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SVTPerformance's Chain of Restaurants
The Blower Bistro
KB 1.7l for a 99/01 Cobra?
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<blockquote data-quote="Taz" data-source="post: 2534273" data-attributes="member: 2127"><p>The 2.2L wasn't designed to run at the low speeds required to produce such low boost. I don't think anyone has even bothered to try. Why would they? </p><p></p><p>The screw speed required for a 2.2L to produce 9 psi on a 4.6L motor is well below its recommended operating range, so a 2.2L won't run as efficiently as a 1.7 making 9 psi. For one thing, the 2.2 will be unnecessarily introducing more parasitic drag at any boost level (within the operating range of the 1.7) because of the larger mass you need to spin and the increased volume of air that it's processing on every revolution.</p><p></p><p>On top of that, because the blower will be turning so slowly, it will tend to leak a larger percentage of that air back out past the screws at low engine RPM. (Everything else being equal, the longer the leakage path, greater the amount of leakage from a Roots or screw type blower.) Unfortunately, if you try to compensate for that low RPM leakage from the 2.2L with a smaller pulley, you're suddenly over 9 psi at higher engine speeds, as soon as the blower begins to gain some efficiency.</p><p></p><p>For anyone intending to run enough boost to require a bigger blower than the 1.7 - say more than 15 psi, the right approach would be to first forge the motor (and lower the static CR if he has aspirations of running on pump gas). Then, throw a 2.2L at it and pulley it up for the desired boost.</p><p></p><p>Personally, I think anybody who believes he can throw a 2.2L at a stock New Edge block and make it work at 9 psi while he saves up his shekels for a forged bottom end is in for a reality check in the very near future. But my "educated guess" aside, for those of us with no immediate plans of running more than 9 or 10 psi boost, the 1.7 is right in its sweet spot, so it's the obvious choice for the job. Why would I want to use an 8-lb sledge hammer to set a finishing nail?</p><p></p><p>T-</p></blockquote><p></p>
[QUOTE="Taz, post: 2534273, member: 2127"] The 2.2L wasn't designed to run at the low speeds required to produce such low boost. I don't think anyone has even bothered to try. Why would they? The screw speed required for a 2.2L to produce 9 psi on a 4.6L motor is well below its recommended operating range, so a 2.2L won't run as efficiently as a 1.7 making 9 psi. For one thing, the 2.2 will be unnecessarily introducing more parasitic drag at any boost level (within the operating range of the 1.7) because of the larger mass you need to spin and the increased volume of air that it's processing on every revolution. On top of that, because the blower will be turning so slowly, it will tend to leak a larger percentage of that air back out past the screws at low engine RPM. (Everything else being equal, the longer the leakage path, greater the amount of leakage from a Roots or screw type blower.) Unfortunately, if you try to compensate for that low RPM leakage from the 2.2L with a smaller pulley, you're suddenly over 9 psi at higher engine speeds, as soon as the blower begins to gain some efficiency. For anyone intending to run enough boost to require a bigger blower than the 1.7 - say more than 15 psi, the right approach would be to first forge the motor (and lower the static CR if he has aspirations of running on pump gas). Then, throw a 2.2L at it and pulley it up for the desired boost. Personally, I think anybody who believes he can throw a 2.2L at a stock New Edge block and make it work at 9 psi while he saves up his shekels for a forged bottom end is in for a reality check in the very near future. But my "educated guess" aside, for those of us with no immediate plans of running more than 9 or 10 psi boost, the 1.7 is right in its sweet spot, so it's the obvious choice for the job. Why would I want to use an 8-lb sledge hammer to set a finishing nail? T- [/QUOTE]
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SVTPerformance's Chain of Restaurants
The Blower Bistro
KB 1.7l for a 99/01 Cobra?
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