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Jeep Wrangler JK
JK General Discussion
Need exhaust suggestions for 2016 Sahara Unlimited with Edelbrock E-Force supercharger
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<blockquote data-quote="Dirty Dog" data-source="post: 452803" data-attributes="member: 24042"><p>That's not necessary. </p><p></p><p>The conventional wisdom is that lower static CR and higher boost makes more power. And this is true. Sort of. Sometimes. Except when it's not.</p><p></p><p>If you're talking about peak power, then this build strategy is great. This is how race engines, which operate in a very narrow RPM range are built. You will see people running 7-8:1 static CR and sky high boost numbers. On the dyno, you will see a powerband that looks like Pikes Peak. Now that's great, when you can selecting transmission and differential gearing to keep the engine in that high-RPM peak all the time. And keep in mind that these low CR/high boost engines are running race gas. The last time I checked, 112 Octane race gas was about $18.00 a gallon. </p><p></p><p>But for a street driven car, that's no good. You need a wide powerband if the vehicle is going to be streetable.</p><p>[ATTACH]122902[/ATTACH]</p><p></p><p>This is an old chassis dyno sheet from my Corvette. The red lines show why the LS is such an amazing engine. That pull was done with the stock LS1 plus Texas Speed & Performance longtube headers, a Cold Air Intake, and a tune. Let's look at those numbers.</p><p></p><p>The stock LS1 made 345HP. A chassis dyno will read lower, because of power used to turn the transmission, driveshaft, differential, wheels, tires... I think that's the most reasonable number, because what ultimately matters is how much power you're putting to the ground. But manufacturers always report the higher number from an engine dyno. Not unreasonable, since that number will apply to all engines, but the RWHP numbers will vary depending on the transmission and such. Driveline loss is accepted to be 15-25%, with automatics losing more. My vette is an M6, so I use 15%. That results in the lowest reasonable crank HP figure.</p><p></p><p>So my mostly stock LS1 made 331HP at the wheels. That works out to 390HP at the crank, 45 more than stock. </p><p></p><p>The stock LS1 made 350lb/ft of torque. Again, that is at the crank. Mine was 334 at the wheels, which (with the 15% loss) works out to 393lb/ft.</p><p></p><p>But here's the thing. The torque curve looks like a table. You have 300+ lb/ft of torque from just off idle all the way to redline. That is what makes a streetable performance engine.</p><p></p><p>Now look at the blue lines. That is a stock-internal LS3 with ported stock heads, roller rockers, doubled valved springs, a cam swap, a Vortech V3Si running 10lbs of boost, the same headers, Random Technology High Flow cats, SLP Loudmouth resonators, and a Magnaflow muffler. Using the same 15% driveline loss, that works out to 834HP/711lb/ft. The torque curve is no longer a table. That is unavoidable with a boosted engine. But it's still pretty flat. You've got 400lb/ft from 2000RPM on up. That makes a car that is mild mannered and totally fine on the street, but will take off like a bullet at any time, from pretty much anywhere in the RPM range. And bear in mind that this is a pump gas tune. Yes, it's premium, which here in the mountains is 91 octane and goes for about $4.50 a gallon. I can run lower octane, and the computer will pull timing. Ick, but I can. </p><p></p><p>This is a car that runs a very traction limited 11.9@123 at a DA of 8800 feet. In exactly the same state it's driven on a 4000 mile road trip. Not even a tire pressure change. You will be comfortable on that road trip, with the AC running and the modern infotainment center streaming music or playing a DVD. </p><p></p><p>That LS3 is currently out. One of the (stock) piston skirts collapsed after about 400 trips down the strip. Just back from the machine shop. We're going to drop the static CR from the factory 10.7 to 10.0 and run a bit more boost. The further down this low CR/high boost road you go, the more peaky the torque curve will be, and the less drivable the car will be.</p></blockquote><p></p>
[QUOTE="Dirty Dog, post: 452803, member: 24042"] That's not necessary. The conventional wisdom is that lower static CR and higher boost makes more power. And this is true. Sort of. Sometimes. Except when it's not. If you're talking about peak power, then this build strategy is great. This is how race engines, which operate in a very narrow RPM range are built. You will see people running 7-8:1 static CR and sky high boost numbers. On the dyno, you will see a powerband that looks like Pikes Peak. Now that's great, when you can selecting transmission and differential gearing to keep the engine in that high-RPM peak all the time. And keep in mind that these low CR/high boost engines are running race gas. The last time I checked, 112 Octane race gas was about $18.00 a gallon. But for a street driven car, that's no good. You need a wide powerband if the vehicle is going to be streetable. [ATTACH]122902[/ATTACH] This is an old chassis dyno sheet from my Corvette. The red lines show why the LS is such an amazing engine. That pull was done with the stock LS1 plus Texas Speed & Performance longtube headers, a Cold Air Intake, and a tune. Let's look at those numbers. The stock LS1 made 345HP. A chassis dyno will read lower, because of power used to turn the transmission, driveshaft, differential, wheels, tires... I think that's the most reasonable number, because what ultimately matters is how much power you're putting to the ground. But manufacturers always report the higher number from an engine dyno. Not unreasonable, since that number will apply to all engines, but the RWHP numbers will vary depending on the transmission and such. Driveline loss is accepted to be 15-25%, with automatics losing more. My vette is an M6, so I use 15%. That results in the lowest reasonable crank HP figure. So my mostly stock LS1 made 331HP at the wheels. That works out to 390HP at the crank, 45 more than stock. The stock LS1 made 350lb/ft of torque. Again, that is at the crank. Mine was 334 at the wheels, which (with the 15% loss) works out to 393lb/ft. But here's the thing. The torque curve looks like a table. You have 300+ lb/ft of torque from just off idle all the way to redline. That is what makes a streetable performance engine. Now look at the blue lines. That is a stock-internal LS3 with ported stock heads, roller rockers, doubled valved springs, a cam swap, a Vortech V3Si running 10lbs of boost, the same headers, Random Technology High Flow cats, SLP Loudmouth resonators, and a Magnaflow muffler. Using the same 15% driveline loss, that works out to 834HP/711lb/ft. The torque curve is no longer a table. That is unavoidable with a boosted engine. But it's still pretty flat. You've got 400lb/ft from 2000RPM on up. That makes a car that is mild mannered and totally fine on the street, but will take off like a bullet at any time, from pretty much anywhere in the RPM range. And bear in mind that this is a pump gas tune. Yes, it's premium, which here in the mountains is 91 octane and goes for about $4.50 a gallon. I can run lower octane, and the computer will pull timing. Ick, but I can. This is a car that runs a very traction limited 11.9@123 at a DA of 8800 feet. In exactly the same state it's driven on a 4000 mile road trip. Not even a tire pressure change. You will be comfortable on that road trip, with the AC running and the modern infotainment center streaming music or playing a DVD. That LS3 is currently out. One of the (stock) piston skirts collapsed after about 400 trips down the strip. Just back from the machine shop. We're going to drop the static CR from the factory 10.7 to 10.0 and run a bit more boost. The further down this low CR/high boost road you go, the more peaky the torque curve will be, and the less drivable the car will be. [/QUOTE]
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Jeep Wrangler JK
JK General Discussion
Need exhaust suggestions for 2016 Sahara Unlimited with Edelbrock E-Force supercharger
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