Adjustable boost on the fly - ?
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Pro
Joined: Jan 2001
Posts: 526
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From: Sierra Madre
Adjustable boost on the fly - ?
Hey everyone,
I was under the impression that the only way you can adjust the amount of boost is by changing the pulley size. However, I was thumbing through some of my old magazines when I ran across this article.
The magazine is High-Tech Performance (May 1998), the article was about a high 9 second '85 IROC with a 305 ci engine and a T-Trim. In one of the pictures, it states
"With the turn of a dial, Preston can adjust the boost pressure via an HKS bypass valve for either race (24 psi) or street (15 psi)."
Can someone explain how this works. I thought the by-pass valve was for compressor surge after the throttle plate closes to prevent damage to the supercharger/turbocharger.
Interesting article, it doesn't get into all the details but it does discuss the same issues that you read on the forum, such as, belt slippage, fuel pressure, and the engine itself like heads and block.
Let me know if anyone wants a copy of the article.
I will scan it and email to anyone.
Thanks again,
Glenn
I was under the impression that the only way you can adjust the amount of boost is by changing the pulley size. However, I was thumbing through some of my old magazines when I ran across this article.
The magazine is High-Tech Performance (May 1998), the article was about a high 9 second '85 IROC with a 305 ci engine and a T-Trim. In one of the pictures, it states
"With the turn of a dial, Preston can adjust the boost pressure via an HKS bypass valve for either race (24 psi) or street (15 psi)."
Can someone explain how this works. I thought the by-pass valve was for compressor surge after the throttle plate closes to prevent damage to the supercharger/turbocharger.
Interesting article, it doesn't get into all the details but it does discuss the same issues that you read on the forum, such as, belt slippage, fuel pressure, and the engine itself like heads and block.
Let me know if anyone wants a copy of the article.
I will scan it and email to anyone.
Thanks again,
Glenn
Melting Slicks
Joined: Mar 1999
Posts: 2,535
Likes: 2
From: Rochester NY
No HKS bypass or bov both are not make to control how psi you want to run. This works on vaccumm source, Example, when you go WOT, the bypass valve/bov don't see vaccum, therefore the bypass/bov will closed. When you let off the throttle and you got vaccum and the bypass valve/bov will open to relieve excess of air.
The only way you can sucessfully control the amount of boost you want to run is to install the wastegate. The wastegate can control psi, such as the turbo car. It works in the same principals. However, you should have a big blower and a good drive belt system, (no belt slip) because you will be constantly compressed air and relieve it thru the wastegate.
The only way you can sucessfully control the amount of boost you want to run is to install the wastegate. The wastegate can control psi, such as the turbo car. It works in the same principals. However, you should have a big blower and a good drive belt system, (no belt slip) because you will be constantly compressed air and relieve it thru the wastegate.
Melting Slicks
Joined: Dec 2000
Posts: 2,719
Likes: 60
From: Fremont Oh
Unless he is messing with the adjustment bolt to where stiffen the spring. My HKS bypass valve has a bolt to adjust the vacuum to where you want it to be fully closed it also has to vacuum boost inlets where you can also have it act like a pop off valve...
"HKS Standard and Racing Bypass valves are push-type valves that utilize calibrated spring rate and vacuum line pressure to remain closed against the pressurized air in the charge pipe. As the throttle plate closes, vacuum is created in the line and combined with the force of the pressurized air in the charge pipe, the blow off valve pushes open and allows pressurized air to escape."
" HKS Racing Bypass Valves function similar to Standard Bypass Valves but incorporate an additional pressurized port to aid under severe boost conditions. They can also be used as safety "pop-off" valves if the second port is connected to a pressure source."
hopefully this helps with the question, I know mine can be adjusted from 6 - I believe 14 pounds...
mo
Melting Slicks
Joined: Sep 2000
Posts: 3,150
Likes: 1
From: Carlsbad, CA CA
Originally Posted by Bruce
No HKS bypass or bov both are not make to control how psi you want to run. This works on vaccumm source, Example, when you go WOT, the bypass valve/bov don't see vaccum, therefore the bypass/bov will closed. When you let off the throttle and you got vaccum and the bypass valve/bov will open to relieve excess of air.
The only way you can sucessfully control the amount of boost you want to run is to install the wastegate. The wastegate can control psi, such as the turbo car. It works in the same principals. However, you should have a big blower and a good drive belt system, (no belt slip) because you will be constantly compressed air and relieve it thru the wastegate.
The only way you can sucessfully control the amount of boost you want to run is to install the wastegate. The wastegate can control psi, such as the turbo car. It works in the same principals. However, you should have a big blower and a good drive belt system, (no belt slip) because you will be constantly compressed air and relieve it thru the wastegate.
I guess it is pointless and a waste of money. Because you still spin the charger the same speed you are just bleeding off boost. So the charger is still working just as hard at 10psi compared to 20psi.
Drifting
Joined: Feb 2002
Posts: 1,937
Likes: 2
From: Arvada CO
you can but it is hard on the blower this is how!~
you run a super small pulley on your blower!
Hence you over spin your blower
So the outcome is you are making allot of boost that can be adjusted with a BOV!
Black Bart had the setup and you can bleed off excess air as you go into higher boost!
But it can be hard on the blower and you have to have no slippage on your blower! like a cog would be fine!
It can be done but very tricky!
you run a super small pulley on your blower!
Hence you over spin your blower
So the outcome is you are making allot of boost that can be adjusted with a BOV!
Black Bart had the setup and you can bleed off excess air as you go into higher boost!
But it can be hard on the blower and you have to have no slippage on your blower! like a cog would be fine!
It can be done but very tricky!
