Guys, I live in Salt Lake City, UT. My car hasn't seen altitude below 4500ft ASL in a few years and my stock MAP sensor is reading lower than normal boost levels as a result. This is fine and expected. The car runs great up here.

Current Setup:
Stock HG F20C
Comptech SC/AC (Novi 1000)
3.6" SOS pulley
AEM EMS
750cc RC Injectors
Header back exhaust & TP - 70mm(could also contribute to my lower boost readings)
No belt slip, I am positive.

My question:
I am considering purchasing SOS's 3.0 inch (good for 12psi on the 2.0L) pulley for the Comptech Supercharger. I want to know if I'll be needing to upgrade my MAP sensor. Right now, I am running the SOS 3.6 inch pulley and I am seeing about 7 psi of peak boost according to my AEM.

I believe the stock MAP sensor is good until 11 psi. I was wondering if anyone with a similar setup is boosting at altitude and if they found at MAP sensor upgrade to be necessary.

Here's my math, can an engineer please verify:

At 5000 ft ASL, air is 85% as dense as it would be as sea level (-3.0% for every 1000ft). So, in theory, my 3.6" pulley which, according to SOS, should see about 9psi at sea level, should see .85 * 9.0 = 7.65psi of boost at peak. The 3.0 inch pulley is said to make 12 psi on the 2.0L at peak and should see .85 * 12 = 10.2 psi of absolute pressure.

Correct me if I'm wrong, but does this mean I don't need to upgrade my map sensor?

Last question, I seem to remember other guys seeing more than these advertised boost levels with a 3.0 inch pulley on the Comptech supercharger (Novi 1000). I always thought a 3.0 inch pulley would yield more like 14 psi at 9000 rpm with this supercharger. If this were the case then I would see 11.9 psi absolute pressure and would need to upgrade the stock MAP...even with the better flowing exhaust.

Here's the link to SOS:
http://www.scienceofspeed.com/produc...00_SC_pulleys/

Thanks for any help!

Jorge

PS - I know I could just be safe and upgrade the stock MAP...it's only $135 for the SOS. But, I want people to understand the effects of altitude on boost levels...plus I'd hate to have to retune my car...I don't have a dyno readily available and street tuning is dangerous!

PPSS - Does anyone know of a dyno in the area I can rent for a bit?

 

im running the 3.2 on my ap1 with the stock map sensor.the max boost the stock sensor will read is 10.6

 

S2, when you say the max boost the stock MAP will read is 10.6, what happens at that point? Are you tuned for the additional boost? What is your altitude?

Thanks!

J

 

I think my initial post has bored everyone on the FI forums. Was it a stupid post or just too long or what?

 

i read it because i am at 5000 ft too but i dont know a dang thing about any of what you asked

 

I make 10-10.5psi with my 3.6 sos pulley, thats more consistent at sea level for a stock to moderate size exhuast. 3.2" pulley is rated at 12-13 at sea level, so your going to be in trouble with the 3", some see as much as 18psi with this one. (3.4" 11psi) is likely as far as your going to get with your stock map sensor at sea level.

Your post is long winded

 

with the emanage you can tune boost/rpm.so near a bit after 8k im making 10.6 so i just added more fuel from 8500-9000 and retarded the timing extra at that point too.im at sea level btw

 

In comparison, aftermarket map sensors (like the GM 3 bar) are cheap. Just get one and have one less thing to worry about.

 

Yeah, you're right...I'll just pickup an aftermarket MAP sensor. I guess I was just hoping we could get some data on boost differentials at altitude. I haven't seen a lot of this information posted before.

 

And sorry if my original post was long-winded...