what causes blower surge...
 

i was wondering what causes blower surge... thx for any info,rm

Ratman!! Where the hell have you been???

Buck

land locked in costa rica and now medellin colombia, but that will be changing as soon as i get my container shipped down with my car, tools, and boat... im building a hotel/hostel on an island a buddy of mine owns about 20 miles off the coast of colombia... it will be a fun project.

how you doing dude, everything good? rm

Huge cam

how huge? you talking huge lift? duration? overlap? a little more info pls. i just bought a blown 496 bbc with a 8/71 on it for my 48 anglia. i want some blower surge just cuz it's cool as hell... i know i will have the only roots blower car in medellin. it will be fun...thx, rm

A lean idle afr makes it surge. It needs to be on the rich side at idle to be smooth.. 13:1 afr and richer.

Do they make any Boost at Idle? My Magnuson Supercharged Silverado still makes about 18" of vacuum at idle and doesn't surge with a 14.7 afr, Do the 8/71 style blowers have any vacuum at idle?

No boost at idle. Vacum until 1800 or so.

It is caused be the different air pressure from top of blower and intake manifold as well as fuel control. If you put a bypass valve in like whipple uses it should stop.

That's a nice setup.. I'm talking about larger cam stuff that has 8-10 in/hg at idle. 14.7 usually surges on those.

All good my man. Can't complain.

Do me a favor and keep in touch. Would love to hear some of your stories around here on a regular basis.

Be safe,

Buck

The surge is caused by the fuel mixture being somewhat lean and by the the turning of the blower rotors.
The fuel mixture gets dumped/pushed in as the rotors spin. If you run them too rich at idle, then the plugs will start to foul out.

There are two things that will cause it. Lean at idle will cause it and the throttle blades not having enough air gap at idle will cause it. If lean it is basically running out of fuel, dieing, then catching fire again when the fuel catches up. If the throttle blades are closed too much it can suck the throttle closed, again die, then the blade will open back up as the motor looses RPM. Is this a carbed or EFI set up?

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will do, but most of stories are not work friendly. lol

carbed, a pair of 750 4150s

my usa tel number is 386-269-1111 give me a ring, we'll catch up

Start with adding fuel to the idle circuit with the mixture screw. That will probably smooth it out then adjust idle speed with the blades as necessary.

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im trying to make mine surge cuz it sounds cool as hell. lol

Awwww sweet! Get that sucker rolling then throw a No Fat Chicks sticker on the air cleaner. :evilb:

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Hey RM good to see you back....hope all is well. Tom

translation "no gorditas"

thx, i been having a LOT of fun the last handful of years....rm

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 )

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.

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:ernaehrung004: 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

how you doing strip... farc is still operating in several parts of the country but we have none of that here... i am way safer here than say gun free chicago, if you are not in the drug trade you have no worries... btw guns are very hard to buy legally here in colombia there are 20 or so murders amonth but it the drug dealers fighting for territory, there was a really well organized crime outfit la officina, the government all but shut them down... now its a free for all with a bunch of small gangs trying to take over... the government should have left well enough alone. lol i managed to buy a sig .380 on street for 700 clams for home protection in case someone gets past my pack of pitbulls. i kid you not, my neighbors run like h3ll when my automatic gates starts to open, they try to get out of sight in a hurry, kind of cracks me up. i have the safest house in my barrio. i am always safety conscious and have had no issues...

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

Strip, you ought to fix that rear wheel, it wobbles a bit.

cant, they said they can not bend it back,funny thing ya cant feel it,

Short answer: Old, outdated technology.:drink:

Does sound cool though.