vahdyx

iTrader: (7)

I keep hearing that FI cars are barely effected by altitude and I just wanna say I disagree with that full heartedly.

I understand NA cars are effected worse, but here in Colorado my experience is not that.

I see countless stock Evos and STIs running 14s and in the 15s when rated 13s at sea level.

We have less air to begin with and FI is moving more less air in a car, but not enough to be considered barely effected by altitude.

Here's some videos and you guys can let me know how you feel about them.

Bandimere Speedway, Morrison, CO. - YouTube

2011 Subaru WRX STI sedan at Bandimere - YouTube

There's a lot of personal experiences where I see fast FI cars do well below their supposed times up here.

Can someone explain why this may not be true.

From what I understand (because of my job) our Torr is 600ish and at sea level it's 760 Torr. That's 14.7psi at sea level and 11.6 up here. When I think about it, it doesn't seem like it a big difference, but can you imagine what your car would be like if it's pushing 11psi instead of 14. 15 instead of 19 etc.

Now I'm just assuming this pressure difference and how it's feeling.

That's where my question comes in. Is FI effected significantly or is it coincidence that I'm seeing 15second STIs a lot up here at bandimere.

I know our calc DA is around 8600ft above sea level at times (thank Drewbroo) so at times like that we're even lower Torr than that.

Anyway educate me someone!

I watch a stock Porsche 911 GT2 run high 13s, that's not right ...

Sonicyeller

You also have to remember that alot of the people racing at the track are not "professionals". So that may account for the lameness of some of the times.

jarhead

Let em keep flappin there gums Vahdyx until they have ran at a high altitude they no not what they say lol. But yes N/A cars are more affected yes but no oxygen is no oxygen no matter what. The DA calculators do not have a calculatiom for only boosted only highly modified and boosted which a ss/tc bolted and tuned is not.

Here are some times at 4,500 ft it is a poorly prepped track though also does not help.
SS/SC stage 2 mid 14,s to mid 15's
MS3 stock 15.3
SS/TC Stock 14.2 the driver is good 14.2 and was no lift shifting.
Camaro ss m6 14.5 stock
Camaro ss m6 and bolted and hpt tuned 14.2 405 hp to the wheels
Camaro SS bolted, tuned, supercharged with drag radials and Pfadt drag racing suspension on his best run 12.2
Camaro ss auto stock Friday night 14.7 was his best run.
Most highly tuned bolted turbo swaped Evos and STI's run Low 14,s high 13,s some can run a high 12 very very few run a 11 with awd here.

LE5_AJ

You're depressing me.

chris88z24

Well, that person is wrong.

Mark Aubele

I think posting ETs is worthless. Post trap speeds. Looking over the results, the stock SS/TC runs about the same as a stock one at sea level. The 405 at the tires Camaro driver needs a new hobby. Trap speed would tell us something, ETs really don't.

Watched the STi video, the slow shifting isn't getting you too much better than low 14s from that car no matter what altitude. Those cars only run high mid 13s at sea level driven well.

defo98

iTrader: (1)

the trap speeds for all those cars were on the boards in the video...

Mark Aubele

I watched the video, didn't see many of the traps for cars listed, regardless, I blame a ton of it on driving. I can't imagine what you have to do to make a ZR-1 trap at 112. Cars trap at near 130 bone stock at sea level. Of course cars are slower at altitude, but FI is affected far less than NA cars.

defo98

iTrader: (1)

yeah definately the zr1 that driver had to suck big time... and idk the strip looks down hill too

JBThrasher22

Autocare physics, hard to beat science. Just saying

Physics answers

FasterIsBetter

Yea, thinner air means less fuel your car can be fed due to less air at your altitude being consumed and therefore less power that can be created on any internal combustion car. It's simple pyrology.

SSlobalt

We don't haz Fizikz!!! We haz Cobaltz!!!11!!

BYT*SS*TURBO

iTrader: (6)

They most certainly are effected, if not more IMO.

Martel18SS

The reason SS/TCs run around the same at altitude as they do at sea level is because they're always making the same power, but pushing more boost. Stock and GMS1 will boost to whatever PSI is needed to make the rated 260/260 and 280/320. That's why FI cars are better at altitude because they can safely(safer anyways) push more boost than at sea level but make the same numbers. If your turbo can push the higher psi, it's not as dangerous as at sea level because you're making less power than at sea level.

BYT*SS*TURBO

iTrader: (6)

Compressing air makes heat, further compressing makes more heat.. heat is the enemy. Def not more safe IMO.

JBThrasher22

Wow please read the link I provided , I really didn't want to explain it why I posted it. It effects N/A cars more over F/I cars because of the DENSITY of the air. As you raise the altitude the density of the air consumed is thinned. Yet a F/I application actually compresses the car which causes the air to retain its density. Thus this allows for a more equivalent air intake as closer to sea level.

Like I said this is one of the basic things you learn in auto-care physics.

*Edit* and Nick is absolutely right, the biggest problems with F/I cars at altitude is heat that is caused due to the compensation for the less dense air. A turbo will work harder in higher elevation.

JBThrasher22

This is wrong sorry

Matt M

The reason some people say that elevation does not affect FI cars is because you can usually add boost to compensate for the air that is less dense to begin with. Basically, if your limitation is the knock threshold which you encounter at 15psi boost at sea level, and you have a turbo that will still be very efficient at 20psi, then this theory would be true. You could simply turn up the boost a few psi until you reach the same power level and knock. The efficiency of the turbo could possibly improve, but worst case, you would only be down a few HP vs. the sea level configuration. I would expect slightly slower spool since the exhaust energy available to spool the turbo will certainly be lower.

Having said that, the stock LNF turbo is by no means capable of being turned up enough to make up for a 5000' increase in elevation. Many of us are using everything that the turbo can dish out. Therefore, moving to a higher elevation will reduce the available airflow to and from the turbo, just the same as it would affect a naturally aspirated motor.

Matt M

As far as the videos go, you can never use an example of one slow car to prove why something may or may not make all cars slow. I have watched Vipers run 13s and 14s down here at 700'. There are approximitely 9.26 million variables that can make a car run slow.

vahdyx

iTrader: (7)

Around that many huh lol.

JBThrasher22

You will have a slower spool rate ( figuratively ) at higher elevation for the fact that wastegate actuation is not achieved at the rotation threshold as at sea level which most are configured for. Hence at sea level say 75k rpm is 125kish ( example ) to achieve the desired boost threshold. Once boost is achieved you then have a very significantly decreased percentage of actually HP loss.

This is the reason for the addition of forced induction on air plane engines which I deal with in the Air Force.

Mark Aubele

Which planes are you speaking of?

Knightwolf

Wow a ZR-1 in the 13's@112? EPIC FAIL.. even at that elevation, that's just pathetic.. and I could hear him bouncing off the rev limiter for a good second at the end of 2nd gear lol.. maybe he should buy a Honda Civic!

And not that it matters, but his RT was like 25 minutes rofl

vahdyx

iTrader: (7)

Yeah lol, You can hear the camera man say, rookie or something like that

But since it's test and tune, RT doesn't matter so in his defense, he got situated before launching.

FrossB

iTrader: (6)

Ill see what i can do this friday at Bandimere!!! but this is kinda getting my hopes down lol