Flex Mode

"HammerheadFistpunch" (hammerheadfistpunch) 06/01/2018 at 17:09 • Filed to: None

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I had an idea as I heard a C2 Vette lumpa lumpa its was across the parking lot not long ago. That great organic lumpy cam noise is a result of having to choose a cam lift profile that suits high rpm breathing. It doesn’t really make sense anymore with today’s variable camming technology which is why its not used OE, not to mention the streetabily and emissions of such a cam.

but it got me thinking, couldn’t a manufacture utilize variable cam profile to do this on command? Switch to a “flex” mode and the cam is locked into its high lift/duration cam profile up to, say 10 mph just for showing off a little? You would need a way to affect lift and duration which is tough with cam in block but you could do with DOHC motors like Ford has going on. What are the downsides? Seems like this would be right up Dodge’s alley if you could do it with cam in block. I mean truthfully isn’t owning a challenger about showing off anyway?

benjrblant > HammerheadFistpunch 06/01/2018 at 17:33

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Like VTEC that works from 1200-2000rpms?

HammerheadFistpunch > benjrblant 06/01/2018 at 17:34

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yeah, thats the idea. Make the engine run like crap to impress people with your badly running but great sounding motor.

Future next gen S2000 owner > HammerheadFistpunch 06/01/2018 at 17:41

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I’ll bet a sophisticated tuner could pull it off.

If only EssExTee could be so grossly incandescent > HammerheadFistpunch 06/01/2018 at 17:48

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Or, now this may sound a bit crazy so bear with me, OR we could just put a Chrysler Marine Hemi in everything and then we won’t have to worry about engines ever not sounding good.

HammerheadFistpunch > If only EssExTee could be so grossly incandescent 06/01/2018 at 17:51

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funny story, one of the things my wife didn’t like about the gx was that it sounded “like a boat”.

Thats my favorite part!

sony1492 > HammerheadFistpunch 06/01/2018 at 17:54

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It would be bad for the motor, the lope sound is the motor experiencing an unhealthy lean condition. If you add a high lift cam you’ll want to raise the idle rpm to keep it out of that lope

HammerheadFistpunch > sony1492 06/01/2018 at 17:56

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should be possible to keep it protected by enriching as needed to keep temps down.

sony1492 > HammerheadFistpunch 06/01/2018 at 18:03

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Depending on the overlap You will be pushing exhaust out the intake and/or be Pulling exhaust back into the combustion chamber. You may run too lean or too rich, in any event the combustion process will not be stable enough to be acceptable.

https://www.quora.com/What-is-it-about-high-duration-cams-that-causes-engines-to-lope-at-idle

The profile at high rpm allows the exiting exhaust to create a vacuum effect that pulls fresh intake air in on the exhaust stroke(the cam has the exhaust valve and intake valve open at the same time, hence overlap) That’s followed by the intake stroke so your packing more air into the cylinder by utilizing part of the previous stroke that can’t be utilized at lower rpm

Ash78, voting early and often > HammerheadFistpunch 06/01/2018 at 18:16

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VVTEC just kicked in, out, then in again, yo!

Censored > HammerheadFistpunch 06/01/2018 at 22:57

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I’d feel bad about myself if I read a post about cam lope and didn’t post this video.

Tristan > HammerheadFistpunch 06/01/2018 at 23:25

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How quickly we have forgotten the Boss 302...

“The TracKey PCM software, installed by an authorized Ford racing dealer after a customer takes delivery of the car, adjusts variable cam timing, spark maps, engine braking, fuel control and other engine parameters – more than 200 in total – to provide a complete race car calibration. The result is an aggressive, race-bred driving experience all the way down to the lopey idle rumbling through the Boss quad exhaust .”

https://jalopnik.com/5687042/this-red-key-turns-your-boss-mustang-into-a-race-car

Variance > HammerheadFistpunch 06/01/2018 at 23:48

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There are actually tuners out there that re-create in modern cars on purpose; I think they’re called lope tunes?