# Altitude affects on TT, JB, or Procede



## DHP (Oct 16, 2005)

OK - been asking friends this question but haven't gotten any solid answers. Some have said that the stock 335 will boost above 8 psi to get better performance at altitude (I live in Denver, 5280 feet). For a normally aspirated engine, there is about a 20% horsepower penalty at our altitude - the 400 HP V8 M3 for example will act like a 320 HP car here. To compensate for altitude, I've read that a stock 335 may use boost up to 11 psi (can't validate this claim). In that case is it worthwhile to buy any of these aftermarket options that in essence turn up the boost? Are there significantly less improvements in horsepower with these products at altitude than at sea level as compared to stock? Thanks!


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## Terry @ BMS (Apr 27, 2007)

See reply in other thread.


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## Eurobahn (Nov 19, 2005)

DHP said:


> OK - been asking friends this question but haven't gotten any solid answers. Some have said that the stock 335 will boost above 8 psi to get better performance at altitude (I live in Denver, 5280 feet). For a normally aspirated engine, there is about a 20% horsepower penalty at our altitude - the 400 HP V8 M3 for example will act like a 320 HP car here. To compensate for altitude, I've read that a stock 335 may use boost up to 11 psi (can't validate this claim). In that case is it worthwhile to buy any of these aftermarket options that in essence turn up the boost? Are there significantly less improvements in horsepower with these products at altitude than at sea level as compared to stock? Thanks!


WE have several customers running our Turbo Tuners in high altitude areas. So far with the exception of a trans up shifting issue due to high torque loading no one has complained about performance. On the contrary everything we have heard is that the cars pull like raped apes!

Jeff
Eurobahn


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## franka (Jan 23, 2006)

If boost is limited by a blow off valve then 8 psi at sea level is the same as 8 psi at altitude, or at least close to it since the blow off valve may be affected by local ambient pressure.


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## midlife (May 10, 2007)

franka said:


> If boost is limited by a blow off valve then 8 psi at sea level is the same as 8 psi at altitude, or at least close to it since the blow off valve may be affected by local ambient pressure.


*i am at 9,000 feet. from all the thread searching and my own experiences:*
1/ get the RPi intercooler - i have it and u should too. any good IC ugrade is good, but:
RPi intercooler is practically take off your bumper (find the do it yourself - vvery helpful), and drop it in. not cutting / car alteratons needed. 
we do not have enough air at altitude, the IC definetly helps with this and other issues.
2/ pm terry at juice box directly. i have the JB1 in for a week now, and although i have yet to make a comparision run - it feels really strong.

at sea level our cars have 8psi of boost. our ecu adapts to higher altitude (i think) up to around 4-5,000 feet. it does so by boosting psi another 3 psi for a total of 8 + 3 = 11psi.
i was told the JB1 (lower boost which is safer than JB2 at altitude) gives u another 2 psi...it is a bit technical, but realize that at sea level ambient air pressure is (i think) 14.7 psi. at atitude, the ambient air pressure is less, so u need more turbo psi boost to get the same MANIFOLD PRESSURE that the car needs for best performance. do some thread searches, but it does not matter that much (except for if too high a turbo boost, u can pop ur turbos) how much boost u have at your altitude. in performance terms i believe it is how much manifold or wastegate pressure you make (which is i think = turbo boost pressure x ambient air pressure). i may not be 100% technically correct, but i hope u get the idea.

again, pm terry at juice box or another vendor if u wish and ask for LBT tune (lower bosst target tune). unfortunately, i am in another forum 90% of the time, but u can PM me here and we can try to work together a bit. i am no expert, but the 2 mods i did listed above have helped alot i believe. also a good drop in filter like k&N or BMC are helpful especially with an ecu tune.

ALL OF US ALTITUDE GUYS SHOULD STICK TOGETHER, because there is not much info out there... good luck


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## midlife (May 10, 2007)

DHP said:


> OK - been asking friends this question but haven't gotten any solid answers. Some have said that the stock 335 will boost above 8 psi to get better performance at altitude (I live in Denver, 5280 feet). For a normally aspirated engine, there is about a 20% horsepower penalty at our altitude - the 400 HP V8 M3 for example will act like a 320 HP car here. To compensate for altitude, I've read that a stock 335 may use boost up to 11 psi (can't validate this claim). In that case is it worthwhile to buy any of these aftermarket options that in essence turn up the boost? Are there significantly less improvements in horsepower with these products at altitude than at sea level as compared to stock? Thanks!


oh, btw, since u know about the bad things about being at altitude, think of this:

at sea level, a stock 335 will keep up or is = to laast years M3.
at your altitude, last years m3 will probably lose about 20% power. u will lose alot less.

i am sure u can walk last years m3 at your altitude no problem. do the mods i suggest and it really should be NO CONTEST at all :rofl:


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