Andial951

Just wondering what the average rwhp gain per psi was. I think it may vary depending on the set up of your car and whether or not you have the right chips to support the increased boost. But on average what could I expect?

fast951

On a nicely setup 2.5l it's 12-15rwhp up to the limit of the turbo or head or ...

Laust Pedersen

Since this can be asked for any turbocharged engine, a more general approach to an estimate would be to stay with relative numbers as far as possible:

The HP increase going from 0 to 14.5 psi boost with a more than ideal intercooler capable of preventing a temperature increase of the charge air and assuming no other additional losses would yield a 100% increase of the HP.
Then guesstimate the reductions from the ideal for example 10% for non ideal intercooler, 5% for extra flow restriction passing the intake valves, 15% for extra back pressure (reduced intake filling) and 5% for extra friction and pumping losses. This then results in a more realistic 100% - 10% - 5% - 15% - 5% = 65% HP increase. Lastly divide this by 14.5 psi resulting in 65% / 14.5 psi = 4.5%/psi HP increase. Now apply that to whatever starting HP you have for example 300 HP and you will get 300HP * 4.5%/psi = 13.5 HP/psi

Laust

PS My reduction numbers are quite arbitrary, but it certainly would be an advantage to get more realistic numbers, since they show where to look for potential improvements.

hosrom_951

Timing plays a huge role here, look at special tool's pump gas run vs xylen/pump gas mix.

almost 400whp @ 19.4psi on 100% pump gas, with the pump gas/xylene mix, he would have got much more out of it once timing is advanced on the same boost. Offcourse this doesn't mean everyone who advances their timing would get the same results, but you get the idea.

Andial951

well I suppose the only way to know for sure is to do a run on a dyno at different PSI to see exactly what the increase is.