North American Turbocoupe Organization



Boost readings and Detonation Quetions
Noname
Guest
#1
Now that I have my aftermarket boost valve hooked up.What are the normal vacuum readings at idle? I am only running about 13 pounds of boost right now but at idle it sits at about 21 on the vacuum side of the qauge. Is that about normal?

Second question
In a post somewhere I read that detonation sounds kinda like a soda can tab rattling around in the bottom of a soda can. I have my timing set at 11 BTDC and I am hearing a noise kinda like that but only at certian times and real faint.And sound like it is coming from the turbo area. But it only does it if I am shifting between first and second gears right at the point that you are lifting you foot off the gas to push in the clutch to shift. And also the car must have a little boost running and be shifting atleast 3000 RPMs or above. If I run it up to 3000 RPMs without boost and shift it will not do it. [Image: confused.gif]

Thanks for you help. This car was going to be my toy to play with but my daily driver a 91 Ranger with 258000 miles startd making transmission noises,so I am forced to drive this a little while until I can afford to put a trans in my Ranger. On top of that my wife and I are going to have our first child and all the money is going for baby stuff. [Image: biggrin.gif]

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88: Densecharger air intake system w/ K&N, polished upper from Dan E, Gillis Boost valve,6 point roll cage in the works and several more mods in the plans
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Pete D Offline
Administrator
#2
21" is excellent vacuum at idle.

I don't think it detonation if it doing it as your lifting to shift. It probably noise of the air pressure wave bouncing off the throttle plate back toward the compressor blades. If your not under boost you wouldn't hear it.
Pete Dunham


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jabobia Offline
Member
#3
i agree with pete [Image: biggrin.gif]

if you were to get a BPV/BOV it should stop that noise and give your turbo longer life

that noise happens because your turbo is spinning around 100,000rpm and you shut the throttle plate which causes enormous pressure to build up between the compressor and TB with no where to go, causing the turbo to slow down very rapidly, expelling air out of the compressor inlet and making loud noises not to mention wreaking havoc on the turbo

it is much louder with no VAM and no BPV/BOV...the VAM actually silences it...a BPV/BOV should stop that from happening and save your turbo from stalling, and keep it spinning freely which would also keep boost between gear shifts [Image: smile.gif]

-james

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87 TurboCoupe - 5spd

[This message has been edited by jabobia (edited 10-07-2003).]
87 Thunderbird TurboCoupe - 2.3T, T5, 3.55L - K&N, 18psi - [email protected](2.37 60')
88 Thunderbird Sport - 5.0SO, AOD, 2.73L - [email protected](2.39 60')
www.cardomain.com/id/jabobia
jabobia.com
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Noname
Guest
#4
OK that puts my mind at ease. I didnt want to harm my motor. By BOV I assume you mean a blow off valve? Is that right? What is a good source on getting one?

Thanks Again James

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88: Densecharger air intake system w/ K&N, polished upper from Dan E, Gillis Boost valve,6 point roll cage in the works and several more mods in the plans
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jabobia Offline
Member
#5
Quote:Originally posted by alliepearl:
OK that puts my mind at ease. I didnt want to harm my motor. By BOV I assume you mean a blow off valve? Is that right? What is a good source on getting one?

Thanks Again James


yes

BOV = blow off valve/dump valve
BPV = bypass valve/diverter valve

either will work well, but a BPV would be quieter

the general concensus on BPV/BOV's are, for VAM systems, a dual-piston type works best by ensuring there are no leaks.

a few that come to mind are the bailey evo dv26 and dv30; forge atom ram/piston ram

there was/is a group buy on bailey evos on turboford.org's message board, and bob sells the forge valves on his website www.40bob.com

-james

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87 TurboCoupe - 5spd
87 Thunderbird TurboCoupe - 2.3T, T5, 3.55L - K&N, 18psi - [email protected](2.37 60')
88 Thunderbird Sport - 5.0SO, AOD, 2.73L - [email protected](2.39 60')
www.cardomain.com/id/jabobia
jabobia.com
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