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Originally Posted by arghx
(Post 12295766)
Wait. You're trying to lower exhaust manifold backpressure (turbine inlet pressure) by changing the intake manifold?
No I considered the intake manifold to help with flow and equalize front/rear rotor. My primary goal is to lower egt's and make them more efficient.(The turbos). |
If the goal was some specific power/torque level, you could argue that having a better balanced manifold with less restriction means the turbos don't have to work so hard and the boost could be turned down.
But that's not how people actually mod their cars. They just try to squeeze whatever they can out of it without an immediate catastrophe and with some imputed safety margin. I myself do/have done it. There are a few basic ways to reduce EGT's: 1) Advance the combustion. Make the engine burn faster (probably not going to happen if we assume a fixed fuel type and fixed combustion chamber) or advance the spark (knock is then a concern). 2) Make the mixture richer. 3) Increase the size of the turbine housing so that the turbine is more efficient and your turbine inlet pressure is reduced (requires different turbo, makes boost threshold happen at higher rpm). 4) Reduce turbine speed (turn down the boost). If you're actually targeting a specific power or torque level, and will then use a more efficient intake manifold as an opportunity to detune the engine to achieve that power level, your approach will work. If you're just going to run as much boost and/or timing as you think you can get away with (what everybody does, understandably) you're going to end up with more power/torque and no additional safety margin. The concept of trade off between output and longevity/reliability doesn't change; the laws of physics are still the laws of physics. |
Originally Posted by arghx
(Post 12295925)
If the goal was some specific power/torque level, you could argue that having a better balanced manifold with less restriction means the turbos don't have to work so hard and the boost could be turned down.
But that's not how people actually mod their cars. They just try to squeeze whatever they can out of it without an immediate catastrophe and with some imputed safety margin. I myself do/have done it. There are a few basic ways to reduce EGT's: 1) Advance the combustion. Make the engine burn faster (probably not going to happen if we assume a fixed fuel type and fixed combustion chamber) or advance the spark (knock is then a concern). 2) Make the mixture richer. 3) Increase the size of the turbine housing so that the turbine is more efficient and your turbine inlet pressure is reduced (requires different turbo, makes boost threshold happen at higher rpm). 4) Reduce turbine speed (turn down the boost). If you're actually targeting a specific power or torque level, and will then use a more efficient intake manifold as an opportunity to detune the engine to achieve that power level, your approach will work. If you're just going to run as much boost and/or timing as you think you can get away with (what everybody does, understandably) you're going to end up with more power/torque and no additional safety margin. The concept of trade off between output and longevity/reliability doesn't change; the laws of physics are still the laws of physics. I prefer race gas over AI for a high boost map. I.will use 93 shell for my pump gas map (as I am now). 500hp would be a nice number on twins, the ultimate end goal. But the envelope has already been pushed and 2 guys got damn close or right at it. Those were ported motors, nothing missed and both using AI. I considered the intake because for several reasons, those that I listed and the safe margins. I believe the exhuast side of the turbo is where the answer is. Personally, I would like 400rwhp on 93 shell(no AI) running EGTs simular to 360rwhp or 14 psi. It would be nice to avg 15 to 16hp per lb.of boost with these BNR (GT28's). I love the sequencial, really don't want to do a single. |
Your car is in a good spot, as-is. Balljoint basically mutilated his twins to make that power. It's not a real-world water mark. Mrrx7tt made 420 believable rwhp on a real street setup with BNRs and AI+. PS the aussie boys are making big power on their twins with the stock manifolds too.
Pushing for 400-500rwhp with the twins is like trying to hug a cactus. If you really want that power, then you should go single. The 8374 supports 400+ on pump and spools real fast. |
Originally Posted by Narfle
(Post 12295960)
Your car is in a good spot, as-is. Balljoint basically mutilated his twins to make that power. It's not a real-world water mark. Mrrx7tt made 420 believable rwhp on a real street setup with BNRs and AI+. PS the aussie boys are making big power on their twins with the stock manifolds too.
Pushing for 400-500rwhp with the twins is like trying to hug a cactus. If you really want that power, then you should go single. The 8374 supports 400+ on pump and spools real fast. I have a buddy in Fla, he made 440hp SAE 100 actane vp, at 21 psi. Same set up I have. IRP tuned a large streetport with BNR's and made 456 rwhp on a Mustang dyno, that is 500 on a dynojet. Just by tuning my current set up in Fall/winter air we estimate 400 rwhp 18 psi, but I want to spin these in the 20+ psi range on race gas. Problem is, in Texas, even though these dyno's correct, the humid air/ DA always hurts what the turbos do. Learned that with my boosted motorcycles. The internet and dyno sheets seem to be a reality for alot of people. I will say that 360rwhp on pump gas feels alright, and blows anything under $50k away from a roll on while keeping great reliability. Thanks for all the input. |
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