an M-Tech box, to give the correct curve that we wanted. This graphs shows 3 runs on the same engine/cylinder, with no other changes than the setting on the M-Tech box. The scooter was ticking over at 17 degrees BTDC and would retard back closer to 12 degrees depending which setting was used. Obviously on the green (least) setting it would only have come back to say 16/15 degrees at peak RPM, a bit further on the middle setting and right back to 12 on the red (most/fastest) setting.

First curve (green) shows the M-Tech on the lowest setting (setting 1: least retard effect)
Second curve (blue) shows the M-Tech on the middle setting (setting 8: medium retard effect)
Third curve (red) shows the M-Tech on the highest setting (setting F: most/fastest retard effect)



It can be seen in this particular instance that the least amount of retard showed highest peak power, but then the curve drops off sharply and quickly....compared to the last curve where the peak power is lowest, but the scooter revs on much more.

I ended up using setting '4' on this scooter, which meant we were left with a good compromise between peak power and over-rev. Once the jetting was then cleaned up it provided a lovely curve, with nice power, good rev-on, and didn't run too hot.

[tony]

What you should try dan is once you have arrived at a setting then do ten more runs in a row. In quick succession and look at the graphs.

[drunkmunkey6969]

To watch the heat in the pipe you mean? As in...heat/tuned length etc?

[tony]

as your dyno is a sweep type dyno keep running again and again and look to see the effects.

[drunkmunkey6969]

Never done ten additional runs once a setting has been achieved. But have run the same scoot 15 times in total though, through various configurations (each test has 3 runs, so that's 45 runs!). Once I achieved final settings have then done 2 more sets of 3 back to back to confirm results.

Also use a laser temp gun to monitor start/finish temps on cylinder, head and crankcasings etc....so I can monitor like for like when needed, or step up in heat range when needed.

[Rude De]

A-B Honda Factory race Kits. Have the ignitions mapped out to the pipes. These Ignition Retarders are really an Ounce of Prevention too Costly Pounds Of Cure "holed piston and seizures". Programmable ignitions or preprogrammed ignition curves to the pipes power curve are the real deal for power and reliability.
And at some point a micro computer with egt cht oxy inputs and output for powerjet. :ninja:

[tony]

well your pipe is a set spec. Unless your name is keith terry the pipe is fixed. The ign can stretch the restrictions of the pipe. Using an ecu with tps and a map sensor maybe the future when coupled to egt.
The egt/powerjet type map unit has been around for a long time from honda. And used on the bsso track for some time too.

[drunkmunkey6969]

Yes, mapable ignitions and multi powerjet related gismos are used on track, and yes heat ranges changes pipes tuned length etc.....but this has to be put into perspective for the everyday user and the thousands of daily scooter riders....not 20 blokes on a track. So until its affordable and available off the shelf, we should be experimenting to see what is the best we can do with the tools available to serve the daily scooter rider......as well as developing new stuff on the track, in the hope that (as often happens) the stuff on the track gets picked up by a manufacturer and made affordable/available to the daily user. These little boxes are only 80 quid, and any scooter rider can fit one....or take one to thier local mechanic/dyno centre to be fitted.....and as mentioned, a helpful prevention method against costly cure (along with performance benefit options too).

I use one of these boxes on my scoot, and a 20 quid power jet....I know which settings to have both set at to tootle around on.....but in one click of a screwdriver I know what effect a small change will make to both performance and running temps if I want a mad blast (say up a sprint track?)...which makes the cost to benefit ratio very attractive.

[mnpes]

EFFECTS OF THE IGNITION TIMING ~ Graham Bell

How changes in the static ignition timing affects the power band

Advancing the Ignition
The timing will make the power band hit harder in the mid range but fall flat on top end Advancing the timing gives the flame front in the combustion chamber, adequate time to travel across the chamber to form a great pressure rise
The rapid pressure rise contributes to a power band's ~ The "Hit"
In some cases the pressure rise can be so great that it causes an audible pinging noise from the engine
As the engine rpm increases, the pressure in the cylinder becomes so great that pumping losses occur to the piston. That is why engines with too much spark advance or too high of a compression ratio, run flat at high rpm.

Retarding
The timing will make the power band smoother in the mid-range and give more top end over rev. When the spark fires closer to TDC, the pressure rise in the cylinder isn't as great
The emphasis is on gaining more degrees of retard at high rpm
This causes a shift of the heat from the cylinder to the pipe. This can prevent the piston from melting at high rpm, but the biggest benefit is how the heat affects the tuning in the pipe
When the temperature rises, the velocity of the waves in the pipe increases
At high rpm this can cause a closer synchronization between the returning compression wave and the piston speed
This effectively extends the rpm peak of the pipe

With the Agusto Module ~ 3 set maps are available ~ 6-7 and 8000 models
The M-Tech unit is an Adjustable 16 Map Unit
Reference is made to the 3 settings of the Augusto units ~ Which can be dialled in

The Characteristics of these modules can be further altered by the exhaust system regarding the Heat affects ~ Especially with exhausts having a Stinger ~ Basically a Bleed Valve

To Big
The Stinger generally reduces Optimum Exhaust temperature for maximum RPM

To Small
The Stinger restricts the scavenging affect ~ The heat builds up and can"t dissipate



"Inspector Gadget"
Was set-up with 2 egt"s when experimenting with modified exhausts/endcans
Very useful when it came to modifying mechanical Mufflers ~ Suzuki rg - DJ Style Microns etc
and Stinger sizing .......

PS .......
Regarding Powerjetting ~ Especially Running Unfiltered ~ As I was

Had some strange instrument readings recently
Initially put it down to bad fuel after checking the carbs internals
Emptied the tank but still showing these wierd readings about 3/4 throttle
Not letting it get the better of me swopped everything it could possibly be on the ht side
Still there
Stripped the Powerjet down
Didn"t do that initially as I had loctited the bellmouth on ~ For fear of it being pinched
It had the smallest bit of crap in the venturi tube imaginable ~ Cleaned it out - Back to normal
So don"t rely 100% on them and occasionally check them