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SVTPerformance's Chain of Restaurants
The Blower Bistro
Compression ratio question for 12lbs of boost
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<blockquote data-quote="IUP99snake" data-source="post: 13910884" data-attributes="member: 7060"><p>Is this a street car? Do you plan on running any more boost in the future? </p><p></p><p>If this is purely a street car and you don't plan on running any more boost, I recommend going with a higher compression ratio. </p><p></p><p>If you plan on adding more boost in the future, it might be wise to go with a slightly lower CR around 9.5:1 or so. </p><p></p><p>Since you have a centri blower, it's only going to make 12 LBS of boost at redline. The other 99% of the time, it's going to be making less than 12 LBS. And when you're driving around town, you're probably not going to get into the boost at all. It's almost as if you're driving a car without a blower when you're cruising around in traffic. With that being said, you want it to make good bottom end off boost power. </p><p></p><p>You can pull timing right at the top to eliminate the chance of detonation, while still maintaining good power at lower boost levels throughout the rest of the RPM range. </p><p></p><p>Worst case scenario, you can always get meth injection to help manage detonation.</p><p></p><p>Compression is just one way to manage detonation. There are lots of other ways to manage detonation, such as ignition timing, fuel delivery, fuel type, etc. etc. Unlike all the other ways of managing detonation, compression is the one thing that can't be changed once it's set in stone. </p><p></p><p>Prior to my existing combination, I had a forged 8.5:1 motor with 99/01 heads & cams. I got it because I wanted plenty of room to expand without the rotating assembly being the limiting factor. It was an absolute dog on the street. </p><p></p><p>Because a centri only makes peak boost at peak RPM, you had to work hard and rev it to the moon to get it up and going. For example, If I floored it in second gear, the tires would stick until it got above 5K RPM and then the tires would break loose. </p><p></p><p>My existing combination is much more fun to drive on the street. The throttle response is a lot quicker and you don't need to rely as much on the boost to get up and go. </p><p></p><p>On the dyno, the low compression motor made more "peak" HP, it was the high compression motor that made more power throughout most of the RPM range.</p></blockquote><p></p>
[QUOTE="IUP99snake, post: 13910884, member: 7060"] Is this a street car? Do you plan on running any more boost in the future? If this is purely a street car and you don't plan on running any more boost, I recommend going with a higher compression ratio. If you plan on adding more boost in the future, it might be wise to go with a slightly lower CR around 9.5:1 or so. Since you have a centri blower, it's only going to make 12 LBS of boost at redline. The other 99% of the time, it's going to be making less than 12 LBS. And when you're driving around town, you're probably not going to get into the boost at all. It's almost as if you're driving a car without a blower when you're cruising around in traffic. With that being said, you want it to make good bottom end off boost power. You can pull timing right at the top to eliminate the chance of detonation, while still maintaining good power at lower boost levels throughout the rest of the RPM range. Worst case scenario, you can always get meth injection to help manage detonation. Compression is just one way to manage detonation. There are lots of other ways to manage detonation, such as ignition timing, fuel delivery, fuel type, etc. etc. Unlike all the other ways of managing detonation, compression is the one thing that can't be changed once it's set in stone. Prior to my existing combination, I had a forged 8.5:1 motor with 99/01 heads & cams. I got it because I wanted plenty of room to expand without the rotating assembly being the limiting factor. It was an absolute dog on the street. Because a centri only makes peak boost at peak RPM, you had to work hard and rev it to the moon to get it up and going. For example, If I floored it in second gear, the tires would stick until it got above 5K RPM and then the tires would break loose. My existing combination is much more fun to drive on the street. The throttle response is a lot quicker and you don't need to rely as much on the boost to get up and go. On the dyno, the low compression motor made more "peak" HP, it was the high compression motor that made more power throughout most of the RPM range. [/QUOTE]
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SVTPerformance's Chain of Restaurants
The Blower Bistro
Compression ratio question for 12lbs of boost
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