Weltmeister chips question
04-08-2005, 11:41 PM
#31
Race Director
"I'm assuming I'll be able to map that with an ApecI right? I could set it to pull 16 psi or so to maybe 5,500 RPM and then maybe 15 at 6,000, 14 at 6,500? Would something like that work or should I just get the Guru ones?"
Sure, we can work up a deal for the GURU package. Ties into that other "special" upgrade you were interested in...
"Also I have never seen exhaust pressure in the 50+ range on these cars, only in the 40's. But who knows the KKK turbine isn't that efficient, so maybe."
The exhaust pressure goes up exponentially with the desired boost. That's because a small turbine's that forced to generate a lot of power to spin a big compressor-wheel or to spin a small one really fast, ends up generating a lot of back-pressure. The kink in the curve happens around 20psi where each additional psi above that requires more and more exhaust-pressure to drive the turbo. At 23-25psi, we're looking at 60psi in the ehxaust... whereas 18psi only requires about 30psi (also dependent upon RPM).
"This means that the intake pressure only needs to be ~1/3 the exhaust pressure + the spring pressure. "
Yup, except that to overcome the spring-pressure alone, you need the minimum spring-rate pressure. So a 1-bar spring will require 1-bar of boost-pressure to equalize the spring-pressure. Then additional boost is needed to overcome the exhaust exhaust-pressure.
If you have a surface-area ratio of 4.4:1, then to overcome 60psi of pressure in the exhaust, you'll need an additional 13.6psi on top of spring's 14.5psi to open the wastegate = 28psi mininum boost that you can't get below. This is if you have the banjo-bolt hooked directly up to the wastegate; with any boost-controllers in the way, your boost will most likely be higher than 28psi. I don't think ANYONE is using a Tial in a configuration where exhaust-pressure pushes the wastegate closed. Another issue is that you end up with a rising boost-curve 14-psi in midrange, then 18psi -> 20psi -> 25psi -> 30psi as RPMs and exhaust-pressure increases.
This is one of the cleanest wastegate installs I've ever seen:
Doesn't require a back and forth movement of the exhaust to dump out the wastegate like on our system.
Sure, we can work up a deal for the GURU package. Ties into that other "special" upgrade you were interested in...
"Also I have never seen exhaust pressure in the 50+ range on these cars, only in the 40's. But who knows the KKK turbine isn't that efficient, so maybe."
The exhaust pressure goes up exponentially with the desired boost. That's because a small turbine's that forced to generate a lot of power to spin a big compressor-wheel or to spin a small one really fast, ends up generating a lot of back-pressure. The kink in the curve happens around 20psi where each additional psi above that requires more and more exhaust-pressure to drive the turbo. At 23-25psi, we're looking at 60psi in the ehxaust... whereas 18psi only requires about 30psi (also dependent upon RPM).
"This means that the intake pressure only needs to be ~1/3 the exhaust pressure + the spring pressure. "
Yup, except that to overcome the spring-pressure alone, you need the minimum spring-rate pressure. So a 1-bar spring will require 1-bar of boost-pressure to equalize the spring-pressure. Then additional boost is needed to overcome the exhaust exhaust-pressure.
If you have a surface-area ratio of 4.4:1, then to overcome 60psi of pressure in the exhaust, you'll need an additional 13.6psi on top of spring's 14.5psi to open the wastegate = 28psi mininum boost that you can't get below. This is if you have the banjo-bolt hooked directly up to the wastegate; with any boost-controllers in the way, your boost will most likely be higher than 28psi. I don't think ANYONE is using a Tial in a configuration where exhaust-pressure pushes the wastegate closed. Another issue is that you end up with a rising boost-curve 14-psi in midrange, then 18psi -> 20psi -> 25psi -> 30psi as RPMs and exhaust-pressure increases.
This is one of the cleanest wastegate installs I've ever seen:
Doesn't require a back and forth movement of the exhaust to dump out the wastegate like on our system.
