Max boost

[wasinger3000]

My statement does not negate your "claim" And is exactly what I wanted to avoid. But your continued posts of 25lbs of boost makes other think there is something wrong with there cars. Spikes are irrelevant and prove nothing, stock turbo's are capable producing boost pressures into the 30lbs range. But again irrelevant, cause it well beyond the turbo's peak efficiency. Max boost means absolutely nothing, its the volume of air that turbo can displace efficiently.

Hah, you must not have read the post then. I already said what you are saying. But ok, I'll leave it there. 

 

[91hybrid]

Well, since no one has a compressor map for these the only real way to tell is through measuring the out temperature vs the inlet temperature.

One can get a feel for how hard they are pushing the turbos by looking at the waste gate duty cycle but one needs to understand how maps work with the mass flow and pressure ratio to guess where they would be on the map.

Efficiency is temperature. The loss of efficiency results in hotter output. The flow is there, it's just could be 250 degree instead of 100. Inner coolers and meth come into play to "cheat" the efficiency by cooling the charge back down to a normal temperature that would mimic some one running a turbo in peak efficiency.

John

 

[ZSHO]

In general wouldnt elevation also play a role in more accurate boost readings,and also altitude can spike the readings.

 

[SHOdded]

Useful or not?  You decide:
http://www.rx8club.com/series-i-tech-garage-22/altitude-effects-intake-boost-pressure-52371/
http://www.dieselarmy.com/engine-tech/boosting-altitude-elevation-effects-turbochargers/

 

[Larrylu]

Best read I've seen in a while!  Thanks for posting. Complex topic for sure.

 

[91hybrid]

So if anyone who reads that attachment starts to think....how does density altitude matter then in my car?

Really the only output to da is temperature. Lower da causes pressure ratio to rise which depending on a specific compressor map can move it to the next lower effiency zone. Which in the grand scheme of things is probably pretty small.

The real part of da that drives performance is temperature. Da is comprised of pressure, temperature and humidity. Our cars as discussed above will make the pressure regardless of atmospheric pressure but temperature is the key for us.

With cooler temperatures, our turbo inlet temps are lower so the output will be lower relative and the innercoolers are more efficient both of which result in lower intake charge temperature that do nothing more than to allow us to increase timing. This increase timing (reduced knock) is the power gains people feel. There is a density increase of the charge too (in accordance to ideal gas law) cooler temps same pressure = denser charge, but there is more power to be made through timing then the density differential. Unless of course the temperatures are like 75 deg verses 250 degree that is.

 

[BiGMaC]

Well said 91.... In fact to go a step further, that's why i am seriously looking into meth.. the drop the TB take temp 50 degrees or so and have the "increased octane rating" caused by the meth... all of which allows several changes including a lot of timing advance.

 

[SHOnUup]

Humidity plays a large role in the density of the air also right?

Isn't there less oxygen in the air at higher altitudes, so even though the pressure is there, you're still not getting enough oxygen to burn?

Rich

 

[91hybrid]

Humidity measured in grains per pound of air does matter. Pressure and temp are "generally" bigger levers so to speak but humidity plays a part.

When you go to a track in the mountains the da is lower because of the lower atmospheric pressure even with equal temperature and lower humidity thus slower times.  Pressure is the biggest lever followed by temperature, then humidity.

Pumping water is never fun.

 

[SHOnUup]

Thank you ^^^

Rich

 

[panther427]

What is your negative readings at idle aat sea level