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HELP.... Guide to working out PSI Boost too BHP is it possible ???

whogives

whogives

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67
This may have been asked before ....Sorry if it has

Is it possible to get a very Rough idea of the BHP , when you know the PSI Boost.... s/charger kit ?????
 
Edit. Misread!

Depends on a few things. Always thought 9 psi is about 300 bhp on a K20.
 
Chris. said:
Edit. Misread!

Depends on a few things. Always thought 9 psi is about 300 bhp on a K20.
Click to expand...

My reason for asking is I thought that all standard engines produce 14.7 PSI .. ( Normal air pressure) so if your car has 198 BHP standard and your car produces a boost of 14.7 PSI..... Your BHP is double so would be 396 BHP.

Or boost was 7.35 PSI which HALF it would be 1.5 times (296 BHP)

To be honest I haven't got a clue ...lol :)

But my car is producing a 12 PSI Boost using a CT Supercharger ... I haven't had it on a dyno yet
 
The engine doesn't produce boost.
On a N/A engine, atmospheric pressure (1bar/14.7psi) pushes air into the engine as the piston comes on the down stroke creating a depression.
On a boost application. You'll have atmospheric pressure, plus the charger pressure entering the engine. So 14.7 + 12 = 26.7psi. But this is theoretical...
As to why you only see 12psi on your gauge/map sensor is the Gauge/Map sensors on petrol engines read 0 at atmospheric pressure. As it has to read negative pressure.
On diesels however the map sensor reads the exact pressure including atmospheric. So with the engine off the map sensor would read 1 bar/14.7 psi.


Sent from my iPhone using Tapatalk
 
Ok ........... So if a N/A Engine K20 produces 196 BHP @ 14.7psi (Atmospheric) 196 divided by 14.7 = 13.33 BHP ..... 13.33 X 26.7 psi = 355.91 so this is the BHP being produced .... I know this is theoretical guess work.

But interesting to find out :). My Map has been done by Vit-viper so the car hasn't touched a rolling road.
 
All I will say is that an engine's power output is not relative to it's boost pressure in a linear fashion as you are implying.
 
Yer that's fine .............. like I said I haven't got a clue if it was possible to work out in the first place ............. Its off to the rolling road then :) Thanks for your inputs
 
As Stu said, it isn't a linear line. There are too many variables. Heres the figures from when I was having my turbo built,



As you can see the difference between 7 - 8psi is only 10bhp, but the jump from 11-12psi is 19bhp. It went on to make 467bhp at 14psi.
 
tom83 said:
As Stu said, it isn't a linear line. There are too many variables. Heres the figures from when I was having my turbo built,



As you can see the difference between 7 - 8psi is only 10bhp, but the jump from 11-12psi is 19bhp. It went on to make 467bhp at 14psi.
Click to expand...


Now that's quite interesting .... thanks for that. .......... I'm just struggling to find a rolling road setup .
 
Well managed to get the old girl on a rolling road today..............results 289 BHP @ 8145 RPM ..... 190FT LB

I may have been able to get a couple of more HP redline is know 8500 RPM

But all in all not bad
 
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