Ignition Timing Advance

[richardhaggarty]

I have a '85 GS700. I installed a Dyna 2000 ignition system and coils. The ignition module is "programmable", meaning it allows you to adjust the timing advance curve based on a certain RPM. It comes with a few built in curves but something tells me there are not the best examples for my GS engine (the built in curves go to 16,200 RPMs!).

Anyone have any info on the stock advance curve for a GS700? That would give me a good starting point for tweaking. Also, what is the redline; I don't have the gauge in front of me right now.

Thanks

[richardhaggarty]

I made some progress on my timing problem:

The factory service manual has "Ignition Timing" listed under Specifications>Electrical. It says :

13° B.T.D.C. below 1,500rpm and 35° B.T.D.C. above 2,350rpm

Which, is helpful. However, it doesn't say anything about what is going on between 1,500 and 2,350rpm. I can only assume it some value between 13° and 35°.

Anyone have any idea what the mystery in-between value might be?

Also, given this stock timing set up what would be good streetable performance timing values based on the following modifications I have done to my GS700?

K&N Pod Filters
DynoJet Jet Kit
4 into 2 Stock GSXR 1100 Exhaust

Thanks in advance

Rich

[saaz]

I don't have the exact numbers, but when I put the timing light on (years ago on a GS750) it smoothly advanced from the min to the max. The motor does not spend any time at all at the low values, so setting the max advance to suit your engine mods is more important. Some head work and pistons will increase efficiency of combustion so advance can be changed. With a near stock engine standard timing may be right.

[richardhaggarty]

saaz,

That smooth advance is what has me confused about the stock electronic values. I think that linear increase in the timing advance is due to the nature of the mechanical advance system that was probably on the GS750 you tested. Disclaimer: I am just guessing here.

I thought a linear growth from idle to peak power (≈ 8.5K) made sense too. The DYNA software allows only ten data points to peg a timing advance number to a specific RPM. Since I have a stock engine (internally) I was thinking about using the stock min and max timing advance values and get something like this:

RPM Deg. Advance

1. 100 1
2. 600 10
3. 1000 15
4. 2000 19
5. 3000 23
6. 4000 27
7. 5000 31
8. 6000 35
9. 7000 35
10. 8000 35

..hitting full timing somewhere around 5K or 6K. That was until I found out that under the stock settings max timing advance is reached at 2,350rpm.

Which would look like this:

RPM Deg. Advance

1. 100 13
2. 600 13
3. 1000 13
4. 2000 ?? (Between 1.5K and 2.35K are undefined by the manual)
5. 2350 35
6. 4000 35
7. 5000 35
8. 6000 35
9. 7000 35
10. 8000 35

I am just learning about some of these concepts, but that just doesn't look right to me.

Any internal combustion guru's have any insight?

[earlfor]

[quote=richardhaggarty
I found out that under the stock settings max timing advance is reached at 2,350rpm.

Which would look like this:

RPM Deg. Advance[LIST=1][*] 100 13[*] 600 13[*]1000 13[*]2000 ?? (Between 1.5K and 2.35K are undefined by the manual)[*]2350 35[*]4000 35[*]5000 35[*]6000 35[*]7000 35[*]8000 35[/list]I am just learning about some of these concepts, but that just doesn't look right to me.



The above is correct. On my 1150 with a Dyna 2000, I run 34 deg max and its at max advance at 3500 rpm. The problem with early max advance at lower rpms is with low rpm and large higher gear throttle position, it will go to max advance, overload and give you pre ignition knock. I found no need to have low rpm max advance because when I wanted power, I normally was above 5-6k anyhow. I found the bike ran smoother with the max advance coming in around 3500 rpm.

E.

[richardhaggarty]

Thanks for the reply.

I think I'll take advantage of the multiple selectable curves on the Dyna 2000 and make a few different maps. A stock curve, a curve like earlfors and one with the max timing a little higher. I can try out each one for awhile and compare.

Now, if DYNA would only make a programmable weather module then they would have something.

Rich
♠

[earlfor]

Thanks for the reply.

I think I'll take advantage of the multiple selectable curves on the Dyna 2000 and make a few different maps. A stock curve, a curve like earlfors and one with the max timing a little higher. I can try out each one for a awhile and compare.

Now, if DYNA would only make a programmable weather module then they would have something.

Rich
♠

I believe I used curve 2 on the setup and 34 deg at 3500 rpm.

E.