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I have a 2005 Mini Cooper S. I just replaced my supercharger pulley with a 15% reduced pulley with a +2% ATI Crank pulley. I got NGK BKR8EIX sparks plugs and a 1360mm serpentine belt to complement these upgrades. I have noticed that I have no power of 17 PSI of boost. Looking at the calculated boost on my Bluetooth OBD-II. Once it hits 4000 rpm, it pegs there. If I let off and gradually get back on it, it will rev past 4k, but feels very sluggish. Almost like there is no boost. I have a code P0108, which is relating to the MAP sensor. I ordered a new one and installed it today and I am still having this issue. Is my ECU limiting power to protect the engine?

Any help would be appreciated, thank you!
 

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At 4K the ECU stops using lambda control for fuelling and instead uses its preset map (target), which of course is not adjusted for the additional boost the pulley changes are giving, in other words your car will be running lean. Knock control will be running around -7 thus pulling ignition to stop detonation.
 

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as you have a map sensor fault it dont mean its the sensor a lot of time,, last one i done of these it had same sort thing after top end build and fast road cam fitted etc, and when we stuck it on rollers it would not rev out,, long and short of it cat was blocked and 02 sensors were fairly dead due to age and they all use some oil as get older, this car had valve stem seals worn out all they do it also had worn camshafts below link to this car was 101k ,

also another common one is divertor valve might be faulty, or you have a vac leak from inlet vac pipes down by the throttle body some small hard pipes these snap off for a past time have seen many over the years where people have pulled on them and snapped them not knowing etc
 

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Discussion Starter #4 (Edited)
as you have a map sensor fault it dont mean its the sensor a lot of time,, last one i done of these it had same sort thing after top end build and fast road cam fitted etc, and when we stuck it on rollers it would not rev out,, long and short of it cat was blocked and 02 sensors were fairly dead due to age and they all use some oil as get older, this car had valve stem seals worn out all they do it also had worn camshafts below link to this car was 101k ,

also another common one is divertor valve might be faulty, or you have a vac leak from inlet vac pipes down by the throttle body some small hard pipes these snap off for a past time have seen many over the years where people have pulled on them and snapped them not knowing etc
Well, it is throwing the code P1498, which is for unmetered air after the compressor. I have been trying to diagnose this issue for a while now, but can't pinpoint where the leak is. Would this cause this problem?

I know lots of people run the 15% with the +2% crank with the base map and don't have any issues. Would theirs technically be running lean as well?
 

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all engines as they get above 4000 revs start leaning out as at top of revs the momentum takes over and dont need to keep trowing fuel at as this will melt things,, even when mapping them you always start dropping the fuel off at the top to prevent melt downs or should say the balance , i would not just fit smaller pulley on them without the mapping to go with it believe me you add to much air and dont balance it with fuel it will hurt it over time,,, thin i seen somewhere someone write that no point mapping a r53 as dont map,, hmm i beg to differ we do and that one on that link made 233bhp at wheels on rolling road compared to its 160bhp on first run,,, its done 4000 miles now and still kicks ass, and that was lean out at around 6500 revs ad rev limit raised to match the camshaft as was a fast road cam,, it also ran reduced pulley decat exhaust had new 02 sensors fitted a must do job before mapping anything,, little tip here for people a map is only as good as the 02 sensors and map sensor so best to have new ones for best results,, as worn dirty old sensor are just that a very narrow band of where they still work etc, ,
so your car i would do a smoke test on pressure side of inlet manifold,, also bare i mind a engine is like a pump if you restrict any of ts working it effects the whole system,, so clogged or burnt out cat will have a effect of flow can effect inlet pressure if clogged up ie low map readings,,, also super charger if its very worn it will not grab the air and make the pressure needed for inlet that would flag as inlet pressure fault,, also the pulley belt to it if slips same thing, also of bottom pulley the rubber torsion damper on it fails and starts slipping on its self that so very common on them,, the two vac pipes for crankcase breather and brake servo under the throttle body these crack for a past time... smoke test machines are loads of money, i use smoke pellets sometimes light them and stick on the inlet pipes and wait to find smoke come out just made sure seal the inlet pipe from air filter first lol,
 

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all engines as they get above 4000 revs start leaning out as at top of revs the momentum takes over and dont need to keep trowing fuel at as this will melt things,, even when mapping them you always start dropping the fuel off at the top to prevent melt downs or should say the balance , i would not just fit smaller pulley on them without the mapping to go with it believe me you add to much air and dont balance it with fuel it will hurt it over time,,, thin i seen somewhere someone write that no point mapping a r53 as dont map,, hmm i beg to differ we do and that one on that link made 233bhp at wheels on rolling road compared to its 160bhp on first run,,, its done 4000 miles now and still kicks ass, and that was lean out at around 6500 revs ad rev limit raised to match the camshaft as was a fast road cam,, it also ran reduced pulley decat exhaust had new 02 sensors fitted a must do job before mapping anything,, little tip here for people a map is only as good as the 02 sensors and map sensor so best to have new ones for best results,, as worn dirty old sensor are just that a very narrow band of where they still work etc, ,
so your car i would do a smoke test on pressure side of inlet manifold,, also bare i mind a engine is like a pump if you restrict any of ts working it effects the whole system,, so clogged or burnt out cat will have a effect of flow can effect inlet pressure if clogged up ie low map readings,,, also super charger if its very worn it will not grab the air and make the pressure needed for inlet that would flag as inlet pressure fault,, also the pulley belt to it if slips same thing, also of bottom pulley the rubber torsion damper on it fails and starts slipping on its self that so very common on them,, the two vac pipes for crankcase breather and brake servo under the throttle body these crack for a past time... smoke test machines are loads of money, i use smoke pellets sometimes light them and stick on the inlet pipes and wait to find smoke come out just made sure seal the inlet pipe from air filter first lol,
Wow! This is a very helpful response. Turns out because of the increase in pressure it kept blowing the vacuum hose on the intake manifold off. So I picked up some vacuum fittings and replaced the ones I could see and added a hose clamp to the one on the intake manifold. It seems to have fixed my problems. I am able to rev over 4k and the P1498 code hasn't shown up yet. The engine seems to be running much smoother as well.

It pulls like crazy now! I am so excited!
 

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Wow! This is a very helpful response. Turns out because of the increase in pressure it kept blowing the vacuum hose on the intake manifold off. So I picked up some vacuum fittings and replaced the ones I could see and added a hose clamp to the one on the intake manifold. It seems to have fixed my problems. I am able to rev over 4k and the P1498 code hasn't shown up yet. The engine seems to be running much smoother as well.

It pulls like crazy now! I am so excited!
honestly if there is one thing worth doing to the r53 after a reduced pulley its a run on rolling road and mapped as per the session as such its really a night and day thing ,, we done my r56 the other week and 206bhp at wheels on rebuilt motor and it now will pull hard from no revs all way up so much more fun to drive
 

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honestly if there is one thing worth doing to the r53 after a reduced pulley its a run on rolling road and mapped as per the session as such its really a night and day thing ,, we done my r56 the other week and 206bhp at wheels on rebuilt motor and it now will pull hard from no revs all way up so much more fun to drive
I plan on getting a custom map, but I'd like to put bigger injectors on and a cat cam before that.
 

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if there is one extra i can honestly say makes a massive difference is below fast road cam it dont hurt the idle or low revs when mapped right,, i stuck one in that r53 but was on a 100k bottom end that did have new big end bearings as crank was not worn,, and 233bhp was last run that said could of pushed it more but really more needs to be forged etc and thats big money
link below for cam, also on that cam the power comes in hard at top of rev limit and get the best out of it by tapping the rev limiter up we only done 500 revs extra on this one as was a part rebuild,, but a forge motor would take more, we found just has the cam came in hard the limiter beat it back again,,, i drove a few times after and it was like standing on land mine lol
 
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