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How To Tune To Stop Flutter/bovs Causing Stalling.

Rolls

By Rolls,
in Engines & Forced Induction

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Rolls Grand Master

Rolls

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Just out of curiousity where/what would you change in the tune to stop AFM cars stalling when running with a atmo bov/no bov causing flutter. I know you can tune it out as VL turbos and R31 redtop rb20dets never came with bovs and fluttered from the factory without stalling.

I imagine the cause of the stalling is where it runs very rich just after throttle off, would simply pulling all fuel from ~400rpm fix the issue? So when it stumbles it doesn't add even more fuel causing it to stall? Have any tuners looked at the stock redtop tunes to see what is different? I personally run the stoc recirc valve but I'm curious what the difference is.

One thing I have noticed is the redtop rb20s have a strange cylinder sticking out the intake that leads to nothing. This is post AFM and looks a bit like a buffer, could this be what they used to stop the stalling issues? Eg it buffers the fluctuations in pressure in the intake causing less AFM voltage fluctuation?

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GTSBoy Grand Master

GTSBoy

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That would be a resonant chamber - just for noise tuning, although they can have a little influence on total power (in NA engines) by affecting the resonances in the inlet tract. I wouldn't expect any such effect upstream of a turbo however.

I would think that playing with the timing at the low rev high(er) load cells would be needed as well as fiddling with the mixtures. Kinda depends on what load cells it's actually accessing when the stall occurs though, because you wouldn't want to have to butcher the tune in those cells if they also happened to be cells that were accessed during normal operation, which is entirely possible.

Rolls Grand Master

Rolls

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because you wouldn't want to have to butcher the tune in those cells if they also happened to be cells that were accessed during normal operation, which is entirely possible.

Totally agreed, mainly why I mentioned the 400rpm cells as these would never really be accessed apart from when starting or the engine is stalling.

If anyone does have stock redtop rb20 maps, would you be able to look at these areas to see if there is anything stand out that might have been done for this reason?

75coupe Grand Master

75coupe

Posted
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Is this just an rb20 thing as Ive had my rb25 tuned with atmo bov (it was easier to install that way, less plumbing less fab) and I have no stalling issues, tuner did say the bov was quite good at staying closed and zero leak at the wrong times...

Legionnaire Collaborator

Legionnaire

Posted
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If anyone does have stock redtop rb20 maps, would you be able to look at these areas to see if there is anything stand out that might have been done for this reason?

Got any p/n's for ECU that came with bovless vehicles? I can check maps in Nistune and post 'em here.

The Mafia Grand Master

The Mafia

Posted
Posted

Apparently some BOV users accept this fact.

And still have that little shimmer of hope that a girl will hear it, strip naked, and dive into their car. (Hopefully before it coughs up a heap of black smoke and stalls)

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