high altitudes and boosting

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turbo970
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high altitudes and boosting

Post by turbo970 »

at being 7000 feet above sea level can i get away with a lil extra boost seeing the air is thinner? just something i been thinking about. i do have a tmic just not installed an the weather has been fair cold out lately
dankberries
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Re: high altitudes and boosting

Post by dankberries »

The factory ECU will compensate for altitude. So it shouldn't make much difference. Stock ECU max boost level is arould 13.5.
Last edited by dankberries on Mon Nov 04, 2013 6:12 am, edited 1 time in total.
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turbo970
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Re: high altitudes and boosting

Post by turbo970 »

reason i ask is i googled boosting in high altitudes and some sites say ya could some say no. my mbc is set at 10 psi.
dankberries
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Re: high altitudes and boosting

Post by dankberries »

The factory ECU utilizes the MAP & MAF sensors to compensate for changing situations such as altitude and temp.
If you are running the stock turbo then turning the boost to 10lbs is not a problem .
Note that increasing boost will increase temps and having an intercooler becomes essential. Also increasing boost will decrease the life of the turbo.
93 impreza rally muffin
93 legacy ss Tarmac Terminator
89 Nissan 240sx sr20
90 Nissan 240sx 2jz
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turbo970
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Re: high altitudes and boosting

Post by turbo970 »

well if i can get some stuff sold i want to get a td04 so i can do my tmic. i ran my car at 11 psi for a day and it felt better than 10 psi. i really only get into boost while passing on the high way
Legacy777
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Re: high altitudes and boosting

Post by Legacy777 »

There is a little over 6 psia difference in air pressure between sea level and 7,000 ft.

http://www.avs.org/chapters/nccavs/pdf/ ... itudes.pdf

So technically, you should be able to bump up your boost easily another 5 psig. What I would suggest is putting the stock boost control setup back on and see what boost level it allows you to run. The stock boost at sea level is around 8.6 psig. I don't think you'll see the ECU allow you to boost another 6 psig, but you never know. Let us know what the stock ECU allows you to boost at, and that will allow us to better give you advice to what would be a safe boost level at that elevation.
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turbo970
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Re: high altitudes and boosting

Post by turbo970 »

well my gauge i have says its 10 psi and when it was set it 11 the needle stopped at the very edge of the 10 so if i figured it was at 11 lol. whats the difference between psi and psig and with the factory ebc the needle stops a lil before the 10 in my gauge
Legacy777
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Re: high altitudes and boosting

Post by Legacy777 »

Psi is actually an incomplete unit. There are two different pressure indications, psig & psia. Psig is Pounds per square inch gauge and psia is pounds per square inch absolute. Think of it this way. Gauge pressure is just measuring the indicated pressure. So if you blow up a balloon, lets say it has 1 psig associated with it. This gauge pressure does not account for the pressure that the atmospher exerts on everything around it. To measure this, you need to measure something in absolute terms. So if we take that same balloon example, absolute pressure = gauge pressure + atmospheric pressure. At sea level the absolute pressure in the balloon would be 1 psi + 14.696 psi = 15.696 psia.

So from your observations, it looks like the factory is maybe allowing the boost to be about 1 psig greater to acheive the same air flow at your elevation as it would acheive at sea level. You can probably go a little higher in boost, but you'd really want an AFR gauge to see what your AFR's are.

The other thing to keep in mind is that the fuel octane rating is different in Colorado at the higher elevations then what some folks can get at sea level. Typically 91 octane is the highest octane rating you can get in the higher elevations. They do this because the air fuel mix in the cylinder is a little leaner and less likely to pre-ignite compared to if it was at sea level. At sea level, 92-93 octane is typical (except in California, they only get 91....don't ask me why).

So I'm not sure if I answered your question or just blabbered on :) If not, let me know.
Josh

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turbo970
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Re: high altitudes and boosting

Post by turbo970 »

you did. so will u still need a tmic to bump it to 11?
Legacy777
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Re: high altitudes and boosting

Post by Legacy777 »

It would be a good idea to get one. Without knowing what the intake air temps are after the turbo, it'd be kind of hard to say for sure, but you might be able to sneak by without one for a little bit.
Josh

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1990 Legacy (AWD, 6MT, & EJ22T Swap)
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turbo970
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Re: high altitudes and boosting

Post by turbo970 »

well its been dipping into the 30's weather wise and i'm saving for td04 to go with my 07 tmic. and i notice my temp gauge runs lower when i'm at 11 psi. like stated before i'm not always using boost. mainly go into boost when passing on the hightway. so basically just short burst of boost
Legacy777
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Re: high altitudes and boosting

Post by Legacy777 »

Like I said...it's kind of hard to say for sure, but you'd probably be ok with the air temps being colder.
Josh

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turbo970
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Re: high altitudes and boosting

Post by turbo970 »

sweet. i'm hoping to have a td04 and my tmic installed by spring. and i also add a bottle of race fuel concentrate when i fill up
dankberries
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Re: high altitudes and boosting

Post by dankberries »

I ran 12lbs, no intercooler, vf11 all winter and it was fine. However in the summer time having the intercooler is a must at that boost.
I also ran a td04, top mount, 13lbs, for a few years no issue.
93 impreza rally muffin
93 legacy ss Tarmac Terminator
89 Nissan 240sx sr20
90 Nissan 240sx 2jz
killajamal wrote:Dank is actually German for "silly term which the kids have come up with to describe exceptionally choice marijuana.''
turbo970
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Re: high altitudes and boosting

Post by turbo970 »

so if the weather is cold 11 or 12 psi warmer turn it down and do inner cooler, sweet, i just need to get the funds for a td04
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