Timing at cruising speeds

[07heri]

We're tuning a friends bike in the timing area.  I've had no issues when I ran mine at 45 even in the summer months, 100 degree days.  I've read where some say don't run that much timing at cruise.

What's the general consensus for timing this area?  And more importantly...why?

Saying it's too much...or not enough...or just right....doesn't help me or anyone learn.  If 45 is too much please help me out by explaining.

I guess part 2 of the question is how to fill in the cells around the cruise range.  What I mean is would you use the same timing degree for 500 rpms up and down of right where he cruises?  Would you also use the same degree for 1 map column behind and one past cruise range?

I'm sure others will learn from this too...so thanks

[04XL1200C]

Add as much as you can on a hot day with out pings... Every bike is different! My friend helped me write a map on his bike... I loaded into mine (same year make model engine size) we where running different pipes... My bike pinged his disnt Infact he could run "5deg" more than me... His bike is fed mine is Cali!


Sent from my iPhone on the flip side.

[07heri]

Add as much as you can on a hot day with out pings... Every bike is different! My friend helped me write a map on his bike... I loaded into mine (same year make model engine size) we where running different pipes... My bike pinged his disnt Infact he could run "5deg" more than me... His bike is fed mine is Cali!


Sent from my iPhone on the flip side.

That's pretty much what I have been doing but I've read where some disagree.  Was just curious about the reasons why some might agree or disagree.

[04XL1200C]

Well the idea is that your tunning for max HP right? And the max HP is right before ping! More heat = HP ( you get the point actually in truth HP is tq* rpm but that's a different topic) bottom line is that if you want "safe" then tune lower is you want more HP then you need to tune for the most you can get away with. A performance system (not a emissions system) uses temp and knock sensor to get the most advance! ( the s&s IST comes to mind)

Most of the time I try and tune max advance at wot and try for a middle of the road # for cruz because if you take a trip and carry more weight or long steady rpm it's a good idea to be a little conservative in that are of the map because of changes in load.


Sent from my iPhone on the flip side.

[07heri]

And the max HP is right before ping!

I don't much agree with this comment.  Without having a dyno to tell you right where the max numbers are it's a guess.  It may be possible to go right past the max hp/tq numbers, advance some more and not ping.  Advancing right up to ping, from what I understand could actually show lower numbers than 5 6 7 degrees prior, in some situations.

Anyway, you're kinda blowing this out of proportion.  I was after why some feel 45 is too much at cruise, or is it really too much.  I see plenty of maps at 45 yet I also read where folks say 45 is too much.  Just wanted to see if I could get some clarification from any tuning gurus here.

[Tsani]

From my understanding, the 45* thing has more to do with the overall crappy gas we are getting these days.

[07heri]

From my understanding, the 45* thing has more to do with the overall crappy gas we are getting these days.

So, 45* is used because of the junk added to gas or don't go as high because of the junk in the gas?  You kinda left me hanging....lol

[Hilly13]

The latter Heri

[hrdtail78]

People seem to make blanket statements all the time about what is good and bad.  Never run 45 degree's advance, never leaner than 14.2, on and on.  It would be nice if they backed up their statement with anything.

There are way too many variables to consider.  A stock bike with a decent stage one has no problems with 45 at 50kpa 2500.  Not my timing satiety for a 4.125 bore w/ 195 ccp though.  So it boils down to give the engine what it wants.  Same engine build with different pipes might just like different things.  With what most of us have as for as tuning tools.  Getting up to the ragged edge of knock and then pulling back 3-4 points is the best thing going besides sinking money into some expensive testing equipment.

I understand this isn't a direct answer to the question posted.  There is no direct answer.

[strokerjlk]

Are you actually running 45 deg at cruise, of is it just in the map?
45 deg works real well on decel .

Basically, if combustion starts too soon, the gas pushes back on the piston as it is coming up in the compression stroke, creating negative work which reduces torque.  If the spark is too late, peak cylinder pressure is reduced, and hence, so is expansion work.  So there is an optimum spark for maximum torque.  If one were to draw out a curve of torque vs advance, (starting out below MBT), as spark is advanced torque will increase until MBT timing is reached, after which point further advance will cause torque to go back down.  The top of the curve is somewhat flat, so the percentage increase in tq drops off as spark advance approaches MBT.

[Overcamber]

good explanation stroker

[sfmichael]

MBT = ? Maximum Best Timing   

I'm assuming by the context of the post that it's maximum timing, just trying to figure out the acronym, your post doesn't say.

[strokerjlk]

Sorry yes .
Maximum brake tq
Or
Maximum brake timing
Depends on who's teaching the class
Same theory. Diff terminology

[sfmichael]

thanks stroker 

[Admiral Akbar]

Jim and Jason..



Max

[07heri]

Are you actually running 45 deg at cruise, of is it just in the map?
45 deg works real well on decel .

Basically, if combustion starts too soon, the gas pushes back on the piston as it is coming up in the compression stroke, creating negative work which reduces torque.  If the spark is too late, peak cylinder pressure is reduced, and hence, so is expansion work.  So there is an optimum spark for maximum torque.  If one were to draw out a curve of torque vs advance, (starting out below MBT), as spark is advanced torque will increase until MBT timing is reached, after which point further advance will cause torque to go back down.  The top of the curve is somewhat flat, so the percentage increase in tq drops off as spark advance approaches MBT.

He had 47 in the map and it didnt ping. That's what prompted me to ask.  I remember reading somewhere that 45 wasn't good so figured I'd toss it out here for opinions.   All the cells around 2500 and 50k had the same 47.  I had him ride it at 47 and then I changed it to 42 and had him ride it again.  He didn't know which numbers I used and he couldn't tell the difference.  So just left it at 42 to err on the safe side.   

[strokerjlk]

Are you actually running 45 deg at cruise, of is it just in the map?
45 deg works real well on decel .

Basically, if combustion starts too soon, the gas pushes back on the piston as it is coming up in the compression stroke, creating negative work which reduces torque.  If the spark is too late, peak cylinder pressure is reduced, and hence, so is expansion work.  So there is an optimum spark for maximum torque.  If one were to draw out a curve of torque vs advance, (starting out below MBT), as spark is advanced torque will increase until MBT timing is reached, after which point further advance will cause torque to go back down.  The top of the curve is somewhat flat, so the percentage increase in tq drops off as spark advance approaches MBT.

He had 47 in the map and it didnt ping. That's what prompted me to ask.  I remember reading somewhere that 45 wasn't good so figured I'd toss it out here for opinions.   All the cells around 2500 and 50k had the same 47.  I had him ride it at 47 and then I changed it to 42 and had him ride it again.  He didn't know which numbers I used and he couldn't tell the difference.  So just left it at 42 to err on the safe side.

good move. less chance of knock activity that way. you could drop it to 35 and he couldn't  tell the diff.

[oldguy]

Just as an aside, if you monitor the kpa at the areas you are looking to change timing, you should see the kpa increase as the timing gets too advanced, wouldn't you??