05-08-2013, 11:44 AM
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#11 (permalink)
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Master EcoModder
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I would think that some bubble wrap and shove them in a manila envelope would be good.
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05-08-2013, 03:48 PM
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#12 (permalink)
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Master EcoWalker
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Saw the presentation...
but what about the Lupo having a top speed of 266 km/h? Even with near perfect streamline, that would require about 150 hp / 115 kW or so?
The power needed to reach a certain speed is a 3rd power function of that speed. Doubling the speed requires 8 times as much power.
I mean, the original 3L has a top speed of 165 km/h. It would need over 4 times as much power to reach 266 km/h, and different gearing, tires, etc.
The Lupo GTI is more than twice as powerful as the 3L and still barely touches 200 km/h...
If you can achieve the same speed from the 3L with all the aero work, that would be an accomplishment.
Claiming it can do 266 km/h may raise doubt about the truthfulness of the whole project and distracts from the goal you are trying to achieve.
I would not post that speed even if it were true and proven, just for that.
(see the Wikipedia article on the VW Lupo)
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05-08-2013, 05:04 PM
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#13 (permalink)
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Mechanical engineer
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Would you post 0-62 time? It should be under 7s if there is enough grip.
Targets of lupo 2L project:
- primary goal to prove it can reach 2l/100km @ 100 km/h speed
- secondary goal to prove you dont need 200-400 hp to have fast car. You need light and low drag vehicle
- Prove you can have fast and efficient car in same package.
Top speed estimation is based on drag equation calculations. CdA value 0,375 is roughly 35% lower than stock lupo 3L, even more compared to GTI model. So GTI can do 202 km/h with 125 hp I can do roughly 35% higher top speed with "same" power as I have lower friction factors on bearings and such.
Note that top speed is also something that will be tested at Germany after that fuel consumption targets reached. You might not like to drive fast but most people do.
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05-08-2013, 06:27 PM
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#14 (permalink)
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Master EcoWalker
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Quote:
Originally Posted by Vekke
Would you post 0-62 time? It should be under 7s if there is enough grip.
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Err... how does that relate to this discussion?
Quote:
Originally Posted by Vekke
...Top speed estimation is based on drag equation calculations. CdA value 0,375 is roughly 35% lower than stock lupo 3L, even more compared to GTI model. So GTI can do 202 km/h with 125 hp I can do roughly 35% higher top speed with "same" power as I have lower friction factors on bearings and such.
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Ahgh NO as I said before speed and the power needed to achieve it do not relate linearly, but to the 3rd power. 35% less drag will have the same effect as (100/65 - 1 =) 54% more power, but that will give you just a (1.54^(1/3) - 1 =) 15% higher speed.
As the L3's gearing is long it might be even slightly more than that, but even so you should be happy with anything close to 190 km/h.
If you want to reach 266 km/h you will have to reduce the drag to 24% of the original L3, not 65%.
Quote:
Originally Posted by Vekke
Note that top speed is also something that will be tested at Germany after that fuel consumption targets reached. You might not like to drive fast but most people do.
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Glad you do. Looking forward to that, as you know I'm very interested in the project.
Don't want to put you down... but 266 km/h cannot be achieved this way, because the relation between speed and power is not what you thought it was.
I like to drive fast, but the fuel consumption rises in tandem with the power needed so I seldom do high speeds anymore.
I will do so though next July as I will then take the Insight to Germany's Autobahns. The 90 hp and .28 Cw should allow it to reach 185 km/h. I'd love to find that out.
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05-09-2013, 09:12 AM
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#15 (permalink)
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0-62 relates only in that way if you think its appropriate use that to tell car is fast rather than top speed. I think the top speed gives better impression about what kind of car the lupo actually is.
Drag equation - Wikipedia, the free encyclopedia
So Fd=0.5xair thicknessxVxVxCdxA
I used 25 celsius thickness
Stock lupo GTI at 205 km/h= 0.5x1,184x56,9x56,9x0,34x2,00=1303
Lupo 2L at 266 km/h=0,5x1,184x72,2x72,2x0,375 (lupo 2L CdxA)=1157
GTI has 5 hp more but that will go to conquer higher frictions of the GTI than my lupo 2l.
Lupo 2L drag force @266 km/h should be lower than GTIs @ 205 km/h so what formula do you think I should use to get better results?
I get same power estimations with ecomodder fuel consumption calculator so I believe my calculations are correct.
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05-09-2013, 03:44 PM
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#16 (permalink)
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Master EcoWalker
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You cannot use the drag equation to calculate how much power you'd need, as it produces the force needed, not the power. It wouldn't matter much if the speed in the comparison was the same, but it isn't. Multiply the result with the speed difference and you will find the 3L needs 28% more horsepower than the GTI has to reach 266 km/h.
So your extra aeromodded 3L needs about 157 hp to reach 266 km/h.
The 3L produces just 60 hp.
Unless you did a hefty engine swap you won't break the 200 km/h barrier.
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05-09-2013, 04:43 PM
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#17 (permalink)
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EcoModding Lurker
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Quote:
Originally Posted by RedDevil
The 3L produces just 60 hp. Unless you did a hefty engine swap you won't break the 200 km/h barrier.
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I think 3L's power output is irrelevant to your discussion. Both the GTI and the 2L produce ~120hp.
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05-09-2013, 06:23 PM
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#18 (permalink)
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Master EcoWalker
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That is a hefty engine swap then, doubling the original power.
Anyway, lookup the data on cars that can achieve 266 km/h, you will only find cars that have more than 250 hp. To make a road legal car that only needs 157 hp to do that is a fantastic achievement.
120 hp won't bring it beyond say 245 km/ h though. A very good result nonetheless.
What worries me is that this car was not designed to handle this speed, so it may be quite dangerous to try to do them without proper suspension firming and the like. When you test a cars ability outside its designed operating window, take small steps at a time and evaluate them thorougly.
The kammback design generates some lift. At normal speeds this plays no big role, but at very high speeds it may contribute to instability and bad controllability. It may need a spoiler... and some extra hp.
I am worried for your safety right now.
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Last edited by RedDevil; 05-09-2013 at 06:40 PM..
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05-09-2013, 08:29 PM
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#19 (permalink)
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Master EcoModder
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I do not see any problem with him getting to 152.2mph I have had three different cars 2 GM 3800 to 112 Limiter and a ford 500 to 115. That was not hard the 3800 Grandprix would get to 86mph in 1/4 mi (~10hp over stock)and still have two gears to go.
Over all what will limit him is gearing and keeping it in a good TQ RPM. Yes power will be limiting but what can go faster (not quicker) 100hp w/ 180tq or 180hp w/ 100tq?
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05-10-2013, 05:03 AM
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#20 (permalink)
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Master EcoWalker
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266 km/h in a very small car is quite something different from 180 km/h (112 mph) in a big car. Incomparable, in fact.
I have driven several cars over Germany's Autobahns at speeds close to their max. I can tell you that a smal car like the '85 Honda Civic Mark 3 becomes hard to control at 180 km/h while it works perfectly well at 175. The Lupo is smaller than the Civic was.
A Mazda 3 series was fine up to 205 but not beyond.
An Impreza Turbo WRX can do 245 and still feel stable, but it has a lot of fairings and a big wing all designed to create downforce.
Even German car companies get it wrong sometimes, like Audi did with the first gen TT; a small but powerful car that became lethally unstable at top speed.
Of cars rhat have crashed at those speeds it can be quite hard to determine the make and model and retrieve more than 90% of the driver.
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2011 Honda Insight + HID, LEDs, tiny PV panel, extra brake pad return springs, neutral wheel alignment, 44/42 PSI (air), PHEV light (inop), tightened wheel nut.
lifetime FE over 0.2 Gmeter or 0.13 Mmile.
For confirmation go to people just like you.
For education go to people unlike yourself.
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