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As I said before (regarding boost conditions): Nothing.
Weights and springs just modify the timing depending on engine RPM. You need some way of tuning/changing the spark curve that knows when you're in boost.
You need a way to back-off/retard the timing when the engine goes into boost. The vacuum advance canister reduces the timing when you increase the engine load, but I don't know whether (or how much or how well) your advance canister reacts to positive (above atmospheric) pressure. I'd ask the collective to see if anyone here has experience with stock distributors in boost setups.
I have 1 similar to this that's been modified with adjustable limiting plates on how far it can advance or back off
Count me as being stupid, but just where do you get vacuum on a boosted engine. My engine has a vacuum/ boost guage and it only shows boost and never reads any vacuum. Much less the vacuum operated wiper door and head lights ceased to operate. T
I have 1 similar to this that's been modified with adjustable limiting plates on how far it can advance or back off
Originally Posted by terrys6t8roadster
Count me as being stupid, but just where do you get vacuum on a boosted engine. My engine has a vacuum/ boost guage and it only shows boost and never reads any vacuum. Much less the vacuum operated wiper door and head lights ceased to operate. T
I had this similar problem with keeping crankcase pressure slightly negative for return oil to drain.
I put a fitting on my inlet filter with check valves on all other normal vac lines
You can get this too effective with wrong side fitting......I filled my catch can up & started sucking oi in my inletl (stained filter)
Everything works normal then boost closes check valves & inlet vacuum takes over under boost
I figured all this out the hard way lol
I had this similar problem with keeping crankcase pressure slightly negative for return oil to drain.
I put a fitting on my inlet filter with check valves on all other normal vac lines
You can get this too effective with wrong side fitting......I filled my catch can up & started sucking oi in my inletl (stained filter)
Everything works normal then boost closes check valves & inlet vacuum takes over under boost
I figured all this out the hard way lol
Just what amount of vacuum signal do you get? Don't need vacuum for headlights or wipers, went with FIA headlights and built an electric wiper door opener, just wondering if something like your setup would be good for the PVC circuit. T
Last edited by terrys6t8roadster; Apr 26, 2018 at 10:26 AM.
Just what amount of vacuum signal do you get? Don't need vacuum for headlights or wipers, went with FIA headlights and built an electric wiper door opener, just wondering if something like your setup would be good for the PVC circuit. T
That was my main reason for installing it...oil backed up under full boost
Not sure what it pulled it was enough to keep crankcase negative....I will put my guage on it & let you know
If you need more just add a short pipe
The 5 pin module retards the ignition timing 10 degrees when the pin with the black arrow in the photo below is grounded.
To hook it all up you just plug the 4 wires in the HEI to the 4 other pin on the module like they are on the stock 4 pin module. You then run a wire from the pin with the arrow to one side of the pressure switch. The other side of the switch, run a wire to ground. Hook the switch to a manifold vacuum/pressure source. That's all there is to it.
Of course you still have some adjustments to make. Start the pressure switch out at 1 to 2 psi.
I would limit the the distributor to 20 degrees advance. You can find how to limit the advance with a search here or google. I would put a limiter on the vacuum advance so you can adjust that also. This can be found in a search too.
I would set the timing to 36 degrees total all in at 2800 to 3000 rpm, which would give you 16 degrees at idle. Hook the vacuum advance to ported vacuum source. As terrys6t8roadster has stated, there will be little no no vacuum in the manifold to use, so ported is the only way to go.
You'll have to just play with what manifold pressure (boost) to retard at and the maximum timing it will run best. You'll also have to experiment with the vacuum advance limiter to get the best off idle response and cruise smoothness and gas mileage.
Mike
Last edited by v2racing; Apr 26, 2018 at 06:16 PM.
The 5 pin module retards the ignition timing 10 degrees when the pin with the black arrow in the photo below is grounded.
To hook it all up you just plug the 4 wires in the HEI to the 4 other pin on the module like they are on the stock 4 pin module. You then run a wire from the pin with the arrow to one side of the pressure switch. The other side of the switch, run a wire to ground. Hook the switch to a manifold vacuum/pressure source. That's all there is to it.
Of course you still have some adjustments to make. Start the pressure switch out at 1 to 2 psi.
I would limit the the distributor to 20 degrees advance. You can find how to limit the advance with a search here or google. I would put a limiter on the vacuum advance so you can adjust that also. This can be found in a search too.
I would set the timing to 36 degrees total all in at 2800 to 3000 rpm, which would give you 16 degrees at idle. Hook the vacuum advance to ported vacuum source. As terrys6t8roadster has stated, there will be little no no vacuum in the manifold to use, so ported is the only way to go.
You'll have to just play with what manifold pressure (boost) to retard at and the maximum timing it will run best. You'll also have to experiment with the vacuum advance limiter to get the best off idle response and cruise smoothness and gas mileage.
Mike
Ok so it just grounds it to base timing then use my limiter plate to fine tune?
Is there a reference on degrees per pound
Ok so it just grounds it to base timing then use my limiter plate to fine tune?
Is there a reference on degrees per pound
The module retards the timing 10 degrees when the pin with the arrow is grounded. The switch is an on/off pressure switch. It's all or none. If your want to pull timing out by degrees per PSI, you will need an expensive programmable ignition that uses a MAP sensor or a fuel injection system.
I was just trying to give you a cheap alternative so you don't blow your engine all over the pavement.
The module retards the timing 10 degrees when the pin with the arrow is grounded. The switch is an on/off pressure switch. It's all or none. If your want to pull timing out by degrees per PSI, you will need an expensive programmable ignition that uses a MAP sensor or a fuel injection system.
I was just trying to give you a cheap alternative so you don't blow your engine all over the pavement.
Mike
And I do appreciate the ideas not being smart with you just asking to understand & get info to help
I've learned a lot from knowledgeable people on here
And I do appreciate the ideas not being smart with you just asking to understand & get info to help
I've learned a lot from knowledgeable people on here
I didn't think you were being smart. I was just explaining how it works and why I posted it here. We're good!
I didn't think you were being smart. I was just explaining how it works and why I posted it here. We're good!
Mike
Ok yeah I had installed a advance limiting plate I can adjust from previous tuning that might be useful since u mentioned it....I guess I'm use to everything being a debate & pissing matches forum I tried on my import 🤣
The 5 pin module retards the ignition timing 10 degrees when the pin with the black arrow in the photo below is grounded.
To hook it all up you just plug the 4 wires in the HEI to the 4 other pin on the module like they are on the stock 4 pin module. You then run a wire from the pin with the arrow to one side of the pressure switch. The other side of the switch, run a wire to ground. Hook the switch to a manifold vacuum/pressure source. That's all there is to it.
Of course you still have some adjustments to make. Start the pressure switch out at 1 to 2 psi.
I would limit the the distributor to 20 degrees advance. You can find how to limit the advance with a search here or google. I would put a limiter on the vacuum advance so you can adjust that also. This can be found in a search too.
I would set the timing to 36 degrees total all in at 2800 to 3000 rpm, which would give you 16 degrees at idle. Hook the vacuum advance to ported vacuum source. As terrys6t8roadster has stated, there will be little no no vacuum in the manifold to use, so ported is the only way to go.
You'll have to just play with what manifold pressure (boost) to retard at and the maximum timing it will run best. You'll also have to experiment with the vacuum advance limiter to get the best off idle response and cruise smoothness and gas mileage.
Mike
What's your thoughts on this little piston I ran across for timing control....maybe with some limiting adjustments? Not ruling out previous idea just picked it up for less than 20 bucks
As I said before (regarding boost conditions): Nothing.
Weights and springs just modify the timing depending on engine RPM. You need some way of tuning/changing the spark curve that knows when you're in boost.
You need a way to back-off/retard the timing when the engine goes into boost. The vacuum advance canister reduces the timing when you increase the engine load, but I don't know whether (or how much or how well) your advance canister reacts to positive (above atmospheric) pressure. I'd ask the collective to see if anyone here has experience with stock distributors in boost setups.
Mounting a small pnumatic piston in distributor with an adjustable stop I can set timing to back off any number of degrees
It starts to actuate @ 1 psi.....does it matter how fast timing is pulled or exact degree per pound of boost?
Just what amount of vacuum signal do you get? Don't need vacuum for headlights or wipers, went with FIA headlights and built an electric wiper door opener, just wondering if something like your setup would be good for the PVC circuit. T
My Twin Turbo SBC make 14 inchs Vacuum at an idle. There is zero Boost on a Turbocharged Engine when there is no load.
From: I tend to be leery of any guy who doesn't own a chainsaw or a handgun.
Originally Posted by Bbowers77
Mounting a small pnumatic piston in distributor with an adjustable stop I can set timing to back off any number of degrees
It starts to actuate @ 1 psi.....does it matter how fast timing is pulled or exact degree per pound of boost?
First, I'm trying to figure out how you're implementing that cylinder. Are you running boost into one port and atmosphere into the other, and the piston moves because of the pressure differential (Is the vacuum advance canister retained or removed)? Or.....?
Regarding boost retard, I would shoot for real time tracking of the boost gain and timing reduction. The exact amount of retard per pound of boost would likely depend on your mixture temperature and your A/F ratio. One to two degrees retard per pound of boost increase seems to be a common starting point.
First, I'm trying to figure out how you're implementing that cylinder. Are you running boost into one port and atmosphere into the other, and the piston moves because of the pressure differential (Is the vacuum advance canister retained or removed)? Or.....?
Regarding boost retard, I would shoot for real time tracking of the boost gain and timing reduction. The exact amount of retard per pound of boost would likely depend on your mixture temperature and your A/F ratio. One to two degrees retard per pound of boost increase seems to be a common starting point.
Ok.....yeah removed vac advance can put piston in its place
The plan is to drop timing with piston as boost pressure rolls in....it will have a adjustable max & normal return spring
ive seen how to use a pressure switch with 5 pin module & drop 10 degrees & seems like I will have more control on it like I'm setting it up
First, I'm trying to figure out how you're implementing that cylinder. Are you running boost into one port and atmosphere into the other, and the piston moves because of the pressure differential (Is the vacuum advance canister retained or removed)? Or.....?
Regarding boost retard, I would shoot for real time tracking of the boost gain and timing reduction. The exact amount of retard per pound of boost would likely depend on your mixture temperature and your A/F ratio. One to two degrees retard per pound of boost increase seems to be a common starting point.
It backs off timing 8 then return s with no boost .. spools fine feeling the pull now.....only has 1 problem if you straight stomp it looses all power.....but u ease on it gradually floor it does fine
