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DIY Turbo Discussion greddy on a 1.8? homebrew kit?

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Old 01-03-2007, 04:10 PM   #21
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Quote:
Originally Posted by braineack View Post
man, on the dyno I could make Brad run at 60psi or 120psi at 12psi, with the tiniest little turn of the ****.


Are you running a restrictor on the vacuum line?

when you described what Corky said to do I was thinking this (see image)

But it makes sense to just open up the breather line to help relieve more pressure out of the fmu so the needle valve can work more effiecently.
No restrictor at the moment. I couldn't see it making a difference in the rising rate when at the dyno. But now I know why. Perhaps with the restrictor and the parallel check valves, I could get it a little leaner yet.

Your image is still a concept I will explore if necessary. It would ramp up pressure quickly until the point where the second path opens, then continue to raise pressure, but at a slower rate.
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Old 01-03-2007, 04:17 PM   #22
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yeah.

no seriously, without a restrictor I could barely adjust the pressures anything less than a 10:1 rise. the restrictor gives you a hell of a lot more adjustability, and like corky said, you plain can't bleed off enough.
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Old 01-03-2007, 05:02 PM   #23
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Brain, are you running a restrictor on the vacuum line?
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Old 01-03-2007, 05:06 PM   #24
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when I was using the BEGi yes. I couldn't lower the pressures low enough without one.
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Old 01-03-2007, 06:33 PM   #25
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Restrictor and double check valve ftmfw. Look good to you guys?

(quick street tune between office and house)


Last edited by Ben; 01-03-2007 at 06:54 PM.
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Old 01-03-2007, 09:04 PM   #26
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that looks good....looks like it holds out longer till it drops...and doesn't drop as low....what psi and injectors?
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Old 01-03-2007, 10:33 PM   #27
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yes, it's actually a little richer in the middle and a good bit leaner at the top. my setup is completely the same since i went to the dyno last month. i might be crazy, but i think i saw 10psi on the boost gauge. it's been a solid max 9 psi for the past month, and i haven't touched the mbc. the car is definately more responsive.

the log i posted was the result of 3 or 4 street pulls. compare that to the log from the dyno which was the result of an hour of tuning.
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Old 01-04-2007, 02:03 PM   #28
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Got mine setup...i think I'll try to dual check valves as I don't think I'm bleeding off enough....

Seems to be smoother and holds out as the fuel dumps in, hopefully i can fine tune it a little more....



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Old 01-04-2007, 04:36 PM   #29
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That's pretty good. Here's something to try, might work a little better than where you are now :

Run a 8:1 vortec disc and put a ball n spring mbc between the needle valve and check valve. Set the check valve to open after peak torque. That way the needle won't actually bleed until when it starts going towards 10:1. Hopefully at that point, the needle starts to vent, and slows the rate of rise at higher boost. Should hold a flatter a/f curve that what you showed. If the 8:1 is a little agressive, try the 6:1.

This doesn't accomplish turning the vortec into a afpr, per say. But it allows bleed to slow the rate of rise after a certain point. Between that, and choosing the proper disc, it should give a lot more flexibility... and ultimately, more hp and flatter tq.
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Old 01-04-2007, 05:08 PM   #30
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already has a 6:1 disc in there
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