I have searched and am wondering how much boost the stock internals on a mini cooper s can handle? I understand that the problem is heat and it eventually with to much becomes inefficient but with sufficient coolants and forged internals the mini could handle smaller pullys. Correct?

 

The issue isn't so much boost as it is heat. I'm not aware of any finite numbers on boost that the pistons can take before going kaboom. It's pretty widely accepted that much past 250-260 whp you want to put pistons in. Most of the other internals are pretty bulletproof. If you put anything other than a 11-12% pulley on you're pretty much already overspinning the supercharger past it's intended design.

With a 19% pulley at 7500 RPM's or so you're way past the intended supercharger RPM. You can expect to be replacing supercharger's every 40-50k miles if you plan on spending a lot of time in the upper RPM's with a 19+% reduction. I don't think anyone has gotten much more than 19-20 psi of boost out of the M45. It gets to the point that the air is so hot that even though you're spinning faster it's not making any more boost.

Personally I wouldn't jump up to a 19% unless I planned on setting my rev limit at 7200 and leaving it there. Right now I'm at ~8k with a 15%, though I rarely wind it out that far.

 

It really comes down to inlet temps, exhaust temps, and boost [and thus detonation]. With a single turbo R53 you can get about 310-320wHP out of the stock long block before requiring better pistons [and more than 93 octane]. The pistons end up being the first and biggest weak link. The con-rods and crank seem fine for most reasonable power levels, though I'm sure MEGAmini, Tuls, and RevolutionMINI can comment further as they've done totally insane build-ups.

In most M45 setups you won't need better pistons unless you insist on running a 19% pulley [or faster] at high engine RPM with a really restrictive head, IC, and exhaust. That sort of combo [especially with an overly lean ECU tune] will chunk up a piston in a hurry.

What're you trying to do in terms of engine setup and power? That'd help us offer more accurate advice.

 

The internals(crank and rods) are already forged....

 

nice, thanks for the quick responses

well... im really trying to decide, osbviously i want alot of power but right now im planning out what to purchase and when i can budget these purchases. Im going for a well rounded car but i do want an emphasis on power. I read alot about some namers having trouble with pullys larger than 15% but it sounds like the internals are pretty strong. Could this maybe just be that they have a lighter crank pulley? So really im trying to decide on what pulley i should be getting and if i should even get a new crank pulley. The more i read about my mini the more i believe the most important part of this engine is going to be the cooling modifications. So im trying to get a feel for how much money i would need to put into cooling (new ic, meth injection, hood scoop) in order to get the most out of a pulley

 

hmm thats cool, how do the valves hold up?

 

I suggest you give Jan at Revolution MINI a call. There's not much he HASN'T done yet on these cars. He'll be able to tell you what to do and what not to.

 

i was thinking that, hed be cool with me calling? If im not mistaken hes kinda far away too, does he remote tune from a dyno near me?

 

Where do you live? He'd be fine with you calling, that's why he lists his number on his website :-).

He's in CT right now tuning cars though so 10 PM may not be the best time .

 

just got done tuning... will be up for awhile

 

haha sounds good dude i have a seminar i need done by tommorow, is it ok if i call you tuesday? If not whats a good day and time? O im in jersey too soo ct couldnt be that bad. Please let me know

 

Most I was willing to push on stock engine. Boost was 26/27 PSI, as Ryephile mentioned, the limiting factor is the stock pistons.


GT2871 TURBO CONVERSION
STOCK HEAD/BLOCK
CUSTOM INTAKE MANIFOLD - TUNED RUNNERS W/VELOCITY STACKS
FRONT MOUNT INTERCOOLER
CUSTOM FUEL SYSTEM - RETURN TYPE
RACE GAS: VP MS109

 

Is it really safe to run that much power through the stock pistons? I'd be afraid they'd blow every time I got past 4k RPM's .

 

It's more of an illustration point

 

never melted one running 27psi all last summer on the stock pistons. I tried to blow it up on more than one occasion, no luck.

 

what type of gas did you have? And what AFRs?

 

I would like to know also.