altitude vs horsepower for NA
 

Ok ive been ponering this all day and just cant decide whats up, last night me and my buddy jason raced this mustang v8 and wooped his ass three times in a row, it was on this road out in the middle of nowhere and it was a litttle longer than a 1/4 mile. J has a 89 crx dx with a d16a6 and a t25 pushing stock boost, its only streettuned on a wideband. The mustang had na mods i\h\e and dude was braggin bout a chip(i think that was bull) anyway when you do the math he should have atleast 300hp and the rex has may be 200whp how the ---- did he get wooped that bad? so im trying to figure out if dude was a really bad driver or if altitued (5000ft here) really fucks up NA cars,, does anybody know how much altitude affects hp, for exaple if a car makes 300hp at sea level how much power will said car have at 5000 ft

Re: altitude vs horsepower for NA
 

You're a ricer

Re: altitude vs horsepower for NA
 

my s10 gets 650 more hp at higher altitude.

Re: altitude vs horsepower for NA
 

so much to consider.
weight/ gearing/ and most importantly power band.

Re: altitude vs horsepower for NA
 

donald ftw ;)

Re: altitude vs horsepower for NA
 

yeah but when you add it all up, the mustang should have still won,, they raced three times and the rustang had my boy off the line but only till second gear, as far as i can tell either dude sucked at driving or the NA car with almost a hundred more HP lost a lot of power from sea level... I dont know ---- i wish i made a vid

Re: altitude vs horsepower for NA
 

1000lbs of weight makes up for 100whp. roughly 10lbs kills 1hp when you add weight of like a passenger, kinda like 100lbs is supposed to equal .1 seconds in quarter mile

Re: altitude vs horsepower for NA
 

No, that's not true.

OMG, MY RACING SEAT GAVE ME LIKE 12 HOWRSEPOWER~!!!!!!

It's called power to weight ratio, as well as powerband. Was it a modular engine? I'd be suprised if it made 300 horse without cams.

Re: altitude vs horsepower for NA
 

yea, i dont know anything about the weight/hp ----. i went for a ride in my buddies recently turbo'd ef hatch w/ another buddy in the car.. told him how i was unimpressed and they were both like "well IM killing 15hp, and your fatass is killing 20!"

his cars pretty slow for a boosted B16 EF @ 7psi :1 i've asked him to race me, since he only pulled 13.9/14 flat at the track both on street tires (HX rims + falken azenis) AND slicks. it was fucked up at High School Drags, his dial was 13.7, and on his 3rd run of dial in racing, the tower couldn't read his side dial for some reason, so while he was staging some guy came up to "fix it".... changed it to 18.7 cuz you know, it's just another honda :l

Re: altitude vs horsepower for NA
 

you both have the same atmospheric presure disadvantage. Even though you're compressing the air, its thinner air to begin with

Re: altitude vs horsepower for NA
 

Yeah I went from living in Nebraska to Wyoming and everyone says their cars suck balls here. The only difference I felt in my car was off the launch but after boost I felt no difference till I blew my headgasket. now it doesn't go at all. :-[

Re: altitude vs horsepower for NA
 

ok first of all 10lbs off your car does not equal 1hp, but heres what im thinking as altitude increases hp decreses for NA and FI cars but the rate at which it decreases is much lower in FI applications as there is a compressor feeding in more air, now does anybody have any dynos done at higher altiude of stock cars to compare to the sealevel hp's i know this is kind of dumb but i just want to find out for fun

Re: altitude vs horsepower for NA
 

the dynos around here have told me they use the same formula for both n/a and boosted cars. here is a link to find out the uncorrected horsepower http://wahiduddin.net/calc/calc_hp_dp.htm but right now you are comparing corrected numbers to corrected numbers so change them wont make much sense to change one to uncorrected

Re: altitude vs horsepower for NA
 

Now. Turbocharged cars have a much smaller penalty than N/A or supercharged cars at higher altitude.
Reason is that a turbocharger is atmosphere referenced so a turbo running 1 bar boost at sea level runs roughly 2 bar absolute pressure.
At 0.8 bar absolute atmospheric pressure the turbo car will be at 1.8 bar, still 1 bar above atmospheric but with a bigger pressure ratio. Still only a 10% drop in pressure vs the 20% drop in the atmospheric pressure. And if the turbo car has a closed loop boost controller that's referenced to absolute pressure you can have 2 bar absolute regardless of being at sea level or being in the mountains, within reason. The turbo will have to work harder at higher altitudes (bigger pressure ratio) though so you don't want to go outside it's design limits. A compressor working at a higher pressure ratio means a higher pressure across the turbine too so you do lose some power but it's minimal compared to N/A engines.
It's common to have aircraft engines that are "turbo-normalised", meaning the manifold pressure is kept at 1 bar absolute regardless of altitude. At 0.33 bar atmospheric pressure the turbo will have to work at a pressure ratio of 3.0 to maintain 1 bar absolute in the manifold.
N/A engines really are useless at anything above sea level.

Re: altitude vs horsepower for NA
 

dude even if your at higher altitude blah, blah, blah the crx with its full interior ways about what like a little under or over 1800lbs or something like that and the mustang weights like 3500lbs(depending on which model or engine in it) or over. so the power to weight ratio for the crx is 200hp/1800lbs=1hp/lbs, the mustang has 300/3500lbs=.08hp/lbs, the higher the number is for power to weight ratio the easier its goin to be for your car to get movin. nuff said.