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Old February 13th 2014, 09:29
Samtech Samtech is offline
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Join Date: Jan 2013
Posts: 8
Vacuum shift light

I posted this over on Pelician but those guys didnt really understand what I was
asking about, just some fodder about how I must not be holding the gas down or that I should get a rpm shift light... Which I have...

So how would one go about adding such a thing?
It seems to me that running out of breath and hitting the redline are two different things.
Check out this video;

So on a turbo car would you want a vacuum switch between the airfilter and the turbo inlet set to 1-5 inches or a pressure switch on the manifold set to close at anything below max boost pressure?
I can deal with the light being on while I'm not on it but how do I get that soft glow and modulation?
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Old February 13th 2014, 12:52
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Humble Humble is offline
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Location: Boulder Creek, CA
Posts: 758
To me the the dash light in the video looks to be coming on when the driver is lifting or running part throttle, and that's what you're after? As a matter of personal/racing preference, I wouldn't want to get in the habit of ignoring lights, which is what this would lead to. That being said there are a few ways you could make this happen: a little bit of custom work with an arduino, map sensor and relay, or if you have a megasquirt or other fuel injection computer you could configure on output based on environment variables. To get the soft glow or analog feel you might have to drive it with a pwm circuit, and that should be okay for a small 12v light or led.
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Old February 13th 2014, 21:05
Samtech Samtech is offline
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Yep, that's exactly what I'm after. I'm not in the habit of ignoring lights either but think it might help.
Where my turbo starts falling off and where my over rev ends are two different thing when there's steep hills or flat lands (varied loads). If I could see when its time to shift or time to mash it would be better for me.
I tend to just stay mashed untill the rev light comes on but I've noticed the boost gauge will sometime start to drop off at the top which tells me to shift but I'd rather pick something up in my peripheral vision than look down at a gauge.
I think I'll look into a map/leader follow circuit. Good thinking, thank you.
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