Trailing timing, pros/cons with 0deg. Split?
02-06-05, 06:15 PM
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Trailing timing, pros/cons with 0deg. Split?
G'day all.
Is there any problem/advantage of running the trailing spark plugs at the same time as the leading in all circumstances?
Mainly looking for any problems I might encounter, especially at say. idle.
Obviously at high revs it wouldn't be much of an issue at all, in fact all I can see it doing there is helping combustion.
Also has anyone here had experience with drilling out the trailing plug hole to get a better spark? say the same size as the leading.
Any thoughts at all would be good
Is there any problem/advantage of running the trailing spark plugs at the same time as the leading in all circumstances?
Mainly looking for any problems I might encounter, especially at say. idle.
Obviously at high revs it wouldn't be much of an issue at all, in fact all I can see it doing there is helping combustion.
Also has anyone here had experience with drilling out the trailing plug hole to get a better spark? say the same size as the leading.
Any thoughts at all would be good
02-07-05, 02:11 AM
#2
hope this helps.
Timing By Judge Ito
Once a rotary engine is built correctly, ignition timing is first and foremost. Members need to really pay attention to ignition timing.
I have had people that play around and work on rotaries claim all kinds of bull crap to me. **** like: "a rotary engine has 2 top dead center, one for the leading spark plug and one for the trailing spark plug". They go ahead and claim that the factory yellow mark on the timing pulley is 0 degree or TDC for leading plug and that the red timing mark, is 0 deg. or TDC for the trailing plugs. And they go ahead and tune ignition timing according to that. I just scratched my head and said OK what ever works for you.
Factory timing marks on a rotary engine at idle are as follow. Yellow mark 5 deg. After Top Dead Center and red mark is 20 deg. ATDC. Mazda does this to get a smooth idle. Try and advance ignition timing to about 20 deg. before TDC at idle and 80% of the time, you will get a lumpy idle, bring the timing back to -5 and -20 and smooth as a baby's butt.
Once you understand the factory timing marks, then some adjustments could be made, but first understand what you are doing.
For N/A engines running a very little split will land the most amount of power available, Example: 35 degrees BTDC for Leading and 30 deg. (Running a 5-2 deg. split) BTDC for trailing. 31,32 even 33 deg. BTDC for trailing. Mazda Factory Racing reccomends no split. 35 for lead and 35 for trail. 30 for lead and 30 for trail. 20 for lead and 20 for trail. you guys get the point.
I always run a split for precuation of getting the trailing plug firing before leading. that is a no, no.
On turbo charged engines ignition timing plays a mayor role, because combustion temperatures are much higher then N/A engines the ignition split needs to be greator, to prevent detonation, basically running a little to no split will increase combustion temperature, for N/A that is fine, but for turbo charge is dangerous, since your dealing with elevate combustion temperatures already from boost.
I have played with all kinds of timing advance. a 12 degree split will land some power and maintain reliability.
Fuel octane is also very important, On 116 octane I have used up to 19 degrees BTDC for leading with 32psi of boost and 7 deg. for trailing with no detonation and making well over 650rwhp on a friends drag racing car. Using 93 octane I keep leading down to 15-16-17 deg. btdc with a 12 deg. split and depending the amount of boost.
I also have a serious tip on other factors of igniton timing. to be continue..
I would like to try and help fellow online rotorheads that currently play around and work with rotaries. These tips are important and maybe a moderator might want to pinned this thread.
Ignition timing and how it works.
Mazda has 2 timing marks on the factory pulley. From 1986 to 95 US models timing marks are -5 and -20 at idle. The 3rd gen. Rx7 only has a -20 timing mark, the -5 has to be added to the pulley. Astralian 3rd gen. models have a -5 and -20 timing marks, but the US model doesn't. These timing marks are dead right.
When the engines is revved, timing will advance to the + side or Before top dead center side. At idle the engine is resting in the - side or after top dead center.
I'll like to try and help members understand to which side the timing pulley advances for + timing and how it comes back to - timing @ idle.
If you're standing infront of the car and looking inside the engine bay, the timing pulley has 2 timing marks. The first one, left to right is -20 and usually colored RED, the second timing mark is -5 and usually colored YELLOW. The timing pulley advances timing to your right hand, that would be + timing. Anything to the left side of the timing marks, incuding the factory timing marks on the pulley are to your left hand. Remember the 2 factory timing marks are -5 and -20 at idle.
Once you learn how to identify the factory timing marks, and to which way the engine advances timing then you move on. The leading spark plug is the engines main spark plug. Timing needs to always be adjusted using the leading 1 spark plug. Trailing 1 gets adjusted later.
Depending if you have an electronic distributor, 86 to 91 crank angle sensor, or adjustable timing EMS like haltech, micro tech, Motec, Autronic, etc,etc, engine needs to be revved to about 4,500 rpms to view total timing advance with a timing light.(total timing advance is when the ignition timing will not advance any more,when the engine is revved) At this point make your adjustments to the leading spark plug.
Depending on application, timing would be set. If your running a naturally aspirated engine, timing could be more on 35,30,25 for the leading spark plugs and a 8-3 degree split between leading and trailing spark plugs.
If your running a nitrous oxide engine, timing could be subtracted from your over all N/A timing according to the amount of nitrous being applied. The genereal rule of thumb is, every 25 horsepower increase back up 2 degrees from your basic N/A timing map. If you shot a 50 shot back up 4 degrees from your N/A timing map, this way you start to build a nice Nitrous timing map.
If your boosting a rotary it's all together a different timing map. Depending on how much boost and how much octane, timing, could be adjusted. The split between leading 1 spark plug and trailing 1 spark plug, needs to be larger. From 8-3 degrees for N/A and nitrous, to 12-15 degrees for turbo charged engines.
What is also very crucial is the timing light. Rotaries are a 4 cycle engine, but when it comes down to ignition timing, they work like a 2 stroke engine, firing every 360 degrees instead of every 720 degrees like a 4 cycle piston engine.
Make sure you always use a 2 cycle timing light or your ignition timing will always read off.If you use a 4 stroke timing light, just subtract the number in half. example: If the 4 stroke timing light reads 40 degrees BTDC in all reality your engine is only at 20 degrees BTDC. My timing light is a 2 stroke 4 stroke all in one.
I just realized how long this thread is going to be. I need to address, adjusting timing split between leading and trailing, for early distributors and stand alone ecu's, timing specs that have worked for me across the board and how to use the timing light and avoid a cross magnetic timing signal from one spark plug wire to the other.
I will continue this thread. But if members have questions up to now, just ask me. I'm in the middle of writting a story for Rx Tuner magazine, I'll continue this thread very soon.
Timing By Judge Ito
Once a rotary engine is built correctly, ignition timing is first and foremost. Members need to really pay attention to ignition timing.
I have had people that play around and work on rotaries claim all kinds of bull crap to me. **** like: "a rotary engine has 2 top dead center, one for the leading spark plug and one for the trailing spark plug". They go ahead and claim that the factory yellow mark on the timing pulley is 0 degree or TDC for leading plug and that the red timing mark, is 0 deg. or TDC for the trailing plugs. And they go ahead and tune ignition timing according to that. I just scratched my head and said OK what ever works for you.
Factory timing marks on a rotary engine at idle are as follow. Yellow mark 5 deg. After Top Dead Center and red mark is 20 deg. ATDC. Mazda does this to get a smooth idle. Try and advance ignition timing to about 20 deg. before TDC at idle and 80% of the time, you will get a lumpy idle, bring the timing back to -5 and -20 and smooth as a baby's butt.
Once you understand the factory timing marks, then some adjustments could be made, but first understand what you are doing.
For N/A engines running a very little split will land the most amount of power available, Example: 35 degrees BTDC for Leading and 30 deg. (Running a 5-2 deg. split) BTDC for trailing. 31,32 even 33 deg. BTDC for trailing. Mazda Factory Racing reccomends no split. 35 for lead and 35 for trail. 30 for lead and 30 for trail. 20 for lead and 20 for trail. you guys get the point.
I always run a split for precuation of getting the trailing plug firing before leading. that is a no, no.
On turbo charged engines ignition timing plays a mayor role, because combustion temperatures are much higher then N/A engines the ignition split needs to be greator, to prevent detonation, basically running a little to no split will increase combustion temperature, for N/A that is fine, but for turbo charge is dangerous, since your dealing with elevate combustion temperatures already from boost.
I have played with all kinds of timing advance. a 12 degree split will land some power and maintain reliability.
Fuel octane is also very important, On 116 octane I have used up to 19 degrees BTDC for leading with 32psi of boost and 7 deg. for trailing with no detonation and making well over 650rwhp on a friends drag racing car. Using 93 octane I keep leading down to 15-16-17 deg. btdc with a 12 deg. split and depending the amount of boost.
I also have a serious tip on other factors of igniton timing. to be continue..
I would like to try and help fellow online rotorheads that currently play around and work with rotaries. These tips are important and maybe a moderator might want to pinned this thread.
Ignition timing and how it works.
Mazda has 2 timing marks on the factory pulley. From 1986 to 95 US models timing marks are -5 and -20 at idle. The 3rd gen. Rx7 only has a -20 timing mark, the -5 has to be added to the pulley. Astralian 3rd gen. models have a -5 and -20 timing marks, but the US model doesn't. These timing marks are dead right.
When the engines is revved, timing will advance to the + side or Before top dead center side. At idle the engine is resting in the - side or after top dead center.
I'll like to try and help members understand to which side the timing pulley advances for + timing and how it comes back to - timing @ idle.
If you're standing infront of the car and looking inside the engine bay, the timing pulley has 2 timing marks. The first one, left to right is -20 and usually colored RED, the second timing mark is -5 and usually colored YELLOW. The timing pulley advances timing to your right hand, that would be + timing. Anything to the left side of the timing marks, incuding the factory timing marks on the pulley are to your left hand. Remember the 2 factory timing marks are -5 and -20 at idle.
Once you learn how to identify the factory timing marks, and to which way the engine advances timing then you move on. The leading spark plug is the engines main spark plug. Timing needs to always be adjusted using the leading 1 spark plug. Trailing 1 gets adjusted later.
Depending if you have an electronic distributor, 86 to 91 crank angle sensor, or adjustable timing EMS like haltech, micro tech, Motec, Autronic, etc,etc, engine needs to be revved to about 4,500 rpms to view total timing advance with a timing light.(total timing advance is when the ignition timing will not advance any more,when the engine is revved) At this point make your adjustments to the leading spark plug.
Depending on application, timing would be set. If your running a naturally aspirated engine, timing could be more on 35,30,25 for the leading spark plugs and a 8-3 degree split between leading and trailing spark plugs.
If your running a nitrous oxide engine, timing could be subtracted from your over all N/A timing according to the amount of nitrous being applied. The genereal rule of thumb is, every 25 horsepower increase back up 2 degrees from your basic N/A timing map. If you shot a 50 shot back up 4 degrees from your N/A timing map, this way you start to build a nice Nitrous timing map.
If your boosting a rotary it's all together a different timing map. Depending on how much boost and how much octane, timing, could be adjusted. The split between leading 1 spark plug and trailing 1 spark plug, needs to be larger. From 8-3 degrees for N/A and nitrous, to 12-15 degrees for turbo charged engines.
What is also very crucial is the timing light. Rotaries are a 4 cycle engine, but when it comes down to ignition timing, they work like a 2 stroke engine, firing every 360 degrees instead of every 720 degrees like a 4 cycle piston engine.
Make sure you always use a 2 cycle timing light or your ignition timing will always read off.If you use a 4 stroke timing light, just subtract the number in half. example: If the 4 stroke timing light reads 40 degrees BTDC in all reality your engine is only at 20 degrees BTDC. My timing light is a 2 stroke 4 stroke all in one.
I just realized how long this thread is going to be. I need to address, adjusting timing split between leading and trailing, for early distributors and stand alone ecu's, timing specs that have worked for me across the board and how to use the timing light and avoid a cross magnetic timing signal from one spark plug wire to the other.
I will continue this thread. But if members have questions up to now, just ask me. I'm in the middle of writting a story for Rx Tuner magazine, I'll continue this thread very soon.
Last edited by theflatlander; 02-07-05 at 02:14 AM.
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Akaviri (03-25-22)
02-07-05, 07:22 AM
#3
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ok interesting.
now i don't know a hell of alot about timing lights but why the HELL would a 4-cycle one read 40 when your timing is actually 20?
That makes no sense to me at all.
now i don't know a hell of alot about timing lights but why the HELL would a 4-cycle one read 40 when your timing is actually 20?
That makes no sense to me at all.
02-07-05, 10:19 AM
#4
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because a 4 cycle has to rotate the crank twice as much as a rotary to combust its full displacement. Basically say you had a 1.3liter 4cyl, it would have to turn the crank 4 times to take each piston thru the entire cycle to fully displace its entire capacity. A 1.3L rotary only turns the crank (Eshaft) twice to display its entire compacity. Since a timing light is working off of rpms then its going to be off.
BTW - This is also the reason that most racing circuits double the rotary size and make them race against 2.6L engines. Its because when our eshaft turns 4 times we displace 2.6 liters just like a 2.6liter piston engine would with 4 crank turns.
Stephen
BTW - This is also the reason that most racing circuits double the rotary size and make them race against 2.6L engines. Its because when our eshaft turns 4 times we displace 2.6 liters just like a 2.6liter piston engine would with 4 crank turns.
Stephen
Last edited by SPOautos; 02-07-05 at 10:21 AM.
02-07-05, 04:23 PM
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I understand completly how a rotary engine cycle works SPOautos, thank you anyway.
My problem is I don't see how it would change the ignition timing from 40deg using a 4-cycle timing gun to 20deg using a 2-cycle timing gun?
Maybe I just don't understand how a timing gun works properly, but I think i've got a bit of an idea.
By that same token then you would not be able to time a 4cyl 4-stroke engine with wastespark using a normal 4-cycle timing gun.
That makes even less sense, no?
-Nathan.
My problem is I don't see how it would change the ignition timing from 40deg using a 4-cycle timing gun to 20deg using a 2-cycle timing gun?
Maybe I just don't understand how a timing gun works properly, but I think i've got a bit of an idea.
By that same token then you would not be able to time a 4cyl 4-stroke engine with wastespark using a normal 4-cycle timing gun.
That makes even less sense, no?
-Nathan.
02-07-05, 07:35 PM
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Make sure you always use a 2 cycle timing light or your ignition timing will always read off.If you use a 4 stroke timing light, just subtract the number in half. example: If the 4 stroke timing light reads 40 degrees BTDC in all reality your engine is only at 20 degrees BTDC. My timing light is a 2 stroke 4 stroke all in one.
Since a 2 stroke fires every 360 degrees rather than every 720 you neet to divide the dialed in advance on the 4 stroke light to get the correct reading for the rotary.
I.E. 40 degrees advance on the light will actually be 20 on the rotary engine with a 4 stroke timing light.
I has no effect on the emitted light, as that is triggered by the spark.
02-07-05, 07:40 PM
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Originally Posted by RoyFifo
The above paragraph refers to using the timing advance/retard function of the light.
Since a 2 stroke fires every 360 degrees rather than every 720 you neet to divide the dialed in advance on the 4 stroke light to get the correct reading for the rotary.
I.E. 40 degrees advance on the light will actually be 20 on the rotary engine with a 4 stroke timing light.
I has no effect on the emitted light, as that is triggered by the spark.
Since a 2 stroke fires every 360 degrees rather than every 720 you neet to divide the dialed in advance on the 4 stroke light to get the correct reading for the rotary.
I.E. 40 degrees advance on the light will actually be 20 on the rotary engine with a 4 stroke timing light.
I has no effect on the emitted light, as that is triggered by the spark.
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02-07-05, 07:53 PM
#8
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Ok i can see how that works now.
thank you for that clarification
Now back to the topic, so judge ito doesn't suggest running the split cloase to nothing on a turbo motor.
Yet make more power that way.
Has anyone one here actually have any real world experience with blowing up a motor that can be attributed to having no timing split?
thank you for that clarification
Now back to the topic, so judge ito doesn't suggest running the split cloase to nothing on a turbo motor.
Yet make more power that way.
Has anyone one here actually have any real world experience with blowing up a motor that can be attributed to having no timing split?
02-07-05, 08:10 PM
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I had a question about this
Now he says that for an NA to advance it around 35 degrees BTDC, I'm assuming this is total advance and not idle, right?
Next question is
Am I to assume this is with the distributor and aftermarket EMS only and isn't possible with the CAS? When you adjust the leading timing on the CAS the trailing follows the same path and will always be 15 degrees behind it, right? Or is there some way to change the trailing to be less than 15 degrees behind the leading?
Depending if you have an electronic distributor, 86 to 91 crank angle sensor, or adjustable timing EMS like haltech, micro tech, Motec, Autronic, etc,etc, engine needs to be revved to about 4,500 rpms to view total timing advance with a timing light.(total timing advance is when the ignition timing will not advance any more,when the engine is revved) At this point make your adjustments to the leading spark plug.
Next question is
Depending on application, timing would be set. If your running a naturally aspirated engine, timing could be more on 35,30,25 for the leading spark plugs and a 8-3 degree split between leading and trailing spark plugs.
02-07-05, 08:42 PM
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Originally Posted by dDuB
I had a question about this
Now he says that for an NA to advance it around 35 degrees BTDC, I'm assuming this is total advance and not idle, right?
Now he says that for an NA to advance it around 35 degrees BTDC, I'm assuming this is total advance and not idle, right?
Next question is
Am I to assume this is with the distributor and aftermarket EMS only and isn't possible with the CAS? When you adjust the leading timing on the CAS the trailing follows the same path and will always be 15 degrees behind it, right? Or is there some way to change the trailing to be less than 15 degrees behind the leading?
Am I to assume this is with the distributor and aftermarket EMS only and isn't possible with the CAS? When you adjust the leading timing on the CAS the trailing follows the same path and will always be 15 degrees behind it, right? Or is there some way to change the trailing to be less than 15 degrees behind the leading?
You can change it a little with a dissy though.
The only way to do it with the stock cas it to physically move the pickup inside the CAS.
Can be done but not very adjustable.
02-07-05, 08:55 PM
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So if I don't **** with the inside of the CAS and want to advance, I'm just going to have to live with the fact that the trailing will be 15º behind the leading then?
02-07-05, 09:08 PM
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wow just realised what i said, the cas only has two pickups, the home signal and the other signal whatever its called, doesn't even have a trailing and leading, i was thinking about the dissy i have in front of me..
but basically yes with the stock ECU your stuck with the in-built trailing/leading split.
but basically yes with the stock ECU your stuck with the in-built trailing/leading split.
02-07-05, 09:13 PM
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Ok cool, this is all good stuff. So if I'm looking for best power just go ahead and do 35º total advance for leading and then just let trailing land where it has to, right? Sounds good enough to me until I go wolf standalone
02-08-05, 01:59 AM
#14
Do NOT use 35 degrees total advance at full throttle. He only threw that number out there as an example of A number and not THE number. 35 degrees may be fine under light loads at cruising rpms but it is way too much for full throttle, full power. Aim closer to 25-26 degrees. Even this is subjective based on porting style. If you have really radical porting, you might need less still.
The inside of the crank angle sensor does have a seperate pickup for both the leading and trailing. Open one up. Both trigger wheels are different though. The trailing only has 2 teeth whereas the leading side has something closer to 24 teeth or so. I can't remember exactly how many. The ecu deciphers these signals to make sense.
The closer the timing split, the more likely the chance for detonation. This is most crucial on a turbo motor. Widening the split lessens the likelyhood of it. When an engine gets near detonation, the thing many people do is to back off total advance. In reality you may be able to leave total advance the same but just widen the split. This could potentially make more power on a turbo engine. As with anything it really depends on the circumstances.
The inside of the crank angle sensor does have a seperate pickup for both the leading and trailing. Open one up. Both trigger wheels are different though. The trailing only has 2 teeth whereas the leading side has something closer to 24 teeth or so. I can't remember exactly how many. The ecu deciphers these signals to make sense.
The closer the timing split, the more likely the chance for detonation. This is most crucial on a turbo motor. Widening the split lessens the likelyhood of it. When an engine gets near detonation, the thing many people do is to back off total advance. In reality you may be able to leave total advance the same but just widen the split. This could potentially make more power on a turbo engine. As with anything it really depends on the circumstances.
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Akaviri (06-28-19)
02-08-05, 09:41 AM
#15
Drilling the trailing hole out bigger (like the leading hole) is a baaaddddd idea. The trailing plug is located in the combustion cycle and is a small hole to prevent two things. One is combustion pressure loss/leakage or blow by from one rotor face to the other. The other reaons is this blow by is HOT expanding gas and may cause pre-ignition in the next chamber.
~Mike.............
~Mike.............
02-08-05, 07:49 PM
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Originally Posted by rotarygod
Do NOT use 35 degrees total advance at full throttle. He only threw that number out there as an example of A number and not THE number. 35 degrees may be fine under light loads at cruising rpms but it is way too much for full throttle, full power. Aim closer to 25-26 degrees. Even this is subjective based on porting style. If you have really radical porting, you might need less still.
The inside of the crank angle sensor does have a seperate pickup for both the leading and trailing. Open one up. Both trigger wheels are different though. The trailing only has 2 teeth whereas the leading side has something closer to 24 teeth or so. I can't remember exactly how many. The ecu deciphers these signals to make sense.
The closer the timing split, the more likely the chance for detonation. This is most crucial on a turbo motor. Widening the split lessens the likelyhood of it. When an engine gets near detonation, the thing many people do is to back off total advance. In reality you may be able to leave total advance the same but just widen the split. This could potentially make more power on a turbo engine. As with anything it really depends on the circumstances.
The inside of the crank angle sensor does have a seperate pickup for both the leading and trailing. Open one up. Both trigger wheels are different though. The trailing only has 2 teeth whereas the leading side has something closer to 24 teeth or so. I can't remember exactly how many. The ecu deciphers these signals to make sense.
The closer the timing split, the more likely the chance for detonation. This is most crucial on a turbo motor. Widening the split lessens the likelyhood of it. When an engine gets near detonation, the thing many people do is to back off total advance. In reality you may be able to leave total advance the same but just widen the split. This could potentially make more power on a turbo engine. As with anything it really depends on the circumstances.
Here's another question.
What is a good AFR to run when my car is NA and I advance my timing?
02-09-05, 06:44 AM
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Originally Posted by rotarygod
The inside of the crank angle sensor does have a seperate pickup for both the leading and trailing. Open one up. Both trigger wheels are different though. The trailing only has 2 teeth whereas the leading side has something closer to 24 teeth or so. I can't remember exactly how many. The ecu deciphers these signals to make sense.
The ECU works out the rest via the muti-pulse signal.. i think..
02-09-05, 04:32 PM
#18
The CAS outputs a 12+1 signal on both VR sensors (12 on one, 1 on the other). There is no specific leading or trailing wheel. rotarygod, don't you remember what I wrote on the MS forum? 
I'd never bother using one of those dial type timing lights on a rotary.
I'd never bother using one of those dial type timing lights on a rotary.
02-15-05, 06:39 PM
#19
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most tuners ive talked to run a close split even on turbo engines.
depending on the ems of course. some do not hold rock steady ignition timing and can vary by as much as 5 degrees.
if trailing advances past leading BOOM! your life sucks.
With a dizzy/turbo setup and 10lbs of boost ive allways fired the plugs nearly on top of each other and never noticed any excessive exhaust temperatures
using a total advance of 20 degrees...
with a standalone you can run huge amounts of advance early in the timing curve.
depending on the ems of course. some do not hold rock steady ignition timing and can vary by as much as 5 degrees.
if trailing advances past leading BOOM! your life sucks.
With a dizzy/turbo setup and 10lbs of boost ive allways fired the plugs nearly on top of each other and never noticed any excessive exhaust temperatures
using a total advance of 20 degrees...
with a standalone you can run huge amounts of advance early in the timing curve.
02-15-05, 09:00 PM
#20
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What about running leading only as in a Megasquirt app? I assume that since the trailing never fires that this would also decrease the chances of detonation.
Grant
Grant
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che'srx-7 (01-07-24)
02-16-05, 02:43 AM
#22
Originally Posted by dDuB
How much total advance would you suggest for someone with stock ecu, streetport, full exhaust, intake, ported manifolds/tb, bla bla etc mods?
Here's another question.
What is a good AFR to run when my car is NA and I advance my timing?
Here's another question.
What is a good AFR to run when my car is NA and I advance my timing?
02-16-05, 02:46 AM
#23
Originally Posted by Jeff20B
The CAS outputs a 12+1 signal on both VR sensors (12 on one, 1 on the other). There is no specific leading or trailing wheel. rotarygod, don't you remember what I wrote on the MS forum?
I haven't been over there in a while. I'd like to try running a cas with megasquirt but as of yet don't know how. Did you have any detailed instructions on what to do?
02-16-05, 11:41 PM
#24
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Look under the single turbo forum for discussions on 0 split.
There are some high power tubocharged rotaries running 0 split but with overall timing set to very low advance or even NEGATIVE ADVANCE.
There are some high power tubocharged rotaries running 0 split but with overall timing set to very low advance or even NEGATIVE ADVANCE.