Hey all
I am ready to connect the vortech and fire it up but I need to get the timing sorted. This is my 1st blower build so I have done some research and wanted to know if I have a handle on it. I have a MSD dizzy and a MSD 6al-2 programmable unit with a blaster2 coil with about 8 lbs of boost
From what I understand I need to lock my dizzy as the map sensor tells the unit to pull timing out as boost comes on.
I want to stay in a very safe range of tune until I learn more and drive it for a while. From what I have read, I was thinking of locking the dizzy at 30 degrees and setting the MSD to pull 1 degree of timing for 1 lbs of boost which will give me 22 degrees. If I want to lock it at 30 degrees and my timing at idle is 15 degrees do I lock it at 15 degrees to get 30 or does locking the dizzy at 30 mean I will be running 30 degrees of timing at idle
Any help appreciated
cheers greg
what timing retard with boost? for safe tune
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user-23911
Re: what timing retard with boost? for safe tune
It depends on what fuel you're using, depends on your CR, depends on your charge cooling and depends on your cam duration.
The only safe way is to have a proper electronic knock detection system which will shut the power off if / when you exceed a certain knock limit.
EFI is the way to go, get rid of the dizzy and anything with MSD written on it.
A good safe starting point might be no more than 15 deg advance at full noise.
The only safe way is to have a proper electronic knock detection system which will shut the power off if / when you exceed a certain knock limit.
EFI is the way to go, get rid of the dizzy and anything with MSD written on it.
A good safe starting point might be no more than 15 deg advance at full noise.
Re: what timing retard with boost? for safe tune
I wouldn't lock the distributor! What good does that do?
Re: what timing retard with boost? for safe tune
I don't know a lot about it but I was told to lock it as the msd unit controls the timing according to boost.
Trying to get a hold on it and a safe starting point
Trying to get a hold on it and a safe starting point
Re: what timing retard with boost? for safe tune
You will probably end up locking the distributor and setting it at the maximum timing you plan to run (lets say 30 degrees) then pulling the timing down to 15 at idle with the software, then creating a "curve" with the software to get back to 30 at whatever rpm you want it. There is probably no point wanting 30 degrees (as an example of max advance, YRMV) at any point past the engine making boost since youll be wanting to pull timing out so it will take some experimenting or clever math to find out where you want max timing.
Then set up the boost retard accordingly, conservative to begin with but you might not need to start pulling timing until a few PSI in if the fuel is good and the cylinder pressure not so much. Test, test and more test while trying not to burn up parts.
You won't add timing with the controller, it only allows you to retard it.
Rotor phasing becomes an issue when pulling a heap of timing with the controller, probably not an issue down the shallow end of the boost pool for regular folks but not a great thing for a boosted engine to get it way wrong.
Not an expert so wait for others to critique
Then set up the boost retard accordingly, conservative to begin with but you might not need to start pulling timing until a few PSI in if the fuel is good and the cylinder pressure not so much. Test, test and more test while trying not to burn up parts.
You won't add timing with the controller, it only allows you to retard it.
Rotor phasing becomes an issue when pulling a heap of timing with the controller, probably not an issue down the shallow end of the boost pool for regular folks but not a great thing for a boosted engine to get it way wrong.
Not an expert so wait for others to critique
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pamotorman
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Re: what timing retard with boost? for safe tune
all the SC engines I built were BBC with GMC type SC used in boats. I always used a locked distributor at 30/32 degrees and never had a problem.
Re: what timing retard with boost? for safe tune
How to set the distributor is shown in the MSD (digital programable) al2 ignition box directions.
Read the directions. once the distributor timing base setting is done:
all timing changes are done by the MSD box, based on input and programing.
It is programed using a lap top.
All timing changes are done by the ignition box, according the programing and sensor/switch input.
but:
22 deg timing under full boost will not make any power.
Cannot tell you what amount of timing under boost will work without any information on the engine, fuel etc etc etc. The details matter.
Your question is way too open ended for someone to answer.
Read the directions. once the distributor timing base setting is done:
all timing changes are done by the MSD box, based on input and programing.
It is programed using a lap top.
All timing changes are done by the ignition box, according the programing and sensor/switch input.
but:
22 deg timing under full boost will not make any power.
Cannot tell you what amount of timing under boost will work without any information on the engine, fuel etc etc etc. The details matter.
Your question is way too open ended for someone to answer.
Last edited by F-BIRD'88 on Sat Jul 11, 2015 1:40 pm, edited 1 time in total.
Re: what timing retard with boost? for safe tune
This timing control box and most others do not add timing from what ever you set the distributor timing position at to start with. They only change the timing by taking away more or less timing.
So--- for drag race purpose-- where you do not need a centrifical ( rpm based timing curve and do not need a vacuum ( manifold vacuum engine throttle load varying timing curve ( "vacuum advance')
you only need a base setting and relative boost timing retard.
So set the distributor with a timing light for the most amount of timing needed.
WOT when there is no boost created. ( about 32-36deg)
This is your base setting. This is the idle timing also. The timing does not change with rpm.
Now you need to hook up the map sensor to the intake manifold and program a "boost timing retard curve" with the lap top. For pump gas and a low compression ratio engine (8.5:1 or less and 8 psi boost you want the timing to retard to about 27deg (26 to 30deg) when its under the full boost (8 psi) . The amount of timing retard rate is programed relative the the boost increase rate.
degrees of timing retard per pound of boost.
You must verify it using a mechanics hand pressure/ vacuum pump toll on the Map sensor tube
on the running engine , with a timing light to observe the amount of boost retard created by applying test pressure to the map sensor.
Do not guess.
22d eg timing will not make any power under boost. A high compression ratio engine ( 9:1 or more) will require high octane gas or charge intercooling or water methanol injection or be limited to very modest boost.
(a lot less than 8 psi)
detonation under boost must be avoided. There is a practical limit on retarding the timing under boost to avoid detonation on pump gas. 22deg under boost is a bot too much retard.
If you want to run a rpm based advance curve and or use a vacuum advance curve the the base setting set up of the distributor is going to be different from above.
if you are drag racing with a auto trans and a big cam you do not want or need a rpm based "centrifugal advance curve"
Again 22deg under boost is going to be lame. Better to start tuning by limiting the max boost to a lesser amount, ( say 4-5psi max),, get the tune right, then creep up on the boost.
if the compression ratio is more than 8.5:1 tread lightly on the boost on pump gas.
Get better gas or get intercooling or lower the cr.
Without a intercooler the WOT AFR under boost has to be plenty rich. RICHER than 12.5:1afr.
10.5:1 to 11.5:1 afr is typical. it needs what it needs. start tuning with it rich.
start tuning-testing rich and modest max boost.
So--- for drag race purpose-- where you do not need a centrifical ( rpm based timing curve and do not need a vacuum ( manifold vacuum engine throttle load varying timing curve ( "vacuum advance')
you only need a base setting and relative boost timing retard.
So set the distributor with a timing light for the most amount of timing needed.
WOT when there is no boost created. ( about 32-36deg)
This is your base setting. This is the idle timing also. The timing does not change with rpm.
Now you need to hook up the map sensor to the intake manifold and program a "boost timing retard curve" with the lap top. For pump gas and a low compression ratio engine (8.5:1 or less and 8 psi boost you want the timing to retard to about 27deg (26 to 30deg) when its under the full boost (8 psi) . The amount of timing retard rate is programed relative the the boost increase rate.
degrees of timing retard per pound of boost.
You must verify it using a mechanics hand pressure/ vacuum pump toll on the Map sensor tube
on the running engine , with a timing light to observe the amount of boost retard created by applying test pressure to the map sensor.
Do not guess.
22d eg timing will not make any power under boost. A high compression ratio engine ( 9:1 or more) will require high octane gas or charge intercooling or water methanol injection or be limited to very modest boost.
(a lot less than 8 psi)
detonation under boost must be avoided. There is a practical limit on retarding the timing under boost to avoid detonation on pump gas. 22deg under boost is a bot too much retard.
If you want to run a rpm based advance curve and or use a vacuum advance curve the the base setting set up of the distributor is going to be different from above.
if you are drag racing with a auto trans and a big cam you do not want or need a rpm based "centrifugal advance curve"
Again 22deg under boost is going to be lame. Better to start tuning by limiting the max boost to a lesser amount, ( say 4-5psi max),, get the tune right, then creep up on the boost.
if the compression ratio is more than 8.5:1 tread lightly on the boost on pump gas.
Get better gas or get intercooling or lower the cr.
Without a intercooler the WOT AFR under boost has to be plenty rich. RICHER than 12.5:1afr.
10.5:1 to 11.5:1 afr is typical. it needs what it needs. start tuning with it rich.
start tuning-testing rich and modest max boost.
Last edited by F-BIRD'88 on Sat Jul 11, 2015 1:41 pm, edited 1 time in total.
Re: what timing retard with boost? for safe tune
The simple pink wire 12v switched controlled step retard function on that box allows for a "cranking-start retard" to aid-allow easy hot engine starting with the locked out distributor base timing.
You can also aid hot start slow starter cranking by simply switch interrupting the ignition box power
to interrupt the ignition spark during engine cranking.
You interrupt the small power on sensor wire, not the big 12v + power feed wire (big red).
either method works.
These ignition boxes get eaten by incorrect grounding. Be sure the engine is grounded to both the frame and the body (firewall) of the car. Be sure that all + power and - ground points are clean and tight. Periodic service cleaning of the ground points is required. Especially if the car sits unused for a time.
The recomended spark plug gaps shown in the MSD directions are BS.
You do not want wide spark plug gaps. ALL this does is create in cap cross fire.
and guarantees engine damage and or short rotor cap service life.
missfire and distributor cap and ignition wire crossfire must be avoided.
The bigger the spark plug gap the more likely you will get crossfire/missfire ( especially under boost)
You want the spark plug gap .035" or LESS. Often on a high boost engine the spark plug gap must be REDUCED from the .035" setting to avoid missfire/crossfire under max boost. .025"-.030" is typical under high boost.
DO NOT USE big spark plug gaps. bigger is NOT BETTER.
As said all these ignition boxes that control timing have a effect on the distributor cap/rotor phasing . the phasing moves as the timing is modified. If the phasing is incorrect the thing will misfire/crossfire under boost. Distributor phasing effect under boost retard must be checked.
it is adjusted by moving the mounting position of the Magnetic pickup in the distributor.
You can watch the cap/rotor phasing effect using a timing light on a old idstributor cap that you have "windowed" so you can see the spinning rotor as you change the timing retard by testing.
Big spark plug gaps make this more critical.
The dis cap- rotor phasing must be correct and do not use big spark plug gaps.
You can also aid hot start slow starter cranking by simply switch interrupting the ignition box power
to interrupt the ignition spark during engine cranking.
You interrupt the small power on sensor wire, not the big 12v + power feed wire (big red).
either method works.
These ignition boxes get eaten by incorrect grounding. Be sure the engine is grounded to both the frame and the body (firewall) of the car. Be sure that all + power and - ground points are clean and tight. Periodic service cleaning of the ground points is required. Especially if the car sits unused for a time.
The recomended spark plug gaps shown in the MSD directions are BS.
You do not want wide spark plug gaps. ALL this does is create in cap cross fire.
and guarantees engine damage and or short rotor cap service life.
missfire and distributor cap and ignition wire crossfire must be avoided.
The bigger the spark plug gap the more likely you will get crossfire/missfire ( especially under boost)
You want the spark plug gap .035" or LESS. Often on a high boost engine the spark plug gap must be REDUCED from the .035" setting to avoid missfire/crossfire under max boost. .025"-.030" is typical under high boost.
DO NOT USE big spark plug gaps. bigger is NOT BETTER.
As said all these ignition boxes that control timing have a effect on the distributor cap/rotor phasing . the phasing moves as the timing is modified. If the phasing is incorrect the thing will misfire/crossfire under boost. Distributor phasing effect under boost retard must be checked.
it is adjusted by moving the mounting position of the Magnetic pickup in the distributor.
You can watch the cap/rotor phasing effect using a timing light on a old idstributor cap that you have "windowed" so you can see the spinning rotor as you change the timing retard by testing.
Big spark plug gaps make this more critical.
The dis cap- rotor phasing must be correct and do not use big spark plug gaps.
Re: what timing retard with boost? for safe tune
Intercooling is the way to go with these blowers. if you want safe big supercharged power to go fast/safely Get one. Get a big one.
Intercooling allows big dense COOL supercharged air to get the motor.
Makes big safe power without the need for a lot of timing retard under max boost, on pump gas.
The cooler you make the aircharge temp the BETTER. Cooler is BETTER.
Start by feeding the blower COLD air. Hot air in is BAD.
The next best is Water/methanol injection.
The next best is LOW LOW engine compression ratio (7.5:1+/-)
or high octane gas.
Intercooling allows big dense COOL supercharged air to get the motor.
Makes big safe power without the need for a lot of timing retard under max boost, on pump gas.
The cooler you make the aircharge temp the BETTER. Cooler is BETTER.
Start by feeding the blower COLD air. Hot air in is BAD.
The next best is Water/methanol injection.
The next best is LOW LOW engine compression ratio (7.5:1+/-)
or high octane gas.
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pamotorman
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Re: what timing retard with boost? for safe tune
on the boat engines I used a intercooler since there was lots of cold water availableF-BIRD'88 wrote:Intercooling is the way to go with these blowers. if you want safe big supercharged power to go fast/safely Get one. Get a big one.
Intercooling allows big dense COOL supercharged air to get the motor.
Makes big safe power without the need for a lot of timing retard under max boost, on pump gas.
The cooler you make the aircharge temp the BETTER. Cooler is BETTER.
Start by feeding the blower COLD air. Hot air in is BAD.
The next best is Water/methanol injection.
The next best is LOW LOW engine compression ratio (7.5:1+/-)
or high octane gas.
Re: what timing retard with boost? for safe tune
Thanks for the detailed input guys
I have read what was said and done some research. Great to know about the gaps as my plug gaps are 1.1mm so too big.
From what I understand if I ad 12v to the pink wire it will retard my timing for easy start up. So I would have to have it on a switch and switch it on for start up and switch it off when running.
The other idea I had was from a locked dizzy at 30 degrees, to set the msd to
pull out 20 degrees of timing between 0 and 500 rpm so when cranking I will be at 10 degrees of timing.
Then pull 15 degrees out between 500 rpm and 1200 rpm so i am at 15 degrees for idle
Then with 15 degrees at 1200 rpm set it to be all in by 2500 rpm so I will be at 30 degrees at 2500rpm.
Then I can pull 1 degree of timing out per lb of boost so at full revs I will be at 22 degrees. From there I can adjust the tune a little bit at a time to get a good result.
One issue I have though is I don't actually know what boost I will have. I was asking the vortech shop and they gave me my impeller speed at my rpm limit but said I wont actually know what boost I will get until I hook it up as it varies from build to built.
Does that sound right?
I have read what was said and done some research. Great to know about the gaps as my plug gaps are 1.1mm so too big.
From what I understand if I ad 12v to the pink wire it will retard my timing for easy start up. So I would have to have it on a switch and switch it on for start up and switch it off when running.
The other idea I had was from a locked dizzy at 30 degrees, to set the msd to
pull out 20 degrees of timing between 0 and 500 rpm so when cranking I will be at 10 degrees of timing.
Then pull 15 degrees out between 500 rpm and 1200 rpm so i am at 15 degrees for idle
Then with 15 degrees at 1200 rpm set it to be all in by 2500 rpm so I will be at 30 degrees at 2500rpm.
Then I can pull 1 degree of timing out per lb of boost so at full revs I will be at 22 degrees. From there I can adjust the tune a little bit at a time to get a good result.
One issue I have though is I don't actually know what boost I will have. I was asking the vortech shop and they gave me my impeller speed at my rpm limit but said I wont actually know what boost I will get until I hook it up as it varies from build to built.
Does that sound right?
Re: what timing retard with boost? for safe tune
Not sure what engine you have or compression ratio etc. So, its hard to be very specific.
Just to illustrate, here's what I run;
540 BBC, 8.2 C/R, B&M Megablower (6-71 size Roots type). Had it for ~ 15 years now, some street driving, ~400 drag strip runs over the 15 years.
Currently at about 10 lbs boost (15% overdriven) -- Don't get too caught up in boost numbers - that's just a measure of how much air is backing up in your manifold - EG: put on better flowing heads or cam and it will probably indicate less boost pressure but you'll probably be making more HP.
Timing locked at 32 degrees - I don't pull any timing as boost goes up (if I was 15 lbs or more, I might think about pulling timing - or just lock it at a lower point). .028 plug gap. With low static compression, I don't feel the need for a start retard. Roots blown engines like LOTS of initial advance but not a lot on the top end. (Pulling back to 22 seems very low to me - unless you're running crazy high boost).
If using carbs with power valves, make sure they're boost referenced. I'm currently 4 jet sizes over factory on my 2 x 850 Mighty Demons. Roots blown seem to like being richer than N/A (to a point).
I've been running Avgas 100 LL in mine for about 4 years now and really like it - about 1/4 the cost of race gas yet way better than any pump gas I can buy around where I live.
YMMV
Just to illustrate, here's what I run;
540 BBC, 8.2 C/R, B&M Megablower (6-71 size Roots type). Had it for ~ 15 years now, some street driving, ~400 drag strip runs over the 15 years.
Currently at about 10 lbs boost (15% overdriven) -- Don't get too caught up in boost numbers - that's just a measure of how much air is backing up in your manifold - EG: put on better flowing heads or cam and it will probably indicate less boost pressure but you'll probably be making more HP.
Timing locked at 32 degrees - I don't pull any timing as boost goes up (if I was 15 lbs or more, I might think about pulling timing - or just lock it at a lower point). .028 plug gap. With low static compression, I don't feel the need for a start retard. Roots blown engines like LOTS of initial advance but not a lot on the top end. (Pulling back to 22 seems very low to me - unless you're running crazy high boost).
If using carbs with power valves, make sure they're boost referenced. I'm currently 4 jet sizes over factory on my 2 x 850 Mighty Demons. Roots blown seem to like being richer than N/A (to a point).
I've been running Avgas 100 LL in mine for about 4 years now and really like it - about 1/4 the cost of race gas yet way better than any pump gas I can buy around where I live.
YMMV
Re: what timing retard with boost? for safe tune
Whats the motor combination? What heads and cam? Compression?
It will all depend. Two head chambers will take different timing so it depends what you have.
Generally 1 deg per lb boost is good to do when setting up base map.
22 on 8 psi is most likely very safe even with fast burn type heads like vortecs or afr elimators. Other heads may want alot more.
Set it low and get fuel curve right then work timing in.
It will all depend. Two head chambers will take different timing so it depends what you have.
Generally 1 deg per lb boost is good to do when setting up base map.
22 on 8 psi is most likely very safe even with fast burn type heads like vortecs or afr elimators. Other heads may want alot more.
Set it low and get fuel curve right then work timing in.
Re: what timing retard with boost? for safe tune
I am building an engine to suit supercharging but its a little while away. Will have lower comp and forged pistons etc but I will just use my current engine for now.
Its a Chrysler 360 with edelbrock ally heads and 9.3 comp. It has stock crank, rods and hypoeutectic pistons
Just want to use it as is for now as in have a car run in 2 weeks, but will also fit a cooler in the next couple of months
Its a Chrysler 360 with edelbrock ally heads and 9.3 comp. It has stock crank, rods and hypoeutectic pistons
Just want to use it as is for now as in have a car run in 2 weeks, but will also fit a cooler in the next couple of months