Timing...Initial advance and slope curves as they relate to power output??

[Mcfly]

I have a question about timing.

How does advance/retard and slope relate to power output

On my 107" motor with a DTT TC88 ignition I went from initial of 2 and a slope of 3, which absolutely sucked the power out of my motor, to an initial of 3 and a slope of 4 which really woke up my motor.

Those numbers to me were almost totaly random....I just picked them out of the sky. Verified on a dyno...that change alone netted me about 8ftlbs and 6HP (and recuced the oil temps by 10-15 degrees).

I have played with additional settings like 3&6 3&5 which seemed to have a little if any impact on the feel of the power and based on the butt dyno may have decreased the power.

I am now running initial of 4 and a slope of 4. According to the butt dyno...when compared to the 3/4 setting it doesn't seem any better or worse.

Can someone explain to me exactly WHAT I am doing when I change the initial...and the slope and how they should relate to power output?


Regards

[johnsachs]

McFly,
You're putting more advance in quicker,by going to the higher numbers.
John

[nw_guy4_fun]

You will find the most power at the MBT point. This is generally the point just prior to ping. You will find lots of info on the net regarding this if you search it. The cable and software is usefull to pull out some timing at the "stupid to gun it points" IE 70% throttle 1800 rpm.

[nw_guy4_fun]

BTW in the case of very low dynamic compression (late intake close cams) it may be impossible to get to the ping point and the maximum timing for the best power and torque will be determined on the dyno and by experience.

[Mcfly]

Originally Posted by johnsachs

McFly,
You're putting more advance in quicker,by going to the higher numbers.
John

Thanks John and NW...This much I already knew...I just dont understand the theory behind the action.

I have read that I need to advance it until it pings then back it down a few degrees.

Problem is I'm not sure if I will be able to HEAR it ping. Will I? I have also heard that I can have detonation without pinging. Do I run the chance of engine damage by advancing it until I hear pinging?

The bike runs OK now...how much can I expect to gain by optimizing the timing?

What is the best proceedure to go about trying to find MBT?

[nw_guy4_fun]

On a Crane or DTT start at 0,0 or 0 initial and your current setting for slope if you have no pinging now and move up one notch slope at a time until you experience pinging. Back off one step then start moving the initial up in the same way until you reach the ping point then back off to make it quit. That's it, you are there. If you suspect slight ping that may not be heard that will show on the plugs with the grey beads on the white porceline and at that point I would just go a heat range cooler which will likely cure that.
BTW get the AFR close first before dialing this in

[nw_guy4_fun]

BTW in some cases of low dynamic compression (late close intake cams) you may find this method doesn't work because the motor will never ping and a special curve will be needed for optimum power, WOT looking like about 30max all in at 4K.

[Mcfly]

Originally Posted by nw_guy4_fun

On a Crane or DTT start at 0,0 or 0 initial and your current setting for slope if you have no pinging now and move up one notch slope at a time until you experience pinging. Back off one step then start moving the initial up in the same way until you reach the ping point then back off to make it quit. That's it, you are there. If you suspect slight ping that may not be heard that will show on the plugs with the grey beads on the white porceline and at that point I would just go a heat range cooler which will likely cure that.
BTW get the AFR close first before dialing this in

Excellent...thanks. After I finish adjusting the initial setting should I go back and try to fine tune the slope or leave it alone?

BTW... motor is a 107" all bore motor w/ 10.5:1 flattops and Andrews TW60 cam.

[nw_guy4_fun]

You should be done and no additional work needed