S2000 vs. WRX (also an IROC-Z) @ 5280ft
02-02-2002, 03:50 PM
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S2000 vs. WRX (also an IROC-Z) @ 5280ft
OK, so me and my friend decided to see who was faster. He's got a STOCK WRX, and I've got a STOCK S2K. First off, driving around town getting to the highway. Neither of us could really pull on the other if we were in the same gear (and I was 6K+). No difference.
From a stop, though, it's no contest. WRX is sooo easy to launch I would immediately lose 1 car length even if he had a bad launch. On a side note, it's hard to get the rears to break free at this altitude. You pretty much have to launch at 8K.
Now on the highway. Same thing! I couldn't really gain on him and he couldn't gain on me. We raced multiple times above 60MPH in 3rd and 4th gear (cars are geared about the same), and a little in 5th and really there was no difference. Only thing I noticed was I was slightly gaining a little in 3rd from 80-90. But this goes by pretty fast and I have to shift into 4th.
After a few miles an old IROC-Z comes up from behind and I think he wants to race. We start at about 100MPH (4th now), and we both take off. Neck and neck for a few seconds and then I slowly start to pull, but I don't know if he was letting off the gas at 130+ as we were going too fast at that point to be safe.
WRX: I would say it was a dead heat at all speeds except from a stop. It would take too many tries for both of us to get a perfect launch at the same time, so I have no conclusion, except I would destroy the clutch trying.
Side note: S2K speedo is +4mph over the WRX @ 80mph (s2k:85, wrx:81).
I'm actually not too proud of myself for driving so fast on the highway
From a stop, though, it's no contest. WRX is sooo easy to launch I would immediately lose 1 car length even if he had a bad launch. On a side note, it's hard to get the rears to break free at this altitude. You pretty much have to launch at 8K.
Now on the highway. Same thing! I couldn't really gain on him and he couldn't gain on me. We raced multiple times above 60MPH in 3rd and 4th gear (cars are geared about the same), and a little in 5th and really there was no difference. Only thing I noticed was I was slightly gaining a little in 3rd from 80-90. But this goes by pretty fast and I have to shift into 4th.
After a few miles an old IROC-Z comes up from behind and I think he wants to race. We start at about 100MPH (4th now), and we both take off. Neck and neck for a few seconds and then I slowly start to pull, but I don't know if he was letting off the gas at 130+ as we were going too fast at that point to be safe.
WRX: I would say it was a dead heat at all speeds except from a stop. It would take too many tries for both of us to get a perfect launch at the same time, so I have no conclusion, except I would destroy the clutch trying.
Side note: S2K speedo is +4mph over the WRX @ 80mph (s2k:85, wrx:81).
I'm actually not too proud of myself for driving so fast on the highway
02-02-2002, 04:45 PM
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That won't be the case at low altitudes. Turbo cars do not get affected by hi altitude as they create their own boost and do not rely on atmosphere as much to do so....
You would have pulled away, especially on the highway closer to sea level...
You would have pulled away, especially on the highway closer to sea level...
02-02-2002, 04:51 PM
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Just a heads up for guys up here. Word has it there is a silver S2000 up here in Fort Collins and the driver just so happens to be a representative of the law. You know, a kojak with a kodak, and apprently it is not beyond him to try and entice a street race with someone and you can figure out the outcome. I have wondered how airtight that charge would be with him being off duty(I am assuming this) out enticing street races. Any good lawyers here? Just a heads up.
02-02-2002, 04:54 PM
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That's just a rumor. Hey carace, do you wanna race? I was thinking of a nice 120+ run on north I25. My friend in a white caprice will tail and video the race so I can post in on the club here.
02-02-2002, 05:45 PM
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Turbo cars do not get affected by hi altitude as they create their own boost and do not rely on atmosphere as much to do so....
02-02-2002, 06:20 PM
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Well my car has got some problems right now but I would not mind a ride in your car(you are that cop right!!!!). Milo already handed me a double scoop of whoop ass so I probably would not do so good. I did not get a chance to ask Milo for a ride so maybe you would at some point. I do know of a Golf that would give you a heck of a run. Not a ton of power but the stupid thing probably only weighs 2200 lbs.
02-02-2002, 08:21 PM
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Turbo's are affected, but only about 1/2 as much as NA cars. I think you can look at it this way: partial pressure of O2 in the air is proportional to pressure of the air as a whole. So if you compare the atmospheric pressure of 2 locations, where one is 14psi and one is 13psi, for a NA car you are losing 1/14 of your total oxygen.
For the turbo car, that runs at 14psi, at the lower altitude you are pushing 28psi (14 atmospheric and 14 from turbo) total pressure and at the higher altitude only 27 (14+13). The turbo still puts out 14 since it measures the difference between input and output. So you only lose 1/28 of the oxygen.
Not sure if oxy amounts directly translates into HP, but that's how I see it.
(In reality, at sea level pressure is 14.7, and at 5000ft it's 12.2, which is nearly a 17% loss. The WRX boosts 14 I think, which gives it a 9% loss)
Carace, sorry I didn't respond to your e-mail couple of weeks ago, but I was realy busy at work (and that's where the e-mail goes) and your mail just got lost amongst the other dozens that I got that day. I'd meet up with you one of these days. I'm definitely not that cop! Just messin' around
Links:
Pressure vs Altitude Table
Pressure Unit Converter
For the turbo car, that runs at 14psi, at the lower altitude you are pushing 28psi (14 atmospheric and 14 from turbo) total pressure and at the higher altitude only 27 (14+13). The turbo still puts out 14 since it measures the difference between input and output. So you only lose 1/28 of the oxygen.
Not sure if oxy amounts directly translates into HP, but that's how I see it.
(In reality, at sea level pressure is 14.7, and at 5000ft it's 12.2, which is nearly a 17% loss. The WRX boosts 14 I think, which gives it a 9% loss)
Carace, sorry I didn't respond to your e-mail couple of weeks ago, but I was realy busy at work (and that's where the e-mail goes) and your mail just got lost amongst the other dozens that I got that day. I'd meet up with you one of these days. I'm definitely not that cop! Just messin' around
Links:
Pressure vs Altitude Table
Pressure Unit Converter
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02-02-2002, 08:59 PM
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Power loss at high altitudes depends on many factors on a turbo car (I'm at 3700ft).
First off, is wastegate/boost controller design. Some cars reference "1 bar" to the current atmospheric pressure. So at sea level, it would be 14.7psi. For me, it would be 13psi. When the boost controller is set to 1 bar of boost, at sea level it would provide 14.7psi of boost, or 29.4psi manifold pressure, before signalling the wastegate to open up. At 3700ft, the boost controller would signal the wastegate to open at 13psi, or 26psi manifold pressure. The Apex-i AVC-R boost controller works this way (I have one). In this scenario, the turbo car @ 1 bar would only be generating 88.4% of pressure at 3700ft vs sea level, so the loss would be the same, or very close, as an NA car.
Scenario #2, let's assume our boost controller measures pressure based on a fixed calibration, or we're using a wastegate spring to regulate pressure (which would open up at the same pressure/force at any altitude). The turbo (my stock K26) works great until about 4500rpm, when it won't make any more boost after that point. The turbo won't spin any faster, even with the wastegate completely closed. At 6000rpm, the compression rate of the turbo is fixed. At sea level, 6000rpm, the car would make 10psi, manifold pressure of 24.7psi. At 3700ft, the car would generate a manifold pressure of 21.8psi, so 8.8psi boost (referenced from 13psi as atmospheric pressure). At 4000rpm, however, the turbo is making more than the 14.7psi boost rate, so it can compensate by pushing out manifold pressure of 29.4psi, at 3700ft, or sea level. So we have a gradual drop in power from 4500rpm to 6000rpm at sea level vs 3700ft. We also have a small drop in power before the turbo makes full boost, which you would notice as more turbo lag at the higher altitude.
Scenario #3, let's assume we have the boost controller from scenario #2, and a massive turbo that'll make big boost at high rpm's. In this scenario, there will be no power loss at 3700ft (the turbo can make more than enough boost to compensate for lower atmospheric pressure), but there is more lag, as it takes more time for the turbo to spool up to compensate for the lost pressure. This is what Sev described in his post.
This is all from personal experience on my turbo car, just thought it might be useful for this thread =). I have no clue how the WRX turbo / boost controller is configured. Please correct me if I might have made mistakes in my calculations.
First off, is wastegate/boost controller design. Some cars reference "1 bar" to the current atmospheric pressure. So at sea level, it would be 14.7psi. For me, it would be 13psi. When the boost controller is set to 1 bar of boost, at sea level it would provide 14.7psi of boost, or 29.4psi manifold pressure, before signalling the wastegate to open up. At 3700ft, the boost controller would signal the wastegate to open at 13psi, or 26psi manifold pressure. The Apex-i AVC-R boost controller works this way (I have one). In this scenario, the turbo car @ 1 bar would only be generating 88.4% of pressure at 3700ft vs sea level, so the loss would be the same, or very close, as an NA car.
Scenario #2, let's assume our boost controller measures pressure based on a fixed calibration, or we're using a wastegate spring to regulate pressure (which would open up at the same pressure/force at any altitude). The turbo (my stock K26) works great until about 4500rpm, when it won't make any more boost after that point. The turbo won't spin any faster, even with the wastegate completely closed. At 6000rpm, the compression rate of the turbo is fixed. At sea level, 6000rpm, the car would make 10psi, manifold pressure of 24.7psi. At 3700ft, the car would generate a manifold pressure of 21.8psi, so 8.8psi boost (referenced from 13psi as atmospheric pressure). At 4000rpm, however, the turbo is making more than the 14.7psi boost rate, so it can compensate by pushing out manifold pressure of 29.4psi, at 3700ft, or sea level. So we have a gradual drop in power from 4500rpm to 6000rpm at sea level vs 3700ft. We also have a small drop in power before the turbo makes full boost, which you would notice as more turbo lag at the higher altitude.
Scenario #3, let's assume we have the boost controller from scenario #2, and a massive turbo that'll make big boost at high rpm's. In this scenario, there will be no power loss at 3700ft (the turbo can make more than enough boost to compensate for lower atmospheric pressure), but there is more lag, as it takes more time for the turbo to spool up to compensate for the lost pressure. This is what Sev described in his post.
This is all from personal experience on my turbo car, just thought it might be useful for this thread =). I have no clue how the WRX turbo / boost controller is configured. Please correct me if I might have made mistakes in my calculations.
02-02-2002, 09:06 PM
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Rage,
I thought a turbo wastegate measured the difference between input (atmosphereic) pressure and output (intake manifold) pressure and opened up when it got to a certain point (let's say 14psi). Why would a turbo provide less additional pressure at higher altitutes? Unless, of course, you get to the point where the are is SO thin that the turbo simply can't spin fast enough to make it's specified boos level.
I'll go ask on the WRX board (see my sig?)
I thought a turbo wastegate measured the difference between input (atmosphereic) pressure and output (intake manifold) pressure and opened up when it got to a certain point (let's say 14psi). Why would a turbo provide less additional pressure at higher altitutes? Unless, of course, you get to the point where the are is SO thin that the turbo simply can't spin fast enough to make it's specified boos level.
I'll go ask on the WRX board (see my sig?)
02-02-2002, 09:41 PM
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Like I said, it depends on the boost controller, mechanical or electrical. Electronic boost controllers can compensate. On my AVC-R, I set boost to ridiculous levels. I have it set to 1.6 kg/cm2 (close to 1.6 bar) of boost. At sea level, that would be about 24psi boost. On my MAP sensor, I see 34psi (or approx 19psi at sea level) up here in the thin air.