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Highest compression for boost?
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<blockquote data-quote="IUP99snake" data-source="post: 13078591" data-attributes="member: 7060"><p>E85 is actually around 105 octane. But that wasn't my point. My point was that they chose to build a higher compression motor than stock rather than lowering the compression. Why? They knew even with a massive 4.0 whipple that they'd be pushing it to its limits, so they'd be able to make more power without having to spin the blower faster than its efficient operating range. </p><p></p><p>There's actually a quote from the magazine article of you haven't had a chance to read it yet: "...The biggest factor with this car is the compression..." - "For the '13 [GT500 engine], we built a high compression motor knowing it would make more power with less boost."</p><p></p><p>Take a stock '13 GT500 for example: in addition to the bump in displacement, this motor has higher compression (9.5:1) and more boost (15 PSI, using a more efficient blower) compared to earlier models. </p><p></p><p>With a lower compression motor, you'd need more boost to make as much power. What happens when you run more boost? There are higher parasitic losses and higher IAT's, especially when nearing the design limits of a given blower. Lets say you wanted to make an additional 30 RWHP and you had the choice of higher compression or more boost. If you were to run lower compression and higher boost, your motor would need to make an additional amount of power to spin the blower to make the extra boost necessary for 30 more WHP. The higher compression motor doesn't have to work as hard to make the same amount of power at the wheels because of not only the power advantage but also the lower parasitic losses.</p><p></p><p>With newer engine technologies and better tuning techniques it's possible to run higher compression in boosted applications than ever before. You can change the ignition timing. You can change the type of fuel you run. You can add meth injection (with a timing retard failsafe). You can get a more efficient power adder designed for higher boost that has lower parasitic losses and lower IAT's All of these things are better at managing detonation than going with a lower compression ratio because they can all be changed and tweaked to work as a combination. Compression ratios are set in stone once the motor is built. So I'd rather go more aggressive with the compression and manage detonation with said variables.</p><p></p><p>Just wait until direct injection becomes available in mustang V8 engines. It's coming... The coyote cylinder head already has a boss cast in the combustion chamber where a DI fuel injector would normally be located. It's already designed for it. With DI, it will give tuners even more precise control over fueling to help control detonation, allowing even more compression and more boost. </p><p></p><p>Take the ecoboost motors for example. They all have a 10:1 compression ratio. The twin turbo v6 makes 12PSI in FWD trim and 14PSI in the F150. The 1.6L 4cyl makes 16PSI and the little 1.0L 3 cylinder will make as much as 20 pounds of boost--- STOCK! That's wild. </p><p></p><p>There is no single answer about the highest compression with boost. It depends on pretty much every variable that exists in a gasoline engine, not to mention the extra variables associated with forced induction. </p><p></p><p>But the trend with new engine designs, more sophisticated tuning, and easier access to fuels such as e-85, it's becoming less necessary to sacrifice compression as a means of managing detonation to run big boost. </p><p></p><p>I don't doubt that people will push the limits even further with the next generation of mustangs using direct injection and more sophisticated tuning in addition to proven techniques such as e-85, meth, and more efficient power adders to be able to run even higher compression ratios upwards of 12:1 or hopefully higher than that.</p><p></p><p>Would the mustang aftermarket be as vibrant as it is today if everyone thought conventional wisdom and perceived limitations couldn't be overcome? HELL NO!</p></blockquote><p></p>
[QUOTE="IUP99snake, post: 13078591, member: 7060"] E85 is actually around 105 octane. But that wasn't my point. My point was that they chose to build a higher compression motor than stock rather than lowering the compression. Why? They knew even with a massive 4.0 whipple that they'd be pushing it to its limits, so they'd be able to make more power without having to spin the blower faster than its efficient operating range. There's actually a quote from the magazine article of you haven't had a chance to read it yet: "...The biggest factor with this car is the compression..." - "For the '13 [GT500 engine], we built a high compression motor knowing it would make more power with less boost." Take a stock '13 GT500 for example: in addition to the bump in displacement, this motor has higher compression (9.5:1) and more boost (15 PSI, using a more efficient blower) compared to earlier models. With a lower compression motor, you'd need more boost to make as much power. What happens when you run more boost? There are higher parasitic losses and higher IAT's, especially when nearing the design limits of a given blower. Lets say you wanted to make an additional 30 RWHP and you had the choice of higher compression or more boost. If you were to run lower compression and higher boost, your motor would need to make an additional amount of power to spin the blower to make the extra boost necessary for 30 more WHP. The higher compression motor doesn't have to work as hard to make the same amount of power at the wheels because of not only the power advantage but also the lower parasitic losses. With newer engine technologies and better tuning techniques it's possible to run higher compression in boosted applications than ever before. You can change the ignition timing. You can change the type of fuel you run. You can add meth injection (with a timing retard failsafe). You can get a more efficient power adder designed for higher boost that has lower parasitic losses and lower IAT's All of these things are better at managing detonation than going with a lower compression ratio because they can all be changed and tweaked to work as a combination. Compression ratios are set in stone once the motor is built. So I'd rather go more aggressive with the compression and manage detonation with said variables. Just wait until direct injection becomes available in mustang V8 engines. It's coming... The coyote cylinder head already has a boss cast in the combustion chamber where a DI fuel injector would normally be located. It's already designed for it. With DI, it will give tuners even more precise control over fueling to help control detonation, allowing even more compression and more boost. Take the ecoboost motors for example. They all have a 10:1 compression ratio. The twin turbo v6 makes 12PSI in FWD trim and 14PSI in the F150. The 1.6L 4cyl makes 16PSI and the little 1.0L 3 cylinder will make as much as 20 pounds of boost--- STOCK! That's wild. There is no single answer about the highest compression with boost. It depends on pretty much every variable that exists in a gasoline engine, not to mention the extra variables associated with forced induction. But the trend with new engine designs, more sophisticated tuning, and easier access to fuels such as e-85, it's becoming less necessary to sacrifice compression as a means of managing detonation to run big boost. I don't doubt that people will push the limits even further with the next generation of mustangs using direct injection and more sophisticated tuning in addition to proven techniques such as e-85, meth, and more efficient power adders to be able to run even higher compression ratios upwards of 12:1 or hopefully higher than that. Would the mustang aftermarket be as vibrant as it is today if everyone thought conventional wisdom and perceived limitations couldn't be overcome? HELL NO! [/QUOTE]
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