This is a great thread I found helpful discussing what boost numbers members are getting in relationship to the mods they have added. Thought there was some great information that some may enjoy reading. One thread makes me think going with a 19% pullley and a header may even equate to less boost then a 17% pulley without the header creating more power with similar or even less heat. Yes the supercharger will be spinning faster but the back pressure (boost) or (PSI) will be less which is what creates the overheating of a supercharger resulting in less power.

sounds about right...

but you cant judge the power from the boost pressure at least thats what i experienced
the better the air flow through your engine the less boost is generated. ( at least with the roots like supercharger )

right now i am hitting barely 11psi on a jcw pulley ( and no, there are no boost leaks or a faulty supercharger )

with my old engine ( 16% ( it was a 56.5mm pulley... not sure about the % ) and 103% crank ) i was at ~18psi at first... but while i modified it further ( head, cam, exhaust manifold and so on ) the max. boost dropped to ~14psi while power was going way up ( because of the better air flow trough the engine and lowered intake temp. )


https://www.northamericanmotoring.co...-modified.html

Also, Don't skip over my last thread.....
200WHP sounds good. From a stock JCW to 200WHP should be a noticable difference? Does anyone feel they have found the "WHP sweet spot" for the r53? Should I shoot for more?

 

Had some time to re-read this thread & in reality there are a few inaccuracy's.

Biggest problem is that you're confusing two different things, Boost & Combustion Chamber Cycle, Boost is read Pre-Combustion Chamber and while exhaust flow will have an effect on the Combustion Chamber Cycle and air movement, unless it's so restricted that it's not allowing "all" the Combustion Chamber Pressure to evacuate when the exhaust valves are open and causing it to then "back up" into the Intake System (when the intake valves open) it should have little or no effect on Boost, simply because the pressure readings are created with the exhaust valves closed.

Boost Levels are "mainly" determined by the amount of pressure created by the S/C +/- Air Density, which is most determined by Barometric Pressure/elevation & Heat, and while in theory a 19% pulley may create more Air Flow, the lessened density of the Air due to the extra heat generated can cause lower actual boost levels and less overall power. (this of course is when comparing 2 different engines with the same size Combustion Chambers & Valves)

The above quote is actually correct, but the lower boost #'s were actually created by the larger valves and porting in his Head basicly just giving him more space to fill, not by the Exhaust, the combination of everything will however create more power by allowing better air flow.

 

OP......how much money are you wanting to sink into your daily driver? If you want to make 225-250 hp at the wheels, it's going to cost a fortune. Cam, head, injectors, header, tune, dyno time....and the labor to do all of that can get outrageously expensive in a hurry, especially if you have to pay a shop to do the work.

I don't know if there is a "sweet spot" for an R53....I've never heard anyone say "I liked my mini better when it made less power". It all depends on how much money you want to blow on your car.... Just keep in mind that most stock mustangs, camaros, gto's, and vettes will blow the doors off of a modded mini if you are playing around on the street. Minis are not muscle cars by any means.

Just something to think about.

 

I did provide one thread from the link i provided but you should read the entire thread to see some other boost #'s before and after adding a header. Again i am not here to argue and i am sure you are knowledgeable in the industry but you are incorrect here and should let this one go. It is a fact that exhaust back pressure increases boost. Why do you think many headers will result in a loss in ft lbs tq and a gain in hp? (I know why so please do not try to explain, just trying to help you understand). All the best!

 

 

Wow.