timing and acceleration

#1
I just read this on another thread:

" My advise is install a 4 degree offset key to back your ignition timing from the built-in 32 your billet flywheel has that was engineered to run @ a continuous high rpm in narrow power bands on racing engines to a more acceleration friendly 28 degrees unless you plan on racing your mini bike on an oval. Might go 30 on an engine for a broad torque curve build, depending on application, but never 32 on anything not on a track. This is static timing. No advance mechanism like a car. 32 is 32 at idle and at max rpm. You're killing your low and mid range torque with too much advance."

Live and learn, acceleration friendly is what I'm after, think I'll back mine up 4*. Comments?
 
#2
Timing depends on the chamber in the head and the piston. Small chamber with good squish may run better with less than 32 but 32 was considered best for most of the kart guys. A hemi could probably use more timing so it depends on your combo. Dyno is required for optimum timing. Danny Youngblood is working on a combo adjustable coil mount and outboard bearing for the timing side.
 

delray

Well-Known Member
#3
Timing depends on the chamber in the head and the piston. Small chamber with good squish may run better with less than 32 but 32 was considered best for most of the kart guys. A hemi could probably use more timing so it depends on your combo. Dyno is required for optimum timing. Danny Youngblood is working on a combo adjustable coil mount and outboard bearing for the timing side.
ole4,if a guy wanted to control is timing for is type of application . could the coil be built on a slide unit controlled by a vacuum modulator or some other way?
 

delray

Well-Known Member
#8
guy could almost fab something up on a old flathead Tecumseh that had points. there set up on a slotted adjustable mag... clearances would have to stay tight so the mag doesn't move around and chatter.
I see on is plate adjuster he is using four bolt holes with the wide flange bolt heads and clearances look to be tight , so it just pivots back and forth. little grease on them when he is ready to use it. the movement back and forth will be so slow it should last a long time.
 
#9
guy could almost fab something up on a old flathead Tecumseh that had points. there set up on a slotted adjustable mag... clearances would have to stay tight so the mag doesn't move around and chatter.
I see on is plate adjuster he is using four bolt holes with the wide flange bolt heads and clearances look to be tight , so it just pivots back and forth. little grease on them when he is ready to use it. the movement back and forth will be so slow it should last a long time.
The prototype is not adjustable on the fly. The drawing is of a adjustable idea using a remote carb adjuster cable.
 
#11
...
guy could almost fab something up on a old flathead Tecumseh that had points. there set up on a slotted adjustable mag... clearances would have to stay tight so the mag doesn't move around and chatter.
I see on is plate adjuster he is using four bolt holes with the wide flange bolt heads and clearances look to be tight , so it just pivots back and forth. little grease on them when he is ready to use it. the movement back and forth will be so slow it should last a long time.
A guy did. He posted it about a year ago. He was on here bragging and a few people didnt believe he'd done it, and sure enough, he had run a rod into the shroud to move the mag plate back and forth.

Also some of the vintage karts had ignitions that could be adjusted on the fly, or at least I heard that and have seen the linkages for sale.
 

delray

Well-Known Member
#13
...


A guy did. He posted it about a year ago. He was on here bragging and a few people didnt believe he'd done it, and sure enough, he had run a rod into the shroud to move the mag plate back and forth.

Also some of the vintage karts had ignitions that could be adjusted on the fly, or at least I heard that and have seen the linkages for sale.
yes he did..fasttony? not sure if he actually tried it. think he was hesitant to try it? he also seem to have some problems with that hs-build with the 245 cam. just couldn't get it dialed in right. more of a fixed position/adjustable setup.
 
#14
I thought it was someone else, and it was not a "finished" looking deal, but functional. Anyway, that entire assembly would need to be redesigned for an advance to work decently, like the photo ole4 is showing. I dont think there is enough in an HS for example to make it worth while, although being able to retard the spark for starting might save some fingers.
 
#15
more timing makes more acceleration cause it makes more torque as rpm increases you can retard it back some so it dont fight itself on a automobile set up you time the engine to get the flame travel over the piston so on a dome you run more timing also like ole said the chamber dictates the lead needed
 
#17
the way to do it is to make a digital box that you can move the curve the signal wire from the coil to a timing controller you plot the curve your engine likes like an msd programable box
 

65ShelbyClone

Well-Known Member
#19
If going from 32* to 28* might help on the low-end, then is
the stock timing 24* the ultimate for low-mid?
Reducing spark advance only helps when there was too much already. Pulling more and more out will cause power to drop and exhaust temps to rise. Usually when timing is set on a dyno, more is added until the engine stops making more torque, then it's reduced again slightly for a margin of safety. Utility engines have conservative timing because they run on cheap gas under high load and relatively low revs.
 
#20
Good info, 65SClone, thanks for the input brother,
I'll just go to 28* and be happy with it.
Question: Does one install a regular timing key backward to retard the timing or does
a key have to be fabricated? Will the groove face left or right?
 

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