[bangoos]

If this post is in the wrong part of the forum feel free to move it.

I need to turbo charge a P ported RX8 engine. The well known sea level output at 6500rpm is 250hp for a rotary in this configuration. I want a turbo optimized for 8 to 14k elevation and be able to easily hold 250hp up to my max elevation at the same engine speed, while still being able to boost 10psi in the lower elevations.

I read some of the tech info on how to calculate the correct wheel, but because the calculation appears to only apply to sea level, then the compressor maps seem useless.

For example, if I use the calculation I found: boost psi + 14.7/14.7, I cannot see how it makes sense when the ambient pressure at 10k feet is about 10.1psi

It is rather confusing trying to understanding some technical elements used on this site. I have heard of O trim, P trim, Q trim, and the general numeric trim numbers used, and perhaps could determine a numeric trim value for any wheel, but then I would be guessing my calc is correct for turbonetics.

Another point of confusion is the use of term 'air ratio' when it is often not clear whether in any particular instance it is referring to the compressor or the turbine.

Because the air is considerably thinner at 10k feet and higher, then my spool speed could easily exceed the mechanical limits of the turbine wheel, especially at around 1700 degrees F., which is about the temp of a rotary exhaust at 250hp. This makes determining the correct size for both wheels different than at or near sea level. I need to be able to calculate the correct turbine wheel for the altitude. The compressor wheel should also function to keep the turbine below a certain speed.

I believe how it works is that a lower turbin a/r number is better for lower elevations, and the higher a/r for higher elevations.

All assistance is appreciated.

[Robert]

Originally Posted by bangoos

If this post is in the wrong part of the forum feel free to move it.

I need to turbo charge a P ported RX8 engine. The well known sea level output at 6500rpm is 250hp for a rotary in this configuration. I want a turbo optimized for 8 to 14k elevation and be able to easily hold 250hp up to my max elevation at the same engine speed, while still being able to boost 10psi in the lower elevations.

I read some of the tech info on how to calculate the correct wheel, but because the calculation appears to only apply to sea level, then the compressor maps seem useless.

For example, if I use the calculation I found: boost psi + 14.7/14.7, I cannot see how it makes sense when the ambient pressure at 10k feet is about 10.1psi

It is rather confusing trying to understanding some technical elements used on this site. I have heard of O trim, P trim, Q trim, and the general numeric trim numbers used, and perhaps could determine a numeric trim value for any wheel, but then I would be guessing my calc is correct for turbonetics.

Another point of confusion is the use of term 'air ratio' when it is often not clear whether in any particular instance it is referring to the compressor or the turbine.

Because the air is considerably thinner at 10k feet and higher, then my spool speed could easily exceed the mechanical limits of the turbine wheel, especially at around 1700 degrees F., which is about the temp of a rotary exhaust at 250hp. This makes determining the correct size for both wheels different than at or near sea level. I need to be able to calculate the correct turbine wheel for the altitude. The compressor wheel should also function to keep the turbine below a certain speed.

I believe how it works is that a lower turbin a/r number is better for lower elevations, and the higher a/r for higher elevations.

All assistance is appreciated.

To be sure you get the right turbo for your application I would contact the sales team at 805-581-0333 and they can walk through the specific requirements you have