STI 7, decat, over-boost, restrictor, dawes
30 April 2002 | 12:37 PM
#1
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Joined: Jul 2001
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Hi
I want to decat my STI VII.
This might cause it to over-boost.
Seems there is concensus that enlarging the restrictor hole will go some way to curing this problem.
I have two questions:
1. What will happen if I remove the restrictor totally?
2. This one is more interesting: what if I took out the restrictor, and put a dawes device (or any other MBC for that matter) in its place. Removing nothing else, and setting the dawes to about 0.5 bar boost. My reasoning is that at low boost, the dawes will act as a "super"-restrictor, whilst at higher boost the path will be open, allowing the wastegate to open sooner/faster (keep the car's standard boost control solenoid setup in place).
I want to decat my STI VII.
This might cause it to over-boost.
Seems there is concensus that enlarging the restrictor hole will go some way to curing this problem.
I have two questions:
1. What will happen if I remove the restrictor totally?
2. This one is more interesting: what if I took out the restrictor, and put a dawes device (or any other MBC for that matter) in its place. Removing nothing else, and setting the dawes to about 0.5 bar boost. My reasoning is that at low boost, the dawes will act as a "super"-restrictor, whilst at higher boost the path will be open, allowing the wastegate to open sooner/faster (keep the car's standard boost control solenoid setup in place).
02 May 2002 | 06:44 AM
#2
Thread Starter
Scooby Regular
Joined: Jul 2001
Posts: 326
Likes: 0
Nobody have any views on this?
Explanation of what the restrictor does:
(http://www.xmission.com/~dempsey/perform/instruct.htm)
"A restrictor is a simple vacuum connector with one twist: inside the connector is a brass insert with a small hole in it. The purpose of a restrictor is to delay the time required for vacuum (or boost) to travel through the connector. Why would you want to do this? In our case it helps speed turbo response. By now you've probably noticed that when you floor it the maximum boost level goes high and then settles back down to the preset level. This overshoot is called the boost spike. You can directly control the size of the boost spike by using a larger or smaller orifice in the restrictor: the bigger the restrictor's hole, the smaller the spike; the smaller the hole, the bigger the spike. "
So, if I remove the restrictor, the boost spike will probably disappear...but turbo response will be down.
Fitting a gated boost controller (turbosmart or dawes)in its place, and setting it to a very low value, should give better turbo response (up to a point)...and also make the boost overshoot smaller?
Am I missing something here?
Explanation of what the restrictor does:
(http://www.xmission.com/~dempsey/perform/instruct.htm)
"A restrictor is a simple vacuum connector with one twist: inside the connector is a brass insert with a small hole in it. The purpose of a restrictor is to delay the time required for vacuum (or boost) to travel through the connector. Why would you want to do this? In our case it helps speed turbo response. By now you've probably noticed that when you floor it the maximum boost level goes high and then settles back down to the preset level. This overshoot is called the boost spike. You can directly control the size of the boost spike by using a larger or smaller orifice in the restrictor: the bigger the restrictor's hole, the smaller the spike; the smaller the hole, the bigger the spike. "
So, if I remove the restrictor, the boost spike will probably disappear...but turbo response will be down.
Fitting a gated boost controller (turbosmart or dawes)in its place, and setting it to a very low value, should give better turbo response (up to a point)...and also make the boost overshoot smaller?
Am I missing something here?
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