Blower motor surge
08-28-2019, 12:01 PM
#31
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The reason the daytona box works well, really isnt just the timing. Its the combination of timing, with the carb adjustment. The engine loves lots of timing under load at idle. So, lets say you set the timing to 34 at idle.
The rpms increase, and to get them back down, you close the throttle blades further, which in most cases makes surge happen. Now, when you shift into gear, you tend to get a big rpm drop, because now the engine isnt able to get the air it needs under load. Guys used to drill butterflies for this.
By lowering the base timing, to say 16* at idle, you can now open the throttle blades further, keeping them at the desired amount of exposed transition slot. With the daytona box, when you shift into gear, the box can now add 22* of additional timing, which the engine loves under load. The rpm drop is not as drastic either.
modern efi has an iac, to help control idle airflow . It constantly adjusts airflow to help maintain an idle speed. With carbs, thats not an option. But the fact is, the engine needs air, esp under load.
The rpms increase, and to get them back down, you close the throttle blades further, which in most cases makes surge happen. Now, when you shift into gear, you tend to get a big rpm drop, because now the engine isnt able to get the air it needs under load. Guys used to drill butterflies for this.
By lowering the base timing, to say 16* at idle, you can now open the throttle blades further, keeping them at the desired amount of exposed transition slot. With the daytona box, when you shift into gear, the box can now add 22* of additional timing, which the engine loves under load. The rpm drop is not as drastic either.
modern efi has an iac, to help control idle airflow . It constantly adjusts airflow to help maintain an idle speed. With carbs, thats not an option. But the fact is, the engine needs air, esp under load.
08-28-2019, 12:21 PM
#32
Charter Member # 55
Charter Member
I have adjusted them while in gear...I had someone drive while I was tuning just idling across the lake and I got it running perfect no surge 750-800 in gear A/F 12.5-12.8 and I thought awesome I got it...then I shifted to neutral and the surge was slightly there then went away thought cool another win...then I tried going back into gear and it died immediately....and I was back to square 1....I'm planning to pull the carbs tomorrow and check my blade location in relation to the transfer slots and hopefully find something there...This could be why my 8 idle screws are so sensitive? Possibly getting a "bad" vacuum signal due to the plates not being adjusted properly? just speculating but maybe?
I'm also going to pull the primary power valves and jet accordingly...I don't see a reason to keep them and have numerous people tell me to pull them...my secondaries have always been blocked put going to block the primaries as well
A/F's during the surge are hard to say...the gauge doesn't really react as fast as the surge or at least not at the same rythum at least but you def can see it change while its surging
I'm also going to pull the primary power valves and jet accordingly...I don't see a reason to keep them and have numerous people tell me to pull them...my secondaries have always been blocked put going to block the primaries as well
A/F's during the surge are hard to say...the gauge doesn't really react as fast as the surge or at least not at the same rythum at least but you def can see it change while its surging
If you tune it while idling and moving with it in gear, the load will be much lower and it won't simulate the same load as when its just shifted into gear.
08-28-2019, 12:56 PM
#33
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Makes total sense mild and griff....I'm beginning to think its a combination of small things causing a big thing...we'll see what I can find tomorrow while tinkering and report back...Def all good info to check thanks a ton guys!!
It's a no brainer that if I were to stay with carbs Daytona would be the ignition of choice but I do plan on going EFI sooner than later and I can have timing control with that so I feel like at this point the Daytona would be a waste of money...If I would have researched further before I bought my current setup I would have gone Daytona but is what it is at this point..I'm basically trying to get this thing driveable enough to do final testing and tuning and know I have a good running boat going into winter and I can do the interior this winter and be done and actually enjoy a ride on it next spring for the first time in 2 years lol
It's a no brainer that if I were to stay with carbs Daytona would be the ignition of choice but I do plan on going EFI sooner than later and I can have timing control with that so I feel like at this point the Daytona would be a waste of money...If I would have researched further before I bought my current setup I would have gone Daytona but is what it is at this point..I'm basically trying to get this thing driveable enough to do final testing and tuning and know I have a good running boat going into winter and I can do the interior this winter and be done and actually enjoy a ride on it next spring for the first time in 2 years lol
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08-28-2019, 01:42 PM
#35
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My timing issue that I am diving into is that I initially set the timing at 20 with 10 advance yet after running WOT for 2 passes I stopped to verify the timing and it was at 30 initial so either there is a broken spring or the advance bushings bound up or something...however the idle surge did not change with the extra 10 initial timing...if anything it got slightly better to be honest so that's my first course of action is to get the timing issue figured out whether that be lock it or fix the sticking issue and move to the carbs from there....I did watch the timing while someone else was operating the boat and after it stuck at 30 from idle all the way to 4000 when I told them to stop the timing did not change a bit so something is bound up in there just need to figure out what it is.
08-28-2019, 02:21 PM
#36
My timing issue that I am diving into is that I initially set the timing at 20 with 10 advance yet after running WOT for 2 passes I stopped to verify the timing and it was at 30 initial so either there is a broken spring or the advance bushings bound up or something...however the idle surge did not change with the extra 10 initial timing...if anything it got slightly better to be honest so that's my first course of action is to get the timing issue figured out whether that be lock it or fix the sticking issue and move to the carbs from there....I did watch the timing while someone else was operating the boat and after it stuck at 30 from idle all the way to 4000 when I told them to stop the timing did not change a bit so something is bound up in there just need to figure out what it is.
08-28-2019, 02:23 PM
#37
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Will def check into that as well if everything looks right in there...thanks!!
08-28-2019, 11:27 PM
#38
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https://www.youtube.com/watch?v=ui2g...ature=youtu.be
I was just playing with the idle stuff in the garage .. I don`t have it in learn mode but the EFI varies that timing like Daytona does.
I was just playing with the idle stuff in the garage .. I don`t have it in learn mode but the EFI varies that timing like Daytona does.
09-02-2019, 06:56 AM
#39
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So after messing with it for another day....I said screw it and bought 2 new 950 holley carbs....much much better!! Still a slight surge when it warmed up but a couple more adjustments and I think I'll have it....not sure if the baseplates are bent or what on the old carbs but they were just way too inconsistent something is not right with them...so easiest way out was to just buy new ones and jet accordingly.
Also locked my timing at 30...I know it's not ideal but to take one variable out of the equation and actually get this thing on the water and run it I decided to lock it...can always change it later
Also locked my timing at 30...I know it's not ideal but to take one variable out of the equation and actually get this thing on the water and run it I decided to lock it...can always change it later
