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04212010, 10:47 AM  #45 
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04272010, 03:22 PM  #46 
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Checked boost pressure today.
My calculations were 100% correct Sea level pressure 1019hpa 5300 ft pressure 839hpa (this can be worked out for any altitude) The percentage of air pressure at 5300ft compared to sea level is * derived by 839/1019 = 0,82 I lose 18% at my altitude. This is the ratio you must apply to the boost a pulley generates at * sea level. 95mm pulley 6 psi x 0,82 = 4,92 psi On my runs with the boost gauge connected, the maximum recorded boost * was 0,33 bar = 4,78 psi This proves my theory beautifully. 92mm pulley 7 psi x 0,82 = 5,7 psi 7,5psi x 0,82 = 6,1 psi Based on what we saw with the 95mm pulley boosting at the bottom of * the 66,5 range, I believe the 92mm will boost at 7 808E90 (Ricky) dynoed at 440HP with 4,5psi and he had full ericsson * exhaust. Mine dynoed at 443 HP with 4,78 psi, and i have a full akrapovic. * Makes sense. Therefore on a SC, power is directly proportional to amount of boost, * regardless of altitude, making the effective delta gains compared to ** stock car, much higher at altitude Last edited by Bob MG; 05022010 at 08:59 AM. 
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08312012, 12:46 PM  #47 
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This is a great discussion. I have learned quite a bit, but I don't understand how (if at all) supercharger systems on these cars compensate for cooler than normal temperatures. A standard atmosphere is 15 C at sea level. If the supercharger system is designed for X amount of boost maximum, are there any safe guards for cooler than standard days at sea level, or do you just have to monitor the boost level yourself so that limits aren't exceeded? At altitude, temperature really effects the atmospheric pressure. For instance, here in El Paso, I am sitting at 3,948 feet. A standard day at this elevation would result in a temperature of approximately 7 C. This doesn't happen in the Summer months and we usually see 3035 C in the afternoons. Right this instant at 10:43 AM with a temperature of 27 C, dew point of 3 C and a barometric pressure at 30.13 results in a density altitude of roughly 6,075 feet!
Now on the other hand, place yourself at sea level, winter months and you can see 2000 feet which would raise boost pressure possibly above design limits, no? What's the safeguard for this? I'm asking because I don't know and want a car designed to function in all types of environments (hence my reluctance to supercharge).
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08312012, 01:35 PM  #48 
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Bud the temp variation is slight and the ESS kit allows for variation of around 1 psi either way anyway
Also ECU's adaptation would also take care these normal variations I have done the blower on two of my M3s and had no issue ever. In winter my temp are around 515 deg and summer 2035 deg so similar to your temps I have seen a drop in perceived performance now that temps have warmed up. 
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08312012, 01:36 PM  #49 
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Also of you chat to AJ from ESS the different pulleys are rated at a varied boost pressure
Eg a 92mm is 77,5 psi (depending on density altitude affected by temps) 
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08312012, 05:21 PM  #50  
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09012012, 11:23 AM  #51 
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Bob was 100% right. I have driven down to sealevel & logged boost at both elevations & the boost is around 2 psi more with the same pulley at sealevel vs 5000ft.

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05222013, 03:33 AM  #53 
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Been doing some research. @ROMAN@ESS is there anyway to purchase a smaller pulley then the supplied one Andrew @ AR Design ordered for my Car? We are running the ESS 625 kit, but are only managing 526hp corrected (mid 400's iifc uncorrected) and are trying to find a way to up the boost a pound or 2 safely to get the power on par (or close too) with the 625 guys at sea level (500 uncorrected up here would be great) For reference, he is a dyno of our pull up in Denver. Car will never see sea level, or leave Colorado even.
*EDIT* On a side note, we have a vortech pulley at the shop (3.6" 91.4mm) not sure on the size difference between that and the 625 pulley. We noticed that there is a slight offset in the 625 supplied pulley, so we haven't attempted to try this one out yet. Figured I would touch base with you first to see what the options are.
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05222013, 12:26 PM  #54 
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just curious, as Ive never seen it before, what is the N/A power uncorrected? 
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05222013, 01:38 PM  #55 
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Yea corrected is decent, but the uncorrected was around 46x iirc. Uncorrected preboost with full exhaust, drop in filter was 305hp i believe. Fuck this thin air.
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05222013, 04:34 PM  #56 
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Agree! I was getting 305310 whp here stock.
Will be curious to hear what you find with the blower. If you go with a smaller pulley to increase boost, what happens if/when you choose to go down to sea level?
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05252013, 02:10 AM  #57 
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Out of curiosity what are the boosted M's up in Colorado/5k+ altitude dynoing at?
I've made peak power of 526hp/343tq peaking at 6psi. (ESS 625 kit) Before that, bone stock i was 309, and drop in filter and catless/resonator delete xpipe and oem exhaust mod 349. All runs were done at Finishline
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06142013, 07:00 AM  #58 
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I at 5500 ft altitude and I have a VT2 625 kit boosting at around 7,8 psi
To achieve this boost at my altitude I run a custom 650mm crank and 95mm S/C pulley set up from VT3 kits with a 2130mm belt 
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06142013, 01:01 PM  #59  
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This "quantity" you are referring to is known as D.A. (Density at Altitude). Bob MG is correct, all he will have to do to compensate for his altitude is very basic, and he is already on track to doing it. Superchargers and turbocharger systems do not respond the same way in regards to D.A. The turbo will continue to compress air without the wastegate opening until the target pressure is acheived, it does not care what altitude it is at. The CF supercharged car will generate boost as a function of crank speed and SC pulley speed. Alter the ratio between these two, and you effectively alter the boost pressure (given that D.A. does not change along with ambient temperature). The SC car will be affected by D.A. because it does not have a wastegate boost control system, it is predefined in pulley size and RPM. The higher up you go, the less boost the SC car will generate. Much like in NA form, the SC car will suffer power at higher altitude. 

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06142013, 03:11 PM  #60  
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06142013, 05:31 PM  #61 
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Awesome, what kit/fuel?
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06292013, 11:34 PM  #62 
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Next step after the 3.2" pulley is converting the car to E85. Just trying to figure a way to tune the car once we throw in a larger pump and injectors to handle to E85. At that point I would love to see 650+ on 910psi.
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06302013, 03:27 AM  #63 
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A little fun post pulley install haha. Clearly need some sticky drag radials now!
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07132013, 03:19 AM  #64 
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Swapped pulley to a 3.2" (81mm) and saw 9psi on dyno today and managed to jump from 565 at 7psi and 613 at 9psi.
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07142013, 06:27 AM  #65  
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Smaller than 88mm causes the belt to slip. To get this done correctly you must change your crank to 650mm and then you need to only go to around 92mm to achieve the same level of boost. Also 9psi is too high for the tune you have and you are asking for crap 

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07142013, 07:15 AM  #66  
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