Speaking of velocity stacks...

"BiTurbo228 - Dr Frankenstein of Spitfires" (biturbo228) 04/28/2014 at 16:36 • Filed to: None

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I'll be getting !!!error: Indecipherable SUB-paragraph formatting!!! for the Spitfire. Should I modify them to be various lengths, to spread the resonance across the rev range, or do I keep them all the same length? Not sure it that creates vibrations that are permissible in a race engine like this, but will cause problems in a comparatively long-lived road engine.

Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney > BiTurbo228 - Dr Frankenstein of Spitfires 04/28/2014 at 16:54

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That's a tough question. One part of me loves the clean order of symmetrical stacks. On the other hand, the zaniness and sonorous-nature of variable-length stacks is attractive.

Not a bad problem to have, though.

BiTurbo228 - Dr Frankenstein of Spitfires > Bob Loblaw Made Me Make a Phoney Phone Call to Edward Rooney 04/28/2014 at 17:03

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Not a bad problem at all :)

My thinking would be to have short pipes on the two outermost cylinders (1 and 6), then the next set slightly longer and the innermost set the longest.

That way I'd get 3 different ranges of resonance, and 2 cylinders per area.

RamblinRover Luxury-Yacht > BiTurbo228 - Dr Frankenstein of Spitfires 04/28/2014 at 17:33

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Probably the best result for a well-rounded torque range, but dings your peak a bit, and hurts your "design RPM" roar volume. Might also lead to unpredictable fueling cylinder-to-cylinder. Clearly race engines do all right with single lengths, even not 100% of the time at full throttle.

That being said, unequal length does look cool and might be more genteel in driving.

This gentleman's setup might actually produce a pretty flat torque curve. Blunted effective length that blends from one to the next, and a common plenum so air losses in one pipe aren't confined pressure-wise wholly to one cylinder. That being said, I suspect that realistically no thought at all went into much beyond "looks bitching", and there's not going to be much of a peak, well, anywhere.

BiTurbo228 - Dr Frankenstein of Spitfires > RamblinRover Luxury-Yacht 04/28/2014 at 18:58

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Now that is clever, although the sharp edges of the intakes would hurt flow significantly.

I was just wondering if tuning strong resonance for, say 5250-5750 would actually prove useful compared to tuning mild resonance from 3000-6000. I see what you mean with odd fuelling though, especially if I spend most of my time in a rev-range that favours two cylinders over the rest.

The other issue I was thinking is that if a longer intake tract actually hurts high-rpm breathing, then would the gains from just two cylinders be enough to offset the losses from the others. Clearly it was in the CanAm cars, but I don't quite have the resources, experience or raw intelligence of those guys :S

I do think they'd sound fucking excellent though :) rather than a single pitch roar, you'd get a chord of three different notes.

JACU - I've got bonifides. > BiTurbo228 - Dr Frankenstein of Spitfires 04/28/2014 at 19:18

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All I can hear is "When The Saints Come Marching In"...