Turbo users: Need your psi/hp figures for RX-1 applications

[Jack_Shaft]

Guys,

I was working on developing a spreadsheet that automatically calculates the minimum fuel grade req'd for certain levels of boost and the subsequent hp it produces. I have determined the VE and other factors, but the only problem I have is the relationship between the boost pressure and the hp.

Basically, I know that 8psi = 205hp at sea level, but I have few other figures to help me along the path...

What I need from you turbo fellows are the psi/hp figures that you are running. For example, 10psi = 240hp, 14psi = 275hp... etc.

PLS post up your boost pressure and hp figures to help me populate my table. I will eventually post it here for all prospective turbo buyers/tuners to use.

Thanks!

-JS

 

[sledheadgeorge]

This might vary from one user to another. Different turbos at same boost might produce different hp numbers.

 

[Jack_Shaft]

My inquiry has more to do with the Schwitzer (smaller) turbo unit that comes with the MCXpress kit.

However, for any data higher than 14psi of boost, I will know that the data has to be from a larger turbo since the Schwitzer will top out at about 14psi.

Either way, I guess it would be a good idea to indicate the turbo unit you are using when posting your psi/hp numbers.

Thanks all,

-JS

 

[Jack_Shaft]

Come on fellas, post your psi/hp numbers....

 

[Turbo Tim]

Come on fellas, post your psi/hp numbers....

It may be faster to go to the turbo maufacturer websites .Not too many turbo owners have their sleds dyno'd

 

[jtssrx]

A lot of guys are using to much fuel and causeing heat in there motors. TO much fuel "octain" is just as bad as not enough Octain

 

[snow king]

I would like to know if altatude has a factor on boost and what effect it has on octain. I've read some info but am not clear if it does.

 

[Turbo Tim]

I would like to know if altatude has a factor on boost and what effect it has on octain. I've read some info but am not clear if it does.

Boost is down and power also in the mountains .True of any sled boosted or not .............the turbo + 4 stroke combination loses less horsepower than any other engine configuration.

 

[snow king]

We ride at 7500 to 10000 feet can i run more boost with less octang than
I could at say 2000 feet?

 

[TurboKeith]

Here are some formulas for you. I am including a spreadsheet that will automate the process as well as doing some altitude compensation. These formulas and the spreadsheet will get you pretty close. There is no way for me to be able to tell what the individual motor efficiency's are so like I said these will just get you close. This will put some things in perspective when it comes to hp loss at altitude.

base hp = total hp / (boost + 14.7) *14.7

hp per lb of boost = base hp / 14.7

theoretic hp = boost * hp per lb + base

 

[Jack_Shaft]

Here are some formulas for you. I am including a spreadsheet that will automate the process as well as doing some altitude compensation. These formulas and the spreadsheet will get you pretty close. There is no way for me to be able to tell what the individual motor efficiency's are so like I said these will just get you close. This will put some things in perspective when it comes to hp loss at altitude.

base hp = total hp / (boost + 14.7) *14.7

hp per lb of boost = base hp / 14.7

theoretic hp = boost * hp per lb + base

Thanks for that one formula I was missing.

Now I can directly relate hp to boost pressure, right on.

-JS

 

[Jack_Shaft]

So, with this in mind, at 8psi of boost @ 0ft elev, I can make 216.2hp, etc...

This is great....

 

[TurboKeith]

This should give you a good starting point. This seems to be fairly accurate for the lower boost levels. The higher the boost goes, the more inefficiency's come into play. The pressure drop with altitude is actually on a curve, The 3% per 1000 ft is about as close as I could come to making a linear equation work. Play with the numbers a bit and you'll see why a turbo setup smokes a normally aspirated setup at altitude.

Keith