Split Timing - Theory of Operations (feedback needed)
 

Hey guys, i am starting this post, because i need some info on the ways to set up the trailing timing split. Depending on who you talk to, you will get a slightly different version of what actual timing to run, and since the Haltech has a Rotary Trailing Split timing map, and i know for a fact that proper trail timing can net better torque, i wanted to know what you guys have done, or the engine tuners here know about it.

Now, these comments are based on my experience, which i will admit isnt the most well informed on the actual engine behaviour, since i dont know it all, but together we can sort them out, if anybody can correct me anywhere, please do so.

1. If you dont use trailing split you loose low end torque??

2. Trailing should be constantly split to 15 degrees throughout the entire RPM range??

3. The split should get smaller and smaller as the RPMs are higher??

4. Depending on who you talk to, they will recommend split timing to be anywhere from 10-17 degrees??

So, if anybody has real, actual, mazda info that we can digest, i would greatly appreciate it.

Its tuning...some will say yes, and some with say no.

that statement is dangerous. smaller the split the more likely the trailing could fire before the leading.

but isn't the map set-up VS boost...

the jc cosmo "service highlights" book has the timing map in it. its about 2" by 2" and load isnt defined with units.

the split under boost is always 15 degrees. it does drop near zero in cruise, and its about 10-15 at low rpms.

ted will disagree, but he transcribed it backwards.

over on nopistons henrik posted the timing maps for the s4's and the na's run about 4 degrees of split @high rpms and load, and the t2 runs about 15.

we can argue about why they did that, but they did do it.

Well, i dont wanna argue at all about this, i believe that the better we can get the trailing split map the better the performance from the engine, specially the daily driven/street ones.

So, if we can work together i believe we can get a great trailing map that we can all benefit from. Matt (the HITman)'s trailing map does look like what you just discribed j9fd3s, so im thiking he has done his homework a long time ago. I dont wanna just copy his setups, i wanna find the optimum choice.

Anybody have any actual links or images of a factory mazda trailing map so i could look at it? Does the service manual say anything about it? i have my Mazda 88 Service manual here so ill look to see if i can find anything.

Thanks for the feedback guys, keep it coming.

Oh great... :P


-Ted

Good thread, we definately need more info. I'm looking to re-do the split on the trailing for no and very low boost situations to see if I can net a little more power and/or fuel economy... I was currently thinking I'd mimic the NA maps (makes sense right?), maybe slightly more aggressive since I'm always running at least 91 octane. Then under boost, I'm planning on running a very conservative split.

Have you read through this thread about timing on Teamfc3s?
http://www.teamfc3s.org/forum/showth...threadid=41915

Definately some interesting light shed on the timing and split timing by Judge ITO. Very informative.

Darn it, i have to register to view it. :(

rule of thumb for me is (WOT application). More split timing for more advance and less split timing for less advance.

as for crusing, you want to keep it around 0-5 degrees.

Set your split to 12 degrees under boost and WOT and then tune for it on the dyno, with air fuel readings and 2 ( or 3) EGT sensors.

You are right about all this, but we cannot just tell people to run xx degrees of timing b ecause every engine is different...

So, what you are saying is that the higher the RPM/Load the less timing difference there is between the leading and trailing? is that it? I believe this i already know, what im trying to establish is what kind of timing difference (split wise) is ideal.

The word ideal is relative. If one engine takes 8 degrees split at 25psi and 6000rpms, another engine might blowup at that setting. Like I said, start with 12 and tune for it. There are way too many variables that determine the timing... Portwork, turbo size, AR, intercooler, fuel octane, intake manifold, etc etc etc.

back form the dead!
im trying to figure out this timing thing and would like some info. on it.
back to the other thread for now.;)

Claudio,

There's alot of variables that will determine what is ideal.

Some tuners choose to run very close to no split but overall advance will be different then those who choose to run large splits..

Fuel plays a very large part as well..

a further ressurrection, its been a couple years, what have ya come up with. id really like to understand this better. i keep readin threads that start great an leave ya hangin like its all a great mystery. must be some sort of safe zone guidelines.

off to read the linked threads.. perhaps light will be shed

http://lh4.ggpht.com/_5HTl7wWVj2k/Su...tion%20map.jpg

http://lh6.ggpht.com/_5HTl7wWVj2k/Su...plit%20map.jpg

Can some one explain me how to read and adjust trailing split map... By reading all above, I uderstand that its better to have less split in vacuum and around 15 under boost. By looking at the bottom split/trailing map its the other way around. I got this map from one good guy who seems to know stuff.
Maybe I just don't know how to read it properly.

Thanks

if im reading it right that trailing map looks wrong. Im running a map similar to what steve kan posted up earlier, more advance = more split, less advance = less split. lower split = more power, but at the expense of combustion stability, meaning it could cause detonation in the right circumstances

And split really does make a big difference. Just last weekend i was messing around with it while cruising and you can feel a power difference just changing a few degrees. I was toggling between 5 and 0 split and I could feel the car surge forward when drpping the split towards zero

.