Effects of lightweight at high speeds

[NSX_GTR_LM]

I just wanted to get a clarification, just an FYI, I know F = MA :), but at higher speeds, doesn't light weight lose its effectiveness in helping performance since the drag force begins to approach the weight of the car? Is the argument of my car will take your car out from 100-140 because its lighther is not as effective from 30-80? I know the celicas dont have a ton of downforce either, and therefore there effective weight is not increased very much, but I just wanted to confirm or refute this.

[GTS LAID]

well the force from air resistance increases exponentially with the velocity of the car... the increased air resistance causes instability if both the over and undersides of the car arent designed to wisk the air away efficiently... what happens is that you can start getting eddy currents forming on the underside of the car.. which would push UP on the underbody of the car instead of just going front to back... if this occurs in the front portion of the car... get ready for takeoff... they have plates out for the celica that go underneath the car and help in high speed aerodynamics...


btw typical eddy currents dont form in a car as low as the celica until you reach speeds of 120+ ... hitting a bump would exacerbate the situation because it would increase the effective ground clearance of the car at that moment... so be careful...

[Chui]

Lightweight is ALWAYS a benefit in a performance car. I recall that for every 387 lbs. of weight shed it's as if the care requires one road hp less to push it/pull it across the road at 50 mph. Significant.

I don't think the speeds seen in our economy car platforms is anywhere near high enough to cause enough lift to get us into trouble in a straight line. I think what GTSLAID is trying to say is that the idea is to keep the airflow laminar across the surfaces of the vehicle.

[NSX_GTR_LM]

thanx chui. Is it as drastic of a benefit when you hit higher speeds? I dunno, it just seems to me like the effect would become less and less as drag begins to take more effect. Please correct me if I am wrong though.

[GTS LAID]

well i was watching a show on speed cars the other day.. and they were talking about that race where they race semi-stock cars at very very high speeds for 60 miles in nevada... 3 of the cars ended up at the junkyard... and they werent turning... sure they were going 200+ mph but they're also designed to go faster...


also another thing you might be overlooking is your tires... make sure they're ready to go that fast (it rated and in good condition)

[4PASNU]

I open the Celica up on a stretch of high in Knoxville. It is a stretch about 2 miles long with 6' on each and out in the country, no cops or public. We can get our car up fast. I was just over the 160 INDICATED in the Celica with my current mods. The RSM showed 246 km/h. The car was stuck to the road like glue. I hit a bridge and it did not deter in the slighest. With an upgraded suspension, lightened car and lightweight wheels anything is possible. I weighed the car at a truck stop and with the car on fumes and it weighted 2380. I weigh 175 so do the math. I have kept track of all weights with new parts and old parts and removed parts. To run high speeds pull the muffler and tighten the suspension. I had a 92 4dr Corolla. I could pull just over 100mph when it was new. With a flowmaster, custom cai, springs and struts and wheels the car would pull way past the 110 mark. I ran the Silver State Classic one year and it was clocked at 135mph on one of the straights. Given enough road anything is possible.

Dan

[NSX_GTR_LM]

Originally posted by 4PASNU
I open the Celica up on a stretch of high in Knoxville. It is a stretch about 2 miles long with 6' on each and out in the country, no cops or public. We can get our car up fast. I was just over the 160 INDICATED in the Celica with my current mods. The RSM showed 246 km/h. The car was stuck to the road like glue. I hit a bridge and it did not deter in the slighest. With an upgraded suspension, lightened car and lightweight wheels anything is possible. I weighed the car at a truck stop and with the car on fumes and it weighted 2380. I weigh 175 so do the math. I have kept track of all weights with new parts and old parts and removed parts. To run high speeds pull the muffler and tighten the suspension. I had a 92 4dr Corolla. I could pull just over 100mph when it was new. With a flowmaster, custom cai, springs and struts and wheels the car would pull way past the 110 mark. I ran the Silver State Classic one year and it was clocked at 135mph on one of the straights. Given enough road anything is possible.

Dan


please be careful at those speeds man. If you want to, you can IM me at nsxrlmgt2, I will send you a nice vid that shows how fast things can happen. Its at speeds greater than 160, but this thing was prepared to go fast with plent of downforce and everything. Like gtsLaid said, you never know where there may be bumps, and at those speeds, you dont have nearly the reaction time to compensate.

[4PASNU]

That is why I ONLY do it on this stretch of highway. It is a new road and I know every inch of it. It is a popular place to run for all the local peeps. I got buzzed by a Huyabusa one morning. I was doing 130 and passed me doing over 200mph. He has a turbo. I don't do this type on insane driving when the public is around or anywhere else. I know very much what high speed driving can do. I have the Silver State Classic twice in my life. Street racing is unsafe. I will open the car up every once it a while but only here and only very late at night or early in the morning. Remeber just be safe doing it. Both hands on the wheel seat in the up right postion, no gangsta lean and pedal to the metal and the thing to the floor.

Dan

[NSX_GTR_LM]

Originally posted by 4PASNU
no gangsta lean and pedal to the metal and the thing to the floor.

Dan



HAHAHAHAHAHA, sent the pm back, lemme know wassup

[My2ktoy]

here's a test: get two celica's, same model, same tranny, same mods. put a couple extra people in one of them. race from 100-140. see who wins. ;)

[NSX_GTR_LM]

thats not what I am saying. Its obvious who will win. What I am saying is, does the advantage of light weight have a LESS DRASTIC EFFECT at higher speeds than it does at low speeds, since drag is more important at high speeds.

[Chui]

The drag due to the vehicle punching a hole thru the atmosphere will be the most apparent effect at triple digit speeds - actually, at freeway speeds, too. At lower speeds the weight reduction will be felt immediately - as would a lightened flywheel.

In the case of the lightened flywheel it's "effective mass is reduced". Torque = I*alpha where I is the moment of inertia and alpha is the angular acceleration. Reduce I [via reducing mass], Torque is constant and the rate of acceleration, alpha, increases. Result: Quicker car. But I digress.

One would have to drive two cars - one normal and one with the reduced mass - side by side to really get the idea of what differences the two vehicle setups will have. Put them in 3rd or 4th gear at 30 mph and floor them. The results will show up in a tangible fashion. Try the same thing in 5th gear at 50 mph and the same will evidence itself again. Perhaps less telling, but it will show.

[NSX_GTR_LM]

Originally posted by Chui
The drag due to the vehicle punching a hole thru the atmosphere will be the most apparent effect at triple digit speeds - actually, at freeway speeds, too. At lower speeds the weight reduction will be felt immediately - as would a lightened flywheel.

In the case of the lightened flywheel it's "effective mass is reduced". Torque = I*alpha where I is the moment of inertia and alpha is the angular acceleration. Reduce I [via reducing mass], Torque is constant and the rate of acceleration, alpha, increases. Result: Quicker car. But I digress.

One would have to drive two cars - one normal and one with the reduced mass - side by side to really get the idea of what differences the two vehicle setups will have. Put them in 3rd or 4th gear at 30 mph and floor them. The results will show up in a tangible fashion. Try the same thing in 5th gear at 50 mph and the same will evidence itself again. Perhaps less telling, but it will show.

What alot of people dont know about freeway speeds, at 55 mph, it takes a car with a .30 COD about 7 HP to overcome the drag, whereas at 65 MPH it takes about 12. The speed limit may save gas too ;)

[GTS LAID]

Originally posted by NSX_GTR_LM


What alot of people dont know about freeway speeds, at 55 mph, it takes a car with a .30 COD about 7 HP to overcome the drag, whereas at 65 MPH it takes about 12. The speed limit may save gas too ;)

thats part of the reason the speed limit was reduced in the 70's with the gas crisis and all here in jersey...