the Official "NA Tuning" thread
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Originally Posted by clawhammer,Jan 6 2007, 06:35 PM
It depends on whether the top speed is gearing limited, limited electronically or limited by horsepower.
I'll explain how each of the three things works:
Let's say you have a 600 hp turbo AP1 S2000. At the rev-limiter (9200 rpms) you can still only go 172 mph, even though let's say you could theoretically go 180 mph. But in order to 180 mph, you'd have to rev the engine out to 9700 rpms, which would damage your engine. Therefore you are limited by your redline
BMWs and Mercedes have electronic rev limiters. They are set at 155 mph even though the car has plenty of hp and plenty of rpms left. At that speed, the computer simply shuts off fuel.
If you are limited by horsepower, then increasing your horsepower would increase your top speed. Let's go back to our AP1 S2000 again. Most stock AP1 top out in the 150-155 mph range. As you may know, in order to go faster, the amount of horsepower needed to overcome the air resistance is increasing exponentially. So if you add more horsepower, your top speed increases.
I'll explain how each of the three things works:
Let's say you have a 600 hp turbo AP1 S2000. At the rev-limiter (9200 rpms) you can still only go 172 mph, even though let's say you could theoretically go 180 mph. But in order to 180 mph, you'd have to rev the engine out to 9700 rpms, which would damage your engine. Therefore you are limited by your redline
BMWs and Mercedes have electronic rev limiters. They are set at 155 mph even though the car has plenty of hp and plenty of rpms left. At that speed, the computer simply shuts off fuel.
If you are limited by horsepower, then increasing your horsepower would increase your top speed. Let's go back to our AP1 S2000 again. Most stock AP1 top out in the 150-155 mph range. As you may know, in order to go faster, the amount of horsepower needed to overcome the air resistance is increasing exponentially. So if you add more horsepower, your top speed increases.
So what you're telling me is the s2000 is gear limited? For instance, I know that at 4500 rpms in 6th gear, I'm at 74-75mph in my AP2. If I throw in a turbocharger or blower that will boost my horsepower to significant levels into the equation, my car will still be at that same speed at 4500 rpms and my top speed will still remain the same?
So the only way I can increase the top speed is if I swap out the stock 4.10 for a lower final drive (and thus at the cost of acceleration) ?
That's kinda disappointing to hear.
I mean if the s2k was 155mph drag-limited or limited by horsepower that would make much more sense.
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From: Lewisville, TX
Originally Posted by kenstyle,Jan 7 2007, 04:54 AM
Yes, I understand the fact that most german automobiles are electronically limited to 155 mph.
So what you're telling me is the s2000 is gear limited? For instance, I know that at 4500 rpms in 6th gear, I'm at 74-75mph in my AP2. If I throw in a turbocharger or blower that will boost my horsepower to significant levels into the equation, my car will still be at that same speed at 4500 rpms and my top speed will still remain the same?
So the only way I can increase the top speed is if I swap out the stock 4.10 for a lower final drive (and thus at the cost of acceleration) ?
That's kinda disappointing to hear.
I mean if the s2k was 155mph drag-limited or limited by horsepower that would make much more sense.
So what you're telling me is the s2000 is gear limited? For instance, I know that at 4500 rpms in 6th gear, I'm at 74-75mph in my AP2. If I throw in a turbocharger or blower that will boost my horsepower to significant levels into the equation, my car will still be at that same speed at 4500 rpms and my top speed will still remain the same?
So the only way I can increase the top speed is if I swap out the stock 4.10 for a lower final drive (and thus at the cost of acceleration) ?
That's kinda disappointing to hear.
I mean if the s2k was 155mph drag-limited or limited by horsepower that would make much more sense.
FWIW, I'm at 80 mph at 4950 rpm with 4.57's. And yes, the S2000 is aerodynamically challenged.
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For those who haven't seen this website, the website tells you what speeds you are limited to in each gear. You can also customize the various settings to account for your current configuration.
http://www.turnzero.com/technical_resource...gear_calculator
http://www.turnzero.com/technical_resource...gear_calculator
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Originally Posted by FF2Skip,Jan 7 2007, 06:29 AM
Yes, I, too, am disappointed. I mean, there are plenty of times I've thought to myself, "Gee, if only I could go faster than 147 mph."
FWIW, I'm at 80 mph at 4950 rpm with 4.57's. And yes, the S2000 is aerodynamically challenged.
FWIW, I'm at 80 mph at 4950 rpm with 4.57's. And yes, the S2000 is aerodynamically challenged.
And regarding your above statement, it's moreso about bragging rights than literally being able to reach that top speed. I'd be pretty disappointed if I threw on a huge turbo and dyno'd 450+ rwhp and still theoretically be limited to the stock top speed.
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From: Jacksonville, FL
The s2k is aerodynamically limited to about 150-155...this is dependent on several factors including slope of the road (downhill vs uphill) wind direction (tailwind vs headwind) and air density (temp & alt dependent).
The AP2 is gear limited at 155...so the gear limit and the aerodynamic limit are pretty close. (tire deformation not considered)
The AP1 is gear limited at 170...so it will hit the aerodynamic limit long before the gear limit. (tire deformation not considered)
The AP2 is gear limited at 155...so the gear limit and the aerodynamic limit are pretty close. (tire deformation not considered)
The AP1 is gear limited at 170...so it will hit the aerodynamic limit long before the gear limit. (tire deformation not considered)
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From: Los Angeles, CA
I've had my Ap2 at around 150mph a couple times and the highest I hit was 155 a while back. I had maybe another 100rpm before I was going to hit the rev limiter. Scared the shit out of me the first time I got up that high because the S feels no where near stable that fast. After a couple runs up there it felt normal....guess I got used to it.
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From: Los Angeles, CA
Originally Posted by 2QYK4U,Jan 7 2007, 09:49 AM
^ I'd like to add the following...
If a car is gear limited to 180 but aerodynamically limited to 150, adding more power will overcome the aerodynamic issue leaving you only with the gear limiting issue.
If a car is gear limited to 180 but aerodynamically limited to 150, adding more power will overcome the aerodynamic issue leaving you only with the gear limiting issue.
however it would be one scarey ass trip.
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Originally Posted by HvRRZ,Jan 7 2007, 08:51 AM
I've had my Ap2 at around 150mph a couple times and the highest I hit was 155 a while back. I had maybe another 100rpm before I was going to hit the rev limiter. Scared the shit out of me the first time I got up that high because the S feels no where near stable that fast. After a couple runs up there it felt normal....guess I got used to it.