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The Terminator
Turbo Cobras
How to pick AR for 1000+ twin turbo 4v?
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<blockquote data-quote="tt335ci03cobra" data-source="post: 15521529" data-attributes="member: 68944"><p>Upper rpm power is almost flat but slowly gains. Very happy with the fr500c so far. I'm running the normal plumes, but I could fit the 3/4" shorter ones if I wanted even more top end. It won't match a Sullivan for peak power, but if I had a Sullivan on my current combo it would be very laggy.</p><p></p><p>I'll attach an old dyno from a break in tune that was only spun to 6700rpm. We're now working on 12-30psi tunes and 7500-8000rpm. </p><p></p><p>To the op, if you plan to keep redline rpm to 8000rpms, anything from a .70-.83 will work nicely. The .83 will complement 7000-8000 better, but the .70 won't be far behind, yet it will likely spool noticeably faster. 4r70w gearing is </p><p></p><p>1. 2.84</p><p>2. 1.55</p><p>3. 1.00</p><p>4. .70</p><p></p><p>Using Wallace racings calculator, you'll click 62mph in 1st at 8k and drop to about 4300rpm in second, reach 115mph, drop to about 5500rpm in 3rd, and reach 178mph at 8000rpm.</p><p></p><p>If you get 1200whp to hook and book a 1.2 60ft in a 2750-2900lbs car, you'd be about a 175mph trap speed so the 3.73 is great, but I'd run a .70 a/r. You're spending tons of time below 7000-8000rpm.</p><p></p><p>If you had a 6r80e 6spd auto and 4.10's with 28" tires and the same engine, the. A .83 ar makes sense.</p><p></p><p>I haven't built a 4r70w car with 1200whp and just running the numbers, I don't know how robust it would be with that kind of load.</p><p></p><p>Another option if trap speed is closer to 155mph and you end up running a safer 800-1000whp is to step to a 4.30 rear. With a 4.30, you'll drop to about 4750rpm 1-2, 6000rpm 2-3. At that point, something like a .75-.80 ar starts to make sense since you'll be about half the time above 7000rpm.</p></blockquote><p></p>
[QUOTE="tt335ci03cobra, post: 15521529, member: 68944"] Upper rpm power is almost flat but slowly gains. Very happy with the fr500c so far. I'm running the normal plumes, but I could fit the 3/4" shorter ones if I wanted even more top end. It won't match a Sullivan for peak power, but if I had a Sullivan on my current combo it would be very laggy. I'll attach an old dyno from a break in tune that was only spun to 6700rpm. We're now working on 12-30psi tunes and 7500-8000rpm. To the op, if you plan to keep redline rpm to 8000rpms, anything from a .70-.83 will work nicely. The .83 will complement 7000-8000 better, but the .70 won't be far behind, yet it will likely spool noticeably faster. 4r70w gearing is 1. 2.84 2. 1.55 3. 1.00 4. .70 Using Wallace racings calculator, you'll click 62mph in 1st at 8k and drop to about 4300rpm in second, reach 115mph, drop to about 5500rpm in 3rd, and reach 178mph at 8000rpm. If you get 1200whp to hook and book a 1.2 60ft in a 2750-2900lbs car, you'd be about a 175mph trap speed so the 3.73 is great, but I'd run a .70 a/r. You're spending tons of time below 7000-8000rpm. If you had a 6r80e 6spd auto and 4.10's with 28" tires and the same engine, the. A .83 ar makes sense. I haven't built a 4r70w car with 1200whp and just running the numbers, I don't know how robust it would be with that kind of load. Another option if trap speed is closer to 155mph and you end up running a safer 800-1000whp is to step to a 4.30 rear. With a 4.30, you'll drop to about 4750rpm 1-2, 6000rpm 2-3. At that point, something like a .75-.80 ar starts to make sense since you'll be about half the time above 7000rpm. [/QUOTE]
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How to pick AR for 1000+ twin turbo 4v?
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