604ci build. Ready run msd or ignition box?
03-14-2017, 08:57 PM
#41
Registered
Platinum Member
"May Soon Die" - hadn't heard that one yet... been using "My Spark Died" for years, lol...
Picked up a Daytona last summer and am excited to use it for this summer. I've lost both MSD boxes and magnetic pickups over the years. I will always miss the reliability of the Merc ignition - ran those on my first three boats (with V6 boxes) over 20 years without one issue.
Meanwhile, I do love my MSD E-curve dist in my 64 Vette - it has been flawless for 5 years with no box and has endless adjust-ability for advance curves - VERY helpful for a street tunnel ram setup that seems happiest with 25 initial, 36 total, and about 10 in vacuum, but I sure wouldn't subject the electronics inside those to a marine environment.
Picked up a Daytona last summer and am excited to use it for this summer. I've lost both MSD boxes and magnetic pickups over the years. I will always miss the reliability of the Merc ignition - ran those on my first three boats (with V6 boxes) over 20 years without one issue.
Meanwhile, I do love my MSD E-curve dist in my 64 Vette - it has been flawless for 5 years with no box and has endless adjust-ability for advance curves - VERY helpful for a street tunnel ram setup that seems happiest with 25 initial, 36 total, and about 10 in vacuum, but I sure wouldn't subject the electronics inside those to a marine environment.
Last edited by Hang Time 27; 03-14-2017 at 09:03 PM.
03-15-2017, 10:31 PM
#45
Registered
Platinum MemberJoin Date: Oct 2011
Location: Northern Ohio
Posts: 60
Likes: 0
Received 0 Likes
on
0 Posts
Usually they idle really nice on the dyno, and then when ya put them in thr boat, and shift into gear, they wanna stall out.
One thing i noticed was going from locked at 34, to 18 or so in nuetral idling, was your eyes no longer watered and didnt smell like raw fuel fumes . 34 works really nice in gear under load.
The way me and icdeppl setup our carb blower engines, is they idle around 18* in nuetral nice and clean. When you shift into gear, and the rpm drops below say about 700-750, idle stabilzation kicks in, and raises timing to 36 deg to keep the engine from stalling. The beauty of this, is .....
Anyone whos ever adjusted a distributor on a carbed engine, knows that when you advance the timing , the engine revs higher. The rpm picks up.
The downside, is carbs are not efi. They dont have idle air bypass, nor can they compensate fuel based on load at idle. When you crank the timing up (locked out), you often need to close the throttle blades , to keep it at an acceptable rpm. Say your shooting for 1000rpm in nuetral.
Problem is, that works great with no load. You load the engine when putting it in gear, and all of a sudden, she either dies, or drops big rpm. So you fatten it up via the mix screws, so it wont stall. Then, back in nuetral, shes fat as fuk.
Advancing the timing pulls harder on the carbs . In gear, your afr might be 12.5:1. But when you put it in neutral, it might be 10.5:1. By being able to advance timing, when its in gear, can help narrow that range, and also, minimize the rpm drop, from neutral to in gear. Engines idling at 1100 out of gear, and a sputtering 600 in gear, are a perfect example. Being able to control the timing, you may be able to get a deal that idles at 900 out of gear, and 700-750 in gear.
One thing i noticed was going from locked at 34, to 18 or so in nuetral idling, was your eyes no longer watered and didnt smell like raw fuel fumes . 34 works really nice in gear under load.
The way me and icdeppl setup our carb blower engines, is they idle around 18* in nuetral nice and clean. When you shift into gear, and the rpm drops below say about 700-750, idle stabilzation kicks in, and raises timing to 36 deg to keep the engine from stalling. The beauty of this, is .....
Anyone whos ever adjusted a distributor on a carbed engine, knows that when you advance the timing , the engine revs higher. The rpm picks up.
The downside, is carbs are not efi. They dont have idle air bypass, nor can they compensate fuel based on load at idle. When you crank the timing up (locked out), you often need to close the throttle blades , to keep it at an acceptable rpm. Say your shooting for 1000rpm in nuetral.
Problem is, that works great with no load. You load the engine when putting it in gear, and all of a sudden, she either dies, or drops big rpm. So you fatten it up via the mix screws, so it wont stall. Then, back in nuetral, shes fat as fuk.
Advancing the timing pulls harder on the carbs . In gear, your afr might be 12.5:1. But when you put it in neutral, it might be 10.5:1. By being able to advance timing, when its in gear, can help narrow that range, and also, minimize the rpm drop, from neutral to in gear. Engines idling at 1100 out of gear, and a sputtering 600 in gear, are a perfect example. Being able to control the timing, you may be able to get a deal that idles at 900 out of gear, and 700-750 in gear.
Dan
03-17-2017, 07:04 AM
#46
Registered
iTrader: (1)
Join Date: Sep 2005
Location: West Michigan
Posts: 252
Likes: 0
Received 0 Likes
on
0 Posts
A MAP sensor acts kind of like a vacuum gage. I believe since marine engines really have never needed vacuum advance and we don't use multiple speed transmissions, the throttle position vs. MAP is pretty much linear. So it's unlikely you would change much based on the MAP sensor, probably why Mercury kept it simple. If you found areas in the fuel map that were higher vacuum at a cruising speed or during deceleration, you could theoretically modify the advance to improve fuel economy or reduce heat in the cylinder.
Seems like a lot of work for minimal gains since a carb'd engine isn't actively correcting fuel usage. Your not really working with a full deck of cards without the O2 sensor and fuel regulation built into the same system (like an EFI system does).
03-17-2017, 09:41 AM
#47
Registered
iTrader: (3)
As I understand it, there are switch settings on the Daytona box to use several canned Mercury timing curves, or you can program your own 2D (rpm vs timing) or 3D (rpm and MAP vs. timing) as options. The canned Mercury curves are all 2D (no MAP needed).
A MAP sensor acts kind of like a vacuum gage. I believe since marine engines really have never needed vacuum advance and we don't use multiple speed transmissions, the throttle position vs. MAP is pretty much linear. So it's unlikely you would change much based on the MAP sensor, probably why Mercury kept it simple. If you found areas in the fuel map that were higher vacuum at a cruising speed or during deceleration, you could theoretically modify the advance to improve fuel economy or reduce heat in the cylinder.
Seems like a lot of work for minimal gains since a carb'd engine isn't actively correcting fuel usage. Your not really working with a full deck of cards without the O2 sensor and fuel regulation built into the same system (like an EFI system does).
A MAP sensor acts kind of like a vacuum gage. I believe since marine engines really have never needed vacuum advance and we don't use multiple speed transmissions, the throttle position vs. MAP is pretty much linear. So it's unlikely you would change much based on the MAP sensor, probably why Mercury kept it simple. If you found areas in the fuel map that were higher vacuum at a cruising speed or during deceleration, you could theoretically modify the advance to improve fuel economy or reduce heat in the cylinder.
Seems like a lot of work for minimal gains since a carb'd engine isn't actively correcting fuel usage. Your not really working with a full deck of cards without the O2 sensor and fuel regulation built into the same system (like an EFI system does).
Mercury Marine used to utlize a spark advance feature, that was based off RPM in the Thunderbolt V I believe. What it would do, is slowly increase the timing during cruise, and if RPM increased, it would keep it there or advance it further. They did this , to increase efficiency and response. It was called MBT , for mean best timing.
Mean-Best-Timing (MBT)
Spark Advance
During light load cruising, the ignition modulesearches for the optimal ignition timing. This is also accomplished by small changes to the spark advance. At a given RPM, the module will try to add a small amount of advance and wait to see if there is an RPM change. If RPM increases, it will try to increase timing more. The module will continue to advance timing until it no longer gets an increase inRPM. Conversely, if it senses an RPM drop, it will start to retard some of the spark timing. The approximate RPM range for this feature is 1200-4000 RPM. Within this range, the ignition module can add approximately 10-15 degrees of spark advance to the base spark timing curve.
I wouldn't say that MAP is strictly linear to RPM in boats. I can cruise at 3500RPM, with the tabs down and drives tucked, with a full tank of gas, and have a much heavier load on the engine, at 3500, then say, if I am in calm water, no tab, and drives nuetral with a light load of fuel. On my S/C engines, it could be a difference of being at say, 0", or 2-3lbs of boost, even though rpm is the same.
I know most thing that carbs are simply a garden hose with a ball valve pouring fuel into the engine, but the reality is, carbs are actually very good at metering fuel vs engine load. The key is, you kinda have to know how to tune them, and adjust them.
The daytona ignition setups, are certainly not a modern EFI comparison, nor are they meant to be. However, for those who don't want to spend the money to switch to EFI, they are imo, a much better choice, than the typical MSD marine box, that really does nothing for you.
The multiple spark they sell you on, isn't a "bonus feature". Its a requirement by design, that they NEED multiple spark at lower rpm, because they simply don't fire a single spark very well at low rpm. Thats with all Capacitive discharge ignitions.
03-17-2017, 10:11 AM
#48
Registered
iTrader: (1)
Damn you guys and this forum...
now I'm thinking of buying these and benching my DUI's and 6M boxes. I've fought the rich idle thing for years trying a multitude of things. I like hearing all the good results with these and options it allows. Joe brought up a great point I hadn't thought of with the slow speed night cruising loading the motors down.
now I'm thinking of buying these and benching my DUI's and 6M boxes. I've fought the rich idle thing for years trying a multitude of things. I like hearing all the good results with these and options it allows. Joe brought up a great point I hadn't thought of with the slow speed night cruising loading the motors down.However, Between Daytona, knock sensors, and carbs I think I`m almost to EFI. That`s what I`d do if I were to do it again. Changing jets is getting old.
https://www.youtube.com/watch?v=a2R0Ly41uvo
Last edited by ICDEDPPL; 03-17-2017 at 10:13 AM.
