what causes blower surge...
#23
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A blower engine from my friends boat was surging at idle ,because of his bravo style drive he don,t want the surging ,because of shifting into gear at rpm,s above 1100 could seize the clutch in the bravo,and running too loo rpm would kill the engine when shifting into gear.
He just starting to lean out the fuel mixture at idling and blower surge was gone .... powervalves are still in the carbs ,he said he wanted to find a way to use vacuum at idle under the blower to let the engine suck the powervalves close at idling ,as soon as the throttle blades are opening ,the vacuum is gone and powervalves are open to feed the engine with fuel when its needed .
At idling the engine can run leaner because of no load ,but when load is applied to shift in gear and a tick throttle ,the engine needs fuel to make torque ,if too lean now the engine will backfire ,and or shut down.
This is what we found on his engine ,I have the same engine ,but with the powervalves removed ,and a few sizes up in jets ,but mine was still surging ( and now broken cause a valve dropped down )
He just starting to lean out the fuel mixture at idling and blower surge was gone .... powervalves are still in the carbs ,he said he wanted to find a way to use vacuum at idle under the blower to let the engine suck the powervalves close at idling ,as soon as the throttle blades are opening ,the vacuum is gone and powervalves are open to feed the engine with fuel when its needed .
At idling the engine can run leaner because of no load ,but when load is applied to shift in gear and a tick throttle ,the engine needs fuel to make torque ,if too lean now the engine will backfire ,and or shut down.
This is what we found on his engine ,I have the same engine ,but with the powervalves removed ,and a few sizes up in jets ,but mine was still surging ( and now broken cause a valve dropped down )
#24
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Join Date: Aug 2005
Location: Concord, North Carolina
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Not having a vacuum advance system on the ignition timing. As the load changes from curb idle to in gear idle the timing has to be advanced. When you lean the surge out at curb idle this causes the engine to stall when it is put in gear, at this point the fuel mixture has to start burning sooner. Without the timing change you have to tune in gear idle leaving the engine an overly rich condition in curb idle which cause the engine to surge burn your eyes and so on.
#25
whats up Rat? Glad to see ya back.hey becarefull in Colombia.I have a buddy doing security work for a big oil guy from here and he's in Bogota Colombia.Bad shet going on down there!!
On my Scarab with a bravo I wanted it to surge so I could shift it on the down cycle,instead of banging it in gear,it would surge on the gauge to 400rpm to 1800,the surge would not clear up till 22-2300rpm,the boat would lunge and rock from side to side on each surge that was a 8/ 71 8% over-driven,hyd roller, peek hp was at 7100rpm,it didn't like bravos
Now it just sits in the mancave
Didn't the 2 lobe design surge allot more?
My Whipple will not surge, But I can idle up to around 1500,it will surge for about 5-10 seconds, Im guessing the screw/lobe give a more constant flow of air and fuel,
Rob
On my Scarab with a bravo I wanted it to surge so I could shift it on the down cycle,instead of banging it in gear,it would surge on the gauge to 400rpm to 1800,the surge would not clear up till 22-2300rpm,the boat would lunge and rock from side to side on each surge that was a 8/ 71 8% over-driven,hyd roller, peek hp was at 7100rpm,it didn't like bravos
Now it just sits in the mancave
Didn't the 2 lobe design surge allot more?
My Whipple will not surge, But I can idle up to around 1500,it will surge for about 5-10 seconds, Im guessing the screw/lobe give a more constant flow of air and fuel,
Rob
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#26
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Join Date: Oct 2004
Location: medellin colombia, pablo escobar's lil town
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whats up Rat? Glad to see ya back.hey becarefull in Colombia.I have a buddy doing security work for a big oil guy from here and he's in Bogota Colombia.Bad shet going on down there!!
On my Scarab with a bravo I wanted it to surge so I could shift it on the down cycle,instead of banging it in gear,it would surge on the gauge to 400rpm to 1800,the surge would not clear up till 22-2300rpm,the boat would lunge and rock from side to side on each surge that was a 8/ 71 8% over-driven,hyd roller, peek hp was at 7100rpm,it didn't like bravos
Now it just sits in the mancave
Didn't the 2 lobe design surge allot more?
My Whipple will not surge, But I can idle up to around 1500,it will surge for about 5-10 seconds, Im guessing the screw/lobe give a more constant flow of air and fuel,
Rob
On my Scarab with a bravo I wanted it to surge so I could shift it on the down cycle,instead of banging it in gear,it would surge on the gauge to 400rpm to 1800,the surge would not clear up till 22-2300rpm,the boat would lunge and rock from side to side on each surge that was a 8/ 71 8% over-driven,hyd roller, peek hp was at 7100rpm,it didn't like bravos
Now it just sits in the mancave
Didn't the 2 lobe design surge allot more?
My Whipple will not surge, But I can idle up to around 1500,it will surge for about 5-10 seconds, Im guessing the screw/lobe give a more constant flow of air and fuel,
Rob
i saw the other day you had a listing on speed something website, you were blowing out all kinds of toys gear parts etc... you still have the motor cycle jacket, one of the dudes i rides with could use one.
your engine looks sweet in the pics... kind of kicking myself in the butt for not finishing the mich light boat, but i have had so much fun in costa rica and now colombia... did you know there are no moving violations here. lol the cops dont have enough cars or bikes for real traffic cops, they are actually fighting crime. i have a super moto and ktm rc8 that i ride around 100+ mph all the time...
im building a 67 pro touring camaro, 800hp pump gas bbc, 6sp t56, dse chassis, big brakes and tires, shipping my container down next month. a buddy just gave me a mint totally rust free 48 anglia, so its getting a 496 blower motor, pro street deal, there are a lot of hot rods here but nothing running a roots blowers.. it will be a blast.
i have a sweet finca/farm with a pool and a ton of room if you ever want to bounce down for a long weekend or more...
im buying a lil 26 shamrock next week, w/ a yanmar 170hp diesel to haul people and materials to an island hostel/hotel i am building with a buddy... here is a link to the island it is so beautiful, i think it will rock out from the day we open up... http://www.puntafaro.com/isla.html
take care of yourself..rm
#28